Richard Schwartz and Jacqueline Olds know a lot about love. These Harvard Medical School (HMS) professors and couples therapists study how love evolves and, too often, how it collapses. They have also been happily married for nearly four decades.
Love may well be one of the most studied, but least understood, behaviors. More than 20 years ago, the biological anthropologist Helen Fisher studied 166 societies and found evidence of romantic love—the kind that leaves one breathless and euphoric—in 147 of them. This ubiquity, said Schwartz, an HMS associate professor of psychiatry at McLean Hospital in Belmont, Mass., indicates that "there's good reason to suspect that romantic love is kept alive by something basic to our biological nature."
Rewarding ourselves with love
In 2005, Fisher led a research team that published a groundbreaking study that included the first functional MRI (fMRI) images of the brains of individuals in the throes of romantic love. Her team analyzed 2,500 brain scans of college students who viewed pictures of someone special to them and compared the scans to ones taken when the students looked at pictures of acquaintances. Photos of people they romantically loved caused the participants' brains to become active in regions rich with dopamine, the so-called feel-good neurotransmitter. Two of the brain regions that showed activity in the fMRI scans were the caudate nucleus, a region associated with reward detection and expectation and the integration of sensory experiences into social behavior, and the ventral tegmental area, which is associated with pleasure, focused attention, and the motivation to pursue and acquire rewards.
The ventral tegmental area is part of what is known as the brain's reward circuit, which, coincidentally, was discovered by Olds's father, James, when she was 7 years old. This circuit is considered to be a primitive neural network, meaning it is evolutionarily old; it links with the nucleus accumbens. Some of the other structures that contribute to the reward circuit—the amygdala, the hippocampus, and the prefrontal cortex—are exceptionally sensitive to (and reinforcing of) behavior that induces pleasure, such as sex, food consumption, and drug use.