Arctic Cognition: A Study of Cognitive Performance in Summer and Winter

Evidence has accumulated over the past 15 years that aect in humans is cyclical. In winter there is a tendency to depression, with remission in summer, and this eect is stronger at higher latitudes. In order to determine whether human cognition is similarly rhythmical, this study investigated the cognitive processes of 100 participants living at 698N. Participants were tested in summer and winter on a range of cognitive tasks, including verbal memory, attention and simple reaction time tasks. The seasonally counterbalanced design and the very northerly latitude of this study provide optimal conditions for detecting impaired cognitive performance in winter, and the conclusion is negative: of five tasks with seasonal eects, four had disadvantages in summer. Like the menstrual cycle, the circannual cycle appears to influence mood but not cognition. Copyright # 1999 John Wiley & Sons, Ltd. There are three major astronomical cycles that have a period short enough to be important in the study of behaviour. The first is the 24-hour rotation of the Earth on its axis, the second is the monthly rotation of the moon about the Earth and the third is the 12-month orbit of the Earth around the Sun. While cognitive psychologists have studied the daily cycle using time-of-day as an experimental variable (e.g. Smith