between birth date and sign and personality would show greater correlation between sign and personality than those who didn’t. One hundred twenty-two subjects were divided into three groups: those who were knowledgeable about astrological claims about personality, those who had a “borderline” knowledge, and those who had no knowledge about the alleged relationships. Both the “no knowledge” and “borderline” groups showed no correlation between astrological sign and extroversion or introversion. However, “the knowledgeable group… showed a marked tendency to assess themselves in accordance with astrological predictions” (p. 56). Thus, the original Mayo, White, and Eysenck (1978) results were due to the subjects’ astrological knowledge, which was apparently extensive (Eysenck and Nias 1982). This knowledge biased at least some subjects in the way they reported their personality on the questionnaire. If a subject knew, for instance, that people born under Aries are supposed to be extroverted and he knew that he had been born under Aries, he reported a more extroverted personality. An earlier study by Delaney and Woodward (1974) also demonstrated such behavior. In this study, fifty-five high-school students read personality descriptions based on their birth dates. Half received descriptions that were consistent with traditional astrological teachings (“Aries are extroverted,” for example) and half received descriptions that were just the reverse (e.g., “Aries are introverted”). After reading the descriptions, they were asked to fill out a personality questionnaire. They were told that the purpose of the study was to “attempt to see if astrology has any real predictive value” and that the questionnaire was “concerned with your personality not the personality which was astrologically predicted” (p. 1214). The responses on the questionnaire were influenced by the descriptions of personality that had been read, whether or not those descriptions were those of classical astrology. That is, if a subject was an Aries and had read that Aries people are extroverted, the responses on the subject’s personality questionnaire showed a more extroverted personality. If an Aries was told that Aries people are introverted, the subject’s questionnaire responses showed a tendency toward introversion. In addition to showing that the original Mayo, White, and Eysenck results were not due to astrological influence, these studies further demonstrate how subtle uncontrolled experimental variables can produce results that look as if they support astrological influences. They further show the importance of conducting further studies to confirm the results and control previously uncontrolled variables.
Eysenck and Nias (1982) also failed to find any astrological influence on another major personality variable, emotionality versus stability, although subjects’ knowledge at first resulted in spurious correlations between astrological sign and this personality variable as well.
Another common claim made by astrologers is that a couple’s compatibility is determined, at least in large part, by their sun signs. That is, two people who have “compatible” sun signs will have a better chance of making a successful marriage than two people whose sun signs are “incompatible.” Several studies have shown that in fact sun signs have no influence on marriage or divorce (Dean 1977; Culver and Ianna 1984). In these studies one obtains the birth dates for divorced and nondivorced couples. If sun signs have any influence, pairs with incompatible sun signs should be overrepresented among divorced couples and underrepresented among nondivorced couples. The studies reviewed in these two references reveal no influence of sun signs on marriage or divorce rates.
Culver and Ianna (1984) have further pointed out that astrologers disagree widely on which sun signs are compatible. Figure 8, taken from Culver and Ianna (pp. 132–33), shows the sun signs that Righter (1977), King (1973), Norvell (1975), and Omarr (1972) consider compatible and incompatible. Inspection of the figure shows the great degree of disagreement among these four popular astrologers, each of whom claims validity for his system, but not on the basis of any real data. The lack of agreement among astrologers should not be seen as reducing the importance of the research findings on sun signs and rates of marriage and divorce. These studies show that no combination of sun signs was associated with marriages or divorces. In other words, these studies examined all possible relationships between sun sign and compatibility and found that in no case was there any relationship. They did not simply test the few specific predictions made by astrologers.
Carlson (1985) has performed an extremely thorough and well-designed study of astrological predictions. This study is unique in that the help and cooperation of the astrological “profession” was sought and obtained. “So that the participating astrologers should be respected by the astrological community, we sought the advice of the National Council for Geocosmic Research” (p. 420). Further, the astrologers involved agreed before the study was conducted that the procedures and design constituted a fair test of astrological predictions.
