1. Significant differences exist in brain structure and function between men and women, such as women having on average 11% more neurons and a larger corpus callosum connecting the brain's hemispheres. 2. Exposure to sex hormones like testosterone during fetal and early life development has organizational effects that permanently alter brain wiring and lead to differences in cognitive abilities between men and women on average. 3. Studies using brain imaging techniques have found some cognitive tasks like spatial navigation activate different brain regions in men and women, and men on average tend to excel at spatial and mathematics tasks while women on average excel at verbal memory and fluency tasks.