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The Design of Everyday Things by Donald A. Norman
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Chapter 1 – The Psychopathology of Everyday Things |
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Principles of Design |
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Visibility |
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The right parts must be visible and convey the right message. When the right message is conveyed you can naturally respond to the design. |
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A good conceptual model |
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“The designer provides a good conceptual model for the user, with consistency in the presentation of operations and results and a coherent, consistent system image.” |
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Mapping (Appropriate visible clues) |
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A technical term meaning the relationship between two things. E.G. Turning the wheel of a car left turns the car left. |
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How visible an action is to actual operations. “Visibility indicates the mapping between intended actions and actual operations” |
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Feedback |
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“Sending back to the user information about what action has actually been done, what result has been accomplished.” |
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Immediate Feedback |
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Feed back that occurs instantly |
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Auditory Feedback |
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Feedback resulting from sound. E.G. The ding a computer makes when you do something wrong. |
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Natural Design |
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When a design allows you to respond naturally and without any need to consciously know about the natural signals. |
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Natural Signals |
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Visible parts that cue how something can be used without consciously knowing of them. |
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Natural Mappings |
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Taking advantage of physical analogies and cultural standards to convey mappings of an action to an operation. |
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“There must be a close, natural relationship between the control and its function: a natural mapping” |
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Parts of a Visible Structure |
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Affordances |
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“Refers to the perceived and actual properties of an object, primarily the fundamental properties that determine just how the object could possibly be used.” |
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Constraints |
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Limiting the possible actions that can be made to prevent misusage. |
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Mappings |
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See Principles of Design. |
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Fundamental Principles of designing for people |
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Provide a good conceptual model |
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Make things visible |
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Conceptual Models |
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Design Model |
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Designer’s conceptual model of a design |
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How the designer thinks the design should work and how he perceives others will respond to the device. |
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User’s Model |
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Mental model developed through interaction with the system/design. |
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System Image |
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The physical structure that has been built. This includes the documentation, instructions, and labels. |
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Mental Model |
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Models people have of themselves, others, the environment, and the things with which they interact. |
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“The mental model of a device is formed largely by interpreting its perceived actions and its visible structure(aka system image) .” |
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Chapter 2 – The Psychology of Everyday Actions |
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Misconception |
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Self Blame |
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Blaming the Wrong Cause |
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“People have a tendancey to blame themselves when problems arrise with difficult technologies.”(p40) |
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Blaming the Wrong Cause |
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“Blame and credit can be assessed almost independently of reality” (p40) |
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This is due to the fact a person usually has little information to perceive a event correctly. The mind makes its own conclusions from the information it has. These are often times invalid and the real culprit is never even considered. |
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Learned Helplessness |
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A situation where a person experiences failure at a task, often numerous times and as a result decides the task cannot be done. |
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“In the extreme case, such learned helpless leads to depression and to a belief that the person cannot cope with everyday life at all.” |
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Taught Helplessness |
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When a person feels helpless due to the fact the a an items design provide faulty mental models, and poor feedback that result in failure. |
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I.E. Math phobias often times occur for students because by design it is difficult. |
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The Action Cycle |
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Goal |
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What we want to happen |
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Execution |
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What we do to the world |
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Evaluation |
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Check whether the goal is accomplished |
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Stages of Execution |
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1 |
Goals |
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2 |
An intention to act so as to achieve a goal |
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The actual sequence of actions that we plan to do |
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The physical execution of that action sequence |
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Stages of Evaluation |
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Perception of the world |
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Interpreting the perception according to our expectations |
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Evaluation of the interpretations with what are expectations are. |
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Goals |
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7 Stages of Action |
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2.11.1 |
Forming the goal |
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2.11.2 |
Forming the intention |
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2.11.3 |
Specifying an action |
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2.11.4 |
Executing the action |
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2.11.5 |
Perceiving the state of the world |
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2.11.6 |
Interpreting the state of the world |
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2.11.7 |
Evaluating the outcome |
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Data-driven Behavoir |
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Goals that are formed as a result of events in the world. Thus the goal is the response of the person forming the goal. These goals are not planned and may be malformed or vague. |
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Gulf of Execution |
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“The different between the intention and the allowable actions is the Gulf of Execution. One measure of this gulf is how well the system allows the person to do the intended actions directly, without extra effort.” |
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The VCR is a device that has bridged the gulf by hiding the threading mechinisim by hiding the parts in side the tape. The machine bridges the gulf. |
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Gulf of Evaluation |
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“Reflects the amount of effort that the person must exert to interpret the physical state of the system and to determine how well the expectations and intentions have been met.” |
