Claims of biological determination of gender identity formation ascended while the idea that socialization contributed importantly to gender identity formation became subject to ridicule. Some scientists believe that the correct brain sex alone, formed before birth, leads to proper gender identity formation. As development proceeds into the postnatal period, the child starts to manifest his or her gender identity. In the most extreme version, there are no social influences on brain identity development. Psychologist Melissa Hines and her colleagues studied the gender identity of adult women and men with congenital adrenal hyperplasia. In the case of transgender brain studies, the underlying model is that gender identity is part of brain sex, and quite possibly shaped by prenatal hormone exposures. Regardless of what combination of biological and social forces contributed to gender identity formation, John Money and Anke Ehrhardt believed that gender identity became fixed at some point around 2 years of age.