The relationship between morningness-eveningness, time-of-day, speed of information processing, and intelligence

Morningness-Eveningness refers to individual differences in circadian phase position of spontaneous sleep-wake rhythms and to subject alertness. There is some evidence indicating that performance on cognitive tasks may be influenced by Morningness-Eveningness and time-of-day. Given the potential importance of such a finding for the assessment of cognitive ability we conducted a study assessing the relationship between Morningness-Eveningness, time-of-day, and performance on the Multidimensional Aptitude Battery IQ (MAB-IQ) and Inspection Time (IT) task. Twenty male and 50 female participants classified according to their scores on the Morningness-Eveningness dimension (Horne & Ostberg, 1976) were administered the MAB and IT tasks in the morning (0900 h) and in the late afternoon (1500 h). No significant effect of time of testing, and Morningness-Eveningness was observed except for the Spatial subtest of the MAB. Morning Type-participants performed significantly worse in the morning session in Spatial subtest and better in the late afternoon session and Evening Type-participants performed significantly better in the morning than in the late afternoon session. These results do not support the hypothesis that there is a reliable relationship between Morningness-Eveningness, time-of-day and cognitive ability. (C) 2000 Elsevier Science Ltd. All rights reserved.