Fascinating stuff - I think we did know it but interesting research to test the idea. Depressing though... I got this info at work, btw.
A researcher from the University of Warwick joined a Year Eight class for three months - she attended classes, did PE lessons, took exams, had lunch in the cafeteria, played in the playground and joined them in trips to shopping centres after school. Dr Maria do Mar Pereira found girls feel the need to play down their intelligence to not intimidate boys. By the age of 14 boys had decided that girls their age should be less clever.
She said there are very strong pressures that dictate what is a 'proper man' and a 'proper woman'. Teenagers feel boys should be cleverer, stronger, taller, funnier and boys 'that being in a relationship with a woman who is more intelligent will undermine their masculinity'.
Based on these experiences, she says: “Our ideas of what constitutes a real man or woman are not natural; they are restrictive norms that are harmful to children of both genders. The belief that men have to be dominant over women makes boys feel constantly anxious and under pressure to prove their power – namely by fighting, drinking, sexually harassing, refusing to ask for help, and repressing their emotions.
“Girls feel they must downplay their own abilities, pretending to be less intelligent than they actually are, not speaking out against harassment, and withdrawing from hobbies, sports and activities that might seem ‘unfeminine’.”
She's written a book called Doing Gender in the Playground which has won an award for qualitative research.
NB She did have permission from everyone concerned. And I'm not a PR for her or anything, just got the information at work and thought it was fascinating.