I think that boys just plain will prefer the cars over the doll if you give them the choice, regardless of culture. The story of David Reimer is instructive. The boy at 22 months had a botched circumcision. So the doctors just chopped off his balls and made a vagina for him. He had a horrible time becoming a "girl" and as soon as he was told he was a boy as a teen immediately reverted and lived the rest of his life as a boy as much as he could. The reason his parents told him anyways was because he threatened to take his own life, hating to see the therapist who was trying to make him act like a girl.