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Experience. Health. Direct (e.g., vibration). Stressors. Physiological arousal. Indirect. Direct (e.g., lighting, noise). Information Processing. Input. Performance. Stress, Workload, Accidents, & Errors. Figure 13.1 A representation of stress effects. (Wickens et al, pg.325).
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Experience Health Direct (e.g., vibration) Stressors Physiological arousal Indirect Direct (e.g., lighting, noise) Information Processing Input Performance Stress, Workload, Accidents, & Errors Figure 13.1 A representation of stress effects. (Wickens et al, pg.325)
Psychological Stressors • Fear, embarrassment, loss of esteem, etc. • Effects • Perceptual / attention narrowing or tunneling cognitive tunnel vision • working memory loss • strategic shifts, e.g., tendency to react too quickly • Effect depends on individual factors – • personality traits • level of experience • life stress - and on level of physiological arousal induced by the stressor. • Yerkes-Dobson law
Workload and Performance • Yerkes-Dobson law Low arousal ________________ Moderate arousal ____________ Overarousal _______________
Workload Measures • Time required / Time available (TR/TA) ratio • Based on task analysis • Percentage computed per time unit on task timeline • Useful predictor, but difficult to construct • Primary task measures • measure the influence of mental workload • Secondary task methods • measure the reserve capacity • Physiological measures • allow non-intrusive measures • Subjective measures • SWAT, TLX, etc. FUNCTIONAL MENTAL
An example using NASA TLX • Form two teams. Each team will follow the instructions given to you. • You have 1 minute to complete the task. • The team that comes closest to completing their task with the fewest errors will “win.”
Relative workload scores: • Enter your workload scores below: • What does this say about the relative workload of the two tasks? • What does this say about the subjective nature of the workload scores?
Sleep loss and desynchronization • Fatigue effects on performance • accident rates directly due to fatigue • performance on exams • effect on medical treatment, decision making, etc. • See figure 13.6, pg. 346 • Causes • deprivation • disruption • phase in circadian rhythms • desynchronization – shiftwork strategies • Remediation • get more sleep! • napping • sleep credits • sleep management
Your turn … • On the following pages you will find a checklist of variables that increase the effort demanded by a task. For each of the variables: • define the specific effect in your own word • identify relevant theories, experimental results, or principles from what we have learned so far this term • provide an example of good design • provide an example of bad design • Use the table on the following pages. The first row is filled in as an example.
