Heuristic Evaluation

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Readings

Pages 24-76.

Optional

Featured Responses

Zhiyuan Xu - 2/17/2014 23:17:11

The Human Model Processor is essentially an overarching overview of how the human 'system' inputs and outputs data, with many parallels drawn to an information processing system. It is designed to simplify the human mind and approximate human behavior. The human model processor could be broken down to three subsystems: the perceptual system (sensors and associated buffer memories), the motor system (actual parts that carry out the response), and the cognitive system (Working Memory and Long-Term Memory). Some limits of the Human Model Processor include the fact that memory is limited, and that processing may take time. Areas which the Human Model Processor can expand on include the semantic description of Long-Term Memory, the description of the Perceptual Processor, and the description of the Cognitive Processor. furthermore, while computer memories require access time, the Human Model Processor does not.

Fitt's Law states that the time it takes to quickly move to a target depends on only the ratio between the target's distance and size. It may be good to keep this law in mind when designing certain functions such as swiping motions for smart phones, or two frequently and consecutively used objects. Hick's Law states that the amount of time it takes for an individual to make a choice increases logarithmically to the amount of choices the individual is presented with (ie. H = log_2(n)). This is good to keep in mind for an efficient user interface. Although users may want a variety of choices when it comes to the application, it may be a better idea to present few choices in order for the consumer's decision making process to be expedited. This ties back to the principle of sharpening focus when it comes to choosing the target audience. If the specific audience is known, it becomes easier to narrow down the set of choices that are important for the user.


Christopher Echanique - 2/18/2014 23:37:18

The Human Model Processor is a way to model the human mind as an information-processing system through a set of memories and processors together with a set of principles. It can be broken into three subsystems: the perceptual system, motor system, and cognitive system, with each of these systems defined by its own memories and processors. A number of parameters are used to describe the memories and processors including storage capacity, decay time of an item, the main type of code, and the cycle time. These parameters also define the limits of the Human Model Processor in that each system can only store so much data, retain this data, encode it in a set number of types, and perceive it within a given time interval. In addition, the encoding operation used to store information determines what retrieval cues are effective to providing access to what is stored, thus limiting the ease of access to such information. At times this Human Model Processor system fails to capture certain interactions. An example of this is when a human perceives similar events occurring in a single cycle as a single percept, such as two lights turning on at the same time or rapid clicks occurring in a short time interval. This limitation can be exploited in video frame rates to give the illusion of movement.

Fitts’s Law states that the time required to move a hand to a target depends only on the relative precision required, or the target’s distance and its size. Hick’s Law states that increasing the number of choices a person has will increase decision time logarithmically. Both laws can be useful in designing effective user interfaces. For instance, Fitts’s Law can be considered when designing components that the user will interact with, such as buttons on a mobile application. To minimize the time it takes to click on a button, a designer can reduce the precision required to click the button by making it large enough on the screen. In addition, the designer can reduce the distance between buttons that are frequently pressed in succession in order to further reduce this hand movement time. Hick’s Law can be applied by providing users with minimal options to reduce the decision time. For example, when designing a color-coded note application, the designer can offer a small list of colors instead of allowing the user to select from a large color palette, which will help reduce decision time.

Sergio Macias - 2/19/2014 3:59:13

1) The Human Model Processor is a model to describe the human mind to analyze the time it takes to perform certain actions. It consists of two sets: a set of interconnected memories and processors and a set of principles of operation. Memories and processors are split into three components: perceptual system (which handles, put very simply, what one sees), cognitive system (which handles, put very simply, what one thinks), and motor system (which handles movement). A few important characteristics of these systems can be summed up by the values of a few parameters, which include: processor cycle time, memory capacity, memory decay rate, and memory code type, among others. The limits of the HMP are that it does not capture the subtleties and complexity of the human mind – it regards the human mind like a computer, which is possible of certain actions within a certain time frame. This type of model leaves out many important aspects and features of the human mind however it does this to make the model simpler which in turn makes it easier to understand and use.

2) Fitts’ Law says that the time it takes one to move one’s hand to a desired target is dependent on the relative precision required, which is the ratio between the distance to the target and the size of the target itself. This law helps designers decide where to put specific buttons on a menu screen so that it’s most optimal for the user, in that the user only has to put a little bit of effort to push the button. Hicks’ Law describes the relationship between number of choices and the time it takes for one to make a decision based on those choices; the more choices one has, the more time it will take them to make a decision (logarithmic increase in time). This law can help designers create their menus and lists in such a way that cuts down the processing time required by the user. One example would be to make a list alphabetic so that the user, mentally, breaks the list into sub-categories and helps them more quickly find what they were looking for by giving less overall choices (i.e., they will only look at a certain section of the list, rather than scanning the whole thing which would be linear in time). Another use would be to limit the amount of options per screen so that the user will more quickly make a choice (e.g. like the Google Play Store, which only fits a few apps into the screen at any given time).


Reading Responses

Opal Kale - 2/16/2014 12:30:50

The Human Model Processor can be described by as set of memories and processors together with a set of principles called the principles of operation. It is a cognitive modeling method that calculates how long it takes to perform a certain task. The MHP draws an analogy between the processing and storage areas of a computer, with the perceptual, motor, cognitive and memory areas of the computer user. A limit of the Human Model Processor is that it doesn’t give “justice to the richness of the human mind” since a lot of it is scientific/calculation based.

Fitt’s Law is the time required to move the hand to a target depends on the ratio between the target’s distance and it’s size. Fitt’s Law is helpful in figuring out what is the best design for mouse cursors for onscreen targets, such as a button or a widget.

Hick’s Law describes the time it takes for a person to make a decision as a result of the possible choices the person has; increasing the number of choices will increase the decision time logarithmically. Hick’s law could be useful in designing a UI, specifically in designing a menu. For example, if a list is in alphabetical order then logarithmic time would only be needed in order to make a decision.


Ziran Shang - 2/16/2014 18:00:22

The Human Model Processor is a set of memories, processors, and principles of operation. The model can be used to calculate how long it takes to perform tasks on the computer. The model is made up of the perceptual system, which recognizes and stores information from the physical world, the motor system, which carries out a physical response, and the cognitive system, which deals with long term and working memory.

One of the limits of the Human Model Processor is that it does not take into consideration that people can increase their working memory. The model also chooses to believe that memory comes in chunks that are all or nothing in long term memory, instead of the alternative theory that memory can be made stronger by repetition. The model fails to capture differences among individual users, since it uses average times in calculations. Also, it does not take into account slower times if a user is tired or not fully focused.

Fitts' Law says that the time to move your hand to a target depends only on the relative precision, or the ratio of distance to the target to the size of the target. Hick's Law says that reaction time increase logarithmically with the number of options. These are useful because designers know that they should limit the number of choices presented to the user in order to improve reaction time, and make targets larger especially if a target is far away.


Ryan Yu - 2/17/2014 22:15:25

1) Essentially, the human model processor is a method that is used to model the human mind in an attempt to calculate and estimate how long it takes to perform tasks. As the name suggests, the human model processor attempts to break down the human mind to try to associate each individual aspect of decision making with a tangible value. In doing so, the human model processor breaks down the human mind into three subsystems: the perceptual system, the model system, and the cognitive system, which of which has its own memories and processors.

Briefly, the perceptual system is made up of sensors and buffer memories -- that is, it holds the events and sights that we see, which are later to be processed. This processing is done by the cognitive system, which receives information and helps to make decisions about how to respond to choices that are presented. Finally, the motor system is the physical system that carries out this decided response.

The underlying idea behind the human model processor is that if you can break down every step of a task (such as the movements that are required to navigate through a simple mobile application), then you can predict human performance at each of these steps using the human model processor, thereby evaluating the usability of an application or a product. However, I like to think of this in the sense that the human model processor treats all products and applications in a purely *objective* stance -- that is, it is excellent at evaluating each step of an application's navigation to, say, one of its internal menus, but it does not account for factors that may effect response time on the *user's* end. For instance, it does not account for variations in the clicking/reading habits of users. Furthermore, there are numerous areas where the human model processor could be expanded. For one, when the processor models memory, specifically long-term memory, it does not organize long-term memory into any specific structure -- that is, an improved model of long-term memory would break it apart into subcategories, and would give some hypothesis as to how memories are sorted within the buffer.

Finally, the human model processor fails to capture all computer interactions that are outside of the aforementioned "breaking down" of user-tasks. For instance, it fails to take into account things like frustration at computer lag (and may actually spit out incorrect conclusive data based on this). It also fails to take into consideration that humans don't naturally act on the computer in a systematic fashion -- that is, you can't expect that a human will open an application and proceed to navigate to a specific screen without interruption. He/she will almost definitely be distracted by various things on or off-screen.

2) Fitts' law is an equation that provides an estimate for how long it takes a human hand to move to a target of size S which lies a distance D away. The equation is given by:

Time = I_m * (log_2(D/S + 0.5)), where:

D = distance of target S = size of target

This can be useful for designing user interfaces when a designer wants to optimize the amount of time it takes for a user to interact with the interface. For instance, there might be some buttons on a menu which are projected to see much more frequent use than other buttons. The designer might make use of Fitts' law to make these more-frequently-used buttons larger and closer to the natural position of the human hand (in the holding-a-phone position).

On the other hand, Hick's law essentially provides an estimate for the time it takes for a human to make a decision, given possible choices that he/she has. The equation is given by:

Time = b * log_2(n + 1), where:

b = constant that varies with measured data n = number of equally probable choices

This can be extremely useful for designing user interfaces, as presenting users with choices/options within menus is extremely prominent in applications. Designers could use Hick's law to determine the number of options that they should provide to the user in order to optimize their decision making time. For instance, an extremely simple example would be if a given application wants to ask the user the color of their car -- it would be unfavorable to give the user a list of two hundred different obscure colors to choose from, as this would overwhelm them and severely impair their decision making time. Instead, the designer should offer the user the primary colors as choices, plus maybe a few more popular variants. This, according to Hick's law, would improve reaction time and would not overwhelm the user.


Zhiyuan Xu - 2/17/2014 23:17:11

The Human Model Processor is essentially an overarching overview of how the human 'system' inputs and outputs data, with many parallels drawn to an information processing system. It is designed to simplify the human mind and approximate human behavior. The human model processor could be broken down to three subsystems: the perceptual system (sensors and associated buffer memories), the motor system (actual parts that carry out the response), and the cognitive system (Working Memory and Long-Term Memory). Some limits of the Human Model Processor include the fact that memory is limited, and that processing may take time. Areas which the Human Model Processor can expand on include the semantic description of Long-Term Memory, the description of the Perceptual Processor, and the description of the Cognitive Processor. furthermore, while computer memories require access time, the Human Model Processor does not.

Fitt's Law states that the time it takes to quickly move to a target depends on only the ratio between the target's distance and size. It may be good to keep this law in mind when designing certain functions such as swiping motions for smart phones, or two frequently and consecutively used objects. Hick's Law states that the amount of time it takes for an individual to make a choice increases logarithmically to the amount of choices the individual is presented with (ie. H = log_2(n)). This is good to keep in mind for an efficient user interface. Although users may want a variety of choices when it comes to the application, it may be a better idea to present few choices in order for the consumer's decision making process to be expedited. This ties back to the principle of sharpening focus when it comes to choosing the target audience. If the specific audience is known, it becomes easier to narrow down the set of choices that are important for the user.


Derrick Mar - 2/18/2014 0:54:07

As mentioned in the last page of the reading, the Human Model Processor does not take into account multi-tasking which is very prevalent with mobile and computer use. Additionally, even with the fast, middle, and slowman parameters, it still generalizes the user too much. For example, if you were designing for disabled people, the parameters would change. Most importantly, I think the biggest limit of the Human Model Processor is that it does not take into account any other external variables outside the user. For example, if a user is listening to music or if the user is working a group setting, what happens to the timing response of the visual, cognitive and motor processors? We can also relate this to computer interactions as well. For example, the model fails to capture the effect of multiple windows open on a screen (or any variable involving input/output e.g. size, brightness, etc…), as well as the number of screens (e.g. having a dual monitor).

In short, Fitt’s Law deals with precision and Hick’s law deals with the number of choices. Fitt’s law asserts that distance and the size of the target effects the time required to move to that object (the larger the distance and smaller the target the more corrections are needed and hence more cycles/time). Hick’s law asserts that the time to make a decision is positively correlated with the number of choices involved (e.g. more choices, more time). Clearly, the implications of these laws have an effect on user-interfaces. The goal of a UI is to decrease the time for a user to accomplish his/her goal which means eliminating unnecessary choices and positioning and sizing elements appropriately on the interface. A closer examination shows however, that solely taking into account these laws is not enough to design a great UI. A designer needs to take into account how his/her target users and the trade-offs involve in trying to decrease the time to make a decision or for a user to do an action.


Michelle Nguyen - 2/18/2014 1:30:13

1) The Human Model Processor is a simplified model of how humans process information and is used to predict how long it takes for people to perform a task. It consists of the perceptual system, motor system, and cognitive system, each of which have their own memories and processors. It also has a set of principles of operation. The perceptual system takes auditory or visual stimulus and converts it to an internal representation that can be understood by the mind. The motor system then translates these thoughts into action by activating the muscles. The cognitive system connects the perceptual and motor systems, and relies heavily on the working memory and long-term memory. Since the Human Model Processor is just a simplified model, it is greatly limited. You can not infer from it beyond the average human individual--everyone is different somehow and has different capacities. It does not take into account the person's environment or other people around that person. The Human Model Processor also fails to capture the fact that users may be doing multiple tasks on a computer, and works only for when a user is focused on a single task.

2) Fitts' Law says that the time to move the hand to a target only depends on the size and distance of the target. Hicks' Law says that the time for a person to make a decision increases with uncertainty (such as the number of choices a person has to choose from). These are useful for designing user interfaces because it gives us a good idea of how good a design decision can be without having to test with a user prototype first. The laws give us a guideline for what factors we want to take into account for the user to have a quick, simple experience. For example, with Fitts' Law, we can determine what is good placement for buttons or actions in our UI that the user will be using often. Clearly, we want to make it faster for our users to perform these actions, and Fitts' Law indicates that distance and size are the main factors. Thus, we know to make important buttons larger and closer to the user's mouse or finger. For Hicks' Law, we know to keep the number of choices limited, so as to decrease their uncertainty and therefore reduce the time taken to make decisions. Although we may want to give users a lot of options, Hicks' Law reminds us that we may want to limit these choices in or UI to keep the experience simpler and quicker. Also, whenever we make a design decision, we can always use the equations to calculate the times and figure out if the time it may take for a user to perform the task is within the range we want. If not, we can determine from the equations how much or what we need to change to get within our desired threshold.


Andrew Lee - 2/18/2014 15:19:40

1. The Human Model Processor models the processes of how humans perform tasks, from perceiving the world, to extracting symbolic meaning, to articulating the body. It can be used to estimate the amounts of time to perform tasks. The limits of this model include how the range of times for certain actions can vary wildly, leading to overall time estimates that have a wide range as well. Additionally, it works best when the task break down serially. Some computer interactions it fails to capture are those that involve complex thinking (like chess) and switching to a different specific task.

2. Fitt's Law approximates the time it takes for a user to move a pointer (such as a finger or a mouse cursor) from it's current location to a target location, accounting for the width of the target. The law implies that the greater the distance-to-width ratio, the longer it takes (in logarithmic fashion) for the user to execute this action. This informs UI designers to keep common touch targets closer and larger to avoid hindering the user.

Hick's law approximates the time it takes for a user to select something among various items. The law implies that the greater the number of choices, the longer it'll take for the user to find and select their choice, though the time can be reduced by having nonuniform probabilities in the choices. This informs UI designers to keep the number of choices manageable, and if their frequencies are known, take advantage of that, for example, placing the most frequent choice first.


Charles Park - 2/18/2014 16:11:55

The Human Model Processor is a set of memories and processors together with a set of principles. It calculates how long it takes to perform a certain task (cognitive and motor processing). There are some limitations, however. Memory is a limiting agent, as in the notion of the register containing a fixed set of slots. Processing is another limiting agent. Processing capacity, which is allocated to different tasks or component of a task, usually within a parallel system, can be limited. Therefore it is not possible to formulate experimental ways of distinguishing these alternatives in general. Serial processing systems can mimic parallel ones by rapid switching but cannot fully display the parallel system.

Fitts’ law is a model of human movement which predicts that the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. Hick’s law describes the time it takes for a person to make a decision as a result of the possible choice available: increasing number of choices results in logarithmically increased decision time. Together, these two laws can be used to estimate the user’s interactions with menus therefore helpful to the interface design.


Gregory Quan - 2/18/2014 17:13:58

The Human Model Processor is a model used to calculate the time it takes humans to perform certain tasks. It consists of a perceptual system to perceive visual and auditory input, a motor system to perform tasks, and a cognitive system to process information. The cognitive system can be further broken down into working memory and long-term memory. It does not capture the time to complete complicated tasks, such a dance routine, or perform sophisticated reasoning, such as solving a homework problem. It also fails to capture computer interactions other than typing, viewing objects on a screen, and clicking buttons.

It could be argued that Fitt’s Law does not apply directly to mouse cursor movement because the movement of the physical mouse maps to different amounts of cursor movement on the screen depending on the hardware, software, and user settings. Also, the Human Model Processor does not capture audio input/human speech rate or complicated gestures such as pinch to zoom or other multi-finger gestures.

Fitt’s Law states that the time required to move the hand to a target is proportional to the relative precision required, where precision is the ratio of distance to the target to the size of the target.

Hicks’ Law states that the time required for a person to make a decision based on the number of available choices is logarithmically proportional to the number of choices. Also, the time required depends on the perceived likelihood of the various outcomes: if some outcomes or more likely, the average decision time will be smaller.

These formulas can be useful because they provide guidelines about the time it takes people to perform certain actions and make decisions. Interface designers can use these times to inform their designs. For example, they can calculate how much time it takes an average user to input their ATM PIN on a keypad and decide when to time-out the screen for security reasons. It would be unwise to make the user perform a task that is not humanly possible, such as entering their ATM PIN within a fraction of a second.


