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            LS385T – Software Usability
                   Engineering
                        Week 2 – Norman’s book and
                              mental models



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  1
                First . . . your homework                                                         i
         • Bad designs.
         • Good designs.

         Famous quote: “No one ever raised a statue to
           a critic.” Sibelius

         I want us all to remember that it is easier to
            criticize another design than it is to design
            something.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  2
      I’m gonna go fast because . . .                                                             i
      • It ain’t rocket science.
      • You’ve already read the book.
      • I’d rather make you scramble to keep up
        that bore you.
      • I have 80 slides I’m gonna do in 60 minutes
        (yeah, right!).
            – While I’m presenting this, see if you can
              characterize your good and bad designs that
              you’ve discovered this week in Norman’s
              terms.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  3
                                        Chapter 1                                                 i
         • The PsychoPATHOLOGY of everyday
           things
         • Assumption: We blame ourselves for
           errors, but the real culprit is faulty
           design.
         • Assumption: There’s nothing special
           about computers. They have the same
           sorts of design problems as simpler,
           everyday things.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  4
                                   Good Design                                                    i
         • Well designed objects . . .
               – are easy for the mind to understand
               – contain visible cues to their operation
         • Poorly designed objects . . .
               – provide no clues, or
               – provide false clues.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  5
                               Natural Signals                                                    i
         • Natural signals lead to natural design.
         • A metal plate “naturally” is to be pushed.
         • Visible hinges “naturally” indicate
           attachment, and that the other side
           swings open. (And swings open
           TOWARD me?)



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  6
                                          Mapping                                                 i
         • Mapping is a relationship between two
           things (e.g., between what you want to
           do and what appears possible).
         • Good design allows for a clear (visible)
           mapping between . . .
               – intended actions and
               – actual operations.
         • Now -- think of what this might mean in a
           web site.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  7
                                   Good Design                                                    i
      • Principles of good design
            – the importance of visibility
            – appropriate clues
            – feedback of ones actions.
      • Just so you’ll know -- others have proposed
        OTHER principles of good design. Go
        check out the web site of Bruce Tognazzini:

      http://www.asktog.com/basics/firstPrinciples.html

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  8
                          “First Principles”                                                      i
         “The following principles are                         •    Efficiency of the user
            fundamental to the design                          •    Explorable Interfaces
            and implementation of                              •    Fitts’s Law
            effective interfaces,                              •    Human-Interface Objects
            whether for traditional GUI                        •    Latency Reduction
            environments or the web.”                          •    Learnability
         • Anticipation                                        •    Metaphors, Use of
                                                               •    Protect Users’ Work
         • Autonomy                                            •    Readability
         • Color Blindness                                     •    Track State
         • Consistency                                         •    Visible Interfaces
         • Defaults


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  9
                          Affordance                                           i
    • Affordance is the perceived and actual properties of a
      thing.
       – Primarily those fundamental properties that
         determine how a thing could possibly be used.
       – “Affords” means, basically, “is for.”
       – A chair affords support, therefore affords sitting.
    • Affordances provide strong clues to things’ operations.
    • When affordances are taken advantage of, the user
      knows what to do just by looking.
       – No label, picture, or instruction (“Push”) is required.
       • - When simple things need pictures, labels, or
            instructions, the |design has rbias@ischool.utexas.edu
R. G. Bias | School of Information | SZB 562BB Phone: 512 471 7046 |
                                                                     failed.
                                                                               10
                               Complex World                                                      i
      • 30,000 readily discriminable objects. How do we deal
        with all of them?
         – Partly, the way the mind works.
         – Partly, the information available from the
           appearance of objects.
            – Partly, the ability of the designer to:
                  • make the operation clear,
                  • project a good image of the operation, and
                  • take advantage of the other things people might know.
      • Here is where the designer’s knowledge of the
        psychology of people coupled with the knowledge of
        how things work becomes crucial.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  11
                       Principles of Design                                                       i
         •  Four principles of Design for
            Understandability and Usability.
         1. Provide a good conceptual model.
               – A good conceptual model allows us to
                 predict the effects of our actions.
               – Simply knowing the relationship between
                 the controls and the outcomes.



