Levels of hormone exposure in the womb helps determine which academic discipline researchers work in, a new study suggests. Perhaps surprisingly, a 鈥渇emale鈥� pattern of exposure was common in scientists, while a 鈥渕ale鈥� pattern dominated in the social sciences.
The survey compared the length of people鈥檚 index (first) fingers with their ring (third) fingers. This comparison is thought to indicate prenatal sex hormone exposure, probably because some developmental genes control the formation of both the reproductive system and the digits.
In the general population, men have a 鈥渄igit ratio鈥� of 0.98 on average 鈥� the index finger being slightly shorter than the ring finger. Women have a digit ratio of 1.0 on average, meaning the two fingers are the same length.
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However the 107 male and female academics surveyed at Bath University, UK, had very similar ratios 鈥� 0.987 for men and 0.984 for women. This suggests the two groups were exposed to the same levels of oestrogen and testosterone in the womb.
Organisational and permanent
Hormone levels also appear to predict which discipline researchers work in. Staff in the departments of chemistry, computer science, mathematics and physics all had average ratios of over 0.995 鈥� close to the female average 鈥� despite 81% of those subjects being male.
In contrast, the staff of the social science departments of economics, education, management, social and policy sciences had an average ratio below 0.98, the male average, despite only 66% of this sample being male.
鈥淚t鈥檚 unnerving to think the profession I鈥檓 in was determined by the hormones I was exposed to in the womb,鈥� says Mark Brosnan, the lead author from the University of Bath, UK, whose work has been submitted to the British Journal of Psychology.
John Manning, an expert on digit ratios from the University of Central Lancashire, is not surprised that hormone levels in the womb can have such an influence. 鈥淭he effect of testosterone on the developing brain is organisational and permanent,鈥� he says.
Visual spatial skills
It is accepted that high levels of prenatal testosterone encourage development of the right side of the brain, which would also encourage the visual spatial skills important in science. Brosnan鈥檚 findings appear to contradict this, with a more 鈥渇emale鈥� pattern found in the scientists studied.
The researchers therefore speculate that exposure to either unusually high or low levels of testosterone in male fetuses could lead to a 鈥渟cientific鈥� brain. From this it would follow that average levels of hormone exposure could lead to a 鈥渟ocial science鈥� brain.
Manning thinks the relatively short index fingers of women in academia shows that early testosterone is an advantage in forging an academic career. 鈥淭o get on, you have to be quite assertive and organised,鈥� he says.