Impulsivity, Time of Day, and Stress: Effects on Intelligence Test Performance

Abstract

Interactive effects of impulsivity (Imp), time of day and time-pressure stress on two uncorrelated intelligence tests were studied in 192 femaleSs in India.Ss were tested under both low and high stress conditions in either the morning (8.00–10.00 a.m.) or the evening (6.30–8.30 p.m.). In general, the pattern of Imp × time of day × stress interactions for correct answers on both intelligence tests was consistent with the hypothesis of phase shift in the diurnal arousal cycles of low and high ImpSs: Low ImpSs outperformed high ImpSs with morning testing, and high ImpSs' performance was improved by stress-induced arousal with evening testing. Less consistent with the diurnal arousal hypothesis was the finding that low ImpSs showed better performance than high Imp subjects under stressful conditions, irrespective of time of day. These data point to the importance of diurnal arousal in the effects of impulsivity on intelligence test performance, but suggest that stress may lead to increased effort in individuals sensitive to aversive stimuli sufficient to abolish the deleterious effects of high arousal.