Spring 2007Human Performance 1H2 Dr. C. Baber 1 Human Performance 1H2 Chris Baber.

Spring 2007 Human Performance 1H2Dr. C. Baber

1

Human Performance

1H2

Chris Baber


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Assessment

• Course-work (50%)– ONE lab report (45%)

• 2500 words• to be handed in THURSDAY week 11• to describe data collection and apply principles

from lectures

– Attendance of sessions (5%)

• Examination (50%)– 2 questions from 3– 1½ hours


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Module Objectives

• Relate cognitive psychology to human-centred system design;

• Employ basic concepts from cognitive psychology;

• Describe the use of products in terms of the requisite cognitive activities.


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Reading ListNorman, D.A.

The Design of Everyday ThingsNew York: Basic Books, 1990

http://www.baddesigns.com/index.shtml

Noyes, J.M. and Baber, C. User-Centred Design of SystemsBerlin: Springer-Verlag, 1999

Smyth, M.M. et al. Cognition in ActionLondon: LEA, 1987

Matthews, G., Davies, D.R., Westerman, S.J. and Stammers, R.B.,Human PerformanceLondon: Psychology Press, 2000

Wickens, C.D.Engineering Psychology and Human Performance,New York: Harper Collins, 1992




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Assumptions

• Much of everyday behaviour is “automatic”– Requires little conscious control– Involves learned routines– Involves expectation (based on

previous experience)– Is error-free (or at least, error-

recoverable)– Is ‘skilled’ (i.e., well-practised)


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Seven Stage Action Model[Norman, 1990]

Form intentionDevelop plan

Perform action

Object in world

Evaluate against goalInterpret object

Perceive state of object

GOAL OF PERSON


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Key point # 1

A ‘User model for designers’ assumes that people actively seek information from the environment and develop expectations of how things work; these expectations influence the ways in which people seek information.


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Key Point #2

• Human Behaviour (as far as this lecture course is concerned) can be defined in terms of:– Conscious, rational activity, such as

problem solving– Pre-conscious, ‘automatic’ activity,

such as schema-driven behaviour


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Key Point # 3

• Problem Solving involves– Framing

• Through representation• Through changing states• Through analogy

– Recognition of ‘affordances’ in the problem space


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Problem Solving• A problem is something that doesn’t solve easily

• A problem doesn’t solve easily because:– you don’t have the necessary knowledge or,– you have misrepresented part of the problem

• If at first you don’t succeed, try something else

• Tackle one part of the problem and other parts may fall into place


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Describing Problem Solving

• Move from Initial State to Goal State through Intervening States (problem space)

• More than one solution• ‘Correct’ solution limited by

boundary conditions• Active involvement and testing

– Means-Ends Analysis


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Keypoint # 4

• In order to learn the correct representation, it is necessary to undo the incorrect representation

• This means that acquiring new knowledge might mean effortfully removing erroneous, old knowledge


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Key point # 5

PERCEPTION involves a set of active processes that impose:

STRUCTURE, STABILITY,

and MEANING on the world


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Key point # 6

• Perception limits are set by sensory / neural mechanisms; but beyond these limits, perception can be cognitively controlled;

• Sensory experiences interpreted in a CONTEXT and derive from a variety of sources


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Automaticity

• Norman and Shallice (1980)• Fully automatic processing controlled by

SCHEMATA

• Partially automatic processing controlled by either Contention Scheduling

• Supervisory Attentional System (SAS)


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Supervisory Attentional System Model

Perceptual System

SupervisoryAttentional

System

Effector System

Contentionscheduling

Triggerdatabase

Control schema


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Contention Scheduling• Gear changing when driving involves many

routine activities but is performed ‘automatically’ – without conscious awareness

• When routines clash, relative importance is used to determine which to perform – Contention Scheduling

• e.g., right foot on brake or clutch


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SAS activation

• Driving on roundabouts in France– Inhibit ‘look right’; Activate ‘look left’– SAS to over-ride habitual actions

• SAS active when:• Danger, Choice of response, Novelty etc.


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Attentional Slips and Lapses

• Habitual actions become automatic• SAS inhibits habit• Perserveration

• When SAS does not inhibit and habit proceeds

• Distraction• Irrelevant objects attract attention• Utilisation behaviour: patients with frontal lobe

damage will reach for object close to hand even when told not to


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Key point # 7

• The design of displayed information INFLUENCES how the user can use that information;

• The design of displayed information should support EXTRACTION of relevant information


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Density and Clutter

• Density is related to available screen space– E.g 80 x 24 line display = 1920

character spaces• The proportion of filled spaces =

Density• Density averages 25% but rarely

exceeds 50%


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Levels of Density

70% density 50% density 30% density

Shneiderman, 1992


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Reducing DensityGrouping / tabulating; Reduce number of words; Reduce number of characters


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Conclusions

• Understanding basic Gestalt principles helps manage focus

• Some objects on a display are more conspicuous than others– Use highlighting sparingly

• Some objects form ‘perceptual groups’ – Use this to help design screen layout and

to minimise risk of confusion


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Keypoint # 8

• Working memory is a volatile storage medium.

• Do not expect people to remember complex information, particularly if they are doing something else at the same time.

• Design information to keep within memory limits, e.g., no more than 9 items to a list

Spring 2007Human Performance 1H2 Dr. C. Baber 1 Human Performance 1H2 Chris Baber.

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