Lisa Mosconi’s new book “The XX Brain” provides a fresh take on the study of sex differences in brains by focusing on hormones (“Your Health: New Wisdom on How the Female Brain Works,” Life & Arts, March 10). While it is exciting to learn about studies that promise to enhance women’s health, the historical quest to document sex differences in brains was founded on the premise that women’s brains are inherently inferior to men’s.

When the American Neurological Association was organized in 1875, two of its leading members—William Hammond and Edward Clarke—focused their research on documenting the “natural” inferiority of women. Hammond claimed that female brains were structurally different from male brains in 19 distinct ways, including weighing less. The brain-weight theory of intelligence was discredited in the early 1900s, but scientists continued to rely on the “greater male variability” hypothesis popularized by Charles Darwin (and more recently reiterated by former Harvard President Larry Summers).