Gender identity develops through the process of interactions of biological, social, behavioral and cognitive-learning factors that occur over time. At birth, almost all infants are socially labeled as either a girl or a boy, based on the appearance of the external genitals. Children may be treated differently, depending upon the labeled sex. As well, a child will act differently by a certain age according to their sex and what they perceive through their gender identity and social influences. .
According to Lawrence Kohlberg's social cognitive theory, children seem to develop gender concept and understanding in three stages. "First comes gender identity, which is simply the child's ability to label his or her own sex correctly and identify other people as men or women, boys and girls" ( Boyd, Bee, Johnson, 2009.p 257). This stage happens around nine months to two years, and they are capable of identifying faces and people as either male or female. When the child acquires language and they begin developing cognitively, they can verbally express themselves as being a girl or boy. This is the early expression of gender identity. Gender stability is the second stage, often understood by age four, "Which is the understanding that you stay the same gender throughout life" (Boyd, Bee, Johnson, 2009. P 257). This is often explored through children seeing that they have different body parts, than the opposite gender, and knowing that their body parts are the same as mom or dads. Often children will relate and compare their gender to parents or siblings. Boys often display their pee pee and say "I'm a boy," and at the same time they can also see a girl and tell everyone that "she doesn't have a pee pee, she's a girl." They come to the realization that their gender is a lifelong component of who they are. The third stage "is the development of true gender constancy, the recognition that someone stays the same even though they appear to change" (Boyd, bee, Johnson.