Prenatal exposure to male hormones influences which activities girls are interested in, but the effects of those hormones do not extend to gender identity, a new study suggests.

The researchers explored how prenatal exposure to androgens -- hormones that are typically higher in males than in females -- affected whether girls played more often with boys or girls. They found that androgen exposure was not associated with girls spending more or less time in activities with other girls, but it was associated with an increased interest and more time spent in activities that have traditionally been thought of as masculine. "People used to think -- and some still do -- that gender development and behaviour is based either on a person's biology or social environment. But I think people now realise that it's both, and the question is how these forces work together," said co-author Sheri Berenbaum, Professor at Pennsylvania State University in the US.

The researchers examined the effects of hormones on sex segregation by studying girls with classical and non-classical congenital adrenal hyperplasia (CAH). Girls with classical CAH are exposed to excess levels of androgens prenatally, while girls with non-classical CAH are not. For the study, published in the journal Archives of Sexual Behaviour, researchers recruited a group of girls between the ages of 10 to 13 with classical CAH and non-classical CAH. They interviewed the girls about their activity interests, gender identity and attitudes about gender roles, among other things.

The researchers found that there was no significant association between androgen exposure and girls' time spent with either boys or girls. But, they did find that girls with classical CAH -- those with prenatal androgen exposure -- spent more time in male-typical activities and less time in female-typical activities.