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  12
         Principles of Design (cont’d.)                                                           i
         2. Make things visible.
         3. The principle of mapping.
               – Natural mapping (taking advantage of
                 physical analogies and cultural standards)
                 leads to immediate understanding.
               – Move the control up, the sound gets
                 louder.
               – Seat adjustment in Fig. 1.13 is a good
                 example.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  13
         Principles of Design (cont’d.)                                                           i
         4. The principle of feedback.
               – Feedback is sending back to the user
                 information about what action actually has
                 been done, what result has been
                 accomplished.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  14
          The Paradox of Technology                                                               i
             – Added functionality generally comes along
               at the price of added complexity.
             – The same technology that simplifies life by
               providing more functions also complicates
               life by making the device harder to learn
               and use.
             – The Paradox of Technology should never
               be used as an excuse for poor design.
             – Added complexity cannot be avoided when
               functions are added, but with clever design
               they can be minimized.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  15
                   Chapter 2 -- Psy of Everyday
                             Actions
                                                                                                  i
         • Norman’s credo on errors -- if an error is
           possible, someone will make it.
         • The designer must design so as to:
               – minimize the chance of errors in the first
                 place
               – minimize the effects of an error
               – make errors easy to detect
               – make errors reversible, if possible.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  16
                                             Models                                               i
      • Mental Models = our conceptual models of the way . . .
        – objects work
         – events take place
         – people behave
      • Mental models result from our tendency to form
        explanation of things.
      • Models are essential in helping us . . .
         – understand our experiences
         – predict the outcomes of our actions
         – handle unexpected occurrences.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  17
                              Models (cont’d.)                                                    i
      • We base our models on whatever knowledge we have:
         – real or imaginary
         – naïve or sophisticated
         – even fragmentary evidence.
      • Everyone forms theories (mental models) to explain
        what they have observed.
      • In the absence of feedback to the contrary, people are
        free to let their imaginations run free.
      • More on models in Chapter 3.



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  18
                                              Blame                                               i
      • People assign causal relation whenever two things
        occur in succession.
      • When we try something and fail, we blame ourselves
        (especially when we know others have succeeded).
      • Thus, a “Conspiracy of Silence,” leading to
         – guilt
         – helplessness
      • Learned Helplessness
      • Taught Helplessness
         – Badly designed objects constructed so as to lead
           to misunderstanding (faulty mental models). Think
           of an internally inconsistent app or web site.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  19
                                     Explanation                                                  i
         • The nature of human thought and
           explanation.
               – We want to have an explanation, and we
                 will construct one in order to eliminate any
                 puzzle or discrepancy in our lives.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  20
                                          7 Stages                                                i
         •  On p. 47 is a series of four figures that
            illustrate Norman’s view of the structure
            of action.
         • Actions have two major aspects:
         1. Doing something (execution)
         2. Checking (evaluation)



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  21
                           7 Stages (cont’d.)                                                     i
         •       Action is broken down into 7 stages:
         1.      Perceiving the state of the world
         2.      Interpreting the perception
         3.      Evaluating the interpretations
         4.      Setting a goal
         5.      Intention to act
         6.      Sequence of actions
         7.      Execution of actions



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  22
                           7 Stages (cont’d.)                                                     i
         • Specific actions bridge the gap between
               – What we would like to do (goals and
                 intentions) and
               – All possible physical actions.
         • 7 stages form an “approximate model,”
           not a complete psychological theory.
         • One key -- continual feedback loop.
               – Process can be started at any point.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  23
                                          Gulfs . . .                                             i
         • Of Execution and Evaluation.
               – Gulf of Execution -- the difference between
                 intentions and allowable actions.
               – Gulf of Evaluation -- difficulty in interpreting
                 the physical state of a “system,” interpreting
                 how well the expectations and intentions
                 have been met.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  24
                                        Designing                                                 i
         • The 7-stage structure can be a valuable
           design aid.
         • Provides basic checklist of questions to
           ask to ensure that
               – the Gulf of Execution and
               – the Gulf of Evaluation
               are bridged.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  25
                         Designing (cont’d.)                                                      i
      • There’s a question to ask for each stage
        (see Fig. 2.7) and they boil down to the
        principles of good design:
            – visibility
            – good conceptual model
            – good mappings
            – feedback.
      • Next time you can’t immediately figure out
        the shower control in a motel, remember
        that the problem is in the design!
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  26
        Chapter 3 - Knowledge in the
          Head and in the World                                                                   i
         • Not all knowledge required for precise
           behavior must be in the head. It can be
           distributed:
               – partly in the head
               – partly in the world
               – partly in the constraints of the world.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  27
                                      Knowledge                                                   i
      •       Precise behavior can emerge from
              imprecise knowledge, because . . .
            1. Information is in the world (e.g., signs).
            2. Great precision is not required. (Not just one
               path to school.)
            3. Natural constraints are present. (Didn’t have
               to worry about going UP as you drove to
               school.)
            4. Cultural constraints are present (e.g., driving
               on the right).
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  28
                                          Behavior                                                i
         • In everyday situations, behavior is
           determined by the combination of . . .
               – internal knowledge
               – external info
               – constraints.
         • There’s a tradeoff between the amount
           of mental knowledge and the amount of
           external knowledge needed.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  29
                                     In the world                                                 i
         • An example.
         • Typing:
               – Letter names on keycaps.
               – Requires that the typist look at keycaps.
               – Goal of power typing is to get that
                 knowledge from the world into the head of
                 the typist.



