The scientific community,[11] where it has commented, claims that astrology has repeatedly failed to demonstrate its effectiveness in numerous controlled studies. Effect size studies in astrology conclude that the mean accuracy of astrological predictions is no greater than what is expected by chance, and astrology's perceived performance has disappeared on critical inspection.[48] When tested against personality tests, astrologers have shown a consistent lack of agreement with these tests. One such double-blind study in which astrologers attempted to match birth charts with results of a personality test, which was published in the reputable peer-reviewed scientific journal Nature, concluded that astrologers' could not solve clients' personal problems by reading individuals' natal charts and that astrologers had no special ability to interpret personality from astrological readings.[49] Another study that used a personality test and a questionnaire contended that some astrologers failed to predict objective facts about people or agree with each other's interpretations.[50] When testing for cognitive, behavioral, physical and other variables, one study of astrological "time twins" showed that human characteristics are not molded by the influence of the Sun, Moon and planets at the time of birth.[48][51] Skeptics of astrology also suggest that the perceived accuracy of astrological interpretations and descriptions of one's personality can be accounted for by the fact that people tend to exaggerate positive 'hits' and overlook whatever does not fit, especially when vague language is used.[48] They also argue that statistical research is often wrongly seen as evidence for astrology due to uncontrolled artifacts.[52]

In another control experiment conducted by ABC's 20/20 team and documented by John Stossel in his best-selling book Myths, Lies & Downright Stupidity, an astrologer was asked to do a chart on Ed Kemper, a serial killer and necrophile. The astrologer compiled a twenty-five-page report, of which identical copies were made and given to a class of college students. The students were each told that it was their own personal horoscope. "A few were 'amazed' that the astrologer could know so much about them. Some said they had been skeptical of astrology, but [that] detailed horoscope had made them total believers." [53] Needless to say, the students were embarrassed, some angry at the revelation that they've been tricked. [citation needed]

A similar experiment was conducted by professional debunker and scientific skeptic James Randi, in which he gave a class of students identical horoscopes, telling each however that it's their own unique personal one prepared by a professional astrologer based on when and where they were born. He gave the students some time to read their horoscope, then asked them to rank the accuracy of the horoscope; the majority of students ranked it 5/5.[citation needed] . He then asked each student to hand his/her horoscopes to the person behind them. Most students were disappointed to see that they've been had, as they found the horoscopes to be quite telling. They believed the horoscope was true because it contained a plethora of vague and general descriptions that flattered the students, descriptions with many misses but "hits" which impressed the students so much that they overshadowed their doubts with the misses. [54] James Randi describes these kinds of descriptions as cold reading, a technique with which you tell people more things about themselves than they actually do by making countless vague descriptions that could apply to almost anyone. A team of famous clinical psychologists also reached the same conclusion after conducting their own set of experiments on astrology, as well as other well-known pseudosciences [55]

http://en.wikipedia.org/wiki/Astrology