Emily Sheng - 2/18/2014 17:21:22

1) The Model Human Processor is made up of a system of perceptual, motor, and cognitive processors and memories. Information first enters the system through the perceptual processor that creates internal representations. Then this information is passed to the cognitive processor to be processed (with the help of the working memory and the long-term memory) and eventually then passed to the motor processor for the Model Human Processor to act based on the input it received through the perceptual processor. The limits of this model is that it is not capable of capturing the rich interaction of systems in a real human. It also fails to capture the access times required to access computer memories.

2) The Model Human Processor is made up of a system of perceptual, motor, and cognitive processors and memories. Information first enters the system through the perceptual processor that creates internal representations. Then this information is passed to the cognitive processor to be processed (with the help of the working memory and the long-term memory) and eventually then passed to the motor processor for the Model Human Processor to act based on the input it received through the perceptual processor. The limits of this model is that it is not capable of capturing the rich interaction of systems in a real human. It also fails to capture the access times required to access computer memories.


Munim Ali - 2/18/2014 18:37:00

1) The Human Model Processor is a quantitative cognitive modeling technique that primarily evaluates task performance time, and uses this as a measure for usability.

Although the HMP does give us valuable insight into usability and task performance, it grossly oversimplifies many facets of human perception of usability and computer interaction. Firstly, the generalizations it makes doesn't cater to a specific target audience (say senior citizens vs teens) which makes it less helpful when developing targeted applications. Secondly, this model fails to capture the aesthetic features needed as far as usability is concerned. Thirdly, it fails to capture the cultural context - people from different cultures respond differently.

2) Fitts' Law: This law is a mathematical formulation of the time required to move the hand to a target of size S which lies a distance D away. The larger the size of the object, the less is the time required. The greater the distance of the object, the more is the the time required.

Hicks' Law: Hick's law states that the time taken by a user to make a decision is proportional to the number of choices presented to him/her.

Both these laws allow designers to predict what design choices they must make to provide a more user-friendly interface (at least in terms of task efficiency). For example, imagine a dictionary with words arranged in a random order the decision time would be linear function of the number of words in the dictionary. On the other hand, if a dictionary is sorted lexicographically the decision time would be logarithmic in the number of words in the dictionary (say the search word starts with a 'b' - the user can narrow down his search to words in the 'b' section of the dictionary). This problem is a perfect example of how Hick's law could help a designer make choices.

Fitts' law could be used by the designers to determine if they want to make buttons larger (for faster action times). The law could also help with button placement.


Rico Ardisyah - 2/18/2014 20:55:51

Human Model Processor is, basically, a model that considers the users who are human beings as computers. This model also calculates the time to perform a certain task. Through this model, we can produce a better user interface. This model can be divided into three interacting subsystems that are perceptual, motor, and cognitive subsystems. Each of subsystem composed of memory and processor. The first system, which is perceptual system, can be considered as an input. This system is responsible for transforming external environment into a form that will be processed by cognitive system. Second, Cognitive System serves to connect input from the perceptual system to the output of the motor system. It is composed of a processor and two memories, working memory and long-term memory. Working memory holds the intermediate products of thinking and representations produced by perceptual system. While, long-term memory holds the user’s mass of available knowledge. Last, Motor System is the output produced after Perceptual and Cognitive Systems process some input. This system controls movement of body, and each movement composed of micro-movement. This system caches common behavioral acts such as typing and speaking. The limit of Human Model Processor is that there is an extreme range of Fastman and Slowman, this will affect that the calculation resulted is very vary and not really accurate. Other than that, the result of Human Model Processor only gives us value without any significant meaning.

Fitt’s law models human motor performance; and it is essentially aimed at arm-hand movement. The law predicts the movement time, which is a function of target distance and width. On the other hand, Hicks law models human reaction time under uncertainty, hence the reaction time increases as the number of choices increases. Fitt’s law shows us that making clickable icons wider and reducing the distance between the icons will decrease the movement time. Grouping the options for user is one of the applications of Hicks’ law. By grouping the options available, it reduces the time for user to take decisions. They are indeed useful for UI.


Justin MacMillin - 2/18/2014 21:40:26

1) The Human Model Processor is comprised of 3 systems: perceptual, motor, and cognitive. The perceptual system is the input from the human’s eyes. The author discusses the finer points about how memories are stored and how the perceptual processor understands and records inputs. Perceptual memories are split into visual and auditory inputs. The perceptual processor can understand inputs at a certain speed. For example, there was a study that proved patients could only hear individual ticks as long as they were 100 msec apart. After that, the ticks blur together making it impossible for the human to understand when one stops and starts again. The motor system is responsible for operating and moving voluntary muscles. The cognitive system connects the perceptual and motor systems. This system is comprised of working memory and long term memory. Working memory is what deals with what the person is currently working on, the immediate task at hand. Long term memory is used to store pieces of information for a long time, such as a name or phone number. The cognitive processor takes in perceptual inputs using previous experiences and sends information to the motor system to carry out actions. A majority of the time the motor system has “muscle memory” and will carry out a familiar action to respond to the current task.

2) Fitt’s Law relates how long it takes for a user to move their hand towards to a target area. His equation relates the “relative precision required,” which is the “ratio between the target’s distance and its size.” Hicks’ Law relates the time for someone to make a decision based on the number of options they have. As the number of options increases, the reaction time increases logarithmically. The time does not increase linearly because the mind organizes the options into groups and then picks from a group instead of all of the options combined. With more input, there are more groups or larger groups and in either case more options are eliminated faster. Fitts’ Law is important to user interfaces because the design of an interface should feel fluid. It should not feel like the user has to move their finger (or their attention for that matter) to all different parts of the screen. For example, the “next” button for a set of menus should stay in the same spot. If the user has to constantly check where the “next” button is that increases their time wasted simply looking for buttons and moving their finger (or cursor) to the button they wish to pick. In my opinion, Fitts’ Law has a lot to do with placement of items in a UI. Designers should be aware of Hicks’ Law because it proves it is okay to have more than a couple options on a single page or activity. Of course it would be ridiculous to put too many options on there, but this law gives designers more room to be more creative with their design. Hicks’ Law is especially surprising to me because I would have expected time to increase linearly or even exponentially because with more options there are more things to consider as the user weighs their best option, and why the implications or results of that choice is better than the rest of the options.


Andrew Fang - 2/18/2014 21:49:35

The Human Model Processor can be decomposed to three main systems: the perceptual, the motor, and the cognitive. Each of these systems is made up of a processor and memory, and the three systems work together to control the human body and dictate how it interacts with foreign entities (such as computers). The perceptual system is filled with sensors that tells the body what it detects. The motor system translates thought to motion by stimulating specific muscles in the body. The cognitive system translates perceptions to motor control (input to output).

This model is good, but we are limited in our ability to accurately predict human performance. There are so many factors that tend to interfere with the simple model that we used to generalize, and there will always be a certain level of uncertainty on how these factors affect human performance. Furthermore, the model was built upon the idea that the system could be separated into various layers that are isolated from one another (with regards to processing and memory). The systems these days, however, are intricately built with inter-woven layers and such a guarantee of independence no longer holds. This model fails to capture semantic memory and the effects of just visual or auditory stimuli. Sometimes, computer interactions do not involve motor skills at all; sometimes the user only needs to stare at the screen and absorb themselves in the movie or plug in their ear buds and enjoy some music.

Fitt’s law says that time required to move to an object depends on the distance to the object and the size of the object. Time increases as distance increases, and it decreases as the size of the object increases. This is because the user must cycle through the perceptual system (to see where the target it), the cognitive system (to figure out how to correct the current course of motion in order to hit the target), and the motor system (to physically change the course of movement). This is useful for designing user interfaces because as designers, we can use this information to know that we should make interactive features of the interface big enough that the ratio of size to distance is large enough that the user will be able to succeed most of the time when attempting to interact with said features.

Hick’s law says that when an individual has to make a decision, response time increases as the number of possible choices increases. In terms of user interface design, this mantra tells us that we should limit the number of choices the user has to choose between. If the user has fewer choices, he can make decisions faster, which results in a greater fluidity of the interface.


Luke Song - 2/18/2014 21:55:58

The human processor is described as a series of systems, both motor and cognitive, working in sequence to carry out tasks. The explanation of what happens in the mind is usually described in delay times to complete certain tasks. Humans are viewed as a collection of different levels of memory, physical control, and mental prowess that take variable times to perform very specific tasks to measure and focus on one cog of the entire machine. However, this doesn't leave much leeway for the description of much more complicated tasks, nor does the description of the human as a set of memory, processors, and principles fit the entire picture.

Fitts' Law describes the time it takes to complete a task on the physical side of things. It states that the time depends on the relative precision that the job requires; a big movement that needs fine precision will take longer than a small task with a lot of room for error. This may be useful if we design an interface that focuses most of the interaction in one area; buttons closer to that area can be smaller and buttons farther away should be bigger, and these should be the least used.

Hicks' Law, on the other hand, focuses on the mental side of time. Apparently, the time it takes to complete a simple task is directly related to the entropy of the decision, which is related to the log of the number of alternatives. Basically, Hicks tells us that when a remote is cluttered with buttons for different functions, it will take people longer to find and do what they want.


Tien Chang - 2/18/2014 22:13:26

1) The Human Model Processor is a set of memories and processors together with a set of principles - this is also called the principles of operation. The Human Model Processor can be divided into the perceptual system (contains sensors and associated buffer memories such as Visual and Auditory Image Store), the motor system (carries out responses), and the cognitive system (symbolically coded information in Working Memory and uses Long-Term Memory for response).

The limit of the Human Model Processor includes the large amount of uncertainty based on physical sciences. Even with ranges set by the Slowman ~ Fastman range, the difference is wide and can still allow potential unforeseen effects to occur. Computer interactions that it has difficulty capturing are perception, motor skill, simple decisions, learning and retrieval, and problem solving.

2) Fitts' Law is the movement of the hand towards a target depending on the relative precision required, or the ratio between the target's distance and its size. Hicks' Law is based on the uncertainty principle that decision time increases with the number of alternative stimuli present.

These laws are incredibly useful as principles in designing user interfaces. Based on Fitts' Law, we understand that for a user interface, the distance away from the target and the size of the target would create a larger possibility of error in pointing. Therefore, it is best to avoid large distances away from the target and a large target size. Hicks' Law is also important for user interface in that designers should not present multiple options for users if they wish for users to quickly use a design. However, if designers wish for users to contemplate options before choosing, it would work in the designers' favor to include many options.


Christopher Echanique - 2/18/2014 23:37:18

The Human Model Processor is a way to model the human mind as an information-processing system through a set of memories and processors together with a set of principles. It can be broken into three subsystems: the perceptual system, motor system, and cognitive system, with each of these systems defined by its own memories and processors. A number of parameters are used to describe the memories and processors including storage capacity, decay time of an item, the main type of code, and the cycle time. These parameters also define the limits of the Human Model Processor in that each system can only store so much data, retain this data, encode it in a set number of types, and perceive it within a given time interval. In addition, the encoding operation used to store information determines what retrieval cues are effective to providing access to what is stored, thus limiting the ease of access to such information. At times this Human Model Processor system fails to capture certain interactions. An example of this is when a human perceives similar events occurring in a single cycle as a single percept, such as two lights turning on at the same time or rapid clicks occurring in a short time interval. This limitation can be exploited in video frame rates to give the illusion of movement.

Fitts’s Law states that the time required to move a hand to a target depends only on the relative precision required, or the target’s distance and its size. Hick’s Law states that increasing the number of choices a person has will increase decision time logarithmically. Both laws can be useful in designing effective user interfaces. For instance, Fitts’s Law can be considered when designing components that the user will interact with, such as buttons on a mobile application. To minimize the time it takes to click on a button, a designer can reduce the precision required to click the button by making it large enough on the screen. In addition, the designer can reduce the distance between buttons that are frequently pressed in succession in order to further reduce this hand movement time. Hick’s Law can be applied by providing users with minimal options to reduce the decision time. For example, when designing a color-coded note application, the designer can offer a small list of colors instead of allowing the user to select from a large color palette, which will help reduce decision time.


Jimmy Bao - 2/19/2014 0:04:23

1) The Model Human Processor can be best described by a set of memories and processors together with a set of principles of operation. The Model Human Processor can be divided into three subsystems: the perceptual system, the motor system, and the cognitive system. Each system has a different task. The perceptual system is associated with sensors and buffer memories; the motor system carries out the response; the cognitive system receives symbolically coded information from the sensory image and uses previously stored information in "Long-Term Memory" to make decisions about how to respond.

The fundamental limits on the rate of user perceptual performance are set by the cycle time of the Perceptual Processors and the fundamental limits on movement are set by he rates of the Perceptual and Motor Processors. The computer interactions that it does capture include the movement of the hand towards a target and keystrokes, so anything that falls out of those categories are not captured.

3) Fitts' Law states that the time to move to something to a designated area or object (in the case of the reading, it was moving a hand to an object) depends only on the relative precision required (the ratio between the target's distance and its size).

On the other hand, Hicks' law describes the time that is required for a person to make a decision from possible choices that they have. The time increases logarithmically as the number of possible choices increases. The reading also calls Hicks' Law the Uncertainty Principle, which states that the decision time increases with uncertainty about the judgment or decision to be made.

Hicks' Law is especially useful for designing user interfaces because if the designer provides the user with too many unnecessary functions, the user's decision time is slowed down. With Hicks' Law in mind, a designer should only provide the user only with choices that are essential for the product's functionality. Too many choices at once will slow down the user's decision time. Fitts' Law is also important for UI design because the time for the hand to reach its target should be relatively short. Designers should design UI with these two laws in mind.


Andrea Campos - 2/19/2014 0:15:59

1) The Human Model Processor is a theoretical model of the way humans process information. It uses an analogy to the way computers process information, such as through processors, memories and code. It allows one to predict the way users would interact with computers, as well as more generally how users themselves behave and react to sensory information. Of course, the model is limited because humans themselves are not machines, and do not operate in such an orderly or reliable fashion. The mind may rely on or be affected by other human variables that are harder to quantify--perhaps things like intuition, one's emotional/mental condition, stress, and other things that machines generally wouldn't have to contend with. For computer interactions, the model failed to capture the cognitive translations that would need to be made when a user touches a trackpad to control a mouse onscreen, rather than just a part of the user's own body.

2) Fitts's Law deals with the time required to move one's hand to a target, stating that such an action depends on the precision required to do it. The more precision, in other words, the greater the ratio between the target's distance and its size, the more time it will take to accomplish this action.

Hicks' Law deals with the conditions of processing that minimize the expected time to perform an action. It states that reaction time is related to uncertainty about whether to respond to a stimulus, and what kind of reaction to make, specifically, that reaction time increases with greater uncertainty.

These can be useful for designing user interfaces because they tell us ways in which we can make them more efficient and easy to understand cognitively for the user. Fitts' Law suggests that elements such as buttons, for example, should require relatively low precision to interact with. This could mean avoiding an interface with small buttons spaced far apart, which will require more time and effort from the user to access. Hicks' Law suggests that our interfaces should avoid bombarding users with a multitude of options, such as too many button choices within a screen or even a button that a user is not sure does anything, which would heighten uncertainty and the amount of time it takes users to come to decisions.


Ian Birnam - 2/19/2014 0:43:00

1) The Human Model Processor (HMP) is a set of memories and processors, together with a set of principles known as "principles of operation." The HMP can be divided into three subsystems: the perceptual system (sensors and buffer memories), motor system (translates thought into action), and the cognitive system (connects the inputs from the perceptual system to the right outputs of the motor system).

Some limitations with the HMP is that it assumes people are doing only one task at a time, therefore ignoring the possibility of multi-tasking. It also doesn't take into consideration the effects on other people besides the user. Finally, it doesn't take into account the environment the user is in, such as weather.

However, in terms of computer interactions, the HMP fails to capture individual differences, mental workload, or the user's fatigue. Similar to what I said in the previous paragraph, the HMP doesn't take into account people besides the direct user, and it only holds for single-tasks. It also lacks the ability to sense whether a user is feeling tired, requiring the use of external laws to determine what's comfortable both mentally and physically for the user.

2) Fitt's Law is a formula used to calculate the time to move the hand to a target of a specific size which lies a certain distance away. Hick's Law is a formula used to describe the time it takes for someone to make a decision based on all the choices available.

Fitt's Law is useful for designing interfaces because it can tell you how long it will take for the user to tap or click something based on where you position the item on the screen. In this way, it can help out with figuring out how interfaces should be structured to minimize time spent moving the hand from point A to point B.

Hick's Law is useful for designing interfaces because it can help inform you if your interface is too complicated for a user to understand, or if too many options are being presented at once. Normally, you want the user to easily be able to make decisions, so when testing out interfaces, Hick's Law could help to figure out which sections of the interface need to be reworked for simplicity.


Eric Hong - 2/19/2014 1:09:59

1) The Human Model Processor is a simplified description of the human mind useful for making predictions of human behavior. The model consists of a set of interconnected memories and processors separated into three main subsystems - a perceptual system, a cognitive system, and a motor system - combined with a set of principles of operation. The Human Model Processor is limited in describing the semantic organization of Long-Term Memory, the intensity and distance of perceptual stimuli, and the control structure of the Cognitive Processor. Furthermore, although the model can predict limits in human ability, it has a more difficult time locating the limiting agent. For example, the decreased performance observed in multitasking can be due either to constraints in working memory capacity or memory processing speed. The main restricting factor cannot be easily determined from the Human Model Processor. Finally, the model fails to capture human-computer interactions such as the increase in emotional frustration when an application continuously freezes. 2) Fitts' Law states that the time to move the hand to a target depends only on the relative precision required, in other words, the ratio between the target's distance and its size. Hicks' Law describes the logarithmic relationship between the number of possible choices in a decision and the time it takes for a person to make a choice. In user interface design, Fitts' Law can be useful to predict the time required for physical movements such as hand motions. Hicks' Law can be used to approximate the amount of mental processing time needed to reach a decision based on the number of choices in the interface. The two laws combined provide an approximation of the time required to accomplish a task, which is useful for evaluating the efficiency of an user interface design.


