Three hypothetical rhythms in human physiology for which there is no empirical evidence. This term is sometimes used as a contraction for ‘biological rhythms’ (see BIOLOGICAL CLOCK), referring to the extensively documented and well-understood CIRCADIAN RHYTHMS that pervade human physiology and other biological systems. This usage leads to great confusion and should be avoided. The concept of three biorhythms (physical, emotional and intellectual cycles with periods of 23, 28 and 33 days), evolved out of numerological musings in the late nineteenth century. These cycles are supposed to be initiated at birth and to express their periodicities stably throughout life. There is no empirical basis for the period lengths attributed to these cycles, although the supposed emotional cycle may have been influenced by the length of the human MENSTRUAL CYCLE. Their beating interactions are supposed to influence each individual's.strength, alertness, MOOD and performance, leading to so-called critical days, and best and worst days for different kinds of athletic and intellectual activities. Periodic interest in biorhythms has been prompted by the appearance of books claiming to predict good days and bad for various activities and, in the modern era, by the development of biorhythms computers.
There are several fatal difficulties with the biorhythms concept.
First, there are no empirical data supporting the existence of the three biorhythms. Second, there is no known physiological mechanism that can give rise to them. Third, empirical tests using records of athletic performances and accidents demonstrate that the calculated biorhythms for individuals have no predictive power. Fourth, studies purporting to demonstrate an influence of biorhythms are methodologically flawed and statistically incompetent. Finally, the concept that these rhythms are initiated at birth and progress throughout life with absolutely fixed periodicities is inherently absurd, given our knowledge of how real biological rhythms function. The sales tactics used for biorhythms books and computers include pointing to particular instances in which a calculated ‘triple-critical’ day for a pilot coincided with a plane crash. These illustrative examples seem to carry more weight with the public than do laboriously calculated statistical demonstrations that plane crashes and car accidents are randomly distributed with respect to the supposed biorhythms of those involved. The concept of biorhythms has more to do with astrology than with biology. By promising effortless predictions of our unknowable futures, astrology and biorhythms both seduce a gullible portion of the population to the profit of purveyors of pseudoscientific nonsense.
BENJAMIN RUSAK
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