Differences and interactions between stresses

This paper reviews a number of experiments in which different stresses have been applied to comparable subjects performing similar tasks. It is argued that, since the effects of the stresses are different, it is not legitimate to think of a single mechanism mediating reaction to stress. Experiments on the simultaneous application of two stresses show that the effects of heat appear to be independent of those of noise and sleeplessness, while the latter two conditions partially cancel each other. It is therefore argued that noise and sleeplessness affect the same mechanism in opposite directions, while heat affects some other mechanism. Tentatively, noise is regarded as over-arousing and lack of sleep as under-arousing.