Abstract
Humans and other mammals have evolved three primary emotion systems for mating, reproduction, and parenting: the sex drive, or lust, characterized by the craving for sexual gratification; attraction, characterized by increased energy and focused attention on one or more potential mates, accompanied in humans by exhilaration, intrusive thinking, and craving for emotional union; and attachment, characterized by close social contact and feelings of calm, comfort, and emotional union. Each emotion system is associated with a discrete constellation of brain circuits, and each evolved to direct a specific aspect of mating and reproduction. The psychophysiological properties of romantic attraction suggest that this emotion system is associated with increased levels of dopamine and norepinephrine and decreased levels of serotonin in the brain; a study using functional magnetic resonance imaging (fMRI) is in progress to investigate the neural architecture of this primary emotion system. During the course of hominid evolution these three emotion systems became increasingly independent of one another, contributing to modern patterns of marriage, adultery, and divorce as well as to the worldwide incidence of stalking, homicide, suicide, and clinical depression associated with rejection in love.
