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Biorhythms is a pseudoscientific belief that claims our daily lives are significantly affected by rhythmic cycles overlooked by scientists who study biological rhythms. Biochronometry is the scientific study of rhythmicity and biological cycles or "clocks," such as the circadian (from the Latin circa and dia; literally, "about a day"). Circadian rhythms are based upon such things as our sensitivity to light and darkness, which is related to our sleep/wakefulness patterns. Biorhythms is not based upon the scientific study of biological organisms. The cycles of biorhythm belief did not originate in scientific study, nor have they been supported by anything resembling a scientific study. The belief has been around for over one hundred years and there has yet to be a scientific journal that has published a single article supporting it. There have been some three dozen studies supporting biorhythms, but each of them suffers from methodological and statistical errors (Hines, 1998). An examination of some 134 biorhythm studies found that the belief is not valid (Hines, 1998). It is empirically testable and has been shown to be false. Terence Hines believes that this fact implies that biorhythms "can not properly be termed a pseudoscientific theory." I would agree on the grounds that biorhythms isn't a theory at all, but a set of beliefs. However, when the advocates of an empirically testable belief refuse to give up the belief in the face of overwhelming evidence against it, it seems reasonable to call the belief pseudoscientific. For, in fact, the adherents to such a belief have declared by their behavior that there is nothing that could falsify it, yet they continue to claim the belief is scientific.

The belief in biorhythms is based more on numerology, testimonials and the Forer effect, mass media hype, and intuition than on scientific study. The belief originated in the nineteenth century with Wilhelm Fliess, a Berlin physician, numerologist and good friend and patient of Sigmund Freud.1  Fleiss was fascinated by the fact that no matter what number he picked he could figure out a way to express it in a formula with relation to either 23, 28 or both.2   The latter number he associated with menstruation and thus when he was convinced that all the world is governed by 23 and 28, he called the 28-day period "female" and the 23-day period "male." In 1904, several years after Fliess's discovery, Dr. Hermann Swoboda of the University of Vienna, claimed he discovered these same periods on his own. In the 1920s, Alfred Teltscher, an Austrian engineering teacher, added the 'mind' period of 33 days, based upon his observation that his students' work followed a 33-day pattern. The belief was popularized in the 1970s by George Thommen (Is This Your Day? How Biorhythm Helps You Determine Your Life Cycles) and Bernard Gittleson (Biorhythm--A Personal Science). Neither book provides scientific evidence for biorhythms. They consist of little more than speculation and anecdotes. However, by now the static idea of periods was replaced with the dynamic notion of cycles, which are now known as the physical, emotional and intellectual cycles. Interestingly, not only did the "female" period become the emotional cycle, but both men and women are said to share the same physical and emotional cycles of 23 and 28 days respectively. One might have expected that, given the different hormonal natures of males and females, the sexes might have at least some unique and distinct rhythmic cycles.

New cycles have been added in recent years. There is the 38-day intuitional cycle, the 43-day aesthetic cycle, and the 53-day spiritual cycle. Others claim there are cycles that are combinations of the three primary cycles. The passion cycle is the physical joined with the emotional cycle. The wisdom cycle is the emotional joined with the intellectual cycle. And the mastery cycle is the intellectual joined with the physical cycle.

However many cycles there are, the function is the same: to predict what kind of day one is likely to have.

Generally speaking, the more positive a cycle is at any given point in time, the better one is able to interact in that arena. For example, high emotional level tends to mean that a person is more stable, is better able to make relationship decisions, and so on. This is not to say that when the cycle is in the negative range that the person is not doing well in that arena, rather, it means that it is harder to do well. --Plan exams when your Intellectual cycle is high. [Facade]

At the moment of birth, the biorhythmic cycles are set to zero. Knowing your birthday, the number of days you have lived and where in each cycle you are can be determined for any given day. A biorhythmic chart for July 24, 1998, for someone born four days earlier would look like this:

Biorhythm chart for a 4-day-old born on 7/20/98

babychart.gif (7000 bytes)

The line going through the middle is the zero line. A cycle is said to be in a positive phase when above the zero line and in a negative phase when below the zero line. A cycle begins in an ascent for the first fourth of a cycle, then half of the cycle is in descent, then the last quarter of the cycle ascends back to the zero line. The cycles repeat until you die. Should you live to be something like 58 years and 66 days old, you will reach the point at which the physical, emotional and intellectual cycles return to the same point on the zero line. For some, this is a moment of  "rebirth."

According to the belief, when certain points on the cycles are reached a person may enjoy special strength or suffer special weakness.  "Switch point days," when cycles cross the zero line on the ascent or descent, are "critical" days. Performance on critical days is supposedly very poor. It has even been predicted that people are especially accident prone on critical days. This empirical claim is easily testable. It has been tested and shown to be false. However, any cycle with an even number of days does not have an exact day in the middle, a fact which has led some "experts" to do some slippery math. For example, one "scientific study," said to support biorhythms, claims that something like 60% of all accidents occur on critical days but critical days make up only 22% of all days. If true, this statistic would not likely be due to chance and biorhythm advocates could justifiably claim their belief had been confirmed by this data. However, biorhythmists include both the day before and the day after a switch point day as "critical" days. Thus, an accurate statistic would be something like about 60% of all accidents occur on about 60% of all days, which is to be expected by chance (Hines).

In any case, according to the belief, critical days are days you want to know about in advance so you can prepare for them. For example, if you are scheduled to take a test that will measure your thinking ability, make sure you do not take the test on a day when your intellectual cycle is at a critical or a low point. Of course, to do well one must also get a good night's sleep, be generally healthy, eat properly, and study, but those preparations will do you no good if your intellectual cycle is not in the right spot. On the other hand, if you are a long distance runner, try to pick your next race date so that you are at a peak on your physical cycle. Of course, you must train properly, eat well, get sufficient rest, be healthy, etc., but these will not suffice if your physical cycle is at the wrong point.

The worst day of all, according to the classical (3-cycle) belief, is the "triple critical," the day when all three cycles are at a  switch point. Next worst is the "double critical", when two cycles meet at the switch point. As you can imagine, it gets very complicated tracing all these cycles on their ascents, descents, switch points, etc. But it does not take a mathematician to figure out that it is going to be easy to find cases that fit the belief. For example, the physical cycle is 23 days long. That means that every 11.5 days is a physical cycle switch over day. So, the odds of, say, having a heart attack on a given physical switch over day are about 1 in 11. Most people would agree that having a heart attack is having a bad physical day. One valid empirical test of the belief would be to collect data on heart attack victims and see if significantly more than 9% (1 out of 11) had their heart attacks on physical switch over days. Instead, the usual evidence given by believers is an anecdote about Clark Gable or someone else who had a heart attack on a switch over day. There are thousands of heart attack victims each year and 1 out of 11 of them would be predicted by chance to have the attack on a switch over day. So, finding several individual cases of people who have serious physical problems on a critical physical day is to be expected, not wowed at.

The ho-hum response that anecdotes such as the Clark Gable story should evoke from a reasonable person should put one to sleep when you consider that biorhythmists generally count the day before and after a critical day as being just as bad as critical days. This means that 6 out of every 23 days (26% of our days) are danger days for the body. Thus, the odds are about one in four that any given person who has a bad physical day is at a "critical" point. Anecdotes of people having bad physical days are particularly inconsequential given such odds. A meaningful test of the belief might be to study heart attack victims. If significantly greater than 25% of the sample have attacks on a critical days, then you have a scoop.

Another typical but useless test of the belief is to keep track of how accurate it is by charting each day and keeping a diary of your days. Actress Susan St. James, a fervid believer in biorhythms, once described on a television talk show how she had done this. If her chart predicted a low emotional day, she was upset that day. If her chart predicted a physical high, she felt great that day. On a day when her intellectual cycle was at a low, she couldn't think straight about anything. In some circles this is known as the self-fulfilling prophecy, the power of suggestion or subjective validation. Whatever you call it, it isn't science.

To demonstrate the folly of using subjective validation to count as support for biorhythms , James Randi had George Thommen, president of Biorhythm Computers, Inc., do a biorhythm chart for Randi and his secretary. One of the listeners to Randi's radio program was selected for an experiment. She was to be given her own personal chart and she was to keep a day-by-day diary for two months and to rate her chart for accuracy. She reported that the chart had been "at least ninety percent accurate." The devious Randi had actually sent her his own chart. He told the subject that he had done this by mistake. She agreed to check her diary with her real chart, which Randi gave her. She reported that the new chart was even more accurate than the other one. Actually, she'd been given Randi's secretary's chart. This kind of data retrofitting is common among believers in such pseudosciences as astrology, graphology and biorhythms. In fact, similar tests of subjective validation, with identical results, have been done on astrological charts and graphological readings. Randi's deception, of course, was not intended to disprove biorhythms, but to call attention to the problem of subjective validation, something consistently overlooked by devotees of astrology, graphology and biorhythms.

Biorhythms is a pseudoscience because there have been several meaningful tests of the belief, all failing to support it (Hines, 1991), yet its advocates refuse to give up the belief. Advocates of this belief have more ad hoc hypotheses to explain away disconfirming evidence than Galapagos has islands. My favorite is the hypothesis that some people are arrhythmic some or all of the time. Any contrary case can be explained away by reference to the case being arrhythmic. Another favorite ad hoc hypothesis concerns Thommen's claim that he could predict with 95% accuracy the sex of a child by the biorhythms of the mother. If, during conception, the mother's physical (masculine) cycle was at a high point, a boy was likely. If, during conception, the mother's emotional (female) cycle was at a high point, a girl was likely. A study done by W.S. Bainbridge, a professor of sociology at the University of Washington, concluded that using the biorhythms your chances of predicting the sex of the child were 50/50, the same as flipping a coin. A defender suggested to Bainbridge that the cases where the belief was wrong probably included many homosexuals, who have indeterminate sex identities!

When the anecdotes don't fit the belief, biorhythmists are likely to modify it. For example, one of the more common ways to defend the belief has been to point out that great feats occur when high in a cycle. Defenders commonly cite the example of Mark Spitz (born 2/10/50) being in a high physical and emotional phase when he won seven gold medals in the 1972 Olympics.

Biorhythm chart for Mark Spitz (9/5/72)

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Note how Spitz's emotional and physical cycles converged on September 5, the day of the Munich massacre. Coincidence? Not to inquiring minds. No doubt this is evidence of synchronicity. Note, too, that his intellectual cycle was very low during this period. Why not conclude that he did so well physically because his mind was inactive. Thus, he was not distracted by doing any serious thinking, a known hindrance to athletic performance. Of course, the simplest idea is that he did so well because he was a damn good swimmer! Those of a logical bent might use Occam's razor to reject biorhythms in favor of this simpler explanation.

However, Reggie Jackson, who was inaugurated into Baseball's Hall of Fame and was born on May 18, 1946, had the greatest day in his brilliant career on October 18, 1977. On that day he hit three consecutive home runs on three consecutive pitches off three different pitchers to help the New York Yankees win the game and the World Series against the Los Angeles Dodgers. Jackson's cycles were all in the low end of their negative phases on that day.

Biorhythm chart for Reggie Jackson (10/18/77)

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Russ Streiffert has an explanation: "Studies have shown that location in the graphic data may be less important than trend or which way your [sic] going. This is a dynamic interpretation as opposed to earlier views.  Briefly starting at the bottom of the graph we have increasing resource discharge (available)...then maximum discharge across the center line...then decreasing discharge approaching the top. Starting back down we have increasing  recharge (unavailable)...maximum recharge across the center line...then decreasing recharge approaching the bottom. In the graph above, notice how Mr. Jackson's resources appear charged (available) and synchronized on October 18, 1977. While this does not constitute proof that these cycles contributed to his achievements, it appears to be an excellent correlation and is certainly not  disproof. " The studies that have shown this are not cited by Mr. Streiffert.

So, when the data seems to conflict with what would be predicted by the belief, we are to engage in a new kind of interpretation. Reggie Jackson was not in a negative phase of all cycles; he was "charged and synchronized." We are to think in terms of recharging our energy as we ascend in a cycle, and discharging energy as we descend (or is it the other way around?). In this dynamic and energetic view, even days in the negative phase of a cycle can be good and days in the positive cycle can be bad and vice-versa, depending upon whether they are ascending or descending, charging or discharging, available or unavailable. Such constructions may make it impossible to refute biorhythms, but they render it untestable and so slippery as to be of little use for predicting the future. What was a pseudoscientific belief because its advocates continued to support it even though it failed all scientific empirical tests, is now a pseudoscience because it claims to be a scientific but it is not empirically testable. Everything can be made to fit the belief, even contrary readings such as those of Mark Spitz and Reggie Jackson, who deserve more credit for their accomplishments than biorhythms can provide.

See also rumpology.


1 Freud's letters to Fliess were preserved, much to Freud's dismay. They were first published in English as Origins of Psychoanalysis: Letters to Wilhelm Fliess Drafts and Notes, 1887-1902. Edited by Marie Bonaparte, Anna Freud and Ernst Kris, translation by Eric Mosbacher and James Strachey (London: Imago Pub. Co., 1954). A more recent translation by Jeffrey Moussaieff Masson is available: The Complete Letters of Sigmund Freud to Wilhelm Fliess, 1887-1904 (Cambridge, Mass.: Belknap Press of Harvard University Press, 1985). Fliess's masterpiece is entitled The Rhythm of Life: Foundations of an Exact Biology (Leipzig: 1906). There is a discussion of Freud, Fleiss and biorhythms in Frank Sulloway's Freud: Biologist of Mind (Cambridge, Mass:; Harvard University Press, 1993).

2 How did Fliess come up with his belief about the magic of the numbers 23 and 28?   Martin Gardner writes:

Fliess's basic formula can be written 23x + 28y, where x and y are positive or negative integers. On almost every page Fliess fits this formula to natural phenomena, ranging from the cell to the solar system....He did not realize that if any two positive integers that have no common divisor are substituted for 23 and 28 in his basic formula, it is possible to express any positive integer whatever. Little wonder that the formula could be so readily fitted to natural phenomena! [Gardner pp. 134-135]

further reading

books and articles

Gardner, Martin. Science: Good, Bad and Bogus (Buffalo, N.Y.: Prometheus Books, 1981), ch. 11, "Fliess, Freud, and Biorhythm."

Hines, Terence M. "Comprehensive Review of Biorhythm Theory," Psychological Reports, 1998, 83, 19-64.

Hines, Terence. "Biorhythm Theory: A Critical Review," in Paranormal Borderlands of Science,  ed.  Kendrick Frazier (Amherst, N.Y.: Prometheus Books, 1991).

Hines, Terence. Pseudoscience and the Paranormal: A Critical Examination of the Evidence (Buffalo, NY: Prometheus Books, 1990).

Randi, James. Flim-Flam! (Buffalo, New York: Prometheus Books,1988), ch. 8, "The Great Fliess Fleece."

websites (for entertainment purposes only!)

Biorhythmic chart generator

Facade biorhythm chart generator

Trusted Tarot Last updated 12-Sep-2014

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