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

2. Spring 2007Human Performance 1H2 Dr. C. Baber 2 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

3. Spring 2007Human Performance 1H2 Dr. C. Baber 3 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.

4. Spring 2007Human Performance 1H2 Dr. C. Baber 4 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

5. Spring 2007Human Performance 1H2 Dr. C. Baber 5 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)

6. Spring 2007Human Performance 1H2 Dr. C. Baber 6 Seven Stage Action Model [Norman, 1990] Form intention Develop plan Perform action Object in world Evaluate against goal Interpret object Perceive state of object GOAL OF PERSON

7. Spring 2007Human Performance 1H2 Dr. C. Baber 7 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.

8. Spring 2007Human Performance 1H2 Dr. C. Baber 8 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

9. Spring 2007Human Performance 1H2 Dr. C. Baber 9 Key Point # 3 Problem Solving involves –Framing Through representation Through changing states Through analogy –Recognition of ‘affordances’ in the problem space

10. Spring 2007Human Performance 1H2 Dr. C. Baber 10 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

11. Spring 2007Human Performance 1H2 Dr. C. Baber 11 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

12. Spring 2007Human Performance 1H2 Dr. C. Baber 12 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

13. Spring 2007Human Performance 1H2 Dr. C. Baber 13 Key point # 5 PERCEPTION involves a set of active processes that impose: STRUCTURE, STABILITY, and MEANING on the world

14. Spring 2007Human Performance 1H2 Dr. C. Baber 14 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

15. Spring 2007Human Performance 1H2 Dr. C. Baber 15 Automaticity Norman and Shallice (1980) Fully automatic processing controlled by SCHEMATA Partially automatic processing controlled by either Contention Scheduling Supervisory Attentional System (SAS)

16. Spring 2007Human Performance 1H2 Dr. C. Baber 16 Supervisory Attentional System Model Perceptual System Supervisory Attentional System Effector System Contention scheduling Trigger database Control schema

17. Spring 2007Human Performance 1H2 Dr. C. Baber 17 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

18. Spring 2007Human Performance 1H2 Dr. C. Baber 18 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.

19. Spring 2007Human Performance 1H2 Dr. C. Baber 19 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

20. Spring 2007Human Performance 1H2 Dr. C. Baber 20 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

21. Spring 2007Human Performance 1H2 Dr. C. Baber 21 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%

22. Spring 2007Human Performance 1H2 Dr. C. Baber 22 Levels of Density 70% density 50% density 30% density Shneiderman, 1992

23. Spring 2007Human Performance 1H2 Dr. C. Baber 23 Reducing Density Grouping / tabulating; Reduce number of words; Reduce number of characters

24. Spring 2007Human Performance 1H2 Dr. C. Baber 24 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

25. Spring 2007Human Performance 1H2 Dr. C. Baber 25 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