Mars effect

Mars effect
A Gauqelin diagram mapping incidence of birth time and latitude to the natal position of Mars relative to the ecliptic of the rotating earth, showing peaks just after its daily rising and culmination in mid-heaven (horizon and mid-heaven are marked by perpendicular lines). The orbit of Mars in the sky is represented by 12 sectors in the circle, 6 above the horizon and 6 below. The drawn line shows the purported higher birth incidence of sports champions in the key sectors 1 and 4 of Mars' orbit.

The Mars effect is a name often used to refer to a reported statistical correlation between athletic eminence and the position of the planet Mars relative to the horizon at time and place of birth. This controversial finding was first reported by the French psychologist and statistician Michel Gauquelin who, in his book L'influence des astres ("The Influence of the Stars", 1955), the first rigorous study of astrological claims,[1] suggested that a statistically significant number of sports champions were born just after the planet Mars rises or culminates. Gauqelin divided the plane of the ecliptic into twelve sectors, identifying two "key" sectors of statistical significance.

Gauquelin's work was accepted by the notable psychologist and statistician Hans Eysenck among others[2] but later attempts to validate the data and replicate the effect have produced uneven results, chiefly owing to disagreements over the selection and analysis of the data set. Since the phenomenon in question depends upon the daily rotation of the Earth, the availability and accuracy of time and place of birth data is crucial to such studies, as is the criterion of "eminence". Later research explains the Mars effect by selection bias, favouring champions who were born in a key sector of Mars and rejecting those who were not from the sample.[3][4]


Reception and replication

Gauquelin's work was not limited to the Mars effect: his calculations led him first to reject most of the conventions of natal astrology as it is practised in the modern west but he singled out "highly significant statistical correlations between planetary positions and the birth times of eminently successful people." This claim concerned not only Mars but five planets, correlated with eminence in fields broadly compatible with the traditional "planetary rulerships" of astrology. However, partly because eminence in sport is more quantifiable, later research, publicity and controversy has tended to single out the "Mars effect".

Belgian athletes – the Comité Para

In 1956 Gauqelin invited the Belgian Para Committee (Comité Para) to review his findings but it was not until 1962 that Jean Dath corroborated the statistics Gauqelin had presented and suggested an attempt at duplication using Belgian athletes. By this time Gauqelin had published Les Hommes et Les Astres (Men and the Stars, 1960), offering further data. The Comité Para tested the Mars effect in 1967 and replicated it, though most of the data (473 of 535) were still collected by Gauquelin himself. The committee, suspecting that the results might have been an artifact, withheld its findings for a further eight years, then cited unspecified “demographic errors” in its findings. Unpublished internal analyses contradicted this and one committee member, Luc de Marré, resigned in protest.[5] In 1983 Abell, Kurtz and Zelen (see below) published a reappraisal, rejecting the idea of demographic errors, saying, “Gauquelin adequately allowed for demographic and astronomical factors in predicting the expected distribution of Mars sectors for birth times in the general population.”[6]

The Zelen test

In 1975 Paul Kurtz's journal The Humanist published an article on astrology criticizing Gauquelin, to which the latter and his wife Françoise responded. Then Professor Marvin Zelen, a statistician and associate of the recently founded Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP, now known as the Committee for Skeptical Inquiry (CSI)), proposed in a 1976 article in the same periodical that, in order to eliminate any demographic anomaly, Gauquelin randomly pick 100 athletes from his data-set of 2,088 and check the birth/planet correlations of a sample of babies born at the same times and places in order to establish a control group, giving the base-rate (chance) expectation for comparison (The 100 random athletes later expanded into a subsample of 303 athletes).

In April 1977 CSICOP researcher George O. Abell wrote to Kurtz stating that Zelen's test had come out in the Gauquelins' favour. The Gauquelins also performed the test that Professor Zelen had proposed and carried out and found that the chance Mars-in-key-sector expectation for the general population (i.e., non-champions) was about 17%, significantly less than the 22% observed for athletic champions. However the subsequent article by Zelen, Abell and Kurtz did not clearly state this outcome but rather questioned the original data. In a rebuttal of the Gauquelins' published conclusion, Marvin Zelen analysed the composition, not of the 17,000 non-champions of the control group, but of the 303 champions, splitting this secondary subsample (which was already nearly too small to test 22% vs 17%) by eliminating female athletes, a subgroup that gave the results most favourable to Gauquelin, and dividing the remaining athletes into city/rural sections and Parisian/non-Parisian sections.

