Kindergarten might have been the wrong word, I'm not a native English speaker. Over here you can have you child on child care / day care or whatever the proper English word might be from more or less the day it's born.
However, why I brought up the study done on the "Kindergarten" was that it showed that we adults treat girls and boys differently even when we ourselves believe that we treat them equally.
And having such a big external factor kind of skews the "my boy choose X himself" big time.
I have a 12 year old boy who loves to cook, clean and likes to watch My Little Pony. I have also a 13 (to be 14 in august this year) year old girl who likes to watch slasher horror flicks and working out in the gym (power lifting) with me.
Should I take this as evidence that all girls likes power lifting and that all boys like to cook and clean? Or can it have more to do with the fact that the kids gravitate towards a "favourite" parent, in this case my boy gravitates more towards my wife while my daughter gravitates more towards me and that this explains quite a bit why they like the things that they like (regarding the Brony-stuff I suppose that the bright colors and happy stories somehow plays well with his autism).