"However, the assertion that these children's genders remain malleable isn't necessarily true. According to the UCSF Center of Excellence for Transgender Health, 'Children as young as 18 months old have articulated information about their gender identity and gender expression preferences.' By the ages of three and four, children are already displaying preferences in gender expression and identity. Indeed, this is the age that many transsexuals report first knowing that they should be the other gender. As children, many of these transsexuals were forced into accepting and conforming to their birth-assigned genders (due to transphobic attitudes in their parents and society), only to transition later in adulthood to their identified genders." -- Julia Serano, "Detransition, Desistance, and Disinformation: A Guide for Understanding Transgender Children Debates", 2016-08-02