Contemporary scientists such as Richard Dawkins and Stephen Hawking regard astrology as unscientific,[46][47] and those such as Andrew Fraknoi of the Astronomical Society of the Pacific have labeled it a pseudoscience.[48] In 1975, the American Humanist Association characterized those who have faith in astrology as doing so "in spite of the fact that there is no verified scientific basis for their beliefs, and indeed that there is strong evidence to the contrary".[49] Astronomer Carl Sagan was unwilling to sign the statement, not because he felt astrology was valid, but because he found the statement's tone authoritarian.[50][51] Sagan stated that he would instead have been willing to sign a statement describing and refuting the principal tenets of astrological belief, which he believed would have been more persuasive and would have produced less controversy than the circulated statement.[52]
Although astrology has not been considered a science for some time, it has been the subject of considerable research by astrologers since the beginning of the twentieth century. In their study of twentieth-century research into natal astrology, former astrologer turned astrology critic Geoffrey Dean, and coauthors, documented this burgeoning research activity performed primarily within the astrological community.[53][edit] ResearchThe 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.[7][54] 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.[55] It has been suggested that other statistical research is often wrongly seen as evidence for astrology due to uncontrolled artifacts.[56]
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.