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  30
                             Knowledge OF and
                              Knowledge HOW                                                       i
         • Knowledge OF = Declarative
           Knowledge
               – Knowledge of facts and rules
               – Easy to write down, teach
         • Knowledge HOW = Procedural Know.
               – Difficult or impossible to write down, teach
               – Best taught by demonstration and learned
                 through practice
               – Largely subconscious
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  31
                                      Constraints                                                 i
      • The power of constraints -- the “memory” for epic poetry
        is found to be mostly reconstruction, with the aid of the
        constraints of rhyme, meter, etc.
      • We use constraints to simplify what we must remember.
      • For example, putting mechanical parts together.
         – Some are constrained by what will and will not fit
            together.
         – Also cultural constraints -- screws tighten clockwise.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  32
                                           Memory                                                 i
         • . . . Is knowledge in the head.
         • Think of all you can remember. Phone
           numbers, postal codes, passwords,
           SSN, birthdays, etc., etc.
         • It’s tough!
               – So, we put memory in the world.
                 (Daytimers. Palm Pilots. Address books.
                 Stickies.)


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  33
                           Memory Structure                                                       i
      • Two major classes of memory: STM &
        LTM
      • STM
            – Memory of the just-present
            – Retained automatically
            – Retrieved without effort
            – Limited capacity (7 +/- 2)
            – Items easily bumped
            – Capacity can be increased by chunking
            – Items retained by rehearsal
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  34
            Memory Structure (cont’d.)                                                            i
      • LTM
            – Memory for the past
            – Storage and retrieval takes time
            – Items stored according to interpretation (multi-
              keyed indexing)
            – Virtually unlimited capacity
            – Storage and retrieval are easier when the
              material makes sense
            – What was the first CVC in last week’s memory
              experiment?
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  35
                            3 Categories of things
                                remembered                                                        i
      •   Memory for arbitrary things, meaningful relationships,
          memory through relationship
      1. For arbitrary things:
         – Rote learning
         – Takes more time to encode
         – When there’s a problem, memorized sequence of
            events gives no hint of what’s gone wrong or how
            to fix it.
         – We impose structure or associations to help
           • E.g., tune to help remember the alphabet
         – Items aren’t understood. No mental model.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  36
                    3 Categories of things
                    remembered (cont’d.)                                                          i
         2. Memory for meaningful relationships
               – Enabled by mental models
               – Interpretation is essential, but it is NOT
                 understanding.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  37
                    3 Categories of things
                    remembered (cont’d.)                                                          i
      3.        Memory through explanation.
            –      Most powerful form of internal memory
            –      Mental models play a major role -- simplify learning because
                   the details can be DERIVED when needed.
                  • NOTE: The use of mental models to DERIVE behavior is
                      not ideal for tasks that must be done rapidly or smoothly.
            –      Designers should provide users with appropriate models,
                   ‘cause people make ‘em up, otherwise.
            –      The power of mental models -- let you figure out what would
                   happen in novel situations.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  38
                                Memory . . .                                                      i
         • . . . is also knowledge in the world.

         • But only available when you are there.
           (What if you don’t see that note you left
           for yourself.)