Seth Anderson - 2/19/2014 1:16:11

1) The Human Model Processor is a conceptual processor made up of three subprocessors: the cognitive processor, perceptual processor, and motor processor, that connects the processes of a computer with the processes of the human mind. In connecting these two concepts, designers can calculate what a human will actually process from information given to them on a screen, and how long it will take them. The limits of this can be seen in variations of different humans: each user will have a different response time, and this cannot be generalized in one formula. The computer interactions the HMP fails to capture are those that run beneath the surface of the interface: notably the processes that connect the bits to the higher level languages. This process cannot truly be mimicked in the human model.

2) Fitts' law predicts the time it will take for a human to physically interact with a computer interface. Hicks' law, on the other hand, calculates the amount of time it takes for a human to actually make a decision based on what they have observed on screen. These calculations can be extremely invaluable when deigning user interfaces. By knowing how long it will take for a user to make a decision, as well as how long it will take for the physical interaction to occur, designers can determine how long prompts should remain on screen, how long tasks can run in the background while users are deciding on a task, and (for time sensitive responses such as games) determine how difficult an interface is based on time given for input.


Will Tang - 2/19/2014 3:00:33

The Human Model Processor is an information processing representation of the human being that seeks to describe human action and decision making in terms of processors and memories. The model is divided into the perceptual system, motor system, and cognitive system. The perceptual system processes sensations of the physical world that are experienced by the body through sensory organs such as the eyes and ears. It serves to process these sensations into internal representations that can be used by other processing units. The motor system maps thoughts to action through the activation of discrete muscle movements. The cognitive system at its most basic level serves to connect inputs from the perceptual system to the outputs of the motor system. It involves more complicated processors and memories than the other systems due to this purpose, and must maintain a working memory of intermediate products of thinking as well as representations from the perceptual system. The Human Model Processor is limited by the reaction times of the various systems that constitute its makeup. One of its major limitations is the continuous cycle of recognize/reaction that occurs in the cognitive system. Storing and retrieving items from long term memory and transferring them to working memory is analogous to retrieving data from disk to main memory, and is not an instantly occurring process. The feedback loop from action in the motor system takes about 200 to 500 milliseconds, which can be seen in the way humans cannot hear morse code if it is broadcasted too rapidly. Another example is the fact that humans can typically read at a maximum rate of around 600 words per minute. The systems of the Human Model Processor are limited by their interactions with one another. One way that the Human Model Processor differs from a computer is the retrieval of memories. While computers must do extra work to retrieve data from disk, this data is rarely corrupted and can be backed up. Human memories are easily corrupted by similar memories, and largely depend on the mental representations. For example, humans may confuse sounds because they have similar mental representations. Sometimes humans are simply unable to remember, and may require external stimuli or a long period of searching in order to recall certain memories.

Fitt's Law states that the time for a person to move their hand to a target depends only on the relative precision required. The relative precision is the ratio between the distance and size of the target. Hick's Law states that the time it takes for a human to make a decision varies logarithmically with the number of possible choices. These laws can be useful for designing interfaces, because they allow the designer to estimate the time required for a user to move through an interface and interact with it. An ideal interface would be streamlined to not require unnecessary time and mental effort on the user's side.


Nahush Bhanage - 2/19/2014 3:00:51

(1) The Human Model Processor is a simplified model of human performance which is intended to provide gross-level predictions of system behavior. It predicts the performance of a system with respect to the time required for a person to complete a task. It focuses on the information processing capabilities of an individual, described in terms of memories, processors and a set of principles. Memories include sensor memories, (which are small buffers holding information sensed from the environment before the data are symbolically encoded), short-term and long-term memory stores (which hold symbolically encoded information). Processors can be divided into three subsystems - (a) perceptual system, which consists of all sensors and associated buffer memories (eg: visual image store), (b) the cognitive system, which receives symbolically coded information from the sensory image stores in its working memory and responds using information from our long-term memory, (c) The motor system actually carries out responses to the cognitive system.

Limitations of the Human Model Processor are as follows: (a) It doesn't account for the possibility that the user might be multitasking while interacting with the interface. For instance, the person may be holding a conversation and composing an email simultaneously. (b) It doesn't take into consideration the person's context and the environmental conditions in which he/she is in. User experience might significantly depend on the context. (c) It's too simplistic when it comes to memories. In reality, memories could be error-prone and unpredictable. (d) The model is not equipped to measure user satisfaction.


(2) Fitts' law predicts that the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. It is used to model the action of 'pointing'.

Fitts' law could be very useful for content placement on the interface. For instance, assuming that the mouse cursor is placed at the center most of the times, it makes sense to place important content in the center. This will reduce the distance to a high frequency target. Such targets if made bigger in size could also reduce the time required for the user to move towards it. On the other hand, elements such as the close button should be placed far away in a corner so that it doesn't get clicked accidentally.

Hick's law relates the time required for a person to make a decision out of a list of possible choices he/she has. To be precise, it states that increasing the number of choices will increase the decision time logarithmically.

Hick's law can be very useful while designing interfaces. For instance, it helps in deciding how to (a) simplify layouts to improve speed or (b) minimize the number of items in a list or menu group for faster decision making. Abiding by this law could help designers create a simple and an unambiguous interface, thus minimizing user response time as much as possible.


Sijia Li - 2/19/2014 3:03:51

1. The Human Model Processor enables user-interface designers to "predict" how users will react to a user interface so that the designers can further improve their interfaces. The Human Model Processor ("Model Human Processor") consists three interacting subsystems: (1) the perceptual system, (2) the motor system, and (3) the cognitive system, each with its own memories and processors (p. 24).

The perceptual system consists of sensors and associated buffer memories; the most important buffer memories is a Visual Image Store and an Auditory Image Store to hold the output of the sensory system while it is being symbolically coded. The cognitive system receives symbolically coded information from the sensory image stores in its Working Memory and uses previously stored information in Long-Term Memory to make decisions about how to respond. The motor system carries out the response. As an approximation, the model incorporates separate processors for each of the subsystems: a "Perceptual Processor" for the Perceptual System, a "Cognitive Processor" for the Cognitive System, and a "Motor Processor" for the Motor System (p. 24).

The Human Model Processor does not capture the idea of "aesthetic design". The model (or theory) does a very good job at quantitatively analyzing and modeling real-world user experience by heavily using Mathematics tools. However, aesthetic design is highly subjective; "how to make an aesthetic design" is not a "quantitative" (or objective) question! Different users may have totally different feeling towards the same user interface design. Although the interface may have been "optimized", some users still don't like it that much simply because they do not think that design fit into their standard of what a aesthetic design should be. Thus, what is subjective remains being subjective. The Mathematics in the Human Model Processor does not capture the subjective aspects, the aesthetic design.


2. Fitts's Law suggests us that, as designers, we should put the most useful (or the most used) buttons at a place which is the most accessible from users' perspective, because it takes time for the motor system to react and to get to the desired place. In this way, it takes shorter time for the user to get to buttons which he uses very often. That is, the users' effort to use a interface will be reduced.

For example, in the design of a calculator, the place of the "f" button should be as close to the numbers pad as possible. In a good design, the "f" button is placed in the row which is right above the numbers pad.

Hick's Law tells us that it takes time for the cognitive system to process "choices"; the time is referred as "Choice Reaction Time" (p. 71-72). Hick's Law suggests that, as designers, we can decrease the "choice reaction time" by reducing the number of alternative stimuli (alternative choices), which is characterized as "n" in the Hicks' Law's formula.

If we are able to combine both Fitts' Law and Hicks' Law, the ideal design will include the following features:

1. Useful buttons are easily accessible. [by Fitts' Law] 2. Only useful buttons will be displayed; rarely-used buttons will either be eliminated or hided under a so-called "advanced option" section. [by Hicks' Law]


Thanks.

Sijia Li


Sijia Li - 2/19/2014 3:04:45

1. The Human Model Processor enables user-interface designers to "predict" how users will react to a user interface so that the designers can further improve their interfaces. The Human Model Processor ("Model Human Processor") consists three interacting subsystems: (1) the perceptual system, (2) the motor system, and (3) the cognitive system, each with its own memories and processors (p. 24).

The perceptual system consists of sensors and associated buffer memories; the most important buffer memories is a Visual Image Store and an Auditory Image Store to hold the output of the sensory system while it is being symbolically coded. The cognitive system receives symbolically coded information from the sensory image stores in its Working Memory and uses previously stored information in Long-Term Memory to make decisions about how to respond. The motor system carries out the response. As an approximation, the model incorporates separate processors for each of the subsystems: a "Perceptual Processor" for the Perceptual System, a "Cognitive Processor" for the Cognitive System, and a "Motor Processor" for the Motor System (p. 24).

The Human Model Processor does not capture the idea of "aesthetic design". The model (or theory) does a very good job at quantitatively analyzing and modeling real-world user experience by heavily using Mathematics tools. However, aesthetic design is highly subjective; "how to make an aesthetic design" is not a "quantitative" (or objective) question! Different users may have totally different feeling towards the same user interface design. Although the interface may have been "optimized", some users still don't like it that much simply because they do not think that design fit into their standard of what a aesthetic design should be. Thus, what is subjective remains being subjective. The Mathematics in the Human Model Processor does not capture the subjective aspects, the aesthetic design.


2. Fitts's Law suggests us that, as designers, we should put the most useful (or the most used) buttons at a place which is the most accessible from users' perspective, because it takes time for the motor system to react and to get to the desired place. In this way, it takes shorter time for the user to get to buttons which he uses very often. That is, the users' effort to use a interface will be reduced.

For example, in the design of a calculator, the place of the "f" button should be as close to the numbers pad as possible. In a good design, the "f" button is placed in the row which is right above the numbers pad.

Hick's Law tells us that it takes time for the cognitive system to process "choices"; the time is referred as "Choice Reaction Time" (p. 71-72). Hick's Law suggests that, as designers, we can decrease the "choice reaction time" by reducing the number of alternative stimuli (alternative choices), which is characterized as "n" in the Hicks' Law's formula.

If we are able to combine both Fitts' Law and Hicks' Law, the ideal design will include the following features:

1. Useful buttons are easily accessible. [by Fitts' Law] 2. Only useful buttons will be displayed; rarely-used buttons will either be eliminated or hided under a so-called "advanced option" section. [by Hicks' Law]


Sergio Macias - 2/19/2014 3:59:13

1) The Human Model Processor is a model to describe the human mind to analyze the time it takes to perform certain actions. It consists of two sets: a set of interconnected memories and processors and a set of principles of operation. Memories and processors are split into three components: perceptual system (which handles, put very simply, what one sees), cognitive system (which handles, put very simply, what one thinks), and motor system (which handles movement). A few important characteristics of these systems can be summed up by the values of a few parameters, which include: processor cycle time, memory capacity, memory decay rate, and memory code type, among others. The limits of the HMP are that it does not capture the subtleties and complexity of the human mind – it regards the human mind like a computer, which is possible of certain actions within a certain time frame. This type of model leaves out many important aspects and features of the human mind however it does this to make the model simpler which in turn makes it easier to understand and use.

2) Fitts’ Law says that the time it takes one to move one’s hand to a desired target is dependent on the relative precision required, which is the ratio between the distance to the target and the size of the target itself. This law helps designers decide where to put specific buttons on a menu screen so that it’s most optimal for the user, in that the user only has to put a little bit of effort to push the button. Hicks’ Law describes the relationship between number of choices and the time it takes for one to make a decision based on those choices; the more choices one has, the more time it will take them to make a decision (logarithmic increase in time). This law can help designers create their menus and lists in such a way that cuts down the processing time required by the user. One example would be to make a list alphabetic so that the user, mentally, breaks the list into sub-categories and helps them more quickly find what they were looking for by giving less overall choices (i.e., they will only look at a certain section of the list, rather than scanning the whole thing which would be linear in time). Another use would be to limit the amount of options per screen so that the user will more quickly make a choice (e.g. like the Google Play Store, which only fits a few apps into the screen at any given time).


Kaleong Kong - 2/19/2014 10:18:39

Human Model Processor (HMP)’s a way to model human behavior into a predictive system, so that scientists/engineers can use that information to estimate user-computer interaction. HMP models a human into three different processors: the perceptual system, the cognitive system and the motor system. The perceptual system corresponds to collect information from the surrounding and stores it into a temporary memory. The cognitive system uses the information of a person’s long term memory and temporary memory to decide how to respond. Finally the motor system carries out the response. One of the limits of Human Model Processor is that it’s all based on estimation, so we can’t accurately predict the outcome of the actual situation. Also, every person is a lot difference from another. The same model may not able to reflect the user-computer interaction for different user. The Model is failed to capture the emotional response of a user. If there is software which is funny, user may tend to laugh at it and this may delay the user response. However, the model has no way to capture this kind of situation.

Fitt’s Law is referring to the time a person takes from his starting point to his target point in a large area. Hick’s Law is referring to the time that a person takes depending on the number of choice that in front of that person. Fitt’s Law is important because user interface always involve of several buttons on the screen. We can use Fitt’s Law to estimate the time that a user’s cursor/finger needs to travel from one button/feature on the screen to another button/feature. With this model, we can figure out that the amount of time that the user finished an action without a decision. Hick’s Law is useful to decide how many buttons/features we can put on our application. In order to have a highly functional application, we often want it carries out more features which may lead to more options on the screen. User may be confused by all those options on the screen and delay his response of making a decision. With the help of Hick’s Law, we can figure out whether our UI is clear enough for the user and also carry out all the functions that we designed.


Jeffrey DeFond - 2/19/2014 10:32:29

1) The human model processor is an attempt to create a metaphor for human behavior. The source domain is computer systems and the target is a human. More specifically a human and the interactions they make with their technology. It describes limitations in memory, and in performing various tasks. While it is a useful metaphor, it is clearly just the most recent example in a long pattern of humanity self describing in terms of the most advanced piece of technology available. This inherently limits the power of the metaphor to describe human behavior (at least until we have the irrationality function as well as the rationality function). I can guarantee that by 2050 (at the latest) we will begin comparing ourselves to quantum computers and their internal workings. In any case the metaphor is useful for describing the limitations of humans visa-vie cognetics, but It will never capture the behavior of a bored web surfer or an artist making graphic art with their machine.

2) Hick’s law describes the time it takes to make a decision based on the number of choices presented (its logarithmic). This is hugely applicable to menu, and layout design, too many choices and the users stack overflows, use too little and you won’t have a well signified/easy to operate system. Fitts law describes a similar logarithmic relation between the time it takes people to move their cursor to a target relative to the distance and size of the target. This is also applicable for how large certain buttons are and how far from the clicker you want various widgets to start. It is hard to say from the reading, and from intuition, if this is faster with touch interfaces or with mice, or if it is different between the two. Based on studies I have read about the cognitive neuroscience of tool use, it is fairly well established that when a person becomes used to using a tool, there is evidence that it extends their motor homunculus to include the tool, this leads me to believe that Fitts law works at the same speed mouse or finger.


Shaina Krevat - 2/19/2014 11:39:37

1. The Human Model Processor is the model of the way the human mind processes and reacts to the world around it. There are three sub-systems in the model – the perpetual system, cognitive system, and a motor system - and two “memory banks” – the long-term memory and the working memory – all of which interact and model the way that the human mind works.

The Human Model Processor does not account for stimulus from touch. For example, the user can feel if their computer is getting warm, and will need to access his or her working and long-term memory for the next step (should I let it cool down? Should I restart my computer?). Also, when it comes to the keyboard or mouse the user most of the time does not look at the keyboard or mouse directly, if anything they are in the peripheral vision. The user uses touch stimuli to know which keys or buttons to press (for example the bumps on the f and j keys to alert the user to the “home row”), which is not accounted for in the Human Model Processor.

2. Fitt’s Law states that the time it takes for a hand to move from rest to the object it wants to touch depends on the “relative precision” – the ratio between the size of the target object and how far it is. Hicks’ Law relates how long a user takes to make a decision as a function of how many choices are presented to a user.

Fitt’s Law can be used when deciding where to put buttons of a certain functionality on a device and how big to make them. For example, on a gaming controller the ‘x’ and ‘y’ buttons – which correspond to moves that will often be done one after another – are very close so that the user does not waste time moving a long distance in order to switch between the two moves. Similarly, buttons that are further away from the frequently used buttons are often bigger, so that the user does not need to worry as much about precision when moving larger distances to press the buttons. For example, on a keyboard the tab, shift, delete (etc.) keys are much bigger than the keys with letters and numbers, because they are further from the center of the keyboard and thus the user will have to move a greater distance and in order to keep constant time, according to Fitt’s Law, they should be bigger.

Hicks’ Law can be used in designing user interfaces to decide how many options should be presented to a user at one time. For example, it would be possible for a Word document to have every single menu option on the screen at all times. However, this would clutter up the user interface and make it nearly impossible for the user to find what they were looking for. By dividing the available options into different toolbars and menus, the user first chooses which menu they want to look at, and then choose the tool the want to use, lowering the amount of time it takes to choose an option.


Allison Leong - 2/19/2014 10:34:38

1. The Model Human Processor (MHP) is a simplified way to think of the human mind as an information processor in order to predict human performance in user-computer interaction, rather than to model what is really going on in the head. The MHP consists of a system of memories and processors as well as a set of principles by which these operate. Three primary systems make up the MHP: the perceptual system, the cognitive system, and the motor system, each with their own memories and processors. The perceptual system codes the sensations of the physical world on the sensory system into mental representations. The cognitive system connects the perceptual input to the motor output. The motor system translates thoughts from the cognitive system into action by controlling voluntary muscles. This model is good for predicting human-computer interaction, but this simplified way of modeling the mind is limited because it strips away many of the nuances and intricacies of psychological processes. Humans are more than functions that process inputs and outputs. Complex mental states play a large role in our interactions with the world. For examples, this model is too limited to account for any emotions that may be a part of a human-computer interaction. How a person feels when interacting with the computer may influence his or her future interaction, and the MPH does not account for this.


