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

Environmental Stressors Effect Stressor Health Input Indirect / IP Performance Light X Noise Vibration Motion Sickness Heat/Cold Air Quality 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. Yerkes-Dobson law ISE 412

Workload and Performance Yerkes-Dobson law Low arousal  ________________ Moderate arousal  ____________ Overarousal  _______________ Note optimal level of arousal (OLA) improvement in performance due to “trying harder” (e.g., threat of loss caused by psych stressor motivates one to work harder and perform better.) Effects of overarousal: attentional and/or cognitive tunneling (good if you are focusing on the correct solution, but bad if not) working memory loss long-term memory may be enhanced (tend to engage in the most available thoughts) some strategic shifts (e.g., “do something now”) ISE 412

Workload Overload Underload Measures Effects Remediation 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 Vigilance decrement Remediation Automation Task sharing Training (performance, task management) Reduce length of vigil, increase rest breaks Signal enhancement Increase level of arousal 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 ISE 412

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.” ISE 412

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? 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 ISE 412

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. ISE 412

Demand checklist Definition Relevant theories, etc. Good design Bad 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 ISE 412

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

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