Before and after publication of Zelen's results astronomer and charter CSICOP member Dennis Rawlins, the CSICOP Council's only astronomer at the time, repeatedly objected to the procedure and to CSICOP's subsequent reportage of it. Rawlins privately urged that the Gauquelins' results were valid and the “Zelen test” could only uphold this and that Zelen had diverted from the original purpose of the control test, which was to check the base rate of births with Mars in the "key" sectors. It appeared to him that the test had minimised the significance of the Mars/key-sector correlations with athletes by splitting the sample of athletes and that the experimenters, who were supposed to be upholding scientific standards, were actually distorting and manipulating evidence to conceal the result of an ill-considered test.

The Kurtz-Zelen-Abell analysis had split the sample primarily to examine the randomness of the 303 selected champions, the non-randomness of which Rawlins demonstrated in 1975 and 1977. Zelen's 1976 "Challenge to Gauquelin" had stated: "We now have an objective way for unambiguous corroboration or disconfirmation .... to settle this question", whereas this aim was now disputed. Rawlins made procedural objections, stating; "... we find an inverse correlation between size and deviation in the Mars-athletes subsamples (that is, the smaller the subsample, the larger the success) — which is what one would expect if bias had infected the blocking off of the sizes of the subsamples".[7]

CSICOP also contended, after reviewing the results, that the Gauquelins had not chosen randomly. They had had difficulty finding sufficient same-week and same-village births to compare with champions born in rural areas and so had chosen only champions born in larger cities. The Gauquelins' original total list of about 2,088 champions had included 42 Parisians and their subsample of 303 athletes also included 42 Parisians. Further, Paris is divided into 20 arrondissements, different economic classes and ethnic groups typically inhabiting different arrondissements. The Gauquelins had compared the 42 Parisian champions (who had been born throughout Paris) to non-champions of only one arrondissement. If the 22% correlation was an artifact partly based on factors such as rural recordkeeping, economic, class or ethnic differences in birth patterns, this fact would be blurred by this non-random selection.

Such elaborate post-test public diversions appeared to mask CSICOP's results. The matter led to a bitter and protracted dispute within CSICOP between Rawlins, Zelen, Kurtz, Abell and Richard Kammann.[8][9] Rawlins was shortly ejected from CSICOP at an unannounced and still obscure "election".

U.S. athletes – CSICOP

At the same time CSICOP began a study of U.S. athletes in consultation with Zelen, Abell and Rawlins. The results, published in 1979[10] showed a negative result. However it emerged that several procedures had contradicted Gauquelin's definition of the effect. His previous experiments had demonstrated that basketball was a sport where there was little or no Mars effect and he therefore suggested that no basketball players be used in the study; yet, 32% of CSICOP's athletes were basketball players.[11] According to Gauquelin, "It is Kurtz himself who pointed out to me at our meeting in Buffalo that in my original sample basketball shows the lowest effect among other sports specialties. I was aware of this, of course, and I suggested to Kurtz it would be preferable to avoid basketball in case of a new test in the USA. This would give a better chance to replicate the Mars effect. But Kurtz did exactly the contrary... He chose for his test an entire Who's Who in Basketball."[12] Gauquelin also contended the KZA group clearly demonstrated an overall preference for mediocre athletes and ignored his criteria of eminence. The Lincoln Library of Sports Champions had been discarded as a source for birth data of outstanding athletes when its "yield strongly supported Gauquelin's hypothesis."[13][14] Furthermore, 8% of CSICOP's sportsmen were born after 1950, contrary to the advice of Dr. Gauquelin who saw the Mars effect disappear in top athletes born after that year[15] (Gauquelin thought this was due to Caesarean sections, forceps assisted births and drug induced births, which began to rise dramatically from the middle of the 20th century and altered the "natural" time of birth).

Ertel and Müller

In 1986 Arno Müller, a clinical psychologist, graphologist and astrologer, and Dr. Suitbert Ertel, a professor of psychology, published their investigation of the Gauquelins’ work.[16] Müller had replicated the Mars effect (but not that of Saturn) for prominent German physicians (also predicted by Gauqelin) while Ertel presented an overview of Gauquelin’s work, with analysis of some of Gauquelin’s data.