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I.E An example give is the VCR. A user is unable to know whether or not a video is in the device after it is inserted. Upon evaluation it may appear the device has a tape in it when really may not. |
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Seven Questions to Ask About a Design |
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Determine The Function of the Device? |
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Tell what actions are possible? |
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Determine mapping from intention to physical movement? |
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Perform the action? |
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Tell if the System is in Desired State? |
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Determine mapping from system state to interpretation? |
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Tell what State the system is in? |
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Principles of good design |
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Visibility |
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A good conceptual model |
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Good mappings |
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Feedback |
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Chapter 3 – Knowledge in the Head and in the World |
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Precise behavior can emerge from imprecise knowledge for four reasons |
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Information is in the world |
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Much of the information a person needs to do a task can reside in the world around them. |
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Great precision is not required |
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Accuracy of knowledge is rarely required. |
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Natural constraints are present |
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The physical properties of objects constrain possible operations: the order in which parts can go together and the way the object can be moved, picked up, or otherwise manipulated. |
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Cultural constraints are present |
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Cultural/social conventions are learned and once learned apply to a wide variety of circumstances. |
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“Information you internally code in memory need be precise enough only to sustain the quality of behavior you desire.” |
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Types of Knowledge |
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Declarative Knowledge (I.E. Knowledge of) |
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The knowledge of facts and rules. I.E. “Stop at red lights” |
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Easy to write down and to teach. |
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Procedural Knowledge (I.E. Knowledge How) |
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The knowledge that enables a person to perform music, to stop a car smoothly with a flat tire on an icy road, to return a serve in tennis, or to move the tongue properly when saying the phrase “frightening witches”. |
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Is often times difficult or impossible to write down and difficult to teach. |
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Best taught by demonstration and best learned through practice. |
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Three Categories of Memory |
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Memory for arbitrary things a.k.a. Rote Learning |
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The items seem to have no meaning and no particular relationship to one other or to things already known |
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I.E. Memorizing the multiplication table |
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Creates problems for two reasons |
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What is being learned is arbitrary; requiring considerable time and effort to leran |
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When a problem arises the memorized sequence of actions gives no hint of what has one wrong, and no suggestion of what might be done to fix the problem. |
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Memory for meaningful relationships |
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Items that have a sensible structure and relationships |
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“A good mental model lies in the ability to provide meaning to things” |
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“A meaningful relationship can be indispensable, but you have to have the right one” |
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Memory through explanation |
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From past experiences and memories a person is able to derive appropriate behavior. |
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Reminding |
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Two aspects to a reminder |
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The Signal |
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The Message |
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“The ideal reminder has to have both components: the signal that something is to be remembered, the message of what it is” |
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“If a design depends upon labels, it may be faulty. Labels are important and often necessary, but the appropriate use of natural mappings can minimize the need for them. Wherever labels seem necessary, consider another design” |
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Tradeoff between knowledge in the world and in the head |
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Retrievability |
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In the world knowledge can be retrieved when ever visible |
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In the head knowledge is not readily retrievable and requires searching or reminding |
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Learning |
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Learning in the world is not required as interpretation substitutes for learning. |
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Knowledge in the mind requires learning that can take considerable time. Learning is made easier if the structure is mapped well to the material. |
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Efficiency of use |
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Ease of use at first encounter; Aesthetics |
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Chapter 4 – Knowing What to Do |
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Classification of Constraints |
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Physical |
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“Physical limitations constrain possible operations. Thus, a large peg cannot fit into a small hole” |
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A physical constraint prevents the wrong action from succeeding only after it has been tried. |
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“Are made more effective and useful if they are easy to see and interpret.” |
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Semantic |
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Constraints that rely upon our knowledge of the situation and of the world. |
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An example of the location of a rider on a motorcycle. The purpose of the windshield is to protect the rider’s face, thus a rider must face forward. |
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Cultural |
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Constraints that are defined from cultural definitions of our surroundings |
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“Cultural issues are at the root of many of the problems we have with new machines” |
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Logical |
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Constraints created by logical relationships between the spatial or functional layout of components and the things that they affect or are affected by. |
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2 design difficulties of switches and buttons |
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How to determine which switch goes with which function? (Grouping problem) |
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Possible solutions |
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Keep the switches for one set of functions apart from the switches that control other functions. |
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Use different types of switches |
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How to determine which switch controls which light?(Mapping problem) |
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“Controls that cause trouble should not be located here they can be operated by accident, especially in the dark, or when the person is trying to use the device without looking.” |
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Questions Which Guide Actions |
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Which part move; which are fixed? |