2. Fitt’s law states that the time it takes to move the hand depends on the relative precision required to reach the target. In other words, it depends on the ratio between the distance to the target and the size of the target. This should be taken into consideration when making decisions on the size and placement of fields/buttons/other targets on a user interface in order to minimize the ratio and improve ease of hand movement over an interface. Hick’s Law of Choice Reaction Time describes the logarithmic relationship between the possible choices and the time it takes the choice maker to reach a decision. This law is useful because it tells us that the time it takes to make a choice is not linear with respect to the number of possible choices, but highly dependent on how the choices are arranged in a hierarchy. This should be taken into consideration when designing the hierarchy of choices in the menus of interfaces, and other choice-making interfaces.


Sang Ho Lee - 2/19/2014 11:44:44

1. The Human Model Processor is a model based on the metaphor of breaking down a complex system, such as the computer, into smaller subsystems that work at times serially, and other times in parallel. These smaller subsystems are the Cognitive System, Motor System, and the Perceptual System. Based on these subsystems, and the components that make up each subsystem, we can gather data by experimentation on things such as the duration and capacity of the Working Memory, and the frequency of a cognition/act cycle. In short, we can equate biological components and actions into abstract "computer-like" terms, and define certain behavior to be atomic (it happens or it doesn't, and isn't interrupted) to measure and quantify using data. There are some limits: 1. the Human Model Processor is solely a prediction model, and does not always accurately predict the correct behavior for humans in extreme ranges for certain parameters, 2. the Human Model Processor doesn't always taken into account the highly parallel nature of human behavior, 3. the Human Model Processor assumes that there is a fixed number of memory registers, when in reality, memory works in multiple levels of depth far greater than Working Memory and Long Term Memory (perhaps levels of caches?). The Human Model Processor fails to capture other I/O methods, such as touch and reflex. It also fails to capture interactions with computer artificial intelligence, be it voice interactions with an "intelligent" computer, etc.

2. Fitt's Law, derived from the time for one cycle of the Perceptual Processor, the Cognitive Processor, and the Motor Processor to perform corrections, defines the time to move a hand to a target. It is based on the idea that moving the hand to a target is not one single continuous movement, but a series of a smaller movements consisting of constant microcorrections. Fitt's Law can be useful when deciding where to position user interface elements that a user constantly interacts with. Optimizing the time to move a hand to the target element can increase efficiency and reduce user frustration. By using the Fitt's Law for all the user elements, and then maximizing efficiency by sorting by the frequency of usage, the designer can find the optimal layout of UI elements. Hick's Law describes the logarithmically increasing relationship between the time for a user to make a decision and the number of equally probable choices the user is presented with. Hick's Law can be used similarly to Fitt's Law-- the designer can minimize the number of cognitive cycles necessary to make a decision. The designer may first narrow down the number of UI elements to the bare essentials. Then by using Hick's law, the designer will calculate the reaction times, and the designer may iteratively add or remove the number of possible decisions for the user to make by finding the balance between the optimal complexity and the optimal number of choices.


Kevin Johnson - 2/19/2014 11:45:07

The Human Model Processor attempts to model the behavior of the human brain systematically. It breaks down the process of "thinking" into discrete steps that mirror human behavior. Each step is assigned a speed and capacity based on experimental data from humans. The resulting process can be used to simulate human reactions to arbitrary input, provided the input can be described numerically to fit the system. One key limitation is that the model does not account for external factors that may influence perception abilities. The model assumes the user is totally devoted to a single task, but a multitasking user, or one distracted by some aspect of the environment, may display different behavior.

Bloch's Law says that the perception of a visual stimulus is a product of intensity and duration. A high intensity, low duration stimulus can generate the same perception as a low intensity, long duration stimulus, provided that the duration is less than the time it takes for a human to react to the stimulus. This suggests that when providing very short stimuli, the intensity of the stimulus must be increased if it is intended to be noticed - and conversely, long stimuli which are not intended to be attention-grabbing should have limited intensity.

Fitt's Law says that the time required to move to a new position is based on a ratio of the distance to the position and the size of the target position. A long movement to a large target can take the same amount of time as a short movement to a small target. This indicates that interaction targets which are far away from each other must be large, while very close interaction targets can be smaller without compromising user accuracy.


Myra Haqqi - 2/19/2014 12:36:20

1) The Human Model Processor comprises the set of memories and processes together, as well as the set of principles, or principles of operation, that guide it. The Human Model Processor consists of three subsystems: perceptual, motor, and cognitive.

The Perceptual System relates to sensors and associated buffer memories, including the Visual Image Store and the Auditory Image Store, which contain the output of the sensory system while it is being symbolically coded. The Auditory Image Store, which handles auditory stimuli, decays more slowly than the Visual Image Store, which contains representations of visual stimuli. In addition to that, the perceptual system is responsible for transporting sensations of physical composition which the body detects via its sensory systems, and forms internal representations of the mind utilizing the integrated sensory systems. The code depends on physical properties of the stimulus, such as the intensity. The cycle time is not constant, as it decreases as the intensity of the stimulus increases.

The Motor System’s primary function is to carry out responses. The role of the motor system begins when chunks in Working Memory are activated. Thoughts are translated into action by means of voluntary muscles. However, movement is not continuous; rather, it is a series of discrete micromovements.

The cognitive system receives symbolically-coded information from sensory stores in its Working Memory, and also uses the information that was initially stored in Long-Term memory, in order to allow the user to think about how he should react to some stimulus. It also connects inputs from the perceptual system of the user to the corresponding outputs of the motor system in order to allow the user to do some action necessary after perceiving some stimulus. This system is far more complicated than the two aforementioned systems, because the cognitive system involves analyzing thoughts that are much more complex.

The purpose of the working memory is to hold information that the user is currently contemplating. It consists of the information in between the thought process and the representations created by the user’s perceptions. The Long-Term memory, on the contrary, stores information that will be utilized in the future. The working memory consists of two kinds of codes: the symbolic or non-physical acoustic and visual code are not affected by physical parameters of the stimulus; however, the non symbolic and physical codes of sensory image stores are, in fact, influenced by physical parameters of stimuli.

Memory can be viewed as consisting of chunks, which are symbols or activated elements in the Long-Term memory which define the Working Memory. These chunks depend on whatever information is stored in the user’s long term memory. When a chunk in the long term memory is activated, then this leads to the previously activated chunks of the long term memory becoming less accessible for the user to readily obtain and use. This is largely due to the fact that there is a finite amount of activation resources. These new chunks also interfere with the older chunks, and therefore the chunk fades away from the Working Memory as time passes.

This decay of the working memory are affected by how many other chunks the user is trying to recall at the time, as well as any interference caused by the endeavor to retrieve similar chunks from working memory, and also the input and retrieval memory strategies that the user takes advantage of when trying to recall information from memory. The pure capacity of the working memory can be bolstered into the effective capacity of working memory when used in conjunction with the long-term memory.

The long-term memory consists of all of the information that the user possesses. It contains a network of similar chunks that can be accessed by means of the working memory. Once information is stored in the long-term memory, it will never be deleted. However, if one is unable to successfully retrieve a chunk, it may be caused by the fact that any proper retrieval associations are not found, or that similar associations to multiple chunks lead to interference with the target chunk that the user is attempting to retrieve. This relates to the principle of operation of encoding specificity, which relates the idea that certain encoding operations that affect how the user perceives something depends on the information stored in the user’s memory, and also, whatever information the user has stored will discern which retrieval cues will allow the user to successfully obtain the chunk that is stored.

For example, in order to decrease the cycle time of the cognitive processor, one can practice more. Also, one can pace the rate at which he completes tasks. Furthermore, if a user exerts an effort to a greater extent to retrieve something, then he will be more likely to retrieve it. Also, reduced accuracy ultimately causes a lessened cycle time. An example of leveraging these facts is that someone who practices reciting a monologue will be able to more easily remember it than he would if he did not practice.

The limits of the Human Model Processor are that it makes several assumptions about the user involved in the user-computer interactions. For instance, the Human Model Processor assumes that there is a defined sequence of events that occur when the user is presented with a stimulus and as the user perceives the stimuli. The Human Model Processor details the relationship between the perceptive, motor, and cognitive systems, and how the systems interact within the user.

Another limitation posed by the Human Model Processor is that there are distinct and delineated roles of each of the three subsystems that are separate with a flow of information through all of them.

Yet another shortcoming of the Human Model Processor is that it assumes that humans’ minds function like computers. For example, it relates the action of the cognitive system as resembling a serial processor, while the recognizing aspect of the cognitive system relates to a parallel processor. This relies on the assumption that the human mind can even be interpreted in terms of computer characteristics. However, the human mind is much more intricate and therefore one cannot assume that it resembles a computer necessarily.

The Human Model Processor fails to capture some computer interactions. This includes the surrounding conditions of the user while the user is using his computer. For example, when a user is using his computer outside in the rain, then his systems are also processing the input of the rain and weather conditions on him. This influences in physical sensations as well as mental thoughts.

Another way in which the Human Model Processor does not address a computer interaction is that while people are on their computer, they may be distracted by external stimuli simultaneously. When someone is interacting with a computer, that is not necessarily the only thing that he is interacting with. For example, if a user receives a phone call while composing an email, then his thought processes will be split among the different stimuli.

Another example of when the Human Model Processor fails to capture a computer interaction is when a user wants to multi-task on the computer. For instance, if a user endeavors to perform a myriad of distinct tasks simultaneously, the Human Model Processor does not succeed in taking this into account. For example, if a user wants to listen to music in one tab, compose an email in another tab, and play solitaire in a different window on his computer, the Human Model Processor does not address the idea that the user can type, click, read, listen, and more at the same time.

The Human Model Processor takes into account that the sets of effectors of a computer user are the arm-hand-finger system and the head-eye system, in terms of the Motor System. However, a user also interacts with a computer by perceiving content. This involves the mind more than solely the physical components involved with computer interactions. For example, when the user views the computer display, he will gain some perceptions of whatever his input is.


2) Fitts’ Law states that the time required for a user to move his hand to some target location only depends on the relative precious required, which can be defined as the ratio between the target’s distance and its size.

Hicks’ Law demonstrates how the fewest number of steps required to process alternatives in order to make a decision relates to the reaction time of a user to a set of choices. When a person must perceive n alternative stimuli, which are associated one-to-one with n responses, then the function H is log(base 2) of (n + 1). The reason it is n + 1 rather than n is because there is uncertainty involved in whether or not to respond, and also how to respond.

These can be useful for designing user interfaces because they provide information about analyzing users’ interactions, and allow designers to design interfaces that will create the best experience for the user.

Fitts’ Law is useful when designing user interfaces because it allows designers to discern how to place objects on an interface in order to minimize the time needed for users to move their hands. For example, in order to design an application, a designer should take into account the time needed to move one’s hand to some location in order to place buttons on the screen. When buttons are conveniently placed, it will enhance the experience of the user.

Hicks’ Law can be used to determine how many options to give to a user and also how to present choices to the user. The more alternatives present, the more steps are needed, and therefore the more time it takes for the user to proceed. Therefore, an example of leveraging Hicks’ Law is to design an interface using the fewest number of options needed to allow the user to spend less time in order to perform whatever tasks he needs to accomplish.


Aayush Dawra - 2/19/2014 12:09:20

Model Human Processor is a cognitive modeling method used to calculate how long it takes to perform a certain task. It draws an analogy between the processing and storage areas of the computer, with the perceptual, motor, cognitive and memory areas (visual image, working memory and long term memory) of the computer user. The main limitation of MHP is that it does not cover the way a person deals with information by not taking into account the environment the user is in while using the interface or for that matter accounting for the fact that the user might be multitasking while interacting with the interface. Looking at multitasking, for instance, if a user is typing on the keyboard while making a phone call alongside, MHP will fail to capture such an interaction. Also, the environment the user is in makes a difference in his/her interaction with the interface. For instance if a user is interacting with an interface with a deadline to meet as opposed to someone who is relaxed without the pressure of a deadline. In this case, both the users would have completely different computer interactions that MHP would be unable to capture.

Fitts Law postulates that the time to move the hand to a target depends only on the relative precision required, that is , the ratio between the target's distance and it's size and it gives a mathematical equation to describe this relation. Fitts Law can help us design better interfaces by keeping in mind that we need to reduce the distance between objects in our interface to increase the interaction speed. For instance, while designing a drop down menu, we should put high frequency items at the top since selecting an item at the top of the menu is faster than selecting one at the bottom because according to Fitts Law, there should be a non-trivial speed difference between the menu items on the top versus the bottom. Also, Fitts Law says that we should have a reasonable size for the objects living in the interface. For instance, if we double the size of icons on our desktop, it will decrease the movement time by a constant amount, according to Fitts Law. According to Hick's Law, the reaction time is slow in proportion to the number of choices presented and he postulated that the decision time for a simple decision is a linear function of the transmitted information. This can be utilized in user interfaces in a number of useful ways. For instance, the number of items displayed in a menu or a list in a user interface can be minimized to improve decision making speed. Also, Hick's Law indirectly claims that simplifying the layouts by removing superfluous lines and embellishments would improve the speed at which the user can possibly interact with the interface.


Anju Thomas - 2/19/2014 12:46:37

1) Describe the Human Model Processor. What are the limits of the Human Model Processor? Which computer interactions does it fail to capture?

The Human Model Processor is a model created to learn the ways human process information, the time it takes to process them and how it affects human action and decision making. In a more techical aspect, it consists of memories, processors and principles, which help human interaction with user interface. There are three main systems consisting of memories and processors that constitute a Modal Human Processor, the perceptual system, the motor system, and the cognitive system.

Perceptual System has sensors and buffer memories, which act as storage of the outputs of the sensory system during the coding process. Cognitive systems a guides in decision making by using the information stored in Working memory from symbolic information gotten from sensory image stores and old information stored in Long term Memory. An automatic response to the information and decision formed by the previous systems, is by the motor system. The three systems can be used parallely do perfrome desired tasks, while parallelism can be restricted for more complex tasks. Memory consists of three main parameters - storage capacity, the decay time, and whether the code is of physical, acoustic, visual or semantic type. Whereas the cycle time is one of the main parameters of a processor. 

The limits of the Human Model Processor include restraining the reason for the information processed and the action performed to simple calculations, when human computer interaction consists of a conglomeration of various aspects, including circumstances, experience, emotions, and skills. The model also is limited in its capacity to measure human satisfaction with the user interface.

Another possible restrain of the model is that it is based on the average human perception, processing of information, and action, which might not account for people of different backgrounds, disabilities or constrains. The model also compares the human cogntion and processing to a computer, which might not be accurate due to the limitations in the speed and complexity that can be processed by a human and the extraordinary speed, accurancy and ease computers can perform calculations.

The model fails to capture the unpredictability and sentimental influence of emotion to the actions they perform which can be of great significance rather than basing it on restricting calculations. The model tries to measure the efficiency of human computer interaction through calculations and strict principles. For example this can be seen in the rationality principle, which expects humans to use a rational reasoning for every action, when in reality it fails to acknowledge the irrational actions performed by some humans due to lack of previous experience or spontaneous actions. It also fails to account for the situations the person is in while interacting with the interface. For instance, the human can be in stress ful situation or time constrained circumstance due to a busy schedule affecting their ways of interaction.


2) Briefly define Fitts' Law and Hicks' Law. How can these be useful for designing user interfaces?

Fitts’ Law is the time measured for a person to move their hand to the desired target with certain size and in certain distance. It is based on the calcuclation Tpos = I log base 2(D/2 + . 5) where I = 100[70-120] msec/bit. It helps evaluate the time needed to move the hand quickly to the desired area, while accounting to differences in distances and size of the target. It especially focuses on basic human computer interaction techniques such as pointing and touch.

It helps improve user interface design as touching and pointing are natural affordances that enable the user to match their intuitive conception to the way an interface works to provide quick and efficient results through actions. It also allows designers to determine the appropriate size and distance with which certain objects are to be presented to the user and its effect on time taken for a user action. For instance to make a design interface more efficient for the user using the Fitt’s law, a designer can place the most important elements on the interface in the most accessible regions and increase its size to make it more visible and quickly accessible to the users.

Unlike Fitt’s law, Hicks’ Law determines the time it takes a person to decide from the possible choices available to them. It uses a logarithmic calculation that bases the speed of a person in decision making with the number of choices they have to pick from. Its main purpose is to determine the rate of gain of information while assessing a certain number of bits. According to its calculation, the approximate reaction time, give n choices is T = b * log base 2 ( n + 1). However, the response time becomes constant eventually despite the increase in possible responses.

Hick’s law can improve user interface design as it displays the effects of giving the user more choices. It helps the designer prioritize between the time with which a desired action is to be performed by the user and the freedom of control given to the user through the variety of choices available to pick from. This can be used to improve user interfaces by limiting the number of options available on menu tabs and by placing the options with the most priority on the interface and excluding unimportant ones.


Christina Guo - 2/19/2014 13:25:33

The Human Model Processor is a tool for abstracting at a high level how the mind works so that human performance relevant to human-computer interaction can be predicted without getting bogged down by all the details of how the mind actually works. It is composed of the three subsystems that control your perception, motor routines, and cognition, each itself composed of memories and "processor." It can be used to predicts thing like cycle times, memory decay rate, and memory capacity (such as the amount of interaction actions the user can learn and memorize). Some limits of the Human Model Processor is that it is a guideline for the average user, but there are a huge range of skills and speed when it comes to interacting with technology. Oftentimes, the range of user skills is not clustered in the middle, but more evenly dispersed throughout the spectrum. By always designing for the middle ground, you may miscalculate interactions if you're targeting a specific user group that may regularly lie at a different part of the spectrum.

Fitt's Law is the time to a move a hand to a target of size s which lies d distance away, given by t = 100 * log (base 2) (D/S + 5). In essence, it says that the time to move your hand depends on the relative precision of the target (given by the size s). It can be useful for designing user interfaces in knowing where to layout specific buttons, taking into account that the user might have to move their hand through multiple locations if they make mistakes and perform unintended interaction. It helps the designer know how long the sequence of actions would take for the user to finally achieve their goal through trial and error. Hick's law is the amount of time it takes for a user to make a choice given the amount of choices. It is useful for designers to help them create a user flow in which each step has the right balance of choices for the user, enough for flexibility but not too much for it to become overwhelming for the user.


