1. INF385P – Software Usability Engineering
Week 2 – Norman’s book and mental models

2. I’m gonna go fast because . . .
It ain’t rocket science.
You’ve already read the book.
I’d rather make you scramble to keep up than 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.

3. Chapter 1 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.

4. Good Design Well designed objects . . . Poorly 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.

5. Natural Signals 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?)

6. Mapping
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.

7. Good Design 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:

8. “First Principles”
“The following principles are fundamental to the design and implementation of effective interfaces, whether for traditional GUI environments or the web.”
Anticipation
Autonomy
Color Blindness
Consistency
Defaults
Efficiency of the user
Explorable Interfaces
Fitts’s Law
Human-Interface Objects
Latency Reduction
Learnability
Metaphors, Use of
Protect Users’ Work
Readability
Track State
Visible Interfaces

9. Affordance
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 failed.

10. Complex World Partly, the way the mind works.
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.

11. Principles of Design
Four principles of Design for Understandability and Usability.
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.

12. Principles of Design (cont’d.)
Make things visible.
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 is a good example.

13. Principles of Design (cont’d.)
The principle of feedback.
Feedback is sending back to the user information about what action actually has been done, what result has been accomplished.

14. The Paradox of Technology
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.

15. Chapter 2 -- Psy of Everyday Actions
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.

16. Models objects work events take place people behave
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.

17. Models (cont’d.) 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.

18. Blame guilt helplessness
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.

19. Explanation 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.

20. 7 Stages of Action
On p. 47 is a series of four figures that illustrate Norman’s view of the structure of action.
Actions have two major aspects:
Doing something (execution)
Checking (evaluation)

21. 7 Stages (cont’d.) Action is broken down into 7 stages:
Perceiving the state of the world
Interpreting the perception
Evaluating the interpretations
Setting a goal
Intention to act
Sequence of actions
Execution of actions

22. 7 Stages (cont’d.) 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.

23. Gulfs . . . 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.

24. Designing 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.

25. Designing (cont’d.)
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!

26. Chapter 3 - Knowledge in the Head and in the World
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.

27. Knowledge
Precise behavior can emerge from imprecise knowledge, because . . .
Information is in the world (e.g., signs).
Great precision is not required. (Not just one path to school.)
Natural constraints are present. (Didn’t have to worry about going UP as you drove to school.)
Cultural constraints are present (e.g., driving on the right).

28. Behavior
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.

29. In the world 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.

30. Knowledge OF and Knowledge HOW
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

31. Constraints
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.

32. Memory . . . 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.)

33. Memory Structure 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

34. Memory Structure (cont’d.)
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

35. 3 Categories of things remembered
Memory for arbitrary things, meaningful relationships, memory through explanation
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.

36. 3 Categories of things remembered (cont’d.)
Memory for meaningful relationships
Enabled by mental models
Interpretation is essential, but it is NOT understanding.

37. 3 Categories of things remembered (cont’d.)
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.

38. Memory . . . . . . 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.)

39. Reminding Rehearsal Notes to self
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.

40. In the World
Lots of products make it easier to put knowledge in the world.
Alarm clocks
Diaries
Calendars
Watches
PDAs

41. Natural Mappings . . .
. . . 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.

42. Tradeoff . . . . . . 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.

43. Ch. 4 -- Knowing what to do 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.

44. Design
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.”

45. Constraints - 4 Classes
Physical
Semantic
Cultural
Logical

46. Physical Constraints 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.)

47. Semantic Constraints
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!

48. Cultural Constraints 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.”

49. Logical Constraints
Logic dictates that all parts be used, and fit together.
Natural mappings work by providing logical constraints.

50. The Problem with Doors
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.

51. The Problem with Switches
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

52. The Problem with Switches (cont’d.)
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.

53. Visibility and Feedback
Visibility -- make relevant parts visible
Feedback -- give each action an immediate and obvious effect

54. Using Sound for Visibility
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.

55. Ch. 5 - To err is human 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”)

56. In terms of the 7 stages of action . . .
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.)

57. Slips
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.)

58. Types of Slips
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).

59. Modes 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.

60. Design Design lessons from the study of slips.
Don’t prevent errors by requiring confirmation.
Rather, eliminate irreversible errors.

61. Mistakes Mistakes as errors of thought. (Competence errors.)
Mistakes result from the choice of inappropriate goals.

62. Three Models of Human Cognition
Photo Album Theory. (BUZZZ. Thank you for playing.)
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.

63. Third Approach -- Connectionist
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.

64. Tasks 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.”

65. Tasks (cont’d.)
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?)

66. Conscious and Subconscious Behavior
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

67. Conscious Thought 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.

68. Designing for Error 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.

69. Ch. 6 -- The Design Challenge
Norman talks about what forces work against evolutionary, or natural design (pp ).
The demands of time (quick product cycles)
The pressure to be distinctive (related to the curse of individuality)

70. Typewriter - Case History
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.

71. Pitfalls Three reasons why designers go astray:
Putting aesthetics first
Designers aren’t typical users
Designers’ clients may not be the users

72. Complexity of the Design Process
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)

73. Finally . . .
. . . toward the end of the chapter (about p. 177) he starts getting into computer systems.
That’s a pointer to our final projects.

74. Ch. 7 - UCD 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.”

75. Principle 1 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.

76. Principle 2 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.

77. 3, 4, 5
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.

78. 6 and 7
Principle 6 -- Design for error. Assume that any error than can be made will be made.
Principle 7 -- When all else fails, standardize.

79. Etc.
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.

80. Next . . . your homework 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.

81. Now . . .
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.”)

82. Next week
We’ll talk about perceptual and cognitive psychology – a little about what we know about how human beings take in and process information.
Homework – good and bad WEB designs, to class next week.
White paper due in five weeks. Don’t forget to have your topic OK’d by me.