Nowadays, gender is defined as a social and physiological characteristics of being a male or a female that an individual adopts from their developmental processes. In the last centuries, formation of individual’s identity was often determined by their sex. The term sex in this context refers to a biological measure which determines whether an individual is a male or female by figuring out the sets of chromosomes (XY for boys and YY for girls). However, in recent years, there has been an argument that biological factors alone do not play a role on gender formation. It is rather a combination of active cognitive processes, physiological processes and social forces. These combination of different factors play a key role on the formation and the development of gender role. Gender role refers to a measure which judges what is appropriate for a gender to do. In addition, it is a set of social and behavioral norms that are specifically associated with a sociocultural setting like the society or the culture that an individual is involved with. In the modern context, male’s role are often considered to be more masculine and aggressive whereas feminine and passive roles are often involved with females. Therefore, this essay will attempt to effectively discuss the formation and the development of gender role in the context of biosocial theory, social learning theory and gender schema theory. Biosocial theory was developed by Money and Ehrhardt on 1972. The theory suggested that children are born gender neutral and the development of gender identity and gender role arises as a consequence of socialization. As the theory suggests that humans are not born with a complete set of gender identity, Money hypothesized that there is a possibility that the children’s sex can be reassigned in the first two years of their life. An animal research was conducted to support the theory. In the research, female rats were injected with testosterones which are set of hormones that are specifically developed by males for their growth, maturation, reproductive systems and etc.. Moreover, the female rats that were injected with testosterones acted as male rats. In addition, it was found out that they did not demonstrate any sign of feminine behaviour in their adulthood even if they were injected with estrogens (female hormone) at that time. These may have been caused as the female rats were injected with male hormones in their early life and developed as a male in their developmental processes. Moreover, it is reasonable to observe such behaviors of the rats as they were developed to be a male and played a social role as a male in their sociocultural settings. Therefore, the injection of estrogen may have not influenced the behaviour of the rats that were injected with testosterones. To further discuss about the biosocial theory on the formation and the development of gender role, a case study of David Reimer will be used. In the case study of David Reimer, Money employed the identical twins as the matched control that could support the biosocial theory. David Reimer was a twin boy which lost his penis as a circumstance of circumcision at 8 months of his life. It was suggested by Money that he should undergo a surgery to change his sex and to raise him as a girl in the future. In addition, there was a replacement of his hormone to develop Reimer as a girl and to demonstrate roles that are associated with females. He was then considered as a girl and his name changed to Brenda. In Money’s articles, it was mentioned that the change in his sex seemed to be successful. However, he wasn’t able to publish evidences that were against is theory and it was later on found out that Brenda felt different with other girls. In addition, it was reported that she felt more attached to the boys. Often, she did not portray feminine and passive characteristics but rather more masculine and aggressive. At the age of 15, her parents told her the truth and therefore she went through a surgery to create a penis, to become a male again. Despite the fact that David had lost his penis at 8 months due to circumcision, he did not demonstrate like a female figure and was not affected by the surgery and hormone replacement when it came to his gender identity. Therefore, the case study of David Reimer disproves that sex of children can be reassigned in their early development stages. Moreover, this case study questions the impact of socialization on individuals that it can reverse biological settings. Biosocial theory suggested that children’s sex can be reassigned in their early stages of development. Moreover, the theory claimed that children are born gender neutral at their birth and that formation of gender is generated through socialization. However, the case study of David Reimer showed that the process of change in his sex from a boy to a girl did not play a role in the way which he identified himself as a girl. Therefore, the case study effectively demonstrated that there were no significant influence of reassignment of sex at the early stages of life in terms of alternating one’s gender identity and gender role. Social learning theory (SLT) was first found by Bandura in 1977. The theory suggested that children learn about gender roles through the observation of same-sex models like their parents and peers. Moreover, it theorized that they learn from “direct tuition” in which they are rewarded and encouraged if they demonstrate socially acceptable gender traits and discouraged for gender inappropriate actions. Moreover, it mentioned that children observe and imitate how others of the same sex behave and act. Such influence is called social approval (encouragement) and social disapproval (discouragement).