Androgens saturate the male fetal brain. The corpus callosum is reduced with resulting hemisphere specialization (e.g., functions in one hemisphere are not duplicated in the other hemisphere). (Joy, Donald M., PhD. Bonding. p 92-93. TX:Word Books, 1985.)

If a “Y” chromosome is present and there is sufficient maternal androgen, a chemical bath occurs to the brain that reduces size of the corpus callosum and allows right hemisphere to flourish. (Joy, Donald, PhD. The Innate Differences Between Males & Females Audio. CO: Focus on the Family, 1967.)