>I have had people tell me that boys like trucks and girls like dresses because of chemical differences in their brains.

In regards to gender differences I find some of the primate evidence[0][1] rather compelling. This doesn't mean that I believe any gender should be treated differently than the other of course but it seems rather obvious to me that some differences exist outside of any conditioning that human societies may provide.

[0]http://news.nationalgeographic.com/news/2010/09/101220-chimp... [1]http://www.bbc.com/news/av/science-environment-29418230/monk...

Note that the primate evidence showed that the girls played equally with the stuffed animals and the wheeled toys.

This reminds me of colour preference, where girls are more likely to say they like pink than boys and so people conclude pink is for girls and blue is for boys, yet if you ask what their favourite colour is, the top pick for both sexes is blue.

So the evidence on trucks doesn't support the claim you replied to, but maybe they'd be on firmer ground if they said boys had proportionately less interest in stuffed toy animals than trucks.

Not all instances of playing with something are equal. In terms of total interactions the females played with both the same number of instances but they also played with the dolls a significantly longer period of time.

Specifically talking about this paper:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2583786/

It seems the duration shows the same pattern as counting the number of interactions:

"males interacted for a greater total time with wheeled than with plush objects while females did not differ in the duration of interactions with the toy types"

Isn't it possible your biology gives you a natural tendency towards certain interests or activities and that these are reinforced and strengthened by society?

I think that's the most sensible hypothesis. Whenever there is a nature vs nurture question, the answer is usually "it's both".

You are talking about gender, as opposed to biological sex? But then, what is gender by that definition? If it is a social construct, what does it even mean to number them - they would be intangible constructs in the first place; it's like arguing there are only X canonical Marvel universes..