How Do I Love Thee?

A growing number of Internet dating sites are relying on academic researchers to develop a new science of attraction. A firsthand report from the front lines of an unprecedented social experiment

But how useful is this sort of data for single people like me? Despite Warren’s disclaimer about what a tough eHarmony match I am, I did finally get some profiles in my inbox. They included a bald man with a handlebar moustache, who was fourteen inches taller than me; a five-foot-four-inch attorney with no photos; and a film editor whose photo shows him wearing a kilt—and not in an ironic way. Was this the best science could do?

When I asked Galen Buckwalter about this, he laughed, indicating that he’d heard the question before. “The thing you have to remember about our system is we’re matching on these algorithms for long-term compatibility,” he said. “Long-term satisfaction is not the same as short-term attraction. A lot of people, when they see their initial matches, it’s like, ‘This is crap!’ ”

In ads and on his Web site, Warren talks about matching people “from the inside out.” Was eHarmony suggesting that I overlook something as basic as romantic chemistry? “When we started out,” Buckwalter said, “we were almost that naive.” But now, he added, eHarmony is conducting research on the nature of physical attraction.

“We’re trying to find out if we can predict physical chemistry with the same degree of statistical certainty that we’ve used to predict long-term satisfaction through our compatibility matching. In general, people seem to be attracted to people who share their physical attributes,” Buckwalter explained, noting that he has found some exceptions, like height preference. “There’s a lot of variability on that dimension,” he said. “A person’s height, it turns out, is not a consistent predictor of short-term attraction.” Meanwhile, Buckwalter’s team is in the process of testing new hypotheses.

“We’re still convinced that our compatibility-matching process is essential for long-term satisfaction, so we’re not going to mess with that,” he insisted. “But if we can fit a short-term attraction model on top of that, and it’s also empirically driven, that’s the Holy Grail.”

Over at, a new site launched by, short-term attraction is already built into the system. This competitor of eHarmony’s was developed with help from’s chief scientific adviser, Dr. Helen Fisher, an anthropologist at Rutgers University, whose research focuses on the brain physiology of romantic love and sexuality. is currently assembling a multidisciplinary group of psychologists, relationship counselors, sociologists, neuroscientists, and sexologists to serve as consultants.

The company sought out Fisher precisely because its market research revealed that although a large segment of singles wanted a scientific approach, they didn’t want it to come at the expense of romantic chemistry. “On most of the other sites, there’s this notion of ‘fitness matching,’ ” Fisher said from her office in New York City. “You may have the same goals, intelligence, good looks, political beliefs. But you can walk into a room, and every one of those boys might come from the same background, have the same level of intelligence, and so on, and maybe you’ll talk to three but won’t fall in love with any of them. And with the fourth one, you do. What creates that chemistry?”

It’s a constellation of factors, Fisher told me. Sex drive, for instance, is associated with the hormone testosterone in both men and women. Romantic love is associated with elevated activity of the neurotransmitter dopamine and probably also another one, norepinepherine. And attachment is associated with the hormones oxytocin and vasopressin. “It turns out,” she said, “that seminal fluid has all of these chemicals in it. So I tell my students, ‘Don’t have sex if you don’t want to fall in love.’ ”

Romantic love, Fisher maintains, is a basic mating drive—more powerful than the sex drive. “If you ask someone to go to bed with you, and they reject you,” she says, “you don’t kill yourself. But if you’re rejected in love, you might kill yourself.”

For’s matching system, Fisher translated her work with neurotransmitters and hormones into discrete personality types. “I’ve always been extremely impressed with Myers-Briggs,” she said, referring to the personality assessment tool that classifies people according to four pairs of traits: Introversion versus Extroversion, Sensing versus Intuition, Thinking versus Feeling, and Judging versus Perceiving. “They had me pinned to the wall when I took the test, and my sister, too. So when approached me, I said to myself, ‘I’m an anthropologist who studies brain chemistry, what do I know about personality?’ ”

Turns out she knew quite a bit: Genes for the activity of dopamine are associated with motivation, curiosity, anxiety, and optimism. Genes for the metabolism of serotonin, another neurotransmitter, tend to modulate one’s degree of calm, stability, popularity, and religiosity. Testosterone is associated with being rational, analytical, exacting, independent, logical, rank-oriented, competitive, irreverent, and narcissistic. And the hormone estrogen is associated with being imaginative, creative, insightful, humane, sympathetic, agreeable, flexible, and verbal.

“So I had these four sheets of paper,” Fisher continued. “And I decided to give each a name. Serotonin became the Builder. Dopamine, the Explorer. Testosterone, the Director. And estrogen—I wish I’d called it the Ambassador or Diplomat, but I called it the Negotiator.” Myers-Briggs, she says, “clearly knew the four types but didn’t know the chemicals behind them.”

The 146-item compatibility questionnaire on correlates users’ responses with evidence of their levels of these various chemicals. One question, for instance, offers drawings of a hand, then asks:

Which one of the following images most closely resembles your left hand?
Index finger slightly longer than ring finger
Index finger about the same length as ring finger
Index finger slightly shorter than ring finger
Index finger significantly shorter than ring finger

The relevance of this question might baffle the average online dater accustomed to responding to platitudes like, “How would you describe your perfect first date?” But Fisher explains that elevated fetal testosterone determines the ratio of the second and fourth finger in a particular way as it simultaneously builds the male and female brain. So you can actually look at someone’s hand and get a fair idea of the extent to which they are likely to be a Director type (ring finger longer than the index finger) or a Negotiator type (index finger longer or the same size).

Another question goes like this:

How often do you vividly imagine extreme life situations, such as being stranded on a desert island or winning the lottery?
Almost never
Most of the time
All the time

“Someone who answers ‘All the time’ is a definite Negotiator,” Fisher said. “High estrogen activity is associated with extreme imagination.”

Presented by

Lori Gottlieb is the author of Stick Figure (2000) and a co-author of the forthcoming I Love You, Nice to Meet You.

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