Part of the Brain: The Inside Story exhibition.

What is love? Neuroscientists can't answer that question yet. But they have learned more about how the feelings that occur when people "bond" are produced in the brain. If you look at how humans bond with their mates and care for their young, you'll see some surprising similarities between us and other species. Can family bonds be strengthened and weakened by chemicals in your brain?

How it Works

Only about 5 percent of mammal species form exclusive, lifelong bonds with their mates. One is the prairie vole: Chemicals in a vole's brain make it link its mate with good feelings, and pairs tend to stay together for life. One of these chemicals is the neurotransmitter oxytocin. Prairie voles with more oxytocin receptors tend to stay with their mates. Voles with low levels mate with new partners.

Oxytocin plays a key role in the bonding process in voles--but what about in humans? In humans, as in prairie voles, oxytocin is released during birth, nursing, and mating--important bonding moments. Inhaling oxytocin in a nasal spray makes people feel more trusting in clinical studies. And in studies, men with naturally low oxytocin levels were less likely to get married.

So is oxytocin the secret of love? No. It is just one chemical messenger in the brain--a small part of a very complicated system. And it's not the only messenger involved in producing feelings of love and affection. Dopamine is a key messenger in the brain's "seeking system" that generates desire, and endorphin activates your pleasure centers when you find what you were looking for.