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When Rutgers University biological anthropologist Helen Fisher began investigating the roots of romantic love, nobody imagined it could be linked to the functioning and structure of the brain.

In those days, the prevailing view was that personality was entirely learned.

However, Fisher, now a senior research fellow at the Kinsey Institute and chief scientific officer of Match.com, was skeptical because she was born an identical twin. So she could observe firsthand how the personalities developed in two people with identical DNA.

The consensus of behavioural experts did not reflect her experience.

“At the time when I started doing this [research], people thought that romantic love was part of the supernatural,” Fisher said. “I thought to myself ‘anger is not part of the supernatural. Fear is not part of the supernatural. Sorrow is not part of the supernatural.’

“Why would love and attachment be part of the supernatural?” she continued. “They’ve got to be housed in the brain.”

To prove this, Fisher assembled a team to conduct a brain-scanning study of those who were happily in love.

Relying on functional magnetic resonance imaging, the team also studied the brain activity of those who had been rejected in love and those who’ve been in love over the long term.

Through this work, they discovered a very specific pathway for intense feelings of romantic love in a small region called the ventral tegmental area.

Also known as the VTA, it resides on the floor of the midbrain in the basal ganglia and is part of the so-called reptilian human brain.

The ventral tegmental area, which is associated with romantic love, is below the hippcampus and behind the amygdala in the brain. Brainstates.org

“It’s way below the cortex where you do your thinking, way below the regions in the middle of your head that organize emotions,” Fisher explained. “This little factory, the VTA, lies right next to the factories that orchestrate thirst and hunger.”

She has concluded that romantic love drives people to form long-term pair bonds to ensure their DNA survives into the future. “I do regard romantic love as a survival mechanism as powerful as thirst and hunger.”

Those who were very happily in love demonstrated a great deal of activity in the VTA, which produces dopamine and projects this neurotransmitter throughout the brain. According to Fisher, dopamine not only generates optimism, focus, motivation, and energy, but is also central to feelings of intense romantic love.

“We also found activity in the nearby region, also in the basal ganglia, that is linked with feelings of deep attachment to a partner,” she added.

She’s deduced that evolution has led to three distinctly different brain systems for mating and reproduction.

One is the sex drive, which causes people to be on the lookout for a range of potential partners.

Romantic love enables someone to focus their mating energy on one person.

And feelings of attachment cause a couple to remain together long enough to raise a single child through infancy.

These conclusions—and her engaging speaking style—resulted in Fisher being named a TED All-Star. On Tuesday (September 10), she'll speak at the Vancouver Playhouse as part of the UBC Connects series launched by the university's president, Santa Ono.

Zebras are one of the animals that sometimes live in harems, with one male and several females.

Mammals often don't form pair bonds

In her interview with the Straight, Fisher pointed out that chimpanzees, ducks, and turtles can't undergo functional magnetic resonance imaging.

"But we do know that this brain circuitry for romantic love is very common in nature," she added.

Scientists refer to it as the "attraction system". And she said that studies of prairie voles and sheep have demonstrated how it becomes activated.

"No bird or mammal will have sex with anything that comes along," Fisher said. "They have favourites. They focus on some and they refuse to copulate with others."

But few mammals—only three percent—form long-term pair bonds.

For rats, the attraction can last only 30 seconds, she said. With elephants, studies have shown that attraction only lasts for about five days.

"Cats don't form a pair bond," she noted. "Deer don't form a pair bond."

Other mammals, like gorillas and zebras, form harems, with one male travelling with five females. A male orangutan may have several female partners in his habitat.

"Our closest relatives, chimpanzees, they hang out in a very large social group of many males and many females," Fisher said. "When a female comes into estrus, or into heat, she will copulate with a lot of different males. She would not form a pair bond with one of them."

Sometimes a female and male chimp will hook up and travel away from the group for a few weeks. But upon their return, Fisher said, the female chimp raises the baby by herself.

Those that do form long-term pair bonds include wolves, foxes, coyotes, dingoes, beavers, and little African antelopes called dik-diks.

Gibbons, including the siaming of Southeat Asia, are the only higher primates apart from human beings that form pair bonds.

"People will often ask: why are we so adulterous?" Fisher said. "That's not really the question. A great many of our primate relatives sleep around. The real question is: why do we bother to pair up at all?

"And why did we evolve this brain circuitry for romantic love and deep feelings of attachment—and jealousy—and all kinds of other brain systems that sustain this pair bond?"

Perhaps the answer can be found in another group of vertebrates.

"Over