All I'm trying to say is that I was of your same opinion, but facts do not support that opinion in my experience. Of course I have not done an actual controlled experiment, just some observations and little tests along the years. Yes, they will play with anything, but they still show preferences. Are those purely social? I'm not sure.
That said, I am still of the opinion that it is indeed mainly social, but that it is less social than one thinks it is, before.
I'd love to see some actual science about this, got any?
I don't have the original study I read (back in a cognitive development class in college), but I believe this one[0] should suffice. The original was a study that monitored groups of kids playing with toys and found the kids didn't develop a gendered preference until parents began interfering with toy selection. If the parents didn't interfere, they wouldn't develop a gendered preference until school age where they began interacting with other children.
That said, I am still of the opinion that it is indeed mainly social, but that it is less social than one thinks it is, before.
I'd love to see some actual science about this, got any?