MENTAL WORKLOAD ASSESSMENT

Learning objectives • Understand the difficulties in defining mental workload.

• Give an account of why the discussion of mental work load is useful

• Critically and comparatively evaluate the different ways of assessing mental workload.

• Have a range of examples of the measurement of mental workload in different real world setting of your choice.

WHAT IS MENTAL WORKLOAD?

• The mental stress and strain of being busy at work

• Excessive ‘mental workload’ often leads to errors

• Mental Workload’ is important in the operation of Safety critical systems

Workload as a construct

• Is it something we can measure.Is it like mass or someone’s temperature

• Is it an idea that can be used to summarise many other things ~ a short hand

• Is it something that links different issues?

• Is it a key idea in Orgnomics

Examples of ‘mental’ tasks

• Vigilance• Problem recognition and diagnosis• Planning and action• Prioritisation• Remembering to do things• Rapid integration• Coping with the unexpected

Mental workload in real life

• Not a new idea– Pilots– GPs– Design team

• These examples show different facets of mental workload

• What are the consequences of high mental workload in these situations

Workload as an organisational issue

• Training• Development• Management style• Equipment• Task organisation

Defining mental workload

• Not easy– A working definition might be ‘the real and

perceived increase in task difficulty caused by any factors that impair decision-making planning and reasoning and other mental tasks concerned with the job in hand’.

• Tautological• The importance of context

Generic measures of Mental workload

• Generic measures are poor as they ignore context.

• For example, same plane, same pilots, different routes.

• Workload is highly context dependent

FACTORS THAT IMPACT UPON OPERATOR ‘MENTAL WORKLOAD’?

• Skill levels• Operating rules and procedures• Operating conditions• Staffing levels• Task allocation• Organisational expectations

Measuring mental workload• Task analysis• Secondary tasks• Physiological correlates• Task performance over a busy time• Subjective ratings• Measuring mental workload over a

busy time

Classic task analysis• A decompositional analysis of operators

tasks• Advantages – anchored in context• Disadvantages – does not deal well with

high levels of task.

Quasi computational Metrics• Attempt to make generic measures.• NASA TLX is one example• Poor validity in real world situations• Advantages – the process is enlightening

even if the result is subjective and possibly misleading.

• Disadvantages – they do away with context which is the main thing.

A note on the mental workload literature

• Large and reef like (some of it is very pretty but much of it is dead!)

• The approaches have various faults, but the d to do away with context.

• Or a wish lists, sting the obvious and then failing to deal with a problem.

• Review them critically

Illustrative Bibliography• Bainbridge, L (1978) Forgotten alternatives in skill and workload. Changes in cognitive

processes with the development of skill, and the implications for mental workload.Ergonomics, 21, 169-185. Simultaneously published as: (1977)

• Bainbridge, L, (1974) Problems in the assessment of mental load)The adaptation of cognitive processes to task demands and mental capacity: some reasons for the lack of correlation between objective and subjective mental workload.Le Travail Humain, 37 (2), 279-302.

• Bainbridge, L (1989) Development of skill, reduction of workload. ()Described by title.In Bainbridge, L. and Ruiz Quintanilla, S.A. (eds.), Developing Skills with Information Technology, Wiley, pp. 87-116.

• Moray, N. Johansson, J. Pew, R. Rasmussen, J. Sanders. A.F., & Wickens, C.D. (1979) Mental Workload, It’s theory and measurement. New York. Plenum Press.

• O’Donnell. R.D, & Eggemeier, F.T., (1986) Workload Assessment methodology, In Boff, K., Kaufman, L., &Thomas, J., (eds) Handbook of perception and Human Performance, Vol II (pp42-1 pp 42-49. new Your, Wiley.

• Schvaneveldt, R.W., Gomez R.L, & Reid, G.B, Recent unpublished report from New Mexico and Arizona State Universities and Armstrong Laboratories, Wright Patterson AFB, http://interlinkinc.net/Roger/Papers/Workload.pdf

• de Waard, D, (1996), The Measurement of Drivers' Mental Workload ISBN 90-6807-308-7 Paperback, 198 pages Published by the Traffic Research Centre (now Centre for Environmental and Traffic Psychology), University of Groningen. http://www.home.zon.be/waard2/mwl.htm

An important thing to rememberWhich comes first?

• The definition?

• The method of measurement?The technical problem?

• The organisational problem?

• And how do these last to things differ or are they really the same.

• Are we interested in high work load only.

Driving a car.

• When learning to drive.

• Variation of familiar route while trying to have telephone conversation.

• Digital versus analogue speedometer.

• Car running badly in heavy traffic.

• Driving van through icy mountain roads.