From before children are even born, as soon as the sex is known, there are societal expectations set.
Once they are born they are constantly exposed to societal expectations, no matter what parents do. They pick up on the smallest thing.
Experiments to try and find some sort of neurological difference fail to actually show anything, where they appear to its either a tiny sample or very poor experimental conditions where the experimenter’s biases could have been transmitted to the child.
These arguments for innate differences are of the same kind as the arguments that women couldn’t vote because their heads were a different size and lacked the ability to make such important decisions, seeking to find justification for the current social order.