Research

The Mars effect: relative frequency of the diurnal position of Mars in the birth chart of eminent athletes.

Studies have repeatedly failed to demonstrate statistically significant relationships between astrological predictions and operationally defined outcomes.^[8][58] Effect size tests of astrology-based hypotheses conclude that the mean accuracy of astrological predictions is no greater than what is expected by chance. For example, when testing for cognitive, behavioral, physical and other variables, one study of 2000 astrological "time twins" born within minutes of each other did not show a celestial influence on human characteristics.^[59] It has been suggested that other statistical research is often wrongly seen as evidence for astrology due to uncontrolled artifacts.^[60]

Experimental psychologists have suggested that several different effects can contribute to perception of astrological accuracy. One observed tendency is known as the confirmation bias, whereby people who are given a set of multiple predictions tend to remember more of the accurate predictions ("hits") than the inaccurate ones ("misses"). Consequently, people tend to recall the set of predictions as being more accurate than it actually was. A second psychological phenomenon is known as the Forer effect, which refers to a tendency for individuals to give high accuracy ratings to descriptions of their personality that are presented to them as tailored specifically for them, but are in fact vague and general enough to apply to a wide range of people. When astrological predictions turn out to correspond with some phenomena but not with others, the recollected integrity of these predictions may stem in part from confirmation bias. When predictions use vague language, their individualized appearance may be partially attributable to the Forer effect.

The French psychologist and statistician who devoted his life to the attempt to demonstrate the validity of certain fundamentals of astrology, Michel Gauquelin, wrote that he had found correlations between some planetary positions and certain human traits such as vocations.^[61] Gauquelin's most widely known concept is the Mars effect, which denotes a correlation between the planet Mars occupying certain positions in the sky more often at the birth of eminent sports champions than at the birth of ordinary people. A similar idea is explored by Richard Tarnas in his work Cosmos and Psyche, in which he examines correspondences between planetary alignments and historically significant events and individuals. Since its original publication in 1955, the Mars effect has been the subject of critical studies and skeptical publications which aim to refute it,^[62][63][64] and of studies in fringe journals used to support or expand the original ideas.^[65][66] Gauquelin's research has not received mainstream scientific notice.