Can Date of Birth Affect Personality?

What does your date of birth say about you? The answer usually depends on how superstitious you are. The astrologers, on the one hand, claim that your date of birth profoundly shapes who you are; the purveyors of common sense, meanwhile, argue that these views are codswallop of the choicest variety.

Until fairly recently, the latter seemed to be in the right. The psychologist Hans Eysenck spent much of the late 70s and early 80s exploring the relationship between star sign and personality traits. What he found was that the zodiac can affect how you describe yourself in personality questionnaires, but

only if you are a believer in astrology already. Young children, or those with no idea that the three ‘water’ signs (Cancer, Scorpio, and Pisces) are supposed to make for more neurotic individuals, were not consistent with astrological predictions.

That would have been the end of it, but a few years ago the Swedish researcher Jayanti Chotai teamed up with Professor Richard Wiseman of the UK to explore this again. Some recent studies had hinted that date of birth did affect certain personality traits, and these researchers wanted to explore this further.

They aimed to study whether there was a link between date of birth and risk-taking, and, specifically, how lucky individuals considered themselves to be. They surveyed 40,000 individuals in the UK, and their results were startling. There was a clear trend for those born in the summer months to be risk-takers and to rate themselves as lucky, and for those born in colder months to be the opposite. The ‘luckiest’ month to be born in was May; the 'unluckiest', October.

There are rational explanations for why this should be the case. Some propose that, since babies born in winter months enter a harsher environment than their summer counterparts, they remain closer to their care-givers and are therefore less adventurous in their first months of life. Others claim that mothers have access to different foods in winter than in summer, and that somehow this affects the neurological development of their offspring.

Regardless of the explanation, the summer/winter divide seems to stand up to scrutiny where astrology does not. In a follow-up experiment conducted in New Zealand, experimenters found that the results were the exact opposite of those in the UK. This time those born in from March to May were less risk-taking and less adventurous, whereas those born from September to February were the most care-free. The difference, of course, is consistent with the reversal of the seasons from the northern to the southern hemisphere.

So perhaps we shouldn’t be so quick to write off the effect of birth dates on our lives and those of our family. The case above illustrates how slight but statistically significant differences can be observed between those born in summer to those born in winter. And who knows? There may be further fascinating discoveries down the line.