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  39
                                       Reminding                                                  i
      • A good example of the interplay between info in the
        world and in your head.
      • Strategies for reminding:
         – Rehearsal
         – Notes to self
         – Put the burden on the thing to be remembered (put
           the book by the door)
      • Two different aspects of a reminder
         – The signal (string around finger)
         – The message (ring around finger)
      • The ideal reminder has both components.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  40
                                    In the World                                                  i
         • Lots of products make it easier to put
           knowledge in the world.
               – Alarm clocks
               – Diaries
               – Calendars
               – Watches
               – PDAs



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  41
                     Natural Mappings . . .                                                       i
      • . . . Reduce the need for information in
        memory.
      • Simple design principle:

      If a design depends on labels, it may be
       faulty.
            Labels are important, and often necessary.
            But the appropriate use of natural mappings
             can minimize their need. (E.g., stove controls.)
            Wherever labels seem necessary, consider
             another design.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  42
                                    Tradeoff . . .                                                i
      • . . . between info in the world and in the
        head.
            – Knowledge in the world acts as its own
              reminder.
            – Knowledge in the head is efficient. (You can
              travel light.)
            – Knowledge in the world is easier (no learn
              time), but often difficult to use. Relies heavily
              on the physical presence of info.
      • See Fig. 3.6, p. 79.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  43
          Ch. 4 -- Knowing what to do                                                             i
         • When we encounter a novel object,
           either
               – We’ve dealt with something similar before,
                 and we transfer old knowledge, or
               – We get instruction.
         • Thus, information in the head.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  44
                                             Design                                               i
      • How can the design of an object (NOTE:
        info in the world) signal the appropriate
        actions?
            – Natural (physical) constraints
            – Affordances, that convey messages about the
              item’s possible uses, actions, and functions
      • “The thoughtful uses of affordances and
        constraints together in design lets a user
        determine readily the proper course of
        action even in a novel situation.”
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  45
                  Constraints - 4 Classes                                                         i
         •   Physical
         •   Semantic
         •   Cultural
         •   Logical




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  46
                       Physical Constraints                                                       i
         • Constrain possible operations
         • Rely on properties of the physical world,
           so no special training is required.
         • Are made more effective and useful if
           they are easy to see and interpret.
         (Example: Glass over fire alarm.)



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  47
                     Semantic Constraints                                                         i
         • Rely on the meaning of the situation to
           control the set of possible actions.
         • Rely on our knowledge of the situation
           and the world.
         Example -- Windshield goes in front of
           rider, in Legos!



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  48
                        Cultural Constraints                                                      i
         • Signs are meant to be read.
         • Guidelines for cultural behavior are
           represented in the mind by schemas.
               – Schemas are “knowledge structures that
                 contain the general rules and info necessary
                 for interpreting situations and for guiding
                 behavior.”



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  49
                         Logical Constraints                                                      i
         • Logic dictates that all parts be used, and
           fit together.
         • Natural mappings work by providing
           logical constraints.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  50
                The Problem with Doors                                                            i
      • An example of applying affordances and constraints to
        everyday objects.
      • When we approach a door we expect to find some
        visible signal.
         – Tells us where to act
         – Next step is to figure out how to act
         – Sometimes we need a manual (a one-word manual)
         – The proper hardware will operate a door smoothly
           PLUS will indicate how the door is to be operated
             • It will exhibit proper AFFORDANCES.
         – Focus on aesthetics can blind the designer (and the
           purchaser) to the lack of usability.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  51
           The Problem with Switches                                                              i
      • 2 fundamental problems
      • Grouping problem (which switch goes with
        which function)
            – Controls that cause trouble should not be located
              where they can be operated by accident.
            – Solution -- separate the switches for two sets of
              functions
            – Another solution -- use different types of switches
            – Combine the two solutions



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  52
                      The Problem with Switches
                               (cont’d.)
                                                                                                  i
         • Mapping Problem (which switch goes
           with which light)
               – Unsolvable given current light switch design
                 (mismatch in spatial arrangement (horiz. vs.
                 vert.) makes a natural mapping impossible.
               – Match the layout of the lights with the layout
                 of the switches.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  53
                  Visibility and Feedback                                                         i
         • Visibility -- make relevant parts visible

