DAY-NIGHT DIFFERENCE IN THE PREFERRED AMBIENT-TEMPERATURE OF HUMAN-SUBJECTS

To investigate the existence of a day-night difference in thermal pref erence, 32 college students (16 male, 16 female) were asked to indicat e a threshold of discomfort in a climate-controlled environment. The e xperiment was performed at two distinct times of day that corresponded to the peaks and troughs of the subject's circadian rhythm of body te mperature. Males, but not females, felt comfortable at a higher ambien t temperature during the trough than during the peak of the body tempe rature rhythm. These data support the hypothesis (derived from animal studies) that behavioral thermoregulation opposes the circadian rhythm of body temperature.