It had been suggested that the Gauquelins might have selected their athletes knowing in advance they had Mars rising or culminating. Ertel indeed discovered a "Gauquelin bias" and sought to solve the problem of determining eminence by noting the number of times an athlete was mentioned in various sport periodicals, biographical dictionaries and sports encyclopedias. Ertel's use of this new standard suggested that Gauquelin bias actually masked the Mars Effect. According to Kenneth Irving, "...when the bias was corrected the Mars effect appeared even stronger than before.[17]

In 1988 Ertel’s investigation was published in The Journal of Scientific Exploration and the next year Müller published a new analysis of 402 Italian writers that failed to replicate Gauquelin’s results showing a significant correlation with the position of the Moon but reported significant correlations for Jupiter together with the significant negative result for Saturn previously noted by Gauquelin with respect to journalists.[18]

In 1992 an article by Ertel in The Skeptical Inquirer used the methods of his 1988 JSE article to demonstrate that the Mars effect is present in CSICOP’s own data and Ertel later contacted Kurtz asking about the way the Zelen test had been conducted. "Who was responsible for increasing emphasis on basketball players and what are the reasons for their increasing numbers?" Receiving no response, Ertel sent him another brief note; "Dear Dr. Kurtz, I hope you understand that fairness, not malevolence, has been guiding my correspondence." Kurtz's secretary then responded that Kurtz was reluctant to pursue the Mars effect any further; "This is not due to any desire to conceal 'misconduct'; it is simply due to his reasonable desire to be left to his work and writing." "But," observed Ertel, "Michel Gauquelin's 'reasonable desire' to have his discovery acknowledged, not smoke-screened by representatives of science, and society's expectation that scientists reveal all secrets of nature without pre-selection should be allowed simultaneous consideration."[19]

CFEPP test

In 1994 the results of a major study undertaken by the Committee for the Study of Paranormal Phenomenon (Comité pour l’Étude des Phénomènes Paranormaux, or CFEPP) in France found no evidence whatsoever of a "Mars Effect" in the births of athletes.[20] The study had been proposed in 1982 and the Committee had agreed in advance to use the protocol upon which Gauquelin insisted. The CFEPP report was “leaked” to the Dutch newspaper Trouw.

In 1990 the CFEPP had issued a preliminary report on the study, which used 1,066 French sports champions, giving full data for the 1,066 as well as the names of 373 who fit the criteria but for whom birth times were unavailable, discussing methodology and listing data-selection criteria. In 1996 the report, with a commentary by J. W. Nienhuys and several letters from Gauquelin to the Committee, was published in book form as The Mars Effect – A French Test of Over 1,000 Sports Champions. The CFEPP maintained that its experiment showed no effect and concluded that the effect was attributable to bias in Gauquelin’s data selection, pointing to the suggestions made by Gauquelin to the Committee for changes in their list of athletes. [20]

Statistical explanation

Some researchers argued that Gauquelin did not adjust the statistical significance of the Mars Effect for multiple comparisons. Simplified and illustrative showcase argument is explained here: There are 10 celestial bodies and 12 sectors for them to be in. Furthermore, there are 132 combinations of sector pairs and thus 1320 different combinations of a planet with two sectors. There is about a 25% chance to find at least one such combination (of one planet and two sectors) for a random dataset of the same size as Gauquelin’s that would yield a result with apparent statistical significance like the one obtained by Gauquelin, as described in an article called "The Saturn-Mars Effect" published in Skeptic Magazine.[21] This implies that after adjusting for multiple comparisons, the Mars effect is no longer statistically significant even at the modest significance level of 0.05 and is probably a false positive.

According to Geoffrey Dean at eSkeptic Magazine, the skeptic's assertion that "the highest mean total is nonsignificantly different from the observed total for Mars in sectors 1 and 4" is falsified by the fact that "right from the start it was known that planetary effects (not just Mars effects) replicate—a point stressed in three of the references Panchin cites. Replication requires profession, planet and sectors to be specified in advance, so counting any planet in any two sectors for any profession is not relevant, especially when you assume that planets move independently (they don’t), that expectancies in each sector are equal (they aren’t), and that demography doesn’t matter (it does)." As of 2007 there are eight independent studies and nearly thirty of Guaqulin's that have successfully replicated The Mars Effect to the degree that results "could not be explained by artifacts of astronomy, demography, bias, data selection, or fraud".[1]

