Pregnant women with high levels of the hormone testosterone have girls who have more tomboy-like behaviour

In this Wellcome Trust-funded study, Professors Melissa Hines and Susan Golombok from City University in London questioned several hundred mothers and their children aged 3.5 years, to assess how ‘sextyped’ the children were--that is how feminine or masculine their behaviour is. Criteria included how rough and active children's play was, whether they liked to play with other boys and girls, and whether they liked particular toys, such as cars or dolls.

The researchers found that there was a clear relationship between high testosterone levels in mothers and masculine behaviour in girls. There was no relationship between sextyped behaviour in boys and mothers’ testosterone levels. The researchers believe that this is due to the fact that testosterone levels are already high in boys, so small differences in mothers levels would not be expected to make a great difference.

They also believe that the lack of relationship between testosterone levels and behaviour could also be explained by greater socialisation pressures on boys to behave like boys should—for example, boys are more disapproved of for playing with dolls than girls are for playing with cars or trucks.

Testosterone was not the only factor that influenced that behaviour of the children. The biggest influence was having older brother or sisters, or parents who showed extremes of masculine or feminine behaviour.

Follow-up: Girls’ Behaviour Related To Testosterone Levels In The Womb, 12 November 2002