040 Human Performance and Limitations topic guide
Stress, Arousal and Performance
Arousal describes a state of physiological and psychological activation, and its relationship with performance follows an inverted-U shape. Too little arousal, boredom or under-load, degrades performance through inattention and slow reactions. Too much arousal, overload or approaching panic, degrades it through narrowed attention and rushed, incomplete decisions. Performance peaks somewhere between the two, and where exactly that peak sits shifts with the difficulty of the task being performed.
Stress is the broader response that arises when perceived demands exceed perceived coping resources. Acute stress is a short, situational spike, reacting to an unexpected system failure, for example, while chronic stress builds from sustained pressures such as finances, personal circumstances or a demanding roster, and it erodes the baseline capacity a person has left to cope with the next acute stressor. The physiological stress response itself includes a raised heart rate, adrenaline release and a narrowing of attention onto the perceived source of threat.
The inverted-U and where performance actually breaks down
Under-arousal shows up as missed cues, delayed reactions and a general disengagement from the task, typically on long, low-workload phases of flight such as a quiet cruise. Over-arousal shows up very differently: attention narrows onto a single perceived threat, peripheral cues and callouts are missed, and decision-making becomes rushed rather than considered.
The peak of the inverted-U is not fixed. A complex, unfamiliar task needs a comparatively lower level of arousal to perform at its best, while a simple, well-practised task can tolerate a comparatively higher level of arousal before performance suffers. Exam stems exploit this directly, varying the described task's difficulty to test whether the reader applies a single arousal threshold to every situation, which is the wrong model.
Acute versus chronic stress and the physiological response
The physiological stress response is driven by the sympathetic nervous system: heart rate rises, adrenaline is released, blood flow redirects toward major muscle groups, and attention narrows onto the perceived threat. This response is adaptive for a short, genuine emergency, which is what acute stress usually describes.
Chronic stress works differently. It accumulates from pressures that may have nothing to do with the flight itself, financial worry or a personal relationship, for example, and it reduces the reserve capacity available to cope with the next acute stressor that does occur in flight. This is why background, off-duty stress is examinable as a threat to in-flight performance even though its source sits entirely outside the cockpit.
Coping strategies examiners accept
Recognised, accepted strategies include structured task prioritisation, deliberately shedding non-essential workload when overloaded, clear communication and delegation through crew resource management, and protecting rest and recovery time before and after duty. Strategies the exam consistently rejects include suppressing or ignoring symptoms, self-medicating, working through overload alone without informing the other crew member, and relying on personal experience to override a workload that has genuinely exceeded capacity.
Worked example
Worked example: recognising overload
Not quite. The correct answer is B.
Correct answer: B
- A. This is the wrong end of the curve. Adding tasks to someone already narrowing their attention under pressure worsens overload rather than fixing disengagement.
- B. Correct. Tunnel vision on one instrument, missed callouts and a missed warning are the classic over-arousal pattern, and the safe response is to reduce demand and restore shared awareness.
- C. This imports a different syllabus topic. Nothing in the stem describes a sensory conflict from manoeuvring, only a narrowing of attention under workload.
- D. This misattributes an in-flight overload response to background chronic stress and wrongly claims the situation cannot be managed in the moment, when workload shedding and CRM are precisely the in-flight management tools available.
Step by step
- Match the described behaviour, tunnel vision on one instrument, missed callouts, and a missed warning, to the over-arousal side of the inverted-U rather than the under-arousal side.
- Under-arousal would look different: slow, delayed responses and missed cues from disengagement, not a narrowing onto one cue.
- The appropriate response to over-arousal is to reduce demand where possible and restore a shared scan, typically through the other crew member's callouts and CRM, not to add tasks or work through it alone.
- Illusions and chronic background stress are real syllabus topics, but nothing in the stem points to sensory conflict from manoeuvring or an off-duty stressor, so both are mismatched to the scenario described.
Common mistakes
Confusing under-arousal and over-arousal symptoms
Both degrade performance, but the correct fix is opposite for each: added stimulation helps boredom and worsens overload, so misreading which side of the curve a scenario describes leads straight to the reverse of the correct action.
Treating the optimum arousal point as fixed
The peak of the inverted-U shifts with task difficulty, and exam stems vary the described task precisely to test whether a single fixed threshold is wrongly applied to every situation.
Picking an unsafe coping strategy as if it were accepted practice
Suppressing symptoms, self-medicating, or pressing on alone without communicating overload are consistently the wrong answers to a best-response question, even when they sound decisive.
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Last reviewed July 2026