Human Overload and Underload
What the domain covers
This domain covers workload: the inverted-U relationship between arousal and performance, overload and underload, and the difference between physical and mental workload. Candidates must understand that both too much and too little demand degrade performance, and that underload produces boredom, complacency and vigilance decrements.
Concepts to master
- Yerkes-Dodson: optimum arousal; too high causes narrowing of attention and errors; too low causes inattention.
- Overload: task shedding, prioritisation errors, tunnel vision, increased error rate.
- Underload: boredom, complacency, reduced monitoring, especially in automated cockpits.
- Automation complacency: over-trust in automation reduces vigilance; automation bias is accepting automated output without checking.
- Workload measurement: subjective ratings, secondary tasks, physiological measures.
Question traps
A frequent trap is assuming that automation always reduces workload; it can increase monitoring workload and induce complacency. Another is assuming that a quiet, low-workload phase is safe; it is often when vigilance failures occur. Also distinguish 'overload' from 'stress' - stress is a response, workload is a demand.
Worked example / rule of thumb
During a long, low-workload cruise, a pilot fails to notice a slow cabin-pressure drift. This is underload and complacency, not overload. Rule of thumb: if the task is monotonous and the error is one of omission, suspect underload; if the task is saturated and the error is one of prioritisation, suspect overload.