A Test of the Intellectual Cycle of the Popular Biorhythm Theory

ABSTRACT

We tested the existence of the intellectual cycle of the popular version of biorhythm theory (Gittelson, 1988; Thommen, 1976). The cognitive performance of some subjects (those in the experimental group, n = 24) was tested first during the low phase and later during the high phase of their intellectual biorhythm cycles. The cognitive performance of other subjects (those in the control group, n = 24) was tested twice at the mid-point of their intellectual cycles. Biorhythm theory predicts that subjects in the experimental group should improve more across testings than subjects in the control group. However, subjects' performance on reaction time, free recall, cued recall, and spatial visualization tasks failed to provide evidence for the intellectual biorhythm. Existing research on the popular version of biorhythm theory is conflicting, and the present findings suggest that if the intellectual biorhythm does exist it is not as strong an influence on cognition as proponents claim.