Ds. Owens et al., Diurnal variations in the mood and performance of highly practised young women living under strictly controlled conditions, BR J PSYCHO, 91, 2000, pp. 41-60
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.