The behavioural effects of single and combined stressors: a test of arousal theory.

Arousal theory assumes that a single physiological dimension underlies the curvilinear (inverted-U) relation of behavioural efficiency to level of stimulation. Traditional tests of this assumption, which involved correlating different physiological measures of arousal, have produced equivocal results. The present study predicted that, if arousal is unitary, then stressors which separately induce it should be additive in their effects on behavioural efficiency. Although curvilinear changes in behavioural efficiency were found for white noise and shock separately, their combination failed to support the prediction.