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A Perceptual Control Theory Approach to Task Analysis

Denham Phipps University of Manchester Don Harris Cranfield University. A Perceptual Control Theory Approach to Task Analysis. What is studied in human factors?.

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A Perceptual Control Theory Approach to Task Analysis

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  1. Denham Phipps University of Manchester Don Harris Cranfield University A Perceptual Control Theory Approach to Task Analysis

  2. What is studied in human factors? • “The study of how humans accomplish work-related tasks in the context of human-machine system operation, and how behavioural and non-behavioural variables affect that accomplishment” (Meister, 1989, cited in Wickens, 1992, p.3)‏ • “[M]achines do not work alone. They work in environments. And so do the [people] who operate them…Our human requirements and our expectations of what a [person] can do in a system depend to a great extent on the kinds of environment into which the system is thrown…” (Chapanis et al., 1949, cited in Bogner, 1994, p.5)‏ • In other words… • How do people behave during work-related tasks? • How does a person’s behaviour relate to the environment in which he or she is situated?

  3. Goal (desired perception of the environment)‏ Gap between desired and actual perception ∑ Perception Behaviour P E R S O N E N V I R O N M E N T From a perceptual control theory point of view…

  4. Controlling the speed of a car • A driver wishes to maintain a speed of 60 mph • Desired perception – speedometer showing ‘60’ • Current perception – speedometer shows ‘45’ • Behaviour – press on accelerator • Current perception – speedometer shows ‘65’ • Behaviour – ease off accelerator • Current perception – speedometer shows ‘60’ • Behaviour – maintain pressure on accelerator

  5. What does PCT contribute to human factors? • Perceptual control theory: • Provides a framework for integrating cognitive and behavioural aspects of task activity • Is ‘actor-centric’ – based on the perception of the person conducting the task • Provides some account of environmental influences on behaviour • Is theoretically coherent

  6. What is task analysis? (Kirwan & Ainsworth, 1992) • A methodology for understanding human activity within a work system • Provides a systematic and descriptive account of what people do in order to achieve a task • It is fundamental to many human factors interventions • Well established; a variety of analysis methods has been established over the last four decades

  7. 0: Make a cup of tea Plan 0: Do 1-2-3-4. Wait for 1 min, then do 5. If tea is not satisfactory then repeat from 1. 1: Collect materials 2: Place teabags 3: Boil water 4: Pour water 5: Serve

  8. Task analysis • Burning issues in task analysis: • Physical tasks vs cognitive tasks • An integration between the two? • Socio-technical systems context • Taking account of environmental variables? • Ability to explain, predict and modify behaviour • Need for a sound theoretical basis? • So – a PCT-based approach to task analysis might be of use

  9. Hierarchical Goal Analysis (Hendy et al., 2002)‏ A cup of tea The components prepared The ingredients mixed The tea served … … The equipment gathered … The tea-bag in the cup or teapot … The water boiled

  10. Feedback Data Current State Goal State Cognitive Processing Behavioural Component • Location of: • water • sugar • milk • tea-bag • kettle • cups • State of water Water boiled or not boiled Tea-bag in cup or not in cup Equipment gathered or not gathered Water boiled Tea bag in cup Equipment gathered Visual info about the equipment Mental model of boiled water and a tea bag in a cup Place tea-bag Boil water Collect equipment Perceptual Task Analysis (Marken, 1999; Farrell & Chéry, 1998; Hendy et al., 2002)‏ Goal: “The components prepared”

  11. Goal (desired perception)‏ Actual perception  Gap Receive Communicate Actor 1 Actor 2 Communicate Receive  Gap Actual perception Goal (desired perception)‏ Layered Protocols (Farrell et al., 1999)‏

  12. E N V I R O N M E N T Layered Protocol Theory applied to HMI (Haakma, 1999)‏ User’s intention ‘Interpretive’ feedback ∑ ‘Expected' feedback Action selection Perception Behaviour P E R S O N

  13. Summary of PCT-based approaches • Similarity to existing task analysis approaches • Basis in PCT • Can account for a range of situations (including collaborative / interactive tasks)‏ • Empirical evidence? • Familiarity of PCT concept? • Definition of ‘goals’ and ‘plans’? An alternative idea – incorporate PCT into an existing method?

