Ever since scientists realized that the seat of love and lust is not the heart but the brain, they've been looking for how the brains of homosexuals and heterosexuals differ. Researchers in Sweden have new clues. Studying brain scans of 90 subjects, they found that the right hemisphere is slightly larger than the left in both men and women who are attracted to women. Men and women attracted to men, on the other hand, have brains that are more symmetrical. Brain symmetry isn't the whole story, and other researchers have found that additional variables as diverse as genes and birth order can play a role.