         • Feedback -- give each action an
           immediate and obvious effect




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  54
               Using Sound for Visibility                                                         i
      • Sounds should be generated to give info about the
        source
      • Should convey something about the actions that are
        taking place
      • Natural sounds (not beeps) reflect the complex
        interaction of natural objects
         – The way one part moves against another
         – The material of which the parts are made -- hollow
           or solid, metal or wood, soft or hard, rough or
           smooth
      • One of the virtues of sounds is that they can be
        detected even when attention is applied elsewhere.
        But, thus, can be obtrusive.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  55
                  Ch. 5 - To err is human                                                         i
         • Errors come in several forms
               – Slips -- result from automatic behavior,
                 when subconscious actions get waylaid en
                 route (“performance errors”)
               – Mistakes -- result from conscious
                 deliberations (“competence errors”)




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  56
                        In terms of the 7 stages of
                                action . . .
                                                                                                  i
         • If you form an appropriate goal, but mess
           up in the performance, you’ve made a
           slip.
         • If you form a wrong goal, you’ve made a
           mistake.
         • Slips are usually small things, relatively
           easy to discover.
         • Mistakes can be more major, harder to
           detect. (Says Norman.)
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  57
                                                 Slips                                            i
         • Show up most often in skilled behavior.
             (Does that seem contradictory? Think about it.)
         • We don’t make many when we are still
           learning.
         • Result from lack of attention. (Or from a
             speed-accuracy tradeoff.)




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  58
                                 Types of Slips                                                   i
      • Capture errors -- a frequently done activity suddenly takes charge
        instead of the intended one (e.g., typing THE instead of THY).
      • Description errors -- the intended action has much in common
        with others possible (e.g., turn on the wrong burner on stove).
      • Data-driven errors -- automatic actions, triggered by the arrival of
        some sensory data, intrude into an ongoing action sequence
        (e.g., pick up the phone when you hear a ring on TV).
      • Associative activation errors -- internal thoughts and associations
        intrude, causing errors (e.g., think you’re leaving a phone
        message for your wife, end with “I love you”).
      • Loss-of-activation errors -- simply forgetting to do something
      • Mode errors -- when devices have different modes of operation,
        and the action appropriate for one mode has different meaning in
        another mode (e.g., hitting the accelerator pedal when in neutral).
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  59
                                             Modes                                                i
         • Modes can be detected only if there is
           feedback.
         • Problem of level -- where (at what level
           in the sequence) is the error?
         • Problems of level constantly thwart the
           correction of error.



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  60
                                             Design                                               i
         • Design lessons from the study of slips.
               – Don’t prevent errors by requiring
                 confirmation.
               – Rather, eliminate irreversible errors.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  61
                                          Mistakes                                                i
         • Mistakes as errors of thought.
           (Competence errors.)

         • Mistakes result from the choice of
           inappropriate goals.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  62
                                Three Models of Human
                                      Cognition                                                   i
      1.        Photo Album Theory. (BUZZZ. Thank you for
                playing.)
      2.        Schema Theory.
            –      Filing cabinet model
            –      Lots of cross-references and pointers
            –      Basic beliefs
                  • There is logic and order to individual structures (schema)
                  • Human memory is associative, with each schema pointing
                       and referring to multiple others (networked!)
                  • Much of the power for deductive thought comes from using
                       the info in one schema to deduce the properties of another.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  63
                           Third Approach --
                            Connectionist                                                         i
            – Still unproven
            – Less logical
            – Each connectionist unit (whatever!) is connected to many
              others
            – Signals are either positive (activation) or negative
              (inhibition)
            – Thoughts = stable patterns of activity
            – New thoughts are triggered by a change in the system
              (from within or without) -- new info arrives and changes
              the pattern of activation and inhibition
            – Referred to as the “multiple exposure” theory of memory
            – Good quote, p. 118, last para., through middle of p. 119.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  64
                                               Tasks                                              i
         • The structure of tasks.
         • Everyday structures are either shallow
           and wide (ice cream list) or narrow and
           deep (cookbook).
         • Any task that involves a sequence of
           activities where the action to be taken at
           any point is determined by its place in
           the sequence is “narrow.”

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  65
                                Tasks (cont’d.)                                                   i
         • Most tasks of daily life are routine.
           Shallow or narrow.

