Validity of Biorhythms for Predicting Death

Summary The theory of biorhythms, supported by some studies and contradicted by others, states that people's lives are affected by a physical, an emotional, and an intellectual cycle or rhythm. The present study used chi-square analyses to investigate the various possible combinations of critical and noncritical days and to test whether death tends to be more prevalent on any particular day of a cycle. The sample consisted of 2,214 persons selected from Webster's American Biographies. No significant effects supportive of biorhythm theory were found.