There are variables that influence the degree of gender expression in humans. Intrauterine high levels of testosterone in female fetuses can make  tomboys out of biological females and  genetic mutations of chromosomes called Androgen Insensitivity Syndrome create both male/female non-functional genitalia in one person.  Of course no one has a monopoly on truth and there are many approaches.  There are child rearing practices that influence gender identity.  My focus here is on how the psyche produces contra-sexual identities through psychological identifications and unconscious mechanisms called [...]