Diurnal variations in the mood and performance of highly practised young women living under strictly controlled conditions

The diurnal variation in a range of psychological functions and core body t emperature were investigated in a series of studies involving a total of 24 highly practised young women who lived in a controlled environment and on a strictly regimented 24-hour routine for 6 or 7 days. Ten participants wer e exposed to the natural light/dark cycle (L/Dc) through windows, whereas t he 14 remaining participants saw no daylight, but all had access to normal clock time. A battery of mood and performance tests was completed every 2 h ours whilst awake (08:00-00:00), resulting in nine equally spaced measures per waking day. Average time of day (ToD) functions were calculated from th e last 5 or 6 days spent in the controlled environment. Significant Too eff ects were found for many of the variables taken although the nature of thes e effects differed across measures, with a 'post-lunch dip' being observed at 16:00 in some variables. Analysis of the standardized data established t hat all variables presented reliably different ToD functions to core body t emperature, whilst factor analyses indicated possible relationships between the variables. It was concluded that those variables that exhibited diurna l variation showed trends that did not parallel those in core body temperat ure.