By Jennifer Viegas, Discovery News
April 24, 2006 — One of the largest studies of the possible link between human traits and astrology found little, if any, connection between the traditional sun signs of the zodiac and characteristics of individuals.
The study adds to the growing body of evidence that there is no scientific basis for star signs, such as Aries, Taurus and so on. These signs are based on the place of the sun in relation to the date of birth of the subject.
The researchers, however, leave open the question as to whether other, more detailed and personal forms of astrology hold any validity.
"When considering the current scientific standing with respect to sun signs, it becomes clear that there is little or no truth in sun signs," said Peter Hartmann, who led the study, which will be published in next month's Personality and Individual Differences journal.
Hartmann, a researcher in the Department of Psychology at Denmark's University of Aarhus, added, "This does not necessarily mean that all astrology is without truth, but only that the independent effect of sun signs is most likely to be irrelevant. As for the weekly horoscope based on mere sun signs, then according to the current scientific standing, there is probably more truth in the comic strips."
Hartmann and his colleagues used computer analysis and statistical methods to study possible astrological connections between over 15,000 individuals. They derived these test subjects from two sources.
The first was the Vietnam Experience Study, which gathered information about intelligence, personality and date of birth for male military veterans. The second was the 1979 National Longitudinal Study of Youth, which included intelligence and date of birth information for males and females aged between 15 and 24 years.
If connections existed over a rate of five percent, they were considered to be valid and not the result of random links.
The scientists could find no relationship between the time and date of a person's birth and their personality traits, which the Vietnam study categorized using terms such as psychoticism, extraversion, neuroticism and social desirability.
The researchers, however, did determine that individuals from the Vietnam test who were born between the months of July and December were slightly more intelligent, by less than one IQ point, than those who were born between January through June.
That finding was reversed for the 1979 youth study. In that case, people who were born January through June had the minute intellectual edge.
Hartmann told Discovery News that although the information about intelligence passed the non-random restriction, he viewed the connection as irrelevant.
"An example: Assuming that you could buy a pill that would increase your IQ with one point, but it would cost you $10,000, would you do it? Probably not, but if you could buy a pill that would increase your IQ by 15 points that would be something else, simply because you get more value for your money," he said.
"The essence here is that there is a difference in determining whether a result is significant, hence whether it is a true effect, or just random occurrence, and then whether this significant effect is relevant and of any interest."
Geoffrey Dean, a former astrologist based in Australia who researches the possible scientific validity of astrology, tracked over 2,000 people who were born within minutes of each other.
The study, which spanned several decades, covered over 100 different characteristics, like marital status, IQ, anxiety, temperament and more. His findings were published in the Journal of Consciousness Studies.
Dean came to a similar conclusion as Hartmann and his team, that date of birth does not affect an individual's personality.