It was not until the 1990s that researchers began to study female neuroanatomy and psychology in their own right. The correlation between hormonal changes (such as those that trigger menstruation) and depression led sociologists to examine cultural factors, while scientists such as neuropsychiatrist Louann Brizendine, of the University of California, San Francisco, looked at the way hormones affect brain function.

In The Female Brain, Brizendine shares the results of two decades of research on female brain chemistry. “There are those,” she writes, “who wish there were no differences between men and women. … . The fear of discrimination based on difference runs deep, and for many years assumptions about sex differences went scientifically unexamined for fear that women wouldn’t be able to claim equality with men.”

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