Tendency to divide world into distinct and non-overlapping characteristics, men and women don"t differ in kind, but in degree of the attributes they possess. 1960s: conceptual mistake to assume men are opposite to women, doesn"t allow people to have male traits if the subject is female and vice versa. 1970s: masculinity and femininity: separate, individual dimensions of each other (not opposite, gender segregation: when separated and allowed to interact with people of the same sex, men and women behave differently. This is because they were raised differently; they were segregated and played differently: gender socialization: different kinds of play. Children acquired and learnt different kinds of attributes of which they carry on to adulthood: at age four ration of same sex : cross sex interaction is 3:1, at age 10 is 10:1.