Pink brains and blue brains

Elliot describes a similar experiment. Babies of about 9 months (i.e. crawling) in neutral baby grows. Put in a room with ramps of different steepnesses, supervised by nursery workers who didn't know the sex of the babies. Boys and girls could tackle the same steepness on average. Then put back in the room with their mothers in charge - the mothers correctly estimated the steepest ramp the boys could get up, and largely left them to explore, while the mothers of girls consistently underestimated what their daughters were capable of and intervened to "rescue" them if they thought they were trying something too difficult (which in fact they were perfectly capable of).

Three months* not three years.

BabyX in a nutshell:

The experiment involved researchers presenting a three year old baby dressed in a yellow baby grow to volunteers, telling the volunteer it was either a girl or boy, and asking them to play with the baby. They left a rag doll, a football and a teething ring in the room.

The researchers found that none of the male volunteers offered the football to the baby when they thought it was a "she", but 89% offered "her" the doll. 80% of the women gave the "boy" the football, and 75% gave the "girl" the doll. This experiment has been repeated and the results were almost identical.

Another similar experiment involved two female and two male babies, first dressed in pink and blue, then dressed in gender-neutral clothes. When the volunteer thought the baby was a boy, they responded much more to movements and praised physical ability. When they thought the baby was a girl, they were much more gentle and talked more to the baby. If they did not know the sex of the baby, the volunteer either asked, or assigned the sex to the baby based on the baby's character (quiet ones were assigned as female, physically active ones were assigned as male).

Also 'Pink Brain, Blue Brain' by Lise Elliot, a neuroscientist whose area of specialisation is the plasticity of the brain during early infancy/childhood. Her central point is that there aren't many robustly replicable studies of cognitive difference, where there are, the "d-values" (the measure of the relative size of the difference between the means of the two populations and their spreads) is tiny, and insofar as you can measure these differences at all, because we know that (a) adults treat babies differently according to their sex from birth onwards and (b) the brain is incredibly plastic, it is impossible to tell whether any measured small differences at a population level between older children or adults are due to nature or nurture.

For a more social sciences based approach I can recommend Deborah Cameron's "The Myth of Mars and Venus".

There's the Baby X study - have you heard of it? Shows that adults impose gender stereotypes on babies from at least the age of three months.

'Delusions of Gender' by Cordelia Fine is excellent on this!