Two researchers called Martin and Halverson challenged Kohlberg’s theory of gender, by arguing that children imitate same-gender models as soon as they learn gender labels. They proposed that a child’s understanding of gender is actually acquired through developing gender schema, which then influence children’s behaviour. Once these have been developed, children identify with and imitate people of the same gender, because they see them as their in-group. They see people of the other gender as the out-group.