  14. What is PCHAT? • Perceptual Control Hierarchical Analysis of Tasks • Draws from: • Perceptual Control Theory • Hierarchical Task Analysis • Soft Systems Methodology (Checkland & Scholes, 1990)‏

  15. What is PCHAT? Five stages: • Identify the context of the task analysis • Define the task (‘CATWOE’)‏ • Create a model of the task • Validate the model • Implement model as a task analysis

  16. Task definition (CATWOE)‏ C – customers (tea-drinkers)‏ A – actors (person or machine making the tea)‏ T – transformation (ingredients > tea; need for tea > satisfied need)‏ W – 'world view' (making tea will satisfy the tea-drinkers)‏ O – owners (the company)‏ E – environment (company allows tea to be drunk; ingredients and equipment are available)‏

  17. Task diagram

  18. Tabular decomposition • Perceptual control loop • Current State (the possible perceptions)‏ • Goal State (the desired perception)‏ • Behavioural elements • Elements (what is used to create the perception)‏ • Critical Values (how the desired perception is identified)‏ • Operations (behaviours required)‏ • Plan (order and timing of operations)‏ • Cognitive elements • Senses (the senses used to create the perception)‏ • Cognitive Resources (relevant memory and knowledge)‏

  19. Evaluation study • Aim: provide evidence for the validity, reliability and usability of PCHAT • Objectives: • Train a group of participants to use PCHAT • Collect task analysis data from a simple task under laboratory conditions • Examine both the process and the output of the task analyses

  20. Methodological considerations • Task analysis data is qualitative – so how is reliability and validity assessed? • Content analysis (Patrick et al, 2000)‏ • Sensitivity index (Baber & Stanton, 1996)‏ • Sampling of participants • Representative of potential task analysts • Design of the task to be analysed

  21. Study design • Ten participants – all postgraduate students in Cranfield University’s School of Engineering • Two laboratory-based analyses – repeated measures, twelve day gap • Participants briefed on the PCHAT process • Video programming explained and demonstrated • Participants carried out task analysis at their own pace

  22. Analysis • Content analysis • Each analysis compared against experimenter's analysis • Reliability index • Calculated for each participant pairing (inter-rater)‏ • Calculated for each trial pairing (intra-rater)‏

  23. Results • Generally good levels of reliability (test-retest RI = 0.62; inter-rater RI = 0.52 & 0.54) – broadly comparable with other studies of task analysis (e.g. Stanton & Young, 1999)‏ • ‘Behavioural’ parts of template – 82% match with ‘model answer’ in first session; 90% match in second session • ‘Cognitive’ parts – 88% and 100% match • ‘Perceptual control’ parts – 64% and 92% match • Some parts of PCHAT worked better than others – less structured sections were most problematic • Possible for participants to understand the PCHAT method • So • Generally good performance using PCHAT • Some room for improvement in the structure and guidance

  24. Conclusions • Potential contribution of PCT to TA • Different ways of developing PCT approaches • Developing from scratch • Revision of existing TA approaches • Future work – refining and evaluating the approaches

  25. References (1)‏ Baber, C., & Stanton, N.A. (1996). Human error identification techniques applied to public technology: predictions compared with observed use. Applied Ergonomics, 27(2), 119-131. Bogner, M.S. (1994). Introduction. In M.S. Bogner (Ed.), Human Error in Medicine (pp. 1-11). Hove: Lawrence Erlbaum Associates. Checkland, P., & Scholes, J. (1990). Soft Systems Methodology in Action. Chichester: Wiley. Farrell, P.S.E., & Chéry, S. (1998). PTA: Perceptual control theory based task analysis. In Proceedings of the Human Factors and Ergonomics Society 42nd Annual Meeting, Chicago, 5-9 Oct (pp. 1314-1318). Santa Monica, CA: HFES. Farrell, P.S.E., Hollands, J.G., Taylor, M.M., & Gamble, H.D. (1999). Perceptual control and layered protocols in interface design: fundamental concepts. International Journal of Human-Computer Studies, 50, 489-520. Haakma, R. (1999). Towards explaining the behaviour of novice users. International Journal of Human-Computer Studies, 50, 557-570.

  26. References (2)‏ Hendy, K.C., Beevis, D., Lichacz, F., & Edwards, J.L. (2002). Analyzing the cognitive system from a perceptual control theory point of view. In M.D. McNeese & M.A. Vidulich (Eds.), Cognitive Systems Engineering in Military Aviation Environments: Avoiding cogminutia fragmentosa (pp. 201-252). Ohio: Human Systems Information Analysis Center. Kirwan, B., & Ainsworth, L. (1992). A Guide to Task Analysis. London: Taylor and Francis. Marken, R.S. (1999). PERCOLATe: Perceptual control analysis of tasks. International Journal of Human-Computer Studies, 50, 481-487. Patrick, J., Gregov, A., & Halliday, P. (2000). Analysing and training task analysis. Instructional Science, 28, 51-79. Wickens, C.D. (1992). Engineering Psychology and Human Performance. NY: HarperCollins.

  27. Thanks for listening! • Questions?

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