Psychophysiological reactions to understimulation and overstimulation

Catecholamine output, heart rate, and performance efficiency were examined in 28 Ss during two contrasting stimulus conditions, one of understimulation, and one of overstimulation. During understimulation the subject spent 3 hr performing a vigilance task, and during overstimulation he was exposed for the same time period to a complex sensorimotor test. Both understimulation and overstimulation produced a significant increase of adrenaline and noradrenaline release as compared with a control condition involving a medium amount of stimulation. Subjects who excreted relatively more adrenaline performed significantly better during understimulation, whereas subjects with relatively lower excretion rates of adrenaline tended to perform better under overstimulation. When performance efficiency was related to heart rate it was shown that high-heart rate subjects performed better during understimulation, while low-heart rate subjects performed better during overstimulation.