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Where should the object be grasped? What part is to be manipulated? What is to be held? Where is the had to be inserted? If it is speech sensitive, where does one talk? |
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What ind of movement is possible: pushing, pulling, turning, rotating, touching, stroking? |
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What are the relevant physical characteristics of the movements? With how great a force must the object be manipulated? How far can it be expected to move? How can success be gauged? |
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Difficulties that result from no visual feedback |
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Trouble remember what place in the length sequence of required steps a person is on |
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Trouble remember what the next step that needs to be done |
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Can’t easily check the information just entered to see if it is what was intended, and then cannot easily change it if they decide it is wrong. |
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“Sometimes things can’t be made visible” |
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When feedback cannot be made visible another option is to use sound to provide feedback. |
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Forms of feedback |
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Audible |
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Cons |
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“Can annoy and distract as easily as it can aid.” |
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Difficult to keep private |
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Sounds are often intrusive |
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Others can monitor your activities |
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There appears to be a happy medium of using sounds and visible feedback. Using sound to much can result in feedback to is later ignored due to repetitiveness or annoyance. |
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Visible |
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Chapter 5 – To Err Is Human |
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Fundamental Categories of Human Error |
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Slips |
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Result from automatic behavior, when subconscious actions that are intended to satisfy our goals get waylaid en route. |
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Mistakes |
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Result from conscious deliberations which are made on the basis of partial or even faulty evidence leading to error. |
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Categories of Slips |
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Capture Errors |
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Occur when a frequently done activity suddenly takes charge instead of the one intended. |
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Description Errors |
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Occur when performing the correct action on the wrong object |
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The more the wrong and right objects have in common, the more likely the errors are to occur. |
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Data-driven Errors |
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Triggered by the arrival of the sensory data in the middle of an on-going sequence of actions causing behavior that was not intended. |
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Associative activation Errors |
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Triggered by internal thoughts and associations that you think should not be said but for some reason you still say them. |
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Loss-of-activation Errors |
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Occurs when the “activation” of the goals has decayed. |
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I.E. When you goto do something then you forget what you were trying to accomplish |
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Mode Errors |
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Occur when devices have different modes of operation and the action appropriate for one mode has different meanings in other modes. |
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Schema Theory |
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File cabinet model wherein there are lots of cross references and pointers to other records. |
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Three Beliefs |
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that there is logic and order to the individual structures |
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that human memory is associative, with each schema pointing and referring to multiple others to which it is related or that help define the components. |
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that much of our power for deductive thought comes from using information in one schema to deduce the properties of another. |
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Economic Theory |
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Based upon a model of the rational human who attempts to optimize personal benefit, utility, or comfort. Defining our actions as based on rational, logic, and orderly. |
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The Connectionist Approach |
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Focuses on the study of the brain the neurons. Thinks of the brain as a huge network of neurons that make connections to allow thought. |
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Models mental or behavioral phenomena as the emergent processes of interconnected networks of simple units. There are many forms of connectionism, but the most common forms use neural network models. |
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There is this idea of common thoughts that mush together and discrepant events that stand out from all others. |
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Structures of Tasks |
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Wide |
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Each point in a tree of possible actions has many other alternatives |
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Deep |
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The number of possible branches in the task tree is tall |
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Shallow |
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Each point have very few possible actions or only one action |
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Narrow |
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The number of possible branches in the task tree is short |
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Design for Error |
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Understand the causes of error and design to minimize those causes |
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Make it possible to reverse actions- to “undo” them- or make it harder to do what cannot be reversed |
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Make it easier to discover the errors that do occur, and make them easier to correct. |
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Change the attitude toward errors. Think of an object’s user as attempting to do a task, getting there by imperfect approximations. Don’t think of the user as making errors; think of the actions as approximations of what is desired. |
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Signals need to be clear else wise they can confuse the user. For example, communicating to the user an error occurred in a way that is consistent with another signal can confuse the user. |
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Forcing Functions |
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Interlocks |
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Forces operations to take place in proper sequence |
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Lock-ins |
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Keeps an operation active, preventing someone from prematurely stopping it |
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Lockouts |
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Prevents someone from entering a place that is dangerous, or prevents an event from occurring. |
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Principles of design |
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Put the required knowledge in the world. Don’t require all the knowledge to be in the head. Yet do allow for more efficient operation when the user has learned the operations, has gotten the knowledge in the head. |
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Use the power of natural and artificial constraints: physical, logical, semantic, and cultural. Use forcing functions and natural mappings. |
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Narrow the gulfs of execution and evaluation. Make things visible, both for execution and evaluation. On the execution side, make the options readily available. On the evaluation side, make the results of each action apparent. Make it possible to determine the system state readily, easily, and accurately, and in a form consistent with the person’s goals, intentions, and expectations. |
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Chapter 6 – The Design Challenge |
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Chapter 7 – User-Centered Design |
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