People’s personalities tend to vary somewhat depending on the season in which they are born, and astrological signs may have developed as a useful system for remembering these patterns, according to an analysis by UConn researcher Mark Hamilton. Such seasonal effects may not be clear in individuals, but can be discerned through averaging personality traits across large cohorts born at the same time of year. Hamilton’s analysis was published in Comprehensive Psychology on May 13.

Psychologists have known that certain personality traits tend to be associated with certain birth months. For example, people born in January and February tend to be more creative, and have a higher chance of being diagnosed with schizophrenia, than people born at any other time of year. And people born in odd-numbered months tend to be more extroverted than those born in even-numbered months.

So it wasn’t unprecedented when a paper appeared in 2013 in the Journal of Social Sciences linking birth month with the likelihood of becoming a celebrity. What was unusual, though, was that one of the authors was an astrophysicist, and the paper’s introduction included an explanation of the physics behind the astrological calendar. The authors argued that astrological ‘signs’ are merely an accident of the sun’s location in the cosmos, but that analysis shows certain zodiac signs have a curious correlation with fame.

The next year, a psychologist published a paper in Comprehensive Psychology purporting to debunk the first paper’s astrological findings. The author claimed that relative age among all the children in the same school grade could explain the zodiac effect, with children who were born earlier in the year, and were comparatively more mature, having more positive experiences overall.

UConn’s Hamilton, a social scientist in the Department of Communication, was unconvinced. He had reviewed the original paper for the Journal of Social Sciences, and considered the data and analysis to be sound. So he set out to debunk the debunking, examine some of the traditional astrological explanations, and see if they could be aligned with known psychological findings.

Traditional Western astrology uses elements (water, earth, air, and fire), sign duality (bright/dark), and sign qualities (cardinal, mutable, and fixed) to describe and categorize seasonal effects on personality. It considers late December through early March as a “wet” time of year, and connects wetness with creativity, for example. “Fixed” signs are said to be more stubborn and persistent than others.

Hamilton looked at the same data from the original paper, a set of 300 celebrities from the fields of politics, science, public service, literature, the arts, and sports. He found that celebrities’ birth dates tended to cluster at certain times of the year. “Wet” signs were associated with a larger number of celebrities, as were signs classified as “bright” and “fixed”.

“Psychologists want to dismiss these astrological correlations,” says Hamilton, “but there are seasonality effects that we have yet to explain.” Hamilton is not arguing that heavenly bodies are the true source of these effects; rather that astrological aspects are just useful tools, or heuristics, that help people remember the timing and patterns of nature.

Hamilton found that relative age of children in a school cohort did have some effect on propensity to become a celebrity. Children who spend their school years slightly older than the average among their peers are somewhat more likely to become famous, perhaps because they have more early success and so have better self-esteem into adulthood.

But Hamilton found that the relative age effect was dwarfed by the effect of being born under a wet astrological sign such as Aquarius or Pisces. Being born under a fixed quality sign – Aquarius, Taurus, Leo, or Scorpio – also increased a person’s chances of achieving celebrity to about the same degree as being older than average in his or her school cohort. In addition, being born under a “bright” sign increased a person’s chances of finding fame.

Hamilton is currently working with other researchers on an analysis of 85,000 celebrities dating from 3000 B.C. to the present era. He says the seasonality effect on celebrity appears to hold true even in this large data set that stretches across millennia and cultures.