Scientists have found a distinct difference between the brains of right-handed people and those of left- and mixed-handed people.

Non-right-handed people have a larger corpus callosum, a clump of nerves that joins the right and left hemispheres of the brain and allows them to communicate with each other, researcher Sandra Witelson writes in the journal Science.

"A bigger corpus callosum may have more nerve fibers," Witelson told Science News. "This would mean there are more connections in the brain and more possibilities for intercommunication."

Witelson studied 42 seriously ill cancer patients, and then examined their brains after they died. Twenty-seven of them were right-handed; the other 15 were considered mixed-handed. Exclusive left-handedness is relatively rare.

The corpus callosa of the mixed-handed people were 11 percent larger than those of the right-handed group.

Witelson theorizes that all fetuses may start out ambidextrous -- with a lot of nerves connecting the two hemispheres -- and that for some reason, as brain functions specialize, most people lose many of those fibers and become right-handed.

Studies, mainly in right-handed people, suggest that the left side of the brain controls language and analytic functions, while the right side controls spatial and nonverbal processes.

These roles may be shared more evenly in non-right-handed people, the journals reports, but it is unclear whether that is an intellectual advantage.