Vinit Nayak - 2/19/2014 13:28:14

The Model Human processor is a series of systems which build on top of one another and each of which contain their own memories and processors. It is comprised of the perceptual, motor and cognitive subsystems. The perceptual, as you may have guessed, deals with all the memories and actions associated with the user's sensations of the "physical world detected by the body's sensory systems." The processor of the perceptual systems deals with units of impulse response to react and understand the given sensations from the user's surroundings. The motor system is the part of the model that converts the sensations and thoughts processed into physical action within the user. The cognitive system acts as a connector in between the other two systems allowing the perceptual system to communicate with and allow the motor system to perform its actions. One of the limits of the model human processor is its memory. It has a short term working memory and a longer term memory. The shorter term memory is far more limited and the type of data it can remember is limited as compared to computers. The human model can only remember certain data types and in that, only chunks of memory as well. An interaction that the Human Model cannot process as fast due to its limits on perception is rapid visual processing on the order of milliseconds that a computer would be able to.

Hick's Law relates the amount of time it takes a user to make a decision based the number of choices he or she has. The law shows the relationship, mathematically, via an equation. This can be very helpful in designing user interfaces when creating any type of interaction that deals with specific timing and needs a high level of accuracy. For example, the equation could be used when creating a multiplier game where timing for each user determines the outcome of a specific action. Fitt's Law relates the amount of time required to move to a target with respect to the distance and size of the target. This has immense applications in mobile gaming apps where users have to click on targets on the screen. The developer can mathematically use a combination of both Hick's and Fitt's law to increase or decrease the difficulty and intensity of the game.


Nicholas Dueber - 2/19/2014 14:17:50

The Human Model Processor is a modeling method used to determine how long it takes a user to complete a task. The modeling method uses times that were recorded from processing runs. With this, they try to model how long it takes the average user to go through tasks. It breaks apart the tasks into several components i.e. cognitive and perceptual. This modeling falls short in that it is unable to capture the variability of the user. What environments they may be working in, and if they are trying to multitask. Therefore, it is not wholly representative of most tasks.

Fitts' Law dictates that the time for a user to go from selecting a target to actually executing movement to a target is a function of space from the target as well as the size to the target. This mean that the farther the target is away and the smaller it is, the longer it will take. This is useful because we know that smaller targets means it will take the user longer to execute as well as proximity of targets. We want to reduce the space required for the user to move to select a target.

Hicks' Law dictates that the number of choices presented to the user, the longer it takes the user to make a decision. This is useful to know because it means that the fewer the choices we give them, the quicker they can get to a functionality that will match their needs. If we think of Hicks' law and Fitts' Law in combination with each other, then we know that the amount of time it takes the user to move from one action to the next will be a function of both options given to user and the spatial locality of the desired operational input from the user to make that choice.


Alexander Chen - 2/19/2014 14:24:29

The Human Model Processor (HMP) is a designer's way of analogizing the human mind to computer information processors. It includes a set of memories and processors for different types of input, and a set of principles that it operates on. We can break down the HMP into 3 subsystems, the perceptual, motor, and cognitive.

The perceptual subsystem is like the I/O on a computer system. It receives information from the physical world and translates that into bits that it can work with. The cognitive subsystem is like the CPU and memory controllers of the computer system, it performs analysis on data, retrieves information from the disk, if necessary, and returns the output as feedback or stores it. LTM would be analogous to our physical disks, where information is stored with no decay and could be considered "infinite" capacity. While the working memory might be the combination of CPU registers and RAM. The HMP model doesn't quite explain how people can multitask, similar to multithreading in a computer system. If our perceptual systems had a short decay time, then, in theory, we shouldn't be able to multitask as well as we do. Conversely, when a computer system is overwhelmed with input, it might be able to cache the input and process those instructions later, whereas HMP would likely just drop the input. Additionally, while data that is processed within a computer has predetermined syntax and jargon, our HMP's cognitive systems might differ from that of another person. Perhaps the way my neural networks stores information differs from yours.

Fitts' Law indicated that the time to move your hand from one location to another depends on the relativity between the size of the target and the distance that you are to move. This explains why tiny keyboards work on smartphones~ where the keys and distance between them are shrunk proportionally. If we were to use a normal sized keyboard layout with tiny keys, people would likely have trouble typing as quickly as they usually do on normal sized keys.

Hicks' Law indicates that decision time increases with uncertainty about the judgement. This means that the more options are presented to the user, the more time it takes them to decide. Although this is not a linear scale, it still puts the burden of deciding what to do on the user.

As UI/UX designers we need to take both of these laws into account when designing interfaces. We need to place buttons that are frequently used together, as close as possible. We need to make sure the sizing is appropriate for the distance that the user's finger needs to travel between the input toggles. When designing menus we have to choose the right amount of options to make the gulf of execution at the semantic level is acceptable, while not overwhelming the user with options that are uncommonly used.


Haley Rowland - 2/19/2014 14:30:16

1) The Human Model Processor is a model of the human mind in the context of a processor. The HMP involves a set of memories and processors which are described by various parameters (storage capacity, decay time, code type, cycle time) and are divided into three subsystems; perceptual, cognitive, and motor. The HMP also involves a set of principles of operation.

The model greatly simplifies the complexity of the human mind. For example, the model does not take into account how emotion or state of mind affects memories and processors, which is an affect that may be quite pronounced. To illustrate, if we consider someone who is “hot-headed” or in an angered state, they are often not able to think clearly or consider previous knowledge (their long-term memory), which is why during an argument, people are advised to take a few seconds to “cool down” and allow one’s rational knowledge to return (an effect of the working and long-term memory systems). The HMP doesn’t capture the user’s conceptual model. Also, because of the publication date of the book, the HMP doesn’t take into account gestures and other ways of computer interaction; it mostly focuses on movement toward a target and keystrokes.

2) Fitts’ Law states that the time to move the hand to a target depends on the distance and size of the target, or the precision required. Hick’s Law describes the relationship between the time required for a person to make a decision and the number of choices presented to the person. Increasing the number of choices increases the decision time logarithmically because a person can organize the choices hierarchically.

These laws are useful in designing user interfaces because the designer must be mindful about the placement of buttons or other interactive features to make related items close together to decrease the time needed to utilize these features. In addition, the designer must take into account the number of options given to the user to the when considering the time required for a user to make a decision.


Zack Mayeda - 2/19/2014 14:35:22

1) The Human Model Processor is a method to model human mental processes and estimate human capabilities of performing tasks. It is composed of three main systems that are intertwined: the cognitive, perceptual, and motor. The cognitive system connects the perceptual system to the motor system and maintains memories in the brain like a filesystem, with recently accessed memories in the working memory, and other memories in the long-term memory. The perceptual system translates physical stimuli into perceptual memories that are stored in working memory. The motor system converts thoughts and intents into physical movements by the human body. The Human Model Processor also involves principles of operation that identify trends in human mental capacity to identify individual stimuli, ability to perceive stimuli, ability to recall memories from long-term memory, and ability parallel process. The Human Processor Model can't perfectly simulate the incredible complexity of the human mind, so it is limited to providing generalizations of how it works and rough estimates on time required for task performance. This model fails to capture time add to task performance time due to distractions. Distractions may appear as a notification on a phone, another app making noise, or any other object in the surrounding environment that is not involved with the measured task. For example, if an interface is frequently used in a noisy environment, it may take the user longer to perform a task than this model estimates.

2) Fitts' Law is the equation that relates target distance and target size to compute the total movement time for the user to touch the target. Hicks' Law is an equation that relates number of observed choices to decision time. These laws can be useful to design interfaces because they can encourage the designer to take certain steps to optimize their products usability and minimize erroneous input. For example, the designer may want to minimize the number of always visible menu items to keep user decision time down. Or, the designer may put frequently used buttons or features in an easy to reach location to cut down on accidental button clicks or taps.


Andrew Chen - 2/19/2014 14:45:31

1. The Human Model Processor is a model that describes how a human turns learned or gathered information into action. It casts this process as a set of interconnected memories and processors and a set of principles of operations. There are three main subsystems of memories and processors: the perceptual, cognitive, and motor system. The perceptual system is the one in which the human perceives and gathers information from the world around them. In the cognitive system, the human processes the gathered information using what it already knows. Finally, the motor system is the one in which the human turns the processed information into physical actions. These systems are casted as computer processors, such that they each have a cycle time parameter. However, they also have the parameters of memory capacity and memory decay rate. The limits of the Human Model Processor are the limits in understanding in the field of psychological sciences.

2. Fitts’ Law states that the amount of time that it takes to move the hand to a target is only based on the target’s size and its distance from the hand. This law is based on the idea that the movement of a hand to a target is a series of adjustments rather than a continuous motion, and each adjustments requires processing by each of the three subsystems. This can be useful to designing user interfaces, because we can see how much the time it takes to move a hand to a target (such as a button) changes depending on where we place it on the interface, and thus we can effectively design our interface layout to minimize certain desired times.

Hick’s Law states that the time it takes to make a choice from a set of possible choices does not increase linearly with the number of choice, but rather logarithmically, because our minds naturally think in a hierarchical manner, and quickly organize the choices into a search tree type structure, in which we choose to follow one particular branch of exploration at each level, until we reach our decision. This can be useful in designing user interfaces, because if it takes the user a certain amount of time to make a decision, then the designer can utilize this delay to do some processing, so that the user does not actually feel the delay.


Everardo Barriga - 2/19/2014 14:54:18

The Human Model Processor consists of sets of memories and processors and some principles of operation. The sets of memories and processors can be broken down into three groups: the perceptive, the cognitive and the motor. Each of these systems come with their own respective memories and processors. The Human Model Processor is a way to describe how us humans process, store and access information. I believe the Human Model Processor deals solely with processing information that is received through the perceptive system but fails to process other information that computers give us. It fails to capture the interactions of emotion and aesthetics, namely how interfaces make us feel.

Fitt’s Law is basically just the time it takes to move your hand to a target. This is calculated as a function of your precision to the target and the ratio of the targets distance and its size. Hick’s law is just the time it takes a person to make a decision based on the amount of choices he/she have. These are very useful because having really small buttons for example would increase your Fitts Law time and perhaps anger the user making them not want your app. Also I believe you want to decrease your Hick’s Law time depending on the situation, for example your startup page should have a decreased Hick’s Law time because your user should be able to get to where they want in as little time as possible. Once they have arrived perhaps to a page showing them clothing options then you could perhaps increase your Hick’s Law time.


Justin Chan - 2/19/2014 14:59:22

The Human Modal Processor is a model by which researchers can prototype human cognition and action. With these prototypes, researchers can predict how long humans will take to complete certain tasks, which obviously is a big issue in the HCI field. The reading breaks down the model into three distinct systems for better granularity and analysis: the perceptual system, the motor system, and the cognitive system.

Some limits of the human modal processor are that it tries to boil down human interaction into a series of numbers and equations. While this provides for a very methodical, predictable, and rational approach – quite beneficial for the “vanilla” case – it is quite easy to realize that humans often times are anything but methodical, predictable, and rational. Inevitable lapses mean that we often make mistakes. Emotion is not necessarily a rational feeling, but as humans, it colors every one of our decisions. These are all issues that the human modal processor fails to take into account.

Fitts’ Law says that the time a user takes to move to an object is proportional to that object’s distance and size. Hicks’ Law says that the more choices a person has, the longer it will take for him to make them. Both of these are quite obvious, but play a huge role in user interface design because they help minimize the total amount of time a user takes in carrying out an action. With mobile applications on the rise, applications that require simplicity given a limited real estate, we can expect these two laws to play an even bigger role in the future.


Matthew Deng - 2/19/2014 15:00:27

The Human Model Processor is a method to calculate the time needed for humans to perform any specific task. It consists of 3 processors: perceptual, cognitive, and motor, as well as areas of memory, and 9 principles of operation that together determine the time to perform a task. The Human Model Processor also models how people's memories interact with and affect their actions. Unfortunately, the Human Model Processor is limited by its focus on individual tasks. It fails to account for multitasking or extraneous influences. Therefore, it will fail to capture things such as human’s fatigue, or distractions that might pop up causing a break in thought, which can drastically cause real interaction time to differentiate greatly from those calculated by the Human Model Processor.

Fitt’s Law says that the time it takes for a person to move their finger to a target is logarithmically proportional to the target’s distance divided by the target’s size. This can be useful for designing user interfaces because it allows designers to think about how much time they want for users to go from one action to the next. For example, if there is a series of pages they want to allow users to rapidly click through, they would leave the next page button in the same location. Distance is equal to 0 so time to react is equal to 0. On the other hand, if the user wants to clear all of their data on the application, there might appear a confirmation popup with a very small “Yes I am sure” option far away from the original “Clear Data” button. This allows the user to have time to think about their decision while they are exacting their finger to the small button. Hick’s Law says that decision time is logarithmically proportional to the the uncertainty of their decision, where the uncertainty can be calculated by the number of possible decisions. One example of how designers can use Hick’s Law to improve user interface is through menus. Having fewer options in a menu that might lead to more specific options will allow users to navigate to their desired option in less time than having every single option in one giant list.


Brian Yin - 2/19/2014 15:11:31

The Human Model Processor is a model which draws analogies between how computers function and how people function. The Human Model Processor contains three key sections of human processing: 1) the perceptual system (perceiving stimuli in the physical world), 2) the motor system (physically carries out actions), 3) the cognitive system (recognizing stimuli from perceptual system, processing the stimuli, and then giving actions for motor system to execute). Each of these systems have their own memories and processors which carry out actions required by the system. Thinking about these activities as three systems allows us to measure the time certain activities will take for a user.

The Human Model Processor has limitations because in achieving simplicity, it removes lots of factors that could affect someone's processing speed. For example, they may be doing multiple tasks at once, which may either provide increase or decrease action speed and/or throughput. Other factors could be environmental. For some people, they think better with music, others may be more productive in a coffee shop.

Fitt's Law states that the amount of time it takes for a user to move their hand to an object of a certain size is dependent upon the distance to the object and the objects size. This would be helpful in user interfaces in order to determine button distances or sizes in order to minimize or maximize time spent to click buttons. Hick's Law states that the more choices a user has, the time it takes to make a decision increases logarithmically. This could be helpful to determine the amount of freedom/choices you want to give the user. If you're looking for an application which is used quickly, you probably would want to reduce the number of choices you give. If you want users to really spend time considering their options, you may decide to give more choices.


DaltonStout - 2/19/2014 15:16:01

The Human Processor Model is a way of describing the human system using computer system terminology to approximate the functions and interactions that occur in the human mind. The Human Processor Model divides the human processor into three main systems: cognitive, perceptual, and motor. The Model describes in technical detail the capabilities and response times of each system even getting so specific, for example, as to describe the retrieval time of chunks from Working Memory or the rate of decay of and Auditory memory. The Model treats the human as a metaphor for a computer, stating that each main system contains its own processors and own memory, both Working and Long-Term. The Model seems to focus on response times of both the human processors but also the human memory. This is where the limits of the HPM and the Slowman/Fastman come from. The Slowman represents the lower side of human response time and the Fastman the highest. This then allows the HPM model to describe the typical response times of tasks (moving frame rate, morse decoding, typing speeds) as intervals of Slow/Middle/Fastman. The computer interactions that the HPM fails to capture have to do with interfacing and networking. A computer can connect to a number of other computers at once and download massive amounts of information to be immediately to be stored in LTM. Computers can also interact with a huge number of other devices, using drivers, hardware ports, etc.

Fitts's Law is an equation derived from the amount of Cognitive, Motor, and Perceptual Processor cycles it takes to move the hand to a certain sized target. The law states that the time required to move a hand to a target relies only on a ratio of the target's distance and it's size. Hick's Law is derived from the average reaction time of a human based on the number of choices. It states that average reaction time of a person increases logarithmically based on the number of choices available to them. Both Fitt's and Hick's Law would be beneficial to a UI or UX designer because they would help them hone the ease and speed at which a person uses an app. By balancing the correct size of buttons as well as distance in between, one can use Fitt's Law to ensure that users can access features of your app swiftly. Similarly, you can uses Hick's to balance the desired amount of choices vs. response time in each view so that the user experience is to your liking.


Jeffrey Butterfield - 2/19/2014 15:27:30

1. The Human Model Processor is a model that provides a representation of how humans process information and respond to it, giving interface designers insight into how to create effective interfaces. The HMP is a combination of "memories" and "processors", as well as a set of "principles of operation" that describe certain patterns or rules that govern human behavior when processing information, making judgments, or performing various other low-level processes while using an interface. 3 systems--perceptual, motor, and cognitive--are each described to have a memories-processors pairing, and each help construct the metaphor that compares a human being to essentially a computer with memory and processing abilities. The descriptions of the HMP in the reading, however, seems to assume that a user is interacting with a traditional desktop computer, so the model does not account for other instances in which a human might interact with an interface. For instance, consider tactile feedback from mobile devices (e.g. vibration). The model seems to focus on visual input when discussing the perceptual system and does not really translate well when talking about "memories of vibrations".

2. Fitts' law dictates that the time required to move a pointer to an object on a screen can be determined based on the distance of the pointer to the object and the size of the object. As the distance increases, the time increases. As the width increases, the time decreases. Hick's law states that increasing the number of choices a user has when making a decision increases the time it takes to make the decision at a logarithmic rate. Both of these laws are useful when developing user interfaces. Because GUIs often involve spatially related objects on a screen, a user is often moving a pointer of some sort to touch an object on-screen. As for Hick's law, sometimes a user interface will require a user to make a decision (e.g. selecting an option from an options menu), so knowing how much time you, as a designer, are "costing" the user by adding additional possible choices to a user-decision helps the designer perform a cost-benefit analysis for adding more choices.


Sol Park - 2/19/2014 15:40:20

1)Model Human Processor is a set of memories and processors with a set of principles. It can be divided into perceptual system, motor system and cognitive system. The limit of the Model Human Processor is that people are not exactly computers. We do not always react the same way under the same circumstances. We don't always follow the model. Also, the Model Human Processor seems to focus on the basic physical interaction between the user and the computer. It is not able to capture aspects of the interace that include feelings and emotions. 2)Fitts' law is a model of human movement that predicts that the time required to rapidly move to a target area. It can be used to model pointing by pointing to an object on a computer monitor using a pointing device. Hicks' law describes the time it takes for a person to make a decision as a result of the possible choices he or she has. It is useful if the list of a menu is listed in alphabetical order, he or she may be able to use a subdividing strategy that works in logarithmic time.


