ABSTRACT
Compared to the physical scientist, at least at levels above the atom, researchers concerned with human performance measurement should get medals of bravery. Or at least, a great deal of sympathy.
— Webb (l)
I. Difficulties in Measuring Performance over Time: Methodological Issues
While the study of any circadian rhythm poses important methodological issues, this is especially true for performance rhythms. The major way in which perfor mance efficiency differs from most physiological measures is that there is usually a large practice or “ learning curve” effect. This means that performance effi ciency will be better on a given trial than on the trials preceding it. The practice effect is extremely difficult to completely eliminate. To illustrate this problem, Monk (2) presented the data from a subject studied by Elliot Weitzman and Janet Zimmerman for 6 months. This subject had to sort a pack of 96 playing cards into
* Current affiliation: University of Montreal, Montreal, Quebec, Canada.
