Astrologers believe date of birth is a strong determinant of a person's character, and recent research suggests they might be on to something. In ancient times, astrology was used to highlight the supposed influence of the heavens on the births of outstanding individuals, such as kings or great leaders (note the association between a bright star and the birth of Christ).
Now, a study of Nobel-winning scientists and top mathematicians, published in Psychological Reports, tests the theory that birth date is an important indicator of future achievement. A significant number of the sample (98 out of 810) were born in March or April, while only 42 had birthdays in December or January. So scientists are far likelier to be Aries than Capricorns.
Similarly, two studies published in Nature have found a heavy bias towards spring and early summer births among entrants to the world's top medical schools. In short, you have a much lower chance of getting in if you were born in winter.
The reason probably has little to do with the influence of the stars. It is more likely that some environmental agent - varying with the seasons and perhaps linked to climate - influences early brain development. The key point appears to be that the season of birth is only relevant when extremes of behaviour such as mental illness or outstanding achievement are being considered.
For example, numerous studies of populations in the northern and southern hemispheres have found that around 10 per cent more schizophrenics are born in winter than in summer; there is less seasonal variation for populations near the equator. Perhaps this is because in cold environments humans wear heavy clothes and stay indoors, so restricting access to the stimuli and physical movement that could be vital to early brain development. Another theory argues that the increased exposure to flu or other viruses just before or after birth causes subtle brain damage to young babies. Then there is the possibility of a foetal nutritional deficiency because the births follow a pregnancy in summer, when the heat tends to lead to reduced food intake.
Another study, which found a significant tendency for the more socially inhibited to be born between March and May - when the top scientists in the first study were born - has produced a theory based on parents'
"procreational habits". Inhibited children tend to have inhibited parents, so birth in early spring may reflect a tendency of shy partners to mate in summer, when there are more chances to socialise and overcome their inhibitions.
This research does not endorse the idea of destiny or fate; after all, it's possible to be a Nobel laureate no matter what month you're born in. It's just that certain months seem favoured. Furthermore, unlike astrology and similar superstitions, this research attempts to find a plausible explanation for how date of birth can determine a person's future. It reminds us that some forces are beyond our immediate control.
Dr Raj Persaud is a consultant psychiatrist at the Maudsley hospital and senior lecturer at the Institute of Psychiatry in London. He is a fellow of University College London, and author of From the Edge of the Couch published by Bantam Press, pound;12.99. Email: firstname.lastname@example.org