Conan Cai - 2/19/2014 15:40:50

Conan Cai - 2/19/2014 15:41:11

The human model processor is a model that tries to describe the steps that happen when a human tries to perform a certain task. By using this model, the usability of a product can be evaluated. There are 3 main parts: the perceptual processor, the cognitive processor, and the motor processor. The perceptual processor encompasses all the senses and serves to translate the physical outside world into internal representations for the mind. Sensations are “coded” into images which are stored in the visual and auditory image stores, which acts like a buffer for incoming stimuli. This stimulus is then transferred into the more long term working memory of the cognitive processor. Data is lost when stimuli comes in faster than can be written out. In addition, the perceptual processor’s cycle time is the smallest unit of sensation that can be distinguished. Multiple stimuli occurring in a time period shorter than the cycle time will be combined into a single stimulus. The cognitive processor serves to connect the perceptual processor with the motor processor to perform an action. However, the cognitive processor does more than that; it needs to be able to “think” and make decisions. The cognitive processor uses two kinds of memory: working and long term. Working memory is the currently active part of long term memory, which can be likened to a computer’s RAM. Long term memory operates more like a computer’s disk drive. These two memories are used together in the recognize-act cycle. Information is retrieved during the recognize stage (long term memory) and acted upon in the act stage (working memory). The cognitive processor takes these decisions and sends them to motor processor to actually carry out the task. This model is very simplistic in terms of modeling a person’s interactions. It doesn’t go into detail on how multitasking and parallel execution affects ongoing tasks. The model also doesn’t say how external environment variables can affect internal cognitive tasks.

Fitt’s law measures the time it takes for a user to move to a target area as a direct function of the target’s distance and size. Hick’s law measures the time it takes for a user to make a decision based on the number of choices that he or she has. Both of these laws are important for designing user interfaces. According to these laws, when creating a user interface, everything from button size and proximity to other buttons to the number of buttons will affect how long it takes a user to “click” on something. Keeping this in mind while designing an interface ensures usability.


Erik Bartlett - 2/19/2014 15:50:23

1) The Human model processor is a conceptual model of how a human receives exterior stimuli (audio, visual, touch) then interprets these inputs, and acts/reacts to them. It, like a computer, can be broken down into a set of memories and processes, along with logical rules that govern operation. The memories and processes compose the underlying systems that is the Human model processor: the perceptual system, the cognitive system, and the motor system. The perceptual is the input, cognitive is the processing, and the motor is the output.

Perception-wise the HMP is limited by it’s cycle time, tp such that any stimulus that is perceived for less than the cycle time will not be operational. The Memory of perception also is limited, as it decays over time (exponentially). The motor system is limited by its cycle time, which tells how long it takes for each micromovement. The cognitive system is limited by how much it can hold in working memory and long-term memory, much like a computer’s Main Memory vs. Disk storage. Working memory is composed of items from long-term memory that are being acted upon, but can only hold so much. The HMP fails to capture processes that happen too quickly for the perceptual system to grasp, cognitive system to process, and motor system to act upon - all of which are limited by their respective cycle rates.

2) Fitt’s Law is a model of human movement and ergonomics that defines a relationship between the size and distance to a target to how quickly a human can move to the target. It gives a mathematical representation to the idea that might seem obvious, that the larger the target is and the closer it is to the human (or finger in a touch arena) the more quickly the user can move to it.

Hick’s law defines a relationship between the number of choices a user has and how quickly they can come to a decision; mainly that as the number of choices increase for the user, the user’s decision time increases logarithmically.

Utilizing these facts a designer can limit the amount of decision and reaction time needed to do a sequence of events. The designer can know that they should limit the number of choices to reduce decision time, while making sure each is available for selection with a relatively short movement to a large signifier. The designer can then decide between the trade-offs of having a selection process that goes multiple levels versus displaying a larger number of smaller items to select from to limit the amount of decisions the user has to make. It can give the designer a quantifiable ability to compare speeds of interfaces.


Jay Kong - 2/19/2014 15:54:47

The Human Model Processor is a model describing the human mind as an information-processing system. The HMP can further be decomposed into three interacting subsystems: the perceptual system, the motor system, and the cognitive system, each with its own memories and processors. The limits of the HMP are essentially the physical limits of the human body. Each processor of a subsystem can only process so much information in a "clock tick" or unit of time. Memories of each subsystem have decay, meaning after a while, objects in the memory will be erased. These are both limits of the HMP that we have no control over. The HMP fails to capture interaction that happens when the user is not devoting their utmost attention of the interface. In the case where the user is on the go and paying attention to their smartphone, the model breaks down because the system is also focusing on other stimuli such as the surrounding environment. In such a case, perhaps the user might even skip out parts of processing due to information overload.

Fitt's Law is a model that predicts that the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. In essence. it describes the movement of moving the hand towards a target is a lot faster in the case the distance is shorter and that the target is larger. Hicks' Law describes how a person's decision making time increases logarithmically in response to the amount of choices that are presented. The more choices there are, the longer it will take the a person to make a choice.

Since a goal of UI design is to minimize cognitive processing time, these two laws are helpful in guiding the UI design process. Fitt's Law restated says that in order to have shorter response times, a UI must not be cluttered and each element must have reasonable dimensions. It also states that groups of similar elements should be close together. For example, the UI element for selecting a font should be close to the UI element for selecting a font size. One can understand this as a variant of spatial locality. Hick's Law restated says that a user should not be presented with too many options at once, as it would be cognitively tolling for the user to select an option given a myriad of choices.


Peter Wysinski - 2/19/2014 15:55:43

The Human Processor Model analyzes cognitive reasoning to determine how long it takes for a user to perform a task. The HPM depicts a connection between the storage and processing of a computer with the perceptual and memory areas of the user. The main limit of the Human Model Processor is that due to its simplistic nature it does not, “do justice to the richness and subtlety of the human mind.” A human mind is far to complex to be analyzed as if it were a machine. As such, the model fails to depict all the processes a human mind goes through which are far from trivial and involve facets such as learning, retrieval of facts or the solution of a problem. This ultimately prevents the HPM from being a prefect depiction of human computer interaction.

Fitts’ law is used to model human computer interaction and states that, “time required to rapidly move to a target area is a function of the distance to the target and the size of the target.” In short it estimates the time it take for a user to point either with a finger or cursor. Hicks’ law describes the relationship between the time it takes for a user to make a decision and the number of choices that they are presented; increasing the number of choice increases the decision time logarithmically. When creating designs, Hicks’ law serves as a reminder to always offer the most relevant choices to users as to prevent confusion. Collectively Fitts’ Law and Hicks' Law can be used to decrease the amount of time a user spends interacting with a computer. By placing relevant buttons next to each other and presenting only relevant options to users, decision can be made quickly and efficiently by the user.


Qianyun Li - 2/19/2014 16:01:57

The Human Model Processor can be described as a set of systems and their interconnections together with a set of "principle of operation". It contains three systems: perceptual, motor and cognitive. Each of these systems have their own memory and processors, which guided by their own principles of operation. The Human Model Processors does not count in the external conditions.

Fitts' Law describes that the time for a user to select a control is proportional to the distance moved and the size of the control. Hick's Law states that user's reaction time can be slowed when they are facing more options to choose from. They both can be very useful when making design decisions. We can use these principles to determine what size we want for our control and what's the optimal number of options we present to our users.



Prashan Dharmasena - 2/19/2014 16:10:55

1) The Human Model Processor is a way of representing the human thought process as a computer to make it easier for programmers/designers to understand how it works and what limitations the human mind has. It has a limit on how many things it can hold in short term memory, it's motor skill, and decision making, among other things.

2) Fitt's Law essentially says that the time it takes to move your hand to a target is related to how far away the target is and the precision required. So, if the target is far away, but also very large, then the time it would take to move your hand would be similar to if the target was closer, but smaller. Hick's Law is that the number of choices given to a user increases decision time logarithmically. Hick's Law is encourages us as designers to simplify the choices we give the user, or group them in a way that allows the user to access them quickly. Fitt's Law encourages us to make targets bigger when we want the user to be able to quickly go through different pages (such as when starting an app for the first time), and make them smaller when users are performing actions that we want to make sure they are really thinking about (such as interacting with app settings or deleting/editing content).


Anthony Sutardja - 2/19/2014 16:18:12

The Human Model Processor is composed of three systems: the perceptual system, motor system, and cognitive system. The perceptual system is an individual's way of receiving sensations and feedback from the physical world to the brain (e.g. sight and smell). The motor system is the individual's way of translating thoughts into physical actions. The cognitive system processes the inputs from the perceptual system and possibly outputs them in the motor system. The limits of the human model processor are modeled by variables which take on a range of constants to account for slow users, average users, and fast users. These variables include cycle time (the duration it takes to an individual to execute a cycle), memory capacity (the capacity of sensory systems as well as cognitive systems), and other attributes.

The Human Model Processor only captures the processes that are measured quantitatively. The Human Model Processor, however, does not consider the state of the mind while evaluating these processes. Both subconscious and conscious emotions can change the way people react to processes. The Human Model Processor doesn't account for how outside variables, like specific colors and sounds, can influence the psychology of an individual's mind. For example,

Fitt's Law is a model of a user's ability to move his/her hand; in particular, it correlates the time it takes for a user to move his/her hand to the relative precision required. Hick's Law is a model of a user's ability to make a decision due to the possible choices he/she is presented. The model specifically describes that the time it takes to make a decision increases logarithmically with respect to the number of choices.

These laws are useful references when designing user interfaces. In particular, they force designers to be aware of how the physical distance in their user interfaces may either positively or adversely affect the user. For example, placing commonly used buttons far away from each other prohibits the user from using the interface effectively. Furthermore, the laws force designers to think about what components are essential to the user interface.


Diana Lu - 2/19/2014 16:25:50

1. The Human Model Processor is a way of modeling human components as processors in order to determine the length of time it takes a person to perform a task. Various systems, like the motor system and perceptual memories, are modeled as processors that have a set cycle time. This allows evaluation of how long a task takes to perform without having to run actual simulations with real people. The human model processors is limited in that it requires very specific knowledge of the user and overall is an aggregate understanding of how long a task takes, but fails to provide much knowledge that actual interaction with a user can provide. Also, it may not be able to catch design flaws in utility that a user can easily identify. In testing of an application, it seems that both the Human Model Processor and experimentation are useful in different aspects. However, the human model processor fails to capture some interactions with the computer such as error with the app or being interrupted, as the model assumes that attention is paid fully to the interaction and nothing else.

2. Fitt's law is used to model the action of pointing to an object on a monitor, or the motion of moving a hand towards a target. Hick's law is used to model the time it takes to make a decision, or the law that determines reaction time to a set of choices. These laws are imperatively useful for designing user interfaces. Fitt's law is useful because it can compare performances of certain user interfaces with respect to the speed or target size, etc. Hick's law is useful because it judges the amount of time necessary to react to a choice, relative to the number of options given, which can shape the way a user interface is designed.


Emily Reinhold - 2/19/2014 16:30:17

1) The Model Human Processor is a way of representing the way humans process information in a simplified manner. It consists of 3 subsystems, which I will break down with my understanding:

- The perceptual system takes information about what a user experiences in the real world and represents it internally as appropriate

- The cognitive system takes the internal representations of information and makes decisions about how to respond

- The motor system takes the information relayed by the cognitive system and actually performs the response

Each subsystem in this model has parameters that define its storage capacity, decay time of an item, the main code type, and the cycle time.

This model is useful to understand how humans process information that is brought to them, so designers can improve the effectiveness of interactions between humans and computers. In the reading, they go into a lot of detail about how to calculate response times to certain physical actions with associated decisions a user needs to make in order to respond. However, these types of calculation rely on the fact that the user already knows what to do. They may need to wait for a physical sensation to occur before deciding what to do, but the key is they know HOW to make their decision before they need to make it. For example, the reading calculates how long it takes a person to determine whether two characters shown on the screen are the same, and then press yes or no depending on the result of their comparison. This experiment relies on the fact that a human knows how to determine if two characters are the same, and can do so accurately.

Often, in user interface/human computer interaction design, a main problem is conveying to the user how they need to make decisions to make their experience enjoyable. The Model Human Processor does not take this type of uncertainty into account. For example, suppose you wanted to predict how long it would take a user to recognize that a page was too small to read, place their fingers appropriately on the screen in preparation for a 'pinch-to-zoom' gesture, perform the 'pinch-to-zoom', and release their fingers from the screen. The Model Human Processor could tell you how to calculate this answer if the user already knows that she needs to 'pinch-to-zoom' in order to achieve her goal of zooming in. But how does the UI designer convey to the user how to do this? If the user needs to learn this step before initiating the response time cycle, how long does that take? This is something the Model Human Processor doesn't answer.

Further, the Model Human Processor is very quantitative in nature. A user's experience is certainly not only based on how fast he/she can respond to certain events that happen in the application. Much more of the user experience comes from a qualitative aspect that is very personal. It can depend on how much a user relates to the problem that the application solves, how busy/clean a user likes her interfaces, how effective a user is at multitasking, etc. The Model Human Processor does not address these qualitative feelings that significantly alter the feelings a user has about her interactions with the computer.

2) Fitts' Law: a relationship for the time required to move one's hand to a target that depends on the distance one needs to move her hand, and the precision required to 'hit' the target.

This can be useful for a UI designer because if Fitts' Law predicts that it will take a relatively long time for a user to move their hand some distance, with a specified precision, that is necessary for the app to perform its functionality, the designer will be warned that something should be redesigned - perhaps the distance should be made smaller by rearranging things on the screen, or perhaps the precision needed should be made less precise so the user has an easier time hitting the target. For example, if the precision needed to press a small button is too high, users will likely have to 'press' the button several times before the desired action is registered. This is a horrible user experience - I have personal reviewed a mobile application in my internship two years ago that had this problem. There was a small icon that, when tapped, led the user to a Help screen. I noticed myself having to tap the icon 4 or 5 times before the Help screen actually came up, and by that time, I had already forgotten why I needed to open the Help screen. The developer changed the precision to be significantly lower so that my finger tap in a more general area of the Help icon pulled up the Help screen.

Hick's Law: an equation that is used to calculate the time it takes for a user to make a decision (choice). The law is in line with our intuition that the greater number of choices one has increases the time it takes for the user to make a decision.

This information can be valuable for UI designers because the user experience is degraded if there are too many choices for a user to consider. For example, imagine if there were 200 Instagram filters that each altered the user's image in different ways. Surely, a user would not want to look through every one of these filters before deciding on one to go with. Thus, the designers at Instagram chose to include only 20 filters, which apparently was a good number to keep the choice reaction time low enough to prevent degradation of user experience.


Brenton Dano - 2/19/2014 16:39:50

1) The Human Model Processor is composed of two parts: a set of memories and processors, and set of "principles of operation." The Human Processor can be split into 3 parts: perceptual system (vision, touch, hearing,etc), motor system (movement), and cognitive system (thinking). The limits of the HMP is that you can't really describe ALL the characteristics of a computer processor to a human. I didn't check when this article was written but my guess it was during the time when there was lots of optimism in AI, where people thought in no time there would be human like computers. The HMP fails to capture the computer interaction of parallelization because the human can't multi-thread. Even though people think they can multi-task it's actually impossible for humans (unless the corpus callosum is severed).

2) Fitt's law says the time to move the hand to a target depends only on the ratio between the target's distance and it's size. When designing UI we want to make sure we have a cluster of frequent keys close to each other. Or we make the keys we have to move from far away bigger. That's why the delete key is bigger than the others. Also, why VIM users can type so fast! Because the control of the cursor is all in buttons close to each other.

Hick's law means it takes longer to make a decision if you have uncertainty about your decision. You should make the frequent buttons do the same thing all the time so the user is certain about what the button is going to do so they can make their decisions faster.


Cory McDowell - 2/19/2014 16:42:12

1) Human Model Processor fails to capture mental interactions. It has excellent physical metrics to see how long it takes a user to complete a task, but we have no way to tell what the user thinks about while using the application or determine their difficulties using it.

2) Fitt’s law is used to show where a user’s attention goes on an app and how long it takes to get there. Hick’s Law measures how long people take to make decisions. Fitt’s law is useful for determining how a user will point on a page, where Hick’s law measures how easily usable a menu screen should be, as we want to provide a interface where users can quickly make decisions based on the options present.


Hao-Wei Lin - 2/19/2014 16:44:42

Model human processor is a model that designer can use to calculate the time required for the users to process certain tasks and their performance. The model treats the users’ interaction with perceptual input and physical output as multiple processors (like that of a computer), which include a perceptual processor, a cognitive processor, and a motor processor, all of which either work in consecutive order or simultaneously. Human processor model also proposes the idea of a visual image storage, an auditory image storage, long term and working memory, all of which work with the human processors, acting as storages. A designer, for instance, can use this model to calculate the decay of a user’s working memory with relation to time, and therefore, can make sure that the design allows the user to obtain his/her working memory, especially when memorizing certain information is required.

A limitation of model human processor is that it doesn’t deal with multitasking. The model only works if the user is focusing on one task at a time. It also doesn’t deal with the environment the user is in. For instance, the user can be performing task while talking to another person at the same time, which would very likely influence his/her performance on the task. There can also be noises in the environment that would change the result of the user’s performance (e.g. if the user works in a construction place with loud noises) The model human processor only capture computer interaction when there is no external distraction, but does not consider the fact that it is usually not the case in reality.

Fitts law reveals that the time required for a user to move his/her hand quickly to a target is a function of the distance to the target and its size. It is useful in interface design because it will make sure that, for instance, the button on a screen is not too small that the user may make error when trying to press the button, or that the button does not require too much traveling of the user’s eye and finger movement, which would potentially results in inefficient, and difficult-to-use interface.

Hicks law states that the time it takes for a person to make a decision is proportionate to the number of potential choices he/she faces (the person’s reaction time eventually becomes constant as the number of potential choices keep increasing). Hicks laws is useful in predicting the time it will take for the user to navigate through, for instance, a menu. If the goal were to have users more accurate when making decision, then it would make sense to allow more reaction time (i.e. more menu options); if the goal were to have users use time more efficiently(e.g. a stock buying interface, it would be better to have fewer menu options at a time so that it doesn’t take too long for the users to decide what stock to buy and miss the opportunities.


