Sex and romance may seem inextricably linked, but the human brain clearly distinguishes between the two, according to a new study. The upshot: Love is the more powerful emotion.

The results of brain scans speak to longstanding questions of whether the pursuit of love and sex are different emotional endeavors or whether romance is just warmed over sexual arousal.

"Our findings show that the brain areas activated when someone looks at a photo of their beloved only partially overlap with the brain regions associated with sexual arousal," said Arthur Aron of the State University of New York-Stony Brook. "Sex and romantic love involve quite different brain systems."

The study, announced today, will be detailed in the July issue of the Journal of Neurophysiology.

Left side, right side

The study was small, however, involving 17 young men and women, all of whom had recently fallen madly in love. They filled out questionnaires while their brains were hooked up to a functional magnetic resonance imaging (fMRI) system.

Romance seems to steep in parts of the brain that are rich in dopamine, a chemical known to affect emotions. These brain regions are also linked by other studies to the motivation for rewards.

"To our surprise, the activation regions associated with intense romantic love were mostly on the right side of the brain, while the activation regions associated with facial attractiveness were mostly on the left," said Lucy Brown of the Albert Einstein College of Medicine.

The study also revealed that as a romance matures, so does the mind.

"We found several brain areas where the strength of neural activity changed with the length of the romance," Brown said. "Everyone knows that relationships are dynamic over time, but we are beginning to track what happens in the brain as a love relationship matures."

Love wins

The processing of romantic feelings involves a "constellation of neural systems." The researchers -- neuroscientists, anthropologists and social psychologists -- declare love the clear winner versus sex in terms of its power over the human mind.

"Romantic love is one of the most powerful of all human experiences," said study member Helen Fisher, an anthropologist at Rutgers University. "It is definitely more powerful than the sex drive."

Fisher said the study might suggest some of the physiology of stalking behavior. Other studies suggest that up to 40 percent of people who are rejected in love slip into clinical depression, she said.

"Rejected men and women in societies around the world sometimes kill themselves or someone else," Fisher said.

Animals, too

There are hints in the study that romance is not a uniquely human trait.

Some of the changes seen with mature romances were in regions of the brain also associated with pair-bonding in prairie voles. Other studies have found that expressions of attraction in a female prairie vole are linked to a 50 percent hike in dopamine activity in the brain region that corresponds to the location where human romance is processed.

"These and other data indicate that all mammals may feel attraction to specific partners, and that some of the same brain systems are involved," Fisher said.

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