What contribution do you think biology and culture make to gender differences? Why is it hard to really determine the impact of biology? What does it mean to be masculine? Feminine? Are these more culturally or biologically based?
I did a study about gender identity in college that showed by the age of 3, gender-biased toys were selected by the like gender meaning boys chose trucks and blocks, girls chose dolls and make-believe things. The professor also commented on this phenomenom being similar across all cultures but I will tell you that biology also influences what we define as masculine or feminine. HOrmones, the size of a certain area in the brain, many different biological/ genetic traits lend itself to influence how "masculine" or "feminine" a boy or girl is.
Role modeling and cultural influences make a big difference but it can't always override genetic differences.