The term stress originates from physical science where it refers to the force placed upon an object to cause straining, bending, or breaking. In the human context and in psychology, however, stress is often used to describe the body's responses to demands placed upon it, whether these demands are favorable or unfavorable. Anything that causes stress is called a stressor. "The military personnel are suffering from occupational stress. A majority (60%) reported suffering from significant work stress. Almost half (42.5%) reported that work stress was a significant contributor to the onset of their mental illness"(1) The aviation environment is a high risk environment and rich in potential stressors such as temperature, acceleration, noise and communication, decompression sickness, vibration, hypoxia, exhaust fumes and motion sickness. Obviously, all these environmental stressors which affecting aviation pilots both civil and military have a negative affect on the safety of flight. For example, "in military aviation the problem of motion sickness is very real and has been responsible for failure during flying training of many hopeful aircrews" (2)
The central point to all these stressors is: the effects of stressors on performance which is somehow complex and varied. The relationship between stress and performance has been verified in many experiments and is explained by Yerkes-Dodson Law: 'Performance-Stress Relation curve'. It looks like an inverted "U". At zero arousal, that is when stress is virtually nonexistent and attention is minimal, as a consequence, the performance is zero or poor. An example of minimal stress is when someone is about to fall asleep. As stress increases, so does the level of attention, resulting in improved performance. At high level of stress, however, performance begins to deteriorate dramatically; and at maximum level of stress, that is at maximum arousal there is also zero performance-here incapacitation occurs by panic action. This is particularly true when one has to perform complex or unfamiliar tasks that require a high level of attention. The Yerkes-Dodson law has become subject of criticism as it fails to consider the effects of particular stressors encountered in aviation. "Based on a review of over 300 studies of aircrew stress, it is noted wide variations in the reported effects of particular stressors. Motivation, often considered a nuisance variable in such research, appeared to be critical and a further finding was that background anxiety (corresponding roughly to life stress) and mission anxiety seemed more likely to impair performance than stressors such as heat"(3).
It is agreed that life stress (both positive and negative) is an important factors which may have some affects on performance. Both major life events such as death of a spouse change in residence or changing job hours and minor life stressors like a social event or a vacation have a cumulative effect that makes total stress-adaptation level, vary from person to person. Life stress may be assessed by questionnaire methods; Schedule of Recent Experiences (SRE) is one of those methods which contain a list of 42 life events. Although, "it is noted several weaknesses in the SRE, such as its failure to distinguish between positive and negative life changes and to address individual differences in the...