Arousal and Workload

Arousal in its most general sense refers to readiness of a person for performing work. To achieve an optimum level of task performance, it is necessary to have a certain level of stimulation or arousal. This level of stimulation or arousal varies from person to person. There are people who are overloaded by having to do more than one task at a time; on the other hand there are people who appear to thrive on stress, being happy to take on more and more work or challenges.

At low levels of arousal, our attention mechanisms will not be particularly active and our performance capability will be low (complacency and boredom can result). At the other end of the curve, performance deteriorates when arousal becomes too high. To a certain extent, this is because we are forced to shed tasks and focus on key information only (called narrowing of attention). Best task performance occurs somewhere in the middle.

Training, preparation, familiarity and confidence will extend the point which the same demands cause excessive arousal. A trainee may show symptoms of over arousal in a circumstance where an experienced operator will remain composed.

In the workplace, arousal is mainly effected by stimulation due to work tasks. However, surrounding environmental factors such as noise may also influence the level of arousal.

Workload – Overload and Underload

A certain amount of stimulation is beneficial, but too much stimulation can lead to stress or over-commitment in terms of time. It is noteworthy that too little stimulation can also be a problem.

Factors Determining Workload

The tasks involved in operating an aircraft usually follow a fairly standard pattern and order, some of which is under the control of the flight crew, and some of which is outside their control. It is more difficult to assess how that work translates into workload.

As noted in the Module on information processing, humans have limited mental capacity to deal with information. We are also limited physically, in terms of visual acuity, strength, dexterity and so on. Thus, workload reflects the degree to which the demands of the work we have to do eats into our mental and physical capacities.

Workload is subjective (i.e. experienced differently by different people) and is affected by:

a) The nature of the task, such as the:

  1. Physical demands it requires (e.g. strength required, etc.);
  2. Mental demands it requires (e.g. complexity of decisions to be made, etc.).

b) The circumstances under which the task is performed, such as the:

  1. Standard of performance required (i.e. degree of accuracy);
  2. Time available to accomplish the task (and thus the speed at which the task must be carried out);
  3. Requirement to carry out the task at the same time as doing something else;
  4. Environmental factors existing at the time (e.g. extremes of temperature, etc.).

c) The person and his state, such as:

  1. Skills (both physical and mental);
  2. Experience (particularly familiarity with the task in question);
  3. Current health and fitness levels;
  4. Emotional state (e.g. stress level, mood, etc.).

As the workload of the flight crew may vary, they may experience periods of overload and underload. This is a particular feature of some flights and sectors, but overloads are often unpredictable.


Overload occurs at very high levels of workload, when the individual’s or crew’s workload exceeds the ability to cope well.

As highlighted previously, performance deteriorates when arousal becomes too high and we are forced to shed tasks and focus on key information. Error rates may also increase.

Overload can occur for a wide range of reasons based on the factors highlighted above. It may happen suddenly (e.g. if asked to remember one further piece of information whilst already trying to remember a large amount of data), or gradually. It is good practice to try to plan tasks such that the flight crew are not left with several things to be done at once, possibly during the final stages of the approach.

Task management between flight crew members can reduce the likelihood of one pilot being overloaded. It is particularly important to ensure that in overload situations, it is always clear as to who is carrying out the vital task of flying the aircraft.


Underload occurs at low levels of workload (when the pilot becomes under aroused).

Underload can result from a task a pilot finds boring, or indeed a lack of tasks. The nature of long-haul flights means that workload tends to come at the start and finish of a flight, with long periods of low workload in the cruise. Hence, unless stimulating “housekeeping” tasks can be found, underload can be difficult to avoid at times.