So there's a balance to be found — Page 129, Lesson 197

I want to walk you through the relationship between stress, arousal, and performance — because this is central to understanding how your own mind and body behave in the flight deck environment. We've already touched on the idea that a certain amount of mental stimulation is important for keeping us aware and vigilant. But here's the other side: too much stress will degrade the performance of both body and mind. So there's a balance to be found. Now, a critical point right away: we are all different. The stress level caused by a particular stressor — that is, anything that produces stress — will differ from one individual to another. The level will largely depend on the person's inborn and learnt characteristics. Your genetics and your life experience together shape how much stress you feel from a given situation. Stress is cumulative. This is a very practical concept for a pilot. If you are experiencing a minor irritation or stress, your stress level will increase disproportionately if another stressor is added — even though the original situation may have been resolved. Let me give you the example from the book: if a pilot has had an argument with a colleague on the ground, then flies and encounters a problem on the flight deck, his or her stress level will rise to a higher level than if the argument had not taken place. The first stressor doesn't just disappear; it leaves a residual effect that amplifies the next one. Experience helps ward off stress. The successful completion of a stressful task will reduce the amount of stress experienced when a similar situation arises in the future. So every time you handle a difficult situation well, you are building a buffer against future stress. In everyday life, too little stimulation may lead to mental unrest. The active man who retires from work frequently becomes bored and irritable; in some cases he may fail to adjust and so develop a chronic illness. So stress isn't just about overload — underload is also a problem. A reasonable level of stress in our life is beneficial. But a high stress level is associated with unpleasant psychological and physiological responses. The book lists them: sweating, dry mouth, difficulty in breathing, increased heart rate, anxiety or apprehension, fatigue, and fear. These are the signs your body gives you when stress is too high. Now let's look at the stress model. Stress arises from the evaluation individuals make of the demands which they perceive to be placed upon them, and the ability they perceive they have to cope with the demand. Notice the word 'perceive' appears twice. It is the person's evaluation of the demands imposed — rather than the actual demands — that will be used in his evaluation of the difficulty of the task. Equally, it is the perception of ability, rather than actual ability, that determines the amount of stress. So stress is not about objective reality; it is about your subjective assessment of the situation and your own resources. From Figure 7.1, you can see that the feedback mechanism is of great importance in determining the amount of stress experienced on subsequent performances of the task. Successful completion of a perceived difficult task will both reduce the perceived demand and increase the perceived ability — thus changing the original evaluation and reducing the stress. And vice versa: failure does the opposite. One of the features of stress is that an event which causes high stress in one individual may not have the same effect on another. It is also a fact that something which is stressful for an individual on one occasion may not be stressful at another time. Stress is subjective — it depends on the person and the moment. Now let's move to arousal and performance. Arousal can be defined as "the measure of the human being's readiness to respond". The relationship between arousal and performance is shown in Figure 7.2. At low arousal levels — such as just after waking or during extreme fatigue — the attentional mechanism is not very active, processing of sensory information is slow, and the nervous system is not operating at its best. So performance suffers when you are under-aroused. And as we've already seen, performance also suffers when you are over-aroused by too much stress. The sweet spot is a moderate level of arousal, where your readiness to respond is optimal.