Cheng Sima - 2/19/2014 16:48:26

1) As the human mind is an information-processing system, the Human Model Processor uses this analogy. The Human Model Processor consists of three interacting subsystems: the perceptual system, the motor system, and the cognitive system. We often perceive input from the external environment through perception, and our cognitive system makes a decision using multiple information and principles, and the motor system executes the response. However, there are some limits of the Human Model Processor. It does not accommodate multitasking, and does not take interaction of interaction with other humans. This also leads to its failure to capture some computer interactions. For example, we often perform many tasks on the computer at the same time. In addition, nowadays many computer interactions are from many different users, hence the trend of crowdsourcing.

2) Fitt's Law is about the total time for a movement to the target area. It says that the time to move to a target depends only on the relative precision required, i.e. the ratio between the target's distance and its size. Hick's Law of choice reaction time describes the time it takes for a person to make a decision as a logarithmic function of the number of choices/alternatives available. These are useful for designing user interfaces because we need to know how many choices for the user to still make a choice in a reasonable amount of time. We also need to know how far we should place different buttons, and other widgets on an app to allow the user to easily navigate through the app.


Armando Mota - 2/19/2014 16:49:58

1) The model human processor is composed of three subunits - the perceptual system, the motor system, and the cognitive system. All three are composed of processors and memories. The perceptual system gathers information from extraneous events through sensory instruments (like the eye, ear, etc…) and transforms them into coded entries in memory. Working memory is an essential part of this process, and the size and abilities of working memory, as well as what kind of percepts we can perceive with these instruments is quantifiable (and has been estimated). The motor system involves a series of micro movements that realize actions in physical form from thoughts/commands. The speed of the motor interaction is also quantifiable. The cognitive system involves tasks from connecting perceptual inputs to motor outputs to the analysis of tasks with integration of information from multiple systems to produce some sort of output or meaningful change in the system. The cognitive system is able to take in multiple sources of input but is only able to produce one output. What the model does is provide a way to think about processes and interactions between cognitive systems in a measured way - interactions can be given a label, in terms of the speed at which they occur and the speed at which they are able to occur/their constraints. Placing upper and lower bounds on a fairly large range (fastman, middleman, slowman) gets us a decent approximation. The main limit of the human model processor is that it is not exact. We can estimate, and we provide a large upper and lower bound to average within, however exact values are not able to be determined yet. Another type of limit for the processor is the speed at which its components can operate. There is a point at which stimuli which happen too close together are indistinguishable by the system’s perceptual instruments. Therefore there is a limit to what the system can detect. Past that point, things either go undetected or multiple events are perceived as one. This model fails to capture the type of interaction in which a person is required to press the appropriate button on a switchboard when it becomes lit, however the destination phone and button are randomly assigned (that is, if 12 buttons were laid out linearly, the first button would not necessarily be routed to phone #1, the second not necessarily to phone #2, etc.)

2) Fitt’s Law relies on the assumption that moving the hand is not one continuous movement but many movements that involve many micro-corrections along the way. Thus, each correction and its related processes can be quantified. What you end up with is a way to describe a hand’s motion that only depends on the relative precision required, or something that is solely dependent on the ratio between the distance to the object and its size. Hick’s law gives us an approximation of how long it takes as a decision’s complexity increases. It is a logarithmic function, so as the complexity increases, the added cost is lessened every time. Fitt’s law is useful for designers because it gives them a quantifiable layout cost - that is, they can know that placing a certain item in a certain spot will cost the user x amount of time to get to other spots. If there are a group of items that are used often together, they should be grouped together to minimize distance. Or, should the designer choose to place an item elsewhere, they can do so knowing that the cost of moving it there is perhaps offset by a greater benefit in another area. Hick’s law gives us an idea of the cost of adding complexity to a system or interface, and allows designers to make decisions based on those costs. The related equations that took probability into account allow us to also estimate these complexity costs given the relative probability each option has of being chosen. For example, if only two options are chosen for a combined 90% of the time, the cost to have 8 other options would be less if there were just 10 equally used buttons.


Stephanie Ku - 2/19/2014 16:53:47

1) The Human Model Processor is a set of memories, processors and principles that models approximations of human behavior. The Human Model Processor is divided into 3 different subsystems, all correlated with one another. Firstly, we have the perceptual system that contains the sensors and associated buffer memories, and then we have the cognitive system that receives symbolically coded information, and lastly, the motor system that carries out the response. For each system, there is a separate processor: perceptual, cognitive, and motor.

There are several limits to the Human Model Processor. The model tries to summarize human behavior into series of numbers calculated by equations. While this is useful for analytical purposes, there are ‘human traits’ that the model cannot take into account of. These are similar to the uncertainties mentioned in the reading. It is hard to quantify human habits, which affects human computer interaction. Similarly, the model fails to capture the human emotion, which can also affect human computer interactions greatly.

2) Hick’s Law states that the more choices a user has, the more time it will take for the user to make a decision (will increase logarithmically). This knowledge is useful when designing user interfaces as it relates to the amount information that should be presented to the user. Take for example, how many options should be given to the user in a menu dropdown.

Fitt’s Law is the time T_pos to move the hand to a target of size S, which lies D distance away. It is calculated by the formula T_pos=I_m * log_2(D/S + 0.5). In other words, the time taken for a user to move his/her hand to the target is proportional to the distance and size of the object. Fitts’ Law can be used to assist user interface design in several ways. Firstly, it can be used to determine which types of user graphical interfaces are preferable. For example, using a drop down menu versus a swipe menu. In addition, it can be really useful for determining what time of input device to use (e.g. touch, button, etc.). This comes in handy when we have to determine which type of user interface to use for machinery, such as medical devices.


Chirag Mahapatra - 2/19/2014 17:03:55

Human Model processor is a modelling method to calculate how long it takes to perform a certain task. It can be described as a set of memories and processors with a set of principles of operation. It has three interacting subsystems: the perceptual system, the motor system and the cognitive system. The memories are defined by parameters such as storage capacity in terms, decay time of an item, main code. The processor parameter is the cycle time.

Limitations of the MHP: - It assumes that people are doing one thing at a time. Most people try to multi-task. E.g. writing articles while keeping a tab on the score. - It does not consider the effect of other people while doing the task. Doing the task in a crowd or while having a conversation is different than doing it alone. - Environmental conditions are not taken into account. Interacting with an interface during extreme weather conditions such as freezing weather is different than doing it in pleasant weather.

The model tries to quantify the speed of reaction of an individual to derive insights about the user's engagement with the interface. However, it struggles to factor in happiness, annoyance and other emotions. It also struggles to account prior interest and fatigue.

Fitt's law: This law defines the time taken to move the hand towards a target of size S and distance D away. Tpos = Im*log(D/S + 0.5)

Hick's law: This law defines the time taken by a person to make a decision as a result of the possible choices he or she has. T = b*log(n+1)

These laws can guide the designer in making choices in context to the user interface. E.g. If the designer wants the user to spend considerable amount of time on an interface, he can increase the likelihood of that by increasing the number of choices. Another example, game designer can design the position of different objects on a touch interface by calculating the time a user will take to get there.


Max Dougherty - 2/19/2014 17:04:16

1. The HMP is a system used to estimate the time taken to finish a defined task. The cognitive model tries to “represent” the brain as a computer. This draws a comparison between memory in the computer versus the brain and processing speed in an analogous manner. Using this model can allow a system designer to identify where a user might have trouble remembering information required to complete the task. Unfortunately, if a user is engaged in not one, but many concurrent tasks, estimations made with this system may be optimistic. The model assumes a specific controlled environment around the user. Prediction when the user is distracted or switching context to and from the system is difficult and requires user testing beyond simulation in the Human Model Processor.

2. Both Fitts’ and Hick’s Law can be used in designing the layout of an interface. Fitts’ law is described as the time required to move and point to desired target as a function of the distance to and size of the target. If an interface requires a user to constantly shift focus and “point” at greater distances, the designer can expect that usability will decrease as the required time for a task increases. Similarly, if the user is required to make a choice between a number of options N, by Hick’s law, the required time is dependent on the size of N. This allows a designer to pinpoint another pitfall in user speed by reducing extraneous options or “focusing” a choice.



Gavin Chu - 2/19/2014 17:06:43

1) The Human Model Processor aims to structure human memories and brain processes. It describes how memories are stored and retrieved, but most importantly, it parametized each process with respect to time, so there's some sort of measurement people can study. Human Model Processor is limited to calculating simple concrete tasks, but in fact, humans are dealing with complex information processing all the time. It is hard to account for processes from multiple stimulus. The Human Model Processor fails to capture long term memory retrieval because humans don't have concrete memories like computers do. The time it takes someone to remember something from long term memory varies a lot, and sometimes humans fabricate missing memories if the pieces aren't clear enough. Computers would never fail to retrieve some data stored on the hard disk unless the hard disk is corrupt of course, in which case correlates to people with memory impairment.

2) Fitts' Law states that the movement speed of hand toward a target depends on the distance to the target and the size of the target. For example reaching for a large button is faster than reaching for a smaller button equally far away because less precision is required. Fitts' Law is useful for designing user interfaces because designer need to account for how long does it take a user to complete an action. If a button is too far away, it requires more time to reach it, and therefore it is a poor design if the goal is pressing the button quickly. Conversely, putting a button far away might also be a good design if the goal is to avoid that button press, for example a "self destruct" button.

Hicks' Law states that the time to process information and come to a decision depends on the number of pieces of information needed to be processed. For example a device with 100 buttons will take longer to process than a device with 10 buttons. Hicks' Law is useful for designing user interfaces because designers don't want to over clutter the interface so that it takes too long for the user to decide what action to take.


Maya Rosecrance - 2/19/2014 17:09:57

The human model processor is a set of memories and processors attached to a set of principles; in effect a model of how the human mind functions, processes data and makes decisions. The limits of the human model processor are the storage capacity, storage time, the type of memory and the cycle time. The decay of memory after a short time causes it to not act like a computer interaction. Fitts law is related the time it takes the human hand to move to a target including the processing time requried. Hick’s Law relates to the time it takes a person to make a decision. These two laws can be useful in designing user interfaces that are only briefly skimmed or require a rapid series of motions such as tapping related games or applications that are used on the go (for example a maps application that should require little processing time and attention to calculate a route so the driver is not distracted).


Daniel Haas - 2/19/2014 17:11:34

1) The Human Model Processor is a model of human interaction based on analogies to computer memory and processing systems. Its main goal is to estimate the time it takes for a human to complete a given complex interaction, which it accomplishes by breaking down every interaction into perceptual, motor, and cognitive components. Each of these components describe a series of actions with an associated time-cost, so by breaking down interactions into their components and deciding whether the components can be parallelized or must be run serially, a total estimated time cost can be calculated.

The model makes a number of assumptions that limit its expressiveness. For example, it assumes that human processing time is independent of environmental conditions, but a user is likely to move much more slowly when using an interface in extreme cold, or under poor visibility, etc. Additionally, the model assumes that users can only do one thing at a time in each subsystem (motor, cognitive, and perceptual), but this doesn't seem obvious. For example, a user could be simultaneously doing things with two hands while using an interface, and the model wouldn't capture such interactions. Finally, the model doesn't account for attention, as it assumes the user is perfectly focused on the task. It can't accurately estimate situations wherein (for example) the user is having a conversation with a friend while using the interface.

2) Fitts' Law describes the time it takes a user to move their hand towards a target on the interface, and states that this time is proportional to the log of the ratio between the distance to be traveled and the size of the target. This suggests that when designing an interface, the designer should identify important or common user movements and specifically build the system to keep the movements short in distance and their destination targets large.

Hick's Law describes the time it takes a user to make a decision between n (equally likely) interaction choices, and states that this time is proportional to the log of n+1 (the n choices and the choice to do nothing). For the interface designer, this suggests that the number of choices available at each single decision point should be limited, so that users can react more quickly.


Daphne Hsu - 2/19/2014 17:11:37

The Human Model Processor is, in short, a way to calculate how long it takes to finish a task. It takes into consideration the perceptual system, motor system, and the cognitive system, along with memories and processors. It can be used to determine whether a user will remember something he or she encountered while doing an activity. One problem with HMP is that it only considers users doing one thing at a time, and it is quite common for humans to be multi-tasking. Another caveat is that HMP doesn't consider what kind of social setting the user is in while doing the activity. For example, the difference between a user at home, and the user holding a conversation over lunch, and doing the same activity.

Fitts' Law is used to portray the act of pointing that predicts how long it takes to move to a target, depending on distance and size of the target. This is useful for designing user interfaces because the designer can calculate how large an icon needs to be in order for the user to optimally click on it, and how far apart to place widgets. Hicks' Law describes the time it takes for a user to make a decision, based on the possibilities he or she has at that moment in time, with increasing number of choices increasing the time in logarithmically. This is useful for designing things such as menu items that are in alphabetical order. If the user knows what they are searching for, he or she can divide the search time in half (in log time).


Doug Cook - 2/19/2014 17:14:03

The Human Model Processor is a representation of human beings based on three main components: (1) the perceptual system, (2) the motor system, and (3) the cognitive system. The limits of the Human Model Processor are the numeric time estimates required for each of these systems to actually produce results based off data, or to simply gather and react to data. This model is simplistic (as models should be) but fails to capture emotional interactions between humans and computers as well as unique affinities that individuals may have for certain behaviors. For example, this model does nothing to represent changes in reaction times for people feeling a certain way about the interface they’re using, which is very relevant to social networking and data concerning other humans. It also fails to capture “learned” reactions which the authors later mention as the cause of outliers in the data (the MIT student who could recall 81 decimals had practiced that skill).

Fitts’s Law states that the time required for a human to reach some target is a function of the target’s distance and size. Hick’s Law states that the time a person takes to make a decision increases logarithmically with the uncertainty, or number of potential choices. These laws are immediately relevant to user interface design because designers face challenges involving placement and organization of elements that the user must communicate with. Considering a simple calculator, the placement of an often-used key (the authors mention the Function key) has an impact on how fast the user can make computations because it may be too far from the number pads to accommodate its use. Hick’s law is often invoked on form inputs because the user will face some number of choices, and there’s a good chance that speed and experience will depend on their ability to actually pick a choice.


Juan Pablo Hurtado - 2/19/2014 17:14:49

1) The Human Model Processor is model for describing the human mind as an information-processing system. It is limited because it just an approximate prediction of gross human behavior.

2) Fitts' Law: "The time to move the hand to a target depends only on the relative precision required, that is, the ratio between the target's distance and its size." Because of this, when you are designing UIs, you should always maintain the distance/size ratio as low as possible, for example, the one with the calculators on the text.

Hicks' Law: "Decision time T increases with uncertainty about the judgement or decision to be made." This means that the user shouldn't be overflowed with options, because if that is the case it will take too much time to make decisions and he will get bored.


Seyedshahin Ashrafzadeh - 2/19/2014 17:16:20

1) Human model processor is a cognitive modelling method to help us remember facts and predict user-computer interaction. Through this model we are able to calculate how long it takes to perform a certain task and evaluate usability of a product. Human model processor is divided into three subsystems: the perceptual system, the motor system, and the cognitive system. Each of these subsystems have their own memories and processors. The perceptual system has sensors and buffer memories. These buffer memories hold the output of the sensory system (like Visual Image and Auditory Image) while they are being symbolically coded. The cognitive system receives these symbolically coded information and stores them in its Working Memory. Then it uses other information in the Long-Term Memory to make decisions. The motor system, therefore, carries out these responses. However, this human process has its own limitation. According to the reading, there are time decays of Visual and Auditory Image Stores and they have certain amount of capacity. Another example from the reading was the experiment done in which subjects were presented with a rapid set of clicks from 10 to 30 clicks per second. The results show that as the experimenter plays the clicks at 10 clicks/sec, the subject is able to hear each click. But when the rate of clicks per second goes up, the subject fuses multiple clicks into a single click. This model allows a system designer to predict the performance of a user to complete a task based on time without performing experiments on the user with the specific design. Some of the limitations of the Model Human Processor is as follow. In this model, it doesn't consider the environmental factors that can affect the user. It doesn't consider the effects of other people while the person is carrying out the task. It assumes that the user is busy doing one thing at a time, while we might carry out different tasks at the same time (multitask). Also, this model is task-structure based instead of user-behavior based. 2) Fitts’ law explains that the time to move the hand to a target depends only on the relative precision required, or in other words it is the ration between the target’s distance and its size. Hicks’ law describes the time it takes for a person to decide based on the possible choices that he/she might have. This relationship is logarithmic and increasing the choices would increase the decision time logarithmically. Based on the Fitts’ law, we are able to predict the time it takes for the user to rapidly move to a target. And based on the Hicks’ law, we are able to predict the time it takes for the user to make a decision based on the possible choices. Therefore, by using these two laws we are able to predict how fast users can decide and get to their target. So they provide us some measures to predict how good our interface is. For example, Fitts’ law can be applied to tasks where the user needs to move a mouse cursor to a specific target. And for the Hicks’ law, we can use it to find the number of choices that we can give to the user based on the amount of time that they have. Based on this law we can balance the number of choices for the user based on their time. And by doing this, improve our interface. An example of Hicks’ law can be preventing any overwhelming amount of choices to the user which can make the interface overwhelming and difficult to use.


Sangeetha Alagappan - 2/19/2014 17:16:53

1) The Human Model Processor is a cognitive model that aids interface designers in analysing the three interacting subsystems of the perceptual, motor and cognitive systems and their memories and processes to predict how a user will interact with the interface (with emphasis on the time it takes to complete a task sequence). It essentially is an analogy between how a human perceives and remembers things and a computer’s processing and storage abilities.

