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A biorhythm is one of three cyclic rhythms that are supposed by some to govern human behaviour.

The physical cycle lasts 23 days, the emotional cycle lasts 28 days and the intellectual cycle lasts 33 days. All three cycles are drawn, apparently arbitrarily, as sinusoidal curves that start with their minimum values at the birth of each individual. (This is one of its dubious assumptions.) Therefore the value of each cycle can be calculated at any given time in the life of an individual, and there are web sites that do exactly that.

The purpose of biorhythms is to enable the calculation of auspicious days for performing or avoiding various activities. By definition, one's birth is an extremely inauspicious event, as is the day about 58 years later when the three cycles are again synchronised at their minimum values! The theory is assumed to apply only to humans.


The theory is usually treated as harmless entertainment, in the same league as horoscopes, and therefore attracts little controversy. (Others consider all forms of pseudoscience harmful.) It does however have echoes of chronobiology, the study of circadian and other rhythms.


The theory may have originated from observations made by Dr. Hermann Swoboda, a psychologist, between 1897 and 1902, on periodic variations in fevers. His interpretation of his own results was influenced by the physician and numerologist Wilhelm Fliess[?]. These two men developed a theory of two cycles of 23 and 28 days. The 33-day cycle was added in the 1920s by German teacher Alfred Teltseher and American psychologist Dr. Rexford Hersey.

External links and references

  • Is This Your Day George S. Thommen (1973)
  • Biorhythm calculator (http://www.krstarica.com/eng/biorhythm/)
  • Gardner, Martin. Science: Good, Bad and Bogus (Buffalo, N.Y.: Prometheus Books, 1981), ch. 11, "Fliess, Freud, and Biorhythm." ISBN 0879755733

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