Gender identity appears to form very early in life and is most likely irreversible by age 4. Although the exact cause of gender identity remains unknown, biological, psychological, and social variables clearly influence the process. Genetics, prenatal and postnatal hormones, differences in the brain and the reproductive organs, and socialization all interact to mold a toddler's gender identity. The differences brought about by physiological processes ultimately interact with social‐learning influences to establish clear gender identity.
Psychological and social influences on gender identity
Gender identity is ultimately derived from chromosomal makeup and physical appearance, but this derivation of gender identity does not mean that psychosocial influences are missing. Gender socialization, or the process whereby a child learns the norms and roles that society has created for his or her gender, plays a significant role in the establishment of her or his sense of femaleness or maleness. If a child learns she is a female and is raised as a female, the child believes she is a female; if a child is told he is a male and is raised as a male, the child believes he is male.
Beginning at birth, most parents treat their children according to the appearance of their genitals. Parents even handle their baby girls less aggressively than their baby boys. Children quickly develop a clear understanding that they are either female or male, as well as a strong desire to adopt gender‐appropriate mannerisms and behaviors. This understanding normally occurs within 2 years of age, according to many authorities. In short, biology sets the stage, but children's interactions with social environments actually determine the nature of gender identity.
Gender roles
Gender roles are both cultural and personal. These roles determine how males and females think, speak, dress, and interact within the context of society. Learning plays a role in this process of shaping gender roles. These gender schemas are deeply embedded cognitive frameworks regarding what defines masculine and feminine. While various socializing agents—educators, peers, movies, television, music, books, and religion—teach and reinforce gender roles throughout a child's life span, parents probably exert the greatest influence, especially when their children are very young.
Developmentalists indicate that adults perceive and treat female and male infants differently. Parents probably do this in response to having been recipients of gender expectations as young children themselves. Traditionally, fathers teach boys how to fix and build things; mothers teach girls how to cook, sew, and keep house. Children then receive parental approval when they conform to gender expectations and adopt culturally accepted and conventional roles. All of these lessons are reinforced by additional socializing agents, such as the media. In other words, learning gender roles always occurs within a social context, with the values of the parents and society being passed along to the children of successive generations.