IMPULSIVITY AND TIME OF DAY - EFFECTS ON PERFORMANCE AND COGNITIVE TEMPO

Previous research has suggested that high impulsive individuals perfor m better in the evening than in the morning because of differential va riations in diurnal arousal rhythms. The current study was designed to determine if these findings could be replicated without external mani pulation of arousal level. Forty subjects (20 high impulsive and 20 lo w impulsive as classified by the Barratt impulsiveness scale) were tes ted twice, once between 8.00 and 10.00 a.m. and once between 6.00 and 8.00 p.m. A variety of performance and cognitive tempo measures were e mployed in the study. No significant interactions between level of imp ulsivity and time of day on performance were observed. However, the re sults did reveal a greater variability of performance and a faster cog nitive tempo in high impulsives as compared to low impulsives, a findi ng that is consistent with previous research. Time of day differences were also discovered on tasks requiring attention, with all subjects p erforming better in the evening on those tasks. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.