Vanessa LoBue, assistant professor of psychology at Rutgers-Newark, has contributed an article at The Conversation that was forwarded to me. When do children develop their gender identity?

It turns out that for young children, initial concepts about gender are quite flexible. In my own research, I’ve found that children don’t begin to notice and adopt gender-stereotyped behaviors (e.g., preferring colors like pink or blue) until the age of two or three. A few years later, their concept of gender becomes quite rigid, and although it becomes more relaxed by middle childhood, even adults have trouble going back to thinking about gender as something that’s flexible.

--LoBue