The X chromosomes that males have one of and females have two of--though one acts as a backup--is a cognitive "hot spot", carrying an unusually large percentage of genes involved in brain manufacture.
Women are genetically more complex, because the active X chromosomes in their cells are a mix of Mom's and Dad's. Men's chromosomes all come from Mom, and their Y chromosome carries less than 100 genes, compared with about 1,500 for the X chromosome.
Men's and women's brains are different structurally and biochemically--men have a bigger amygdala and produce serotonin faster, for example--but we don't know if those differences have significance.
Men and women respond differently to acute stress: women activate the left hemisphere's amydala and remember the emotional details. men use the right amydgdala and get the gist.
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