         • What are NOT everyday activities?
           Those with wide or deep structures, that
           require considerable conscious planning
           and thought, deliberate trial and error.
           (Did someone say surfing the web to find
           some particular info?)
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  66
                   Conscious and Subconscious
                            Behavior
                                                                                                  i
      • Much human behavior is done subconsciously
         – without conscious awareness
         – not available to introspection
      • Subconscious thought matches patterns
         – finding best match between past experience and
           current needs
         – proceeds rapidly, automatically, without effort
         – good at generalizing
         – but can find inappropriate matches
         – a bias towards regularity and structure

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  67
                        Conscious Thought                                                         i
            – Slow and labored
            – Ponder decisions, consider alternatives,
              compare choices
            – Slow and serial
            – Limited by small STM
            – Uses subconscious thought as a tool
            – memory limitation is overcome by appropriate
              organization structure
      • Mistakes are made by mismatch -- by taking current
        situation and falsely matching it with something in the
        past.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  68
                         Designing for Error                                                      i
      • Everyone makes errors
      • Designers make the mistake of not taking errors into
        account
      • Read p. 131 for list of what designers SHOULD do
      • Forcing functions -- form of physical constraint
         – Can’t put convertible top up or down unless the car is
           in “park.”
      • Read “A design philosophy,” p. 140.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  69
      Ch. 6 -- The Design Challenge                                                               i
         • Norman talks about what forces work
           against evolutionary, or natural design
           (pp. 142-143).
               – The demands of time (quick product cycles)
               – The pressure to be distinctive (related to the
                 curse of individuality)




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  70
              Typewriter - Case History                                                           i
         • Note the important design lesson on p.
           150.
         • To wit: Once a satisfactory product has
           been achieved, further changes may be
           counterproductive.
               – (What does that have to say about web site
                 design.)
         • Norman says you have to know when to
           stop.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  71
                                              Pitfalls                                            i
         •  Three reasons why designers go
            astray:
         1. Putting aesthetics first
         2. Designers aren’t typical users
         3. Designers’ clients may not be the users




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  72
                            Complexity of the Design
                                   Process
                                                                                                  i
         • Not a lot of meat in this chapter
         • Understand the concepts of
               – selective attention
               – the problem of focus
         • Understand the “two deadly temptations
           for the designer”
               – creeping featurism
               – worshipping false images (e.g., complexity)

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  73
                                        Finally . . .                                             i
         • . . . toward the end of the chapter (about
           p. 177) he starts getting into computer
           systems.

         • That’s a pointer to our final projects.




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  74
                                    Ch. 7 - UCD                                                   i
         • Chapter 7 is the “punch line” of the whole
           book.
         • User-Centered Design
         • Most of the chapter is given over to
           describing “seven principles for
           transforming difficult tasks into simple
           ones.”


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  75
                                       Principle 1                                                i
         • Use both knowledge in the world and
           knowledge in the head.

         • Here Norman refers to his distinction
           between the mental models of the
           designer and the user, and the
           relationship between these and the
           actual system.

R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  76
                                       Principle 2                                                i
      • Simplify the structure of tasks
      • Here Norman recalls our discussion of STM and LTM,
        and their different weaknesses. He also offers 4 “major
        technological approaches” that “can make the
        mappings more visible or, better, more natural.”
         – 1 Keep the task much the same, but provide mental
           aids.
         – 2 Use technology to make visible what would otherwise
           be invisible, thus providing feedback and the ability to
           keep control.
         – 3 Automate, but keep the task much the same.
         – 4 Change the nature of the task.
R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  77
                                              3, 4, 5                                             i
         • Principle 3 -- Make things visible: Bridge
           the Gulfs of Execution and Evaluation.

         • Principle 4 -- Get the mappings right.

         • Principle 5 -- Exploit the power of
           constraints, both natural and artificial.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  78
                                            6 and 7                                               i
         • Principle 6 -- Design for error. Assume
           that any error than can be made will be
           made.

         • Principle 7 -- When all else fails,
           standardize.



R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  79
                                                  Etc.                                            i
         • He goes on to offer a section on why you
           might want to design something to be
           hard to use ON PURPOSE.

         • And he ends with a few sections on
           writing, the home of the future, and a
           concluding section.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  80
                                           Now . . .                                              i

         • Let’s try to put it in Norman’s terms why
           the good designs were good and the bad
           designs were bad. (“Some important
           feature was, or was not, visible.”)




R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  81
                                       Next week                                                  i
         • We’ll talk about perceptual and cognitive
           psychology – a little about what we know
           about how human beings take in and
           process information.

         • White paper due in four weeks. Don’t
           forget to have your topic OK’d by me.


R. G. Bias | School of Information | SZB 562BB | Phone: 512 471 7046 | rbias@ischool.utexas.edu
                                                                                                  82

				
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