Curt, a five-year-old boy, is intrigued by his mother's cosmetic collection. One day, he tries on his mother's lipstick. When Curt's parents find him with the makeup box, they scold him for behaving like a girl. Curt realizes that it is shameful to play with makeup. Curt's understanding of how children of his gender are supposed to behave can be best explained by the ________ approach to gender development.