Before Chapter 3…Chapter 2 (a bit more)• Norman’s Seven stages of of action – Form the goal– Form the intention– Specify the action – Execute the action– Perceive the state of the world– Interpret the state of the world– Evaluate the outcome

Before Chapter 3…Chapter 2 (a bit more)• Connects the seven stages of action to his principles of design:– Visibility– Good conceptual model– Good mappings– Feedback

• Which results in these heuristics ==>

Before Chapter 3…Chapter 2 (a bit more)

– Norman’s heuristics for good design– Norman says to ask this: – How easy is it to…

•Determine the function of the device•Tell what actions are possible•Determine the mapping of intention to physical movement•Perform the action•Tell if the system is in the desired state•Determine the mapping from the system state to interpretation

•Tell what state the system is in

DOET 3

Knowledge in the headKnowledge in the world

Question of the day…

• Norman claims that precise behavior is determined by:– Knowledge in the head– Knowledge in the world– and.. (what’s the third thing?)

Precise behavior

• The knowledge required for precise behavior is not all in the head… Why?– Information (lots of it!) is in the world

– Perfect knowledge is not required… only just enough to distinguish between the choices

– Natural constraints are present– Cultural constraints are present

Constraints on behavior

• Society has evolved artificial conventions that operate as cultural constraints.– While these have to be learned, once learned, they apply to a wide variety of circumstances.

– Example: Screws go in with a clockwise turn

• The physical properties of objects (natural constraints) constrain possible operations.– Things fit together in certain ways that exclude other choices

– Shape and size determines possibilities

Precise behavior

• Precise behavior is determined by the combination of:– Internal knowledge (knowledge in the head)

– External information (knowledge in the world)

– Constraints (natural and cultural)

The world(The environment)

• Provides constraints that shape behavior

• Can be organized to support behavior– Put the book you need to return against the front door

– Put your keys inside the thing that you must take home with you

Knowledge in the world

• Need not be memorized • BUT:

– Must be read and interpreted– Is more time consuming to access– Is only available when you are where it is

Knowledge in the world

• May not result in fluent behavior (example: typing)– Relying on the knowledge in the world (hunt and peck typing) will work but is slow

– Transfer that knowledge to the head (by learning what movements result in what letters) speeds performance

Interesting side effects:

Knowledge in the world;

Knowledge in the head• Typists cannot arrange keyboard keytops in their proper order.

• We cannot pick out which picture of the penny is accurate– Herb Simon’s Satisficing– We learn just enough to get the job done

Interesting side effects II:

• A chess master can memorize a chess board layout… but they are better than most ONLY if it is a layout that can be legitimately arrived at by following the rules

• Freshmen at Emory were surveyed the day after the first shuttle disaster and then again as they graduated. The more certain they were right, the greater chance they weren’t

Head vs World

• Herb Simon’s ant on the beach parable– The path that an ant takes as it crawls across the beach is complex.

– Where does this complex behavior come from?– Is it in the head of the ant? – Is it even possible for something as small as an ant’s head to contain such complexity?

– Is it the complexity of the beach being acted on by the simple ant?

Kinds of Knowledge

• Procedural knowledge– “Knowledge of how”– Hard to write down– Hard to teach (usually must be demonstrated)•Apprenticeship works well here

• Declarative knowledge– “Knowledge of”– Easy to write down– Easy to teach

Using a structured environment

• Physical arrangement in the world relays information about the relative importance of those items in the world.

• Visibility (or lack of visibility) also relay the relative importance of items.

• Placement can serve to enforce a particular sequence of events

• Placement can serve to enforce a particular timing of events

Precision required?• People store partial descriptions of objects in the world (models of those objects)

• The French coin example– It was different, but not different in ways that the public used to distinguish coin differences

Precision required?• These models are sufficient to solve the problems for which they were learned– Can differ from person to person– By definition these models are not complete– Sometimes they will work on future novel situations, sometimes they will fail

• Gives credence to the saying “to a man with a hammer, everything looks like a nail”

Monday!

Constraints

• Rhyming is a way of constraining possible choices, making “memorization” of easier.

• Combined with meaning, rhyming almost completely specifies the word choices

• Story tellers don’t memorize the story, they memorize the characters, the plot and the rhyming scheme and recreate the story each time. (They store a model of the story)

Structure of human memory

• Long term memory– Permanent– Unlimited– Takes work to access

•…you know that you know the answer but it doesn’t come to you until the next day

• Short term memory– Fleeting– Very limited– Immediately available

Wednesday

Long term memory

• One problem is organizational– You are trying to think of a name but you keep coming up with another name that you know is the wrong name

• Another is representational (the model used)

• Representational can be broken into categories– Memory for arbitrary things– Memory for meaningful relationships (the switch moves in the direction that the handlebar moves)

– Memory through explanation (the development and use of an internal model)

Memory for arbitrary things

• AKA Rote learning; has problems:– Difficult to do– Errors are not made evident by the sequence of actions because they are arbitrary

– People like structure (models) and manufacture them even when they do not exist (is this why acronyms work so well as a learning prop?)

– Reuse of these manufactured models results in inaccurate behavior

Memory for arbitrary things

• AKA Rote learning… the concept of “chunking”– Social security numbers and Phone numbers are broken into groups of 2, 3 and 4 numbers for a reason

– Which is easier to remember?– 4042245509

» or– 404 224 5509– 433600918

» or– 433 60 0918

Memory for meaningful relationships

• A sensible structure (natural mapping) simplifies memory task

• Motorcycle turn switch example which was solved by reinterpretation of the mapping– On left handlebar

•Forward is right •Back is left

– Reinterpret from “it’s on the left so forward is left to…

– “the switch movement maps to handlebar movement”

Memory through explanation

• People are explanatory creatures– We make stuff up just to help us remember– If asked, most people will give you an answer•sometimes what is NOT said is more important than what is said (subjects, dogs & religion)

• Mental models simplify learning because the details can be derived from an appropriate model

• Models are powerful when they are complete enough to allow them to be used to solve novel problems

Reminding

• Two aspects of reminding– The signal – The message

• Personal importance makes it more certain that you will remember to do something in the future (prospective memory)

• Place the reminding burden on the thing itself

Mappings and stoves

• Make the organization of the controls carry the information needed to successfully execute the behavior

• Hint: If labels are needed, the design may be faulty

Knowledge in the world;

Knowledge in the headSummary• Knowledge in the world

– Acts as its own reminder– Easier to learn– Harder to use– Relies on being in the environment

• Knowledge in the head – Is more efficient– May require extensive learning– May need external triggering

Concepts discussed thus far:

(An incomplete list to be expanded later)• You will need to know what these are and how to use them…

The End!