In the first part of the study, 177 subjects were recruited through newspaper ads. Based on their birth date, time, and place, their horoscopes were constructed and then interpreted by the astrologers associated with the study. Each subject was given an interpretation of three different horoscopes. One of the interpretations was of their own horoscope, while the other two were interpretations of horoscopes of two other randomly chosen participants in the study. If astrologers were able to divine personal information from a horoscope, then the subjects should have been able to choose the interpretation of their own horoscope over the interpretations of other individuals’ horoscopes at a rate better than chance.
In the second part of the study, 116 subjects took the California Psychological Inventory (CPI), a widely used test of personality in normal (nonpathological) individuals (Megargie 1972). The astrologers were then given one individual’s horoscope and the CPI personality profile of three subjects. One of the CPI profiles was that of the same subject whose horoscope was given to the astrologer. The astrologers’ task in this part of the study was to pick the CPI profile that matched the horoscope.
The results of both parts of the study provide no support for astrology. Subjects in the first part of the study were unable to pick the interpretation of their horoscope from the interpretation of two other individuals’ horoscopes at a rate above chance. In the second part of the study, the astrologers were not able to match the horoscope of an individual to his or her CPI personality profile at a rate higher than chance. Given two opportunities to provide impressive empirical support for the reality of astrological claims, in a test that respected astrologers agreed beforehand was fair, astrology failed.
Astrologers claim that numerous other personality traits—in addition to physical characteristics, occupation, and medical disorders—are influenced by one’s sun sign. Culver and Ianna (1984) have summarized several studies that examined these predictions. The predictions have been shown to be wrong. For example, of sixty different occupations studied, not one showed any influence of sun signs. That is, members of these sixty occupations were no more or less likely to be born under one sun sign than another. Among the occupations examined were those of actor, pilot, artist, astronomer, banker, baseball player, chemist, teacher, journalist, lawyer, doctor, opera singer, poet, politician, psychologist, and priest. Among the physical characteristics not related to sun sign were blood type, baldness, hair color, height, sex, handedness, and weight. Medical disorders found to be totally unrelated to sun sign included acne, allergies, diabetes, Down’s syndrome, heart attack, infant death, leukemia, lung cancer, multiple sclerosis, stillbirths, stroke, and muscular dystrophy. Age at death is also not related to sun sign. Finally, the following personality traits are not related to sun sign: aggression, ambition, creativity, feelings of inferiority, integrity, intelligence, leadership, self-expression, sociability, tough-mindedness, understanding, and wisdom. All these findings are in strong contrast to the empirically unsubstantiated claims of astrologers. Those claims can now be seen to be simply wrong.
There is more to astrology than sun signs, and the process of calculating a complete and accurate horoscope certainly takes considerable mathematical ability and training. Numerous variables in addition to the sun sign are said to influence the individual. Among these are planetary conjunctions, houses, ascendants, the relationship between the planets, and the planets’ positions in the various signs. Culver and Ianna (1984) have calculated that there are some 1035 possible astrological predictions. This huge number compares with only 1027 grains of sand on the earth. Some of the predictions involving factors more complicated than sun signs have been tested (Dean 1977; Culver and Ianna 1984; Dean 1986–87a, 1986–87b) but, again, these tests provide no support for astrological claims.
When confronted with the negative outcomes of numerous studies, astrologers sometimes argue that one cannot reject the theory until all, or at least a majority, of its predictions have been tested. This is an unsatisfactory defense of astrology for two reasons. First, because there is such a vast number of possible predictions, it would take forever to test even a small percentage of them. Thus, astrologers will always be able to claim that the theory has not been shown to be incorrect even if every future test of astrological predictions shows the predictions to be wrong. Second, as we have seen, it is unnecessary to test every prediction of a theory to show the theory to be incorrect. If the theory’s major predictions are incorrect, the theory is rightly rejected by scientists and time is not spent testing endless minor-detailed predictions. In the case of astrology, the theory’s major prediction is that sun signs influence personality, occupational choice, and so forth. These predictions have repeatedly been shown to be
