Effects of personality on body temperature and mental efficiency following transmeridian flight

Examination of the oral temperature rhythms in a group of young men after an eastward jet-flight across eight time-zones revealed a specific disruption in the rhythm that gradually disappeared over a period of some 10 d. In the first 2 d, the magnitude of the disruption in individual subjects was significantly correlated with the extent of mean postflight loss of speed in performing an arithmetic calculations test, given four times per day in local daytime hours. Within the group, neurotic introverts exhibited the greatest, and neurotic extroverts the least initial rhythm disruption; these two personality groups also showed opposing time-of-day trends in postflight changes in the performance measure. The results are discussed in relation to flight scheduling and to other studies of shifts in activity schedule; they are tentatively accounted for in terms of a postulated dimension of circadian rhythm lability that could be primarily related to extraversion.