However, there are a number of shortcomings with this analogy. The descriptions of the subsystems themselves of the Perceptual and Cognitive Processor and semantic memory are not detailed enough. There are real limitations in the Human Model Processor as well such as not being able to predict how long a user will take on tasks that are not highly practiced, that need to be learned or planned. Using this model, it is also very easy to overestimate the time it takes to accomplish tasks involving multi-tasking. It also doesn’t consider the user in any social, cultural or climate context which might affect a user’s time to complete the task and hence, the Human Model Processor fails to capture interactions beyond the scope of user and computer, excluding the user from any sort of context even if it may affect the output. In its estimation of human performance, this model fails to consider the user’s accumulated knowledge and how it affects the time they take to complete tasks.


2) Fitts’ Law is a highly successful law that predicts the time a user takes to move quickly to a target area, modelling it to be a function of the distance to the target and the size of the target. This is a useful law to consider when designing an interface as it helps designers understand the performance with different input devices (mouse, stylus, finger, etc.) and also how to design certain components like pull down menus or pop-up boxes, or how to utilise screen edges.

Hick’s Law is a model of human reaction time and is very useful in improving productivity and efficiency. It states that a person’s reaction time increases with an increase in the number of choices with the relationship between them modelled as a linear logarithmic function. Hick’s Law is useful in designing better interfaces as it encourages designers to design a simple, straight forward interface with few and clearly distinguishable choices to improve accessibility and to avoid clutter, unnecessary information, distracting colour and graphics. This is being implemented more often now given the rising trend of flat, minimalist design in web and mobile applications.


Fitts’ and Hick’s Laws consider human behavioural psychology and provide a physical measure to help designers determine what design choices would make a better interface.



Tristan Jones - 2/19/2014 17:18:27

1) The human model processor is a way that we UI/UX designers can model how a person works and set upper/lower bounds on how a person reacts to something. For instance, we can do a bunch of experiments and find out that it takes about 100ms [50~200]ms to respond to a pulse of light. We can take this into account in our UI design so we don't have messages pop up to quickly/too long. There are limits to this though. The human model processor makes a lot of assumptions on what the human is doing and the error terms do not account for all of the variation. An example of this is a distracted user: he may miss an important 1s popup even though that is much longer than the 200ms to see and react to it. What does this fail to capture? Definitely my biggest issue with the human model processor is that literally nobody thinks this way. When I see a flash of light, my brain doesn't go like "hey dude i saw this flash of light, now let's react 100ms later, except vary it up a bit between 50-200ms. That's essentially what this model is saying is totally wrong. The model is approaching this in the wrong direction. You can add more and more error terms to the model but it doesn't resolve the fact that the model is fundamentally wrong. If you use the Human Model Processor model, you're bound to get stuff wrong. That's probably why the book is from the 1980s when they thought "hey, let's model the brain as a computer!" when nowadays we have super advanced neuropsychopharmacology to predict what goes on in the brain.

2) Fitt's law: How long does it take for a user to accurately hit a button if he has to move his mouse/hand a distance D? It turns out it's proportional to log(1 + D/S) where S is the size of the button. Hick's law is about when a user sees n options, it takes the user about log(1 + n) time for the user to pick the right one. TBH these are just scientific replications of what we've already covered in issues the come up in user testing. Fitt's law: don't make buttons really small and don't make users jump around a lot. Hick's law: don't give users a huge number of options to select from. I don't really see why these are necessary in UI design, just have a bunch of users test your design and they will tell you these problems. Fitts law and hicks law are just fancy names for UX issues.


Namkyu Chang - 2/19/2014 17:19:56

1) Describe the Human Model Processor. What are the limits of the Human Model Processor? Which computer interactions does it fail to capture?

Card, Moran and Newell describes the Human Model Processor as “1) a set of memories and processors together, with (2) a set of principles”. More specifically, it’s composed of 3 interacting subsystems: “(1) the perceptual system, (2) the motor system, and (3) the cognitive system, each with its own memories and processors.” There are also several limitations to the Human Model Processor, including memory (you can’t just buy an SD card to expand storage for humans, or even if we put it into “memory” we might forget about it after a while) and processing (Einstein might be smart, but can we increase processing capacity of human beings like we can improve CPU performance every few years?).

2) Briefly define Fitts' Law and Hicks' Law. How can these be useful for designing user interfaces?

Fitts’ Law: Tpos = IM log(2)(2D/S), where IM= - (tp+tc+tM)/log2E

This states that the time to move the hand to a target depends only on the relative precision required.

Hick’s Law: T = b * log(2)(n + 1), where T represents average reaction time and n equally probable choices to choose among the choices.

These laws represent the time delay of accomplishing a task through the user’s mental process (Hick’s Law) and physical process (Fitt’s Law). By optimizing the parameters in designing the UI, the designer can reduce the time required to use an interface and make the experience that much smoother for the user.


Steven Wu - 2/19/2014 17:22:59

1) The Human Model Processor is comprised of three different subsystems: the perpetual system, the motor system and the cognitive system. The perpetual system is limited by the constraints on the visual limitations an individual has. This relates to the reaction response time someone has to interact with a product. The motor system still relates to one's process of understand to operate the interface’s functionality at a physical level. One particular thing that separates the cognitive system from the previous two is that ability we have as humans to chunk large quantities for ease of access and retrieval in our minds. By this I mean there is a way for us as human beings to be able to store numbers into chunks of seven plus or minus two. The principle of how memory is maintained in our human minds is rooted from this principle of chunking that allows us to process more information simultaneously. As for the limitations of what humans can do as a model processor, we must be reminded that each of these subsystems have their own constraints. When it comes to watching a moving image, our eyes can only perceive a frame of so fast and some goes for our ability to listen to something as cryptic as Morse code. There are limits on movement for our motor skills as Fitt’s Law describes the constraints we have to accomplish very simple interactive tasks with computers. Repetition and placing certain keys relatively closer to each other help to overcome this obstacle. And finally the cognitive system ties the two together by offering insight on what our limitations will be within the context of physically matching objects together since that requires the processing of learning and retrieval. The concept of learning and retrieval is limited to the user’s personal ability to forgetting just-acquired information. The process of working memory comes as a difficulty as it is very difficult to remember greater than ten things in our minds. To overcome this, chunking must be integrated again to help consulate the issue of memory management for human model processor.

2) Fitt's law relates between the three complexities of the three subsystems of the human model processor. The law states that the time to move the hand to a target depends only the relative precision required, that is, the ratio between the target’s distance and its size. Ergonomics can also come into consideration since this relates to a human user’s distance from the target that he much reach out to. This law has limitations however since it has been shown to apply under a variety of conditions, manipulanda, physical environments and user groups. To this date, Fitt’s law has been used to determine the human model processor of a user clicking to a target on his monitor. This requires the ability to use click-and-drag maneuvers. Similarly used in HCI, Hick’s law relates to an individual’s delayed reaction time when he or she is presented with an increased number of options than from before. With an increasing number of choices displayed to the user, the time it takes for a person to make a decision increases logarithmically. This is largely limited to the cognitive capacity someone has. The law has been applied especially to HCI in the way that it is used for the design of various menus for a UI. Because of this, the user is presented with multiple options to select from and a user must be able to scan the screen for the most optimal selection in as little time possible.


Bryan Sieber - 2/19/2014 17:24:24

The human model processor can be described very similarly to a real computer information system. It is known as the culmination of memories and processes together with the set principles/justifications of certain operations. The human model processor can be split into three subsystems: perceptual, motor, and cognitive systems. All three of these systems work together to provide a response to a certain stimuli (the example in the reading is clicking a button in response to a light shining). Since all humans are different they react differently to different stimuli. This creates an atypical bunch of users. An engineer must be able to overcome this issue by being knowledgeable of the fastman-slowman range, and the typical performance characteristics on a particular process interaction. In the perceptual system the visualization via a human's eyes is obtained in a very narrow region in the eye (~2 degree) known as the fovea, this is a limitation of the perceptual system. The cycle time is a limiting factor as well in the perceptual processor. Occasionally, humans fuse different stimuli together when they occur is rapid succession, they assume that one of the stimuli caused the other. Since, not all humans can read at the same speed, or type at the same speed, or think at the same speed, within a range. The human model processor fails to capture Fitts’ Law, if the object is poorly designed. For example, the calculator in the reading with the oft-used “f” key placed a bit further than it should be, causes much more complications.

Fitts’ Law is used in HCI and ergonomics, and uses a function to determine a set of characteristics based off of a user’s interaction with an object. More specifically, Fitts’ Law predicts the time required to move to a target area, based off the distance to the target and the target’s size. This law is used to recreate the act of pointing, either physically or virtually. Most usually this relates to the act of a user with a mouse, either clicking (or clicking and dragging) to get the mouse to the target location. Hick’s Law is used in justification of design placements with menus and other decision processes. The law states that, if the number of choices increases the user’s decision time will increase logarithmically. If a user is able to determine the ordering of a menu they could implement their own particular search strategy to find what they are looking for in the menu. Both Fitts’ Law and Hick’s Law are useful for designing user interfaces because they take into account all aspects of the design including the placement, alignment, choices, and ordering. These all greatly affect a user’s interaction with the system, and can cause a user to be more dissatisfied with the product if not designed correctly.


Meghana Seshadri - 2/19/2014 17:25:21

(1) The Human Model Processor is a cognitive modeling method that Card, Moran, and Newell created in 1983. This model compared the way humans processed and remembered information in their brain to the processing and storage of information on a computer. By understanding how human’s processed information, Card, Moran, and Newell believed they could then assist human-computer interactive designers in figuring out what types of computer interfaces would produce the best results with users. This model breaks down the steps of humans processing information into three subsystems: perceptual, cognitive, and motor. This model doesn’t cover everything about the way a person deals with information. It doesn’t take multitasking into account. People are very well known for trying to accomplish several things at a time, such as talking on the phone and cooking. It also doesn’t take into account the external conditions that the user could be in. For example the environment a person is in can heavily affect the process of them completing a task. Furthermore, other people around the user can affect the way the user does something or processes something. This type of cognitive modeling also fails to capture any stress, mental workload, or individual differences that the user may have.


(2) Fitts’ Law is used to predict the time, speed, and accuracy that a user takes to physically touch an object with a hand or a finger, similarly to pointing on a computer monitor. This law formulates that the time required to complete this movement is a function of the distance to the target and its size. Basically, the closer and larger a target is, the faster it is to click on it. Because of this basic statement, this law guides user interface designers to create larger targets that will facilitate interaction between the user and the interface. Hicks’ Law analyzes the amount of time a user takes to make a decision when they’re presented with possible choices. It basically describes the notion that the more options a user is presented with, the longer it will take for the user to make a decision. It encourages user interface designers to limit the number of options a user is presented with when navigating through the application or website. This in turn will prevent users from losing time and patience while using the service.


Lauren Speers - 2/19/2014 17:25:39

The Human Model Processor is a description of the human mind as an information-processing system intended to aid in predicting human-computer interactions, not to accurately describe the human mind. The Human Model Processor is composed of Working and Long Term Memory as well as a set of “principles of operation”, and divided into three subsystems – the perceptual processor, the motor processor, and the cognitive processor. Typical human-computer interactions can be expressed in terms of the operations of these three sub-processors, and the model can be used to predict the time actions will take and with what accuracy and ease they can be completed. However, because humans are unique, they cannot all be described by the exact same model. Even when using the Human Model Processor, designers must still account for a range of users. Additionally, the Human Model Processor does not shed light on potential emotional reactions – frustration, relaxation, etc. – that largely affect people’s experiences with UIs.

Fitt’s Law relates total time required for a movement to the relative precision required during the movement (the ratio of the length of the movement to the size of the target). Fitt’s Law is relevant in UI design because it can help designers accurately specify the tradeoffs between different designs that feature the same controls in different locations. Hicks’ Law, on the other hand, defines the time it takes for a person to make a decision as a function of the uncertainty of the decision, where uncertainty can be increased by increasing the number of alternatives, changing the probability of specific alternatives, or creating sequential dependencies between alternatives. One way Hicks’ Law can impact UI design is by suggesting which design alternatives are likely to facilitate faster user decision making and actions.


Patrick Lin - 2/19/2014 17:27:14

1) The Human Model Processor is an approximation of the human mind as an information processing system. The model is composed of the perceptual (senses and memories), cognitive (making decisions), and motor (carrying out responses to decisions) systems, creating analogies to computer processors and memory.

While useful for estimating how a user may perform a task, it does not take into account the environment the task in done in, which may include other people, tasks, or conditions that could affect the user’s focus or comfort. The model assumes tasks can be broken down into concrete steps and time intervals and does not account for a user’s previous experience with similar interfaces, or a user that may be multitasking instead of focusing completely on the test.

2) Fitt’s law is a model used to estimate the time it takes for a person to accurately move to a particular area (e.g. pointing). Hick’s law estimates the time it takes for a person to make a decision based on the choices presented. These laws, in conjunction with the human model processor are useful for UI design because they allow for accurate estimations on how long a user may take to navigate a particular interface and how to make them easier to use. Fitt’s law for example implies having larger buttons and minimizing “travel time” would be easier to click in a mobile app, while Hick’s law suggests not having too many options/clutter.


Robin Sylvan - 2/19/2014 17:27:32

The Model Human Processor, as described by Moran and Newell, simplifies human brain into chunks of processors with memory working together to perform tasks. They broke the Model Human Proessor into three main subsystem – the perceptual system, the motor system, and the cognitive system. Within each subsystem they described processors inside of these systems. With each processor they defined major parameters – storage capacity, decay time of an item, main code type, and cycle time. In the perceptual system, they went into specific values for visual and auditory information. Using perceptual response tests they concluded that there were specific values for how fast the human mind could process this information, the impulse response, and how much it could process at once. For the motor system they also went into the processor speed for creating movements. The cognitive system was interesting because they focused a lot on working memory as well as long term memory. They calculated the decay of objects from working memory, and also postulated that its easier to create new memories about things that are presently more accessible in memory. The Model Human Processor doesn't fully capture all computer-based interactions. Computers, and people too, have processing methods for communication. They didn't go into the processing of interactions between people. Also, they didn't delve into our other forms of sensory input. While smell and taste might not be the most relevant or powerful for information processing, people very often process touch-based information, such as vibrations on a screen from a button press. Fitt's Law describes the time it will take the user to move to a target, based upon the size of a target and the distance they have to move. The formula states that it will logarithmically increase based on the distance divided by size. Hick's law describes the amount of time it will take for a user to make a decision, based on the number of available choices. Hick's law states that the time for a user to make a decision will increase logarithmically based upon the number of choices. These are useful for creating user interfaces because it can help us calculate estimates of how people will interact with our application through theory. We can keep in mind that for users to interact with our application effectively, we should work on minimizing choices and distance between interactions while still letting the user navigate intuitively.


Insuk Lee - 2/19/2014 17:35:36

1. The Human Model Processor defines the workings of the brain in mathematical terms. It is divided into Perceptual, Cognitive and Motor Systems, each of which has their own processors and memories that are interconnected and are expressed in terms of variables such as cycle time, memory capacity, decay rate and memory code type. This is a pretty accurate model of the human brain used to analyze human-computer interaction but there are some limitations. These include the inability to capture the contextual variables such as the aesthetic and intuitive layout of the system - we feel good about the system we used based on the whole user experience, which includes how nice the design is and how easy it is to use, which does not solely depend on the reaction times that are analyzed using the Human Model Processor.

2. Fitt's Law states that the time required to move physically to a target area is related to the distance to the target and the size of the target. This is useful for designing user interface because we can analyze how long it would take for the user to touch or interact with the design as part of the computation of total time to accomplish a task. Hick's Law similarly states that the time required to make a choice is logarithmically related to the number of choices available. This can also be incorporated into the total time because it lets the designers analyze how long it would take a user to find relevant information and make a decision during the interaction with the system.


Aman Sufi - 2/19/2014 17:36:30

1. The Human Model Processor creates an analog of the human mind as an information-processing system, subdivided into three principle units – the perceptual, motor, and cognitive processors, each handling a major part of the functions of our brain and interacting with each other to process information. The perceptual processor handles our ability to process sensory information, and describes our responses to changing our field of perception, for example the turning of the head in response to wanting to view something more than 30 degrees out of line from the fovea. The motor processor describes our motor responses and the cognitive process handles abilities such as the ability to multitask as well as the capability of our long-term, working, and other memories. Almost everything is broken down into estimates of response times of each of the human processors in between cycles of performing tasks or responding to stimuli.

The limits of such a model are that it makes many assumptions based on the most common current psychological theories, such as the model of memories fading as a decay rather than due to interference, or memory being represented as chunks which can be linked to each other to ease in their recollection rather than individual memories with corresponding ‘strength’ values to judge their ease in recollection.

In general, the Human Model Processor fails to capture interruptability of tasks, multi-tasking ability, errors in memory, and the ability to automate certain processes with practice, among other ideas which we don’t fully understand about the human mind.

2. Fitts’ Law: Describes the approximate time required to move the hand to a target of a certain size at a certain distance away.

Hicks’ Law: It basically describes human reaction times based on the uncertainty about the judgment or decision that needs to be handled.

These laws are useful in designing user interfaces because user interfaces, in order to be usable, must cater to the limits of the human mind. If text flashes across the screen to quickly, or a memory matching game attempts to make us remember too many pairs of cards at the same time, our effectiveness to handle and respond to the task at hand will diminish. So we must carefully design UIs to follow the limits of the human mind.


Romi Phadte - 2/19/2014 17:48:01

1) The Model Human Processor can be described by (1) a set of memories and processors together with (2) a set of principles, hereafter called the "principles of operation." It can be be divided into three interacting subsystems (1) the perpetual system, the (2) motor system, and (3) the cognitive system. The limits of the Human Model Processor is that it doesn't cover the environmental conditions of the user while they are interacting with the interface. For example, it assumes that a user does only one thing at a time. However, it is really common to be on the phone and type at the same time or interact with the interface. This also doesn't consider the effects of other people. Ex. Holding a conversation while using an app. Also it doesn't consider the environment. Someone stranded on the side of the road in the freezing snow will have a different experience compared to the experience of an individual comfortable in their office.

2) Fitts law. The time to move to a target area is a function of the distance to the target and the size of the target. Hick's law is the idea that the time it takes for a person to make a decision is a function of the number of decisions a person has. These laws are useful because they tell designers to avoid making interfaces that are excessively tiny and to limit the number of choices a user has. (keep things stupid simple.) These are guiding principles when it comes to design.