The document discusses the concept of level of arousal, which refers to a person's alertness, situational awareness, vigilance, and ability to perform tasks effectively. It describes how performance is related to the optimal level of arousal, neither too low (e.g. fatigue) nor too high (e.g. panic). Factors like workload, task complexity, circadian rhythm, and stress can influence a person's level of arousal. Maintaining the optimal level through measures like fatigue management and stress reduction is important for peak performance.

1. 28/06/22 17.28
Level of Arousal | SKYbrary Aviation Safety
Page 1 of 5
https://skybrary.aero/articles/level-arousal
Level of Arousal
Definition
A person’s Level of Arousal can be described as a function of
alertness, situational awareness, vigilance, level of distraction, stress and
direction of attention. In effect, how ready a person is to perform
appropriate tasks in a timely and effective manner.
Extreme under-arousal is manifest by unconsciousness, possibly caused
by tiredness, fatigue, hypoxia, poisoning or other illnesses.
Extreme over-arousal can be manifest by a range of symptoms that will
be peculiar to the individual, the environment, the task and other factors.
Such symptoms may include: panic, aggression, submission, resignation,
withdrawal, irrational behaviour and mood swings, as well as
unconsciousness.
Somewhere in between the two extremes, a point of optimum-arousal,
which is appropriate and effective for the situation, will exist allowing for
optimum performance. At this point it seems that our mental capacity,
situational awareness, alertness, attention, vigilance, decision-making,
and actions are all heightened in sensitivity and execution – we are in the
zone.
Arousal and Performance
Our performance at work is also affected directly by the number,
complexity and intensity of stressors present and the amount of
subjective stress that we are experiencing. There is also a direct
relationship between stress and arousal. It is therefore useful to connect
levels of arousal with levels of stress. The Yerkes-Dodson Stress Curve is
a simplification that can help to explain the relationship between arousal

2. 28/06/22 17.28
Level of Arousal | SKYbrary Aviation Safety
Page 2 of 5
https://skybrary.aero/articles/level-arousal
and performance.
Yerkes-Dodson Performance/Arousal Curve
At low levels of arousal, our performance level is also low. This may be a
well-balanced situation where we are relaxing and not expecting to
perform to any degree of skill nor exert any energy or brain-power.
However, when due to fatigue or lack of motivation the performance level
achieved does not match the performance level required, we are liable to
miss information, omit actions, to be less vigilant, scan insufficiently,
make mistakes and react much slower to changes. Two specific examples
of under-arousal are important enough to highlight here:
Habituation - this occurs when the sensory stimulation is constant
and unchanging (such as at high level in the cruise, or during a night
shift in ATC with low density traffic). Our sensitivity to input becomes

3. 28/06/22 17.28
Level of Arousal | SKYbrary Aviation Safety
Page 3 of 5
https://skybrary.aero/articles/level-arousal
much reduced.
Lacuna of Indecision - a peculiar situation that can arise following a
period of intense stress, arousal and activity, after which we
effectively go into a "shut-down" condition and are unable to
motivate ourselves to make any decisions or take any action.
Perhaps the most tragic example of this is a fatal accident at Riyadh
in 1980[1].
Some stressor(s) are required to rouse us from a low level of arousal into
the optimum zone. Such stress is often referred to as eustress – or, good
stress. Eustress is less a description of the situation and stressors
present, but refers more to the motivational aspect of stress and an
ability to change our perception of the situation (from one of disinterest
at one end of the scale and from one of fear at the other) to interest and
engagement. It is a positive cognitive response to stress that is healthy,
or gives one a feeling of positive fulfilment[2]. It is in this portion of the
curve that we are more likely to perform effectively, making fewer errors,
better decisions and reacting quickly to changes.
When arousal is too high, perhaps due to overload, then once again we
start to make more errors, find it harder to be decisive and take longer to
react (if at all). One characteristic of over-arousal is our tendency to
narrow attention and focus, such that other information is ignored or just
not sensed. It is not always the most critical element that we dedicate full
attention to either, as we become incapable of assessing risk and
allocating priorities. We may sub-consciously put full attention only onto
a task that we know we can achieve easily! Ultimately we can breakdown
and fail to function all together.
Factors Affecting Level of Arousal
The factors that facilitate a person to perform at an optimal level are
variable and peculiar to the individual, however, certain elements are

4. 28/06/22 17.28
Level of Arousal | SKYbrary Aviation Safety
Page 4 of 5
https://skybrary.aero/articles/level-arousal
often common, such as:
workload
task complexity and difficulty
task familiarity and past experience
circadian rhythm (i.e. previous rest/duty cycles and the time of day
or night)
degree of associated risk if failure occurs
personal, and crew, motivation
the working environment
levels of personal stress
health
interpersonal relationships at work (cooperation and coordination)
Organisations, teams and individuals can take positive actions to facilitate
optimum performance, such as:
moderating and adapting the working environment
pre-planning and briefing to share workload
cross-monitoring and checking procedures
fatigue risk management systems
employee well-being programme (including stress management)
cultivating a professional safety culture
Related Articles
Attention
Decision Making
Fatigue
Fatigue Management: Guidance for Air Traffic Controllers and Air
Traffic Engineers
Stress
Vigilance in ATM

5. 28/06/22 17.28
Level of Arousal | SKYbrary Aviation Safety
Page 5 of 5
https://skybrary.aero/articles/level-arousal
Further Reading
Green, R, G., Muir, H., et al. 1996. Human Factors For Pilots. 2nd
Edition. Aldershot, England. Ashgate Publishing Limited.
Campbell, R, D., & Bagshaw, M. 1999. Human Performance and
Limitations in Aviation. 2nd Edition. Oxford, England. Blackwell
Science Limited.
Coping with long range flying. Recommendations for crew rest and
alertness., Airbus, Cabon, P., et al., Nov 1995.
References
1. ^ Accident Summary - L101, vicinity Riyadh Saudi Arabia, 1980
2. ^ Lazarus, R. S. 1966. Psychological Stress and the Coping Process.
New York, Toronto, London. McGraw-Hill Book Company.