Narrator: This is Science Today. Asymmetries, or rather differences, between the left and right side of the brain routinely show up in human brain imaging and yet, Larry Cahill, a professor of neurobiology and behavior at the University of California, Irvine, says researchers often can't explain why.
Cahill: The sense of the whys is the big 64 thousand dollar question, not just in this immediate area, but in the whole area of human asymmetry. My guess is that as the cortex gets bigger and bigger and more complicated as you go across species, we're going to more and more processing within a hemisphere relative to across a hemisphere.
Narrator: Cahill recently found that men and women use different sides of the brain to store long-term, emotional memories.
Cahill: There's been half a dozen or so brain imaging studies that have shown differences between the brains between men and women in various domains, language or mathematical ability. It's kind of like a few raindrops before a major storm hits. This is another raindrop.
Narrator: For Science Today, Larissa Branin.