MENTAL WORKLOAD ASSESSMENT

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MENTAL WORKLOAD ASSESSMENT
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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.

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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

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Workload as a construct

• Is it something we can measure.Is it like mass
  or someones 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

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Examples of mental tasks

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

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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

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Workload as an organisational issue

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

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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

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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

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FACTORS THAT IMPACT UPON OPERATOR MENTAL
WORKLOAD?

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

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Measuring mental workload

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

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Classic task analysis

• A decompositional analysis of operators tasks
• Advantages anchored in context
• Disadvantages does not deal well with high
  levels of task.

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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.

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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

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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, Its theory and measurement. New York.
  Plenum Press.
• ODonnell. 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

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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.

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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.