1 ISE 412 Stress, Workload, Accidents, & Errors Figure 13.1 A representation of stress effects. (Wickens, pg.325) Information Processing Stressors Experience Health Direct (e.g., vibration) Physiological arousal Indirect Direct (e.g., lighting, noise) Input Performance

2 ISE 412 Environmental Stressors Effect StressorHealthInputIndirect / IPPerformance LightXX NoiseXXXX VibrationXXX Motion Sickness X Heat/ColdXXXX Air QualityXXX

3 ISE 412 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. (see fig. 13.2, pg. 331) Performance Level of Arousal poor good low high

4 ISE 412 Workload OverloadUnderload Measures Time req’d / Time avail. (TR/TA) Primary task measure Secondary task measures Physiological Measures Subjective Measures TR/TA signal detection task performance Effects Fatigue Performance decrement Workload disassociation Future performance Fatigue Vigilance decrement Future performance Remediation Automation Task sharing Training (performance, task management) Reduce length of vigil, increase rest breaks Signal enhancement Increase level of arousal

5 ISE 412 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

6 ISE 412 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

7 ISE 412 Your turn … Table 13.1 (pg. 337) provides 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.

8 ISE 412 Demand checklist Definition Relevant theories, etc. Good designBad design Legibility How easy is it to see the data signal detection theory ATC screen in which incoming aircraft ‘stand out’ weather radar in which cloud cover obscures indicators of tornadoes, etc. Visual search demand Display organization Compatibility Consistency

9 ISE 412 Demand checklist (cont.) Definition Relevant theories, etc. Good designBad design Number of modes of operation Prediction requirements Mental rotation Working memory demand

10 ISE 412 Demand checklist (cont.) Definition Relevant theories, etc. Good designBad design Unprompted procedures S-R compatibility Feedback Precision of action S-R-K