The Measurement of Circadian Rhythms in Psychological Functions

There is now a wealth of physiological evidence that man’s internal body chemistry changes predictably as a function of time of day. It is thus hardly surprising that there are equivalent predictable changes in his mood and performance efficiency, and it is to these psychological circadian rhythms that the present chapter is primarily addressed. In particular, it will be concerned with circadian performance rhythms, the history of their study, the methodological problems connected with measuring them, the forms of rhythms usually found, and the arousal model conventionally used to explain them. A final section is then concerned with some of the practicalities of measuring psychological rhythms, and the direction in which future developments might be expected to lead.