On average, which gender has a larger corpus callosum?

• A. Men
• B. No difference
• C. Both equal when brain size adjusted
• D. Women

Answer: (D)

The corpus callosum is the large bundle that connects the two hemispheres, so scientists look for sex differences in its size as a window into interhemispheric communication. In many studies that measure absolute size, women have been found to have a larger corpus callosum on average. This observation is often interpreted as indicating greater interhemispheric connectivity in women when not adjusting for overall brain size. However, when researchers control for brain size, the difference tends to lessen or disappear, and the evidence for a true gender difference becomes less consistent. So, the best answer in this context reflects the common finding from absolute-size measurements: women.