In the same issue of eSkeptic Magazine a reply was given. "To falsify the claim that the observed Mars Effect is an artifact induced by multiple-comparisons a single reference is sufficient. It must be a well-designed peer-reviewed study that would replicate the Mars Effect at a decent significance level involving a non-biased selection of eminent athletes (eminence being defined before the data is analyzed) and performed in a way that insures the complete independence of the athlete sample from the sample available at the time the Mars Effect was first described as eminent athletes being born more often under planet Mars in sectors 1 and 4". "...available studies allegedly replicating the Mars Effect fail to match some or all of the mentioned requirements. For example Geoffrey Dean states that the Mars Effect is supported by the 303 sports-champions CSICOP test. But these 303 sports-champions were a subsample randomly chosen from Gauquelin’s sample. One may call this is an independent study, but it is not a study performed on an independent sample. Such studies cannot be used to exclude errors introduced by multiple-comparisons". "While Geoffrey Dean claims that the Mars Effect can be replicated he mentions that Gauquelin failed to “observe a consistent Mars effect for sports champions born after 1950” – which seems to be an argument against the previous statement. However, this is in agreement with certain studies, such as the U.S. study performed by Paul Kurtz and colleagues that failed to replicate the Mars Effect".[2]

See also


  1. ^ I.W.Kelly, The Concepts of Modern Astrology: A Critique (University of Saskatchewan, online at
  2. ^ H.J. Eysenck & D.K.B. Nias, Astrology: Science or Superstition? Penguin Books (1982)
  3. ^ Jan Willem Nienhuys (1997). The Mars Effect in Retrospect, Skeptical Inquirer, vol 21 #6, Nov 1997, 24–29. available online
  4. ^ Paul Kurtz, Jan Willem Nienhuys, Ranjit Sandhu (1997). Is the "Mars Effect" Genuine? Journal of Scientific Exploration, Vol. 11 , No. 1, pp. 19–39. available online
  5. ^
  6. ^ The Skeptical Inquirer, 7(3), 77–82.
  7. ^ The Zetetic (Skeptical Inquirer) 2, no. 1, Fall/Winter 1977, p. 81
  8. ^ Dennis Rawlins (1979). Report on the U.S. Test of the Gauquelins, Skeptical Inquirer, Vol 4 #2, Winter 1979/80.
  9. ^ Richard Kamann and Marcello Truzzi, The True Disbelievers, a detailed account of internal events at CSICOP over the course of the Gauquelin 'Mars Effect' affair
  10. ^ Paul Kurtz, Marvin Zelen, and George O. Abell (1979). Results of the U.S. Test of the "Mars Effect" Are Negative, Skeptical Inquirer, Vol 4 #2, Winter 1979/80, 19–26
  11. ^ Kenneth Irving and Suitbert Ertel, The Tenacious Mars Effect, The Urania Trust, London: 1996, p. A2-18.
  12. ^ The Tenacious Mars Effect, p. SE-54
  13. ^ Michel Gauquelin and Françoise Gauquelin (1979). Star U.S. Sportsmen Display the Mars Effect, Skeptical Inquirer, Vol 4 #2, Winter 1979/80, 31–43.
  14. ^ The Tenacious Mars Effect, p. SE-26
  15. ^ The Tenacious Mars Effect, p. SE-27
  16. ^ Zeitschrift für Parapsychologie und Grenzgebiete der Psychologie, 28, 1/2 (pp. 87–135)
  17. ^ Kenneth Irving, The New Astrology in American Astrology, January 1995, p. 50.
  18. ^
  19. ^ The Tenacious Mars Effect, p. SE-56
  20. ^ a b Benski, et al. 1993, as published in The "Mars Effect": A French Test of Over 1,000 Sports Champions, Prometheus Books (1996). ISBN 0-87975-988-7. page ref:13, 15
  21. ^ Alexander Y. Panchin. The Saturn-Mars Effect. Skeptic Magazine Vol 16 #1, 2010

Further reading

  • George O. Abell, Paul Kurtz, and Marvin Zelen (1983). The Abell-Kurtz-Zelen "Mars Effect" Experiments: A Reappraisal, Skeptical Inquirer Vol 7 #3, Fall 1983, 77–82.
  • Michel Gauquelin (1991). Neo-Astrology: A Copernican Revolution, The Penguin Group, London, ISBN 0-14-019318-9
  • Paul Westran (05-09-2008). The Mars Effect as an artifact of Dynamic Astrology, Positive Astrology Article, Online Article
  • Paul Kurtz, Marvin Zelen, and George O. Abell (1979). Response to the Gauquelins, Skeptical Inquirer, Vol 4 #2, Winter 1979/80, 44–63.
  • Paul Kurtz, Jan Willem Nienhuys, and R. Sandhu (1997). Is the "Mars Effect" Genuine?, Journal of Scientific Exploration, vol 11, # 1, Spring 1997, 19–39.
  • Jan Willem Nienhuys (1997). The Mars Effect in Retrospect, Skeptical Inquirer, vol 21 #6, Nov 1997, 24–29. available online
  • John Anthony West (1973). The Case for Astrology, (Goes deeply into the Gauquelin controversy).

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