Human Performance 1H2

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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 List

• Norman, D.A.
• The Design of Everyday Things
• New York Basic Books, 1990
• http//www.baddesigns.com/index.shtml
• Noyes, J.M. and Baber, C.
• User-Centred Design of Systems
• Berlin Springer-Verlag, 1999
• Smyth, M.M. et al.
• Cognition in Action
• London LEA, 1987

Matthews, G., Davies, D.R., Westerman, S.J. and
Stammers, R.B., Human Performance London
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 ModelNorman, 1990
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 doesnt solve easily
• A problem doesnt solve easily because
• you dont have the necessary knowledge or,
• you have misrepresented part of the problem
• If at first you dont 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
Supervisory Attentional System
Control schema
Trigger database
Perceptual System
Effector System
Contention scheduling
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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 Density
Grouping / 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