Why do we fall in love with one person and not another?
This question has vexed philosophers, psychologists and poets for generations. The theories—proximity, pheromones, timing—don’t fully explain the mystery. We can be in a room full of attractive, available strangers—and be open to love—and still choose one person over all others.
A decade ago, the biological anthropologist Helen Fisher set out to answer this question of how we choose whom we love. Dr. Fisher is known for her research scanning the brains of people in various stages of love, and she went looking for neurological clues.
She found them—and, in the process, she developed a broad personality test that, unlike many others, is based on brain science rather than psychology. The Fisher Temperament Inventory measures temperament, which comes from our genes, hormones and neurotransmitters. It can help people understand themselves and why they are attracted to certain people, both romantically and as friends or colleagues. (It turns out some personality types are attracted to people who are the opposite of them, while other types are attracted to people who are similar.) And when you know the personality type of loved ones or co-workers, you will understand how they prefer to communicate and will be able to tailor your approach to what works best. The inventory is so comprehensive that now some companies are using a version of it to help understand and motivate their employees.
To develop her test, Dr. Fisher spent two years reviewing medical and academic literature, searching for the personality traits linked to a biological system. She identified four systems, each with its own host of traits: the dopamine, serotonin, testosterone and estrogen systems. Dopamine and serotonin, which are neurotransmitters, govern our “stay or go” scale, which decides how comfortable we are exploring unknown risks or whether we prefer the familiar. Testosterone and estrogen are hormones and determine the extent to which our brains express male or female traits.
We all have all four systems—as do humans, monkeys, lizards and birds. But we each have different levels of activity in each system. Some of us are dominant in one or, more often, two areas. Some are more balanced. It’s more of a spectrum. “This is a new way of understanding personality,” says Dr. Fisher, who is a senior research fellow at the Kinsey Institute at Indiana University, in Bloomington, Ind., and the author of several books, including “The Anatomy of Love.” “You are not putting people in buckets.”
People high on the dopamine scale tend to be adventurous.Illustration: Thomas Pitilli
The four types are each associated with distinct traits. People high on the dopamine scale tend to be adventurous, curious, spontaneous, enthusiastic and independent. They have high energy, are comfortable taking risks and are mentally flexible and open-minded. Serotonin types are very social, traditional, calm and controlled, conscientious and detail-oriented. They love structure and making plans. Testosterone types are direct and decisive, aggressive, tough-minded, emotionally contained, competitive and logical. They have good spatial skills and are good at rule-based systems, such as math or music. Estrogen types are intuitive, introspective, imaginative, empathetic and trusting. They’re emotionally intelligent.
Serotonin types can be calm, cautious and controlled—and like to make plans.Illustration: Thomas Pitilli
Once Dr. Fisher identified the four types, she created a 56-question survey to measure how much each person expresses the personality traits involved. She partnered with the dating site Chemistry.com, starting in 2006, to run her survey. (Dr. Fisher is a consultant with Match Group, Chemistry.com’s parent company.) Thus far, more than 14 million people have taken the survey, and Chemistry.com uses it to enhance its algorithm for matching singles. Dr. Fisher analyzed the survey results of more than 100,000 people, in six countries. She found that while men typically register higher on the testosterone scale and women on the estrogen scale, as expected, there are no differences between them on the dopamine and serotonin scales.
She also discovered who is attracted to whom. People high in dopamine activity and people high in serotonin activity gravitate toward people like themselves. People high in testosterone or high in estrogen tend to like their opposites.
Estrogen types tend to be, among other characteristics, intuitive, introspective and holistic.Illustration: Thomas Pitilli
To validate that her questionnaire accurately measured brain systems, Dr. Fisher did a series of brain scans on 36 people, after they took her survey; the results were published in “PLOS One” in November 2013. She found that the people who scored high on the dopamine scale showed heightened activity in a pathway of the brain that is dopamine-rich and linked to curiosity, creativity and energy. People who scored high on the serotonin scale showed more activity in a tiny region of the brain linked with social-norm compliance. People who scored high on the testosterone scale showed more activity in the brain regions that govern visual and analytical functions. And people high on the estrogen scale showed more activity in brain regions linked to empathy and imagination.
These days, Dr. Fisher uses her personality inventory to advise marriage therapists, universities and corporations in helping people get along. Companies can purchase a new, second-generation, 50-question version of her questionnaire—focused on workplace behavior and relationships and different from the Chemistry.com survey—through a company she founded with a colleague, called NeuroColor. People who take the test, which costs $300, receive a 22-page profile of their personality, explaining where they are on the scale, how people can best communicate with them based on their personality, and how they can interact effectively with other personality types.
Testosterone types are direct and decisive, aggressive and tough-minded.Illustration: Thomas Pitilli
I took the NeuroColor questionnaire and found the results to be spot-on. It showed me to be high in dopamine and estrogen—a risk taker who is empathetic, intuitive and social. The profile aims to help me understand myself, and offers advice on how I can communicate more effectively with other types and how they can best communicate with me, as well as typical reasons why I might become stressed in the workplace and solutions to reduce this stress. (My favorite line from the report, from a section on what others should do when interacting with me: “Hear her out–even if her approach initially seems crazy or unconventional.”)
Dr. Fisher sums up the relationship advice people can take away from her personality inventory in one line, which she says is a tweak on the Golden Rule. Rather than telling people to “do unto others as you would have them do unto you,” she advises: “Do unto others as they would have done unto themselves.”What’s Your Type?
The Fisher Temperament Index identifies four brain systems linked to personality. Typically, we all express some of each. (This isn’t like other personality tests, where people are put into one box or another.) But many people are dominant in one or two areas: either dopamine or serotonin, and either testosterone or estrogen. Here are the systems:
DOPAMINE—People who are high on the dopamine scale tend to be curious, creative, spontaneous, energetic, restless, enthusiastic, impulsive, and mentally flexible. These are the explorers and the risk takers (personally and in business). They are very good at idea generation. They can’t tolerate people who are boring.
These people are drawn to people like themselves.
SEROTONIN—People who have high serotonin activity are more sociable and eager to belong. They’re quite traditional in their values and less inclined toward exploration. These are the builders and guardians. They’re calm, cautious, controlled, like to make plans, persistent, concrete thinkers, detail-oriented, structured, fact-oriented, loyal. They prefer loyal people over interesting or exciting people.
These people are drawn to people like themselves.
TESTOSTERONE—People expressive of the testosterone system are tough-minded, direct, decisive, skeptical, competitive, emotionally contained, inventive, experimental, exacting, analytical and assertive. They tend to be good at rule-based systems—engineering, computers, mechanics, math, and music. These are the rank-oriented directors.
These people are drawn to people who are the opposite.
ESTROGEN—People who are expressive of the estrogen system tend to be intuitive, introspective, holistic, imaginative, trusting, empathetic, and contextual long-term thinkers. They are sensitive to people’s feelings, and typically have good verbal and social skills. These people are negotiators. They’re big-picture thinkers, tolerate ambiguity well, have mental flexibility and strong executive social skills. They’re highly emotionally intelligent.
These people are drawn to people who are the opposite.Tips
Helen Fisher’s tips on how to communicate with the four personality types on the Fisher Temperament Index:
When interacting with a dopamine type:
Do: be energetic, optimistic and enthusiastic. Be flexible, spontaneous and creative. Explore new information and ideas. Speculate and theorize. Give them variety, possibilities and choices. Be daring.
Don’t: Smother them with details. Go heavy on process. Require rigid schedules or routines. Moralize (avoid “ought” and “should”). Dwell too long on one point. Be repetitive.
When interacting with a serotonin type:
Do: Discuss concrete topics. Be orderly and calm. Make and stick to schedules and plans. Emphasize the “right way” of doing things. Accentuate tradition. Minimize risks and uncertainties. Emphasize details.
Don’t: Present an unsubstantiated point of view. Give unfounded theories or speculations. Use intuitive statements or phrases, such as “I suspect…” Exaggerate. Leave issues unresolved. Be unorganized.
When interacting with a testosterone type:
Do: Be direct and tough-minded. Get to the point. Focus on the goal. Be logical and unemotional. Avoid sustained eye contact. Give the big picture first, then details. Disagree and debate, backed by facts. Engage the person’s sense of fairness. Give orders clearly.
Don’t: Be self-deprecating or minimize your achievements or rank. Apologize unless appropriate. Make moralistic statements (avoid “ought” and “should). Be long-winded, redundant or effusive. Talk about theories without linking them to facts.
When interacting with an estrogen type:
Do: Think contextually and long-term. Balance facts with feelings. Give theories and use ancillary data. Find points of agreement. Appreciate the person’s contributions. Express caring. Reveal your feelings. Sit facing them and use an “anchoring” gaze.
Don’t: Be competitive or confrontational, aggressive or blunt, or impersonal or aloof. Interrupt. Push for a decision before the person has explored all the options. Forget that this type sees meaning in everything.
Write to Elizabeth Bernstein at firstname.lastname@example.org or follow her on Facebook, Instagram and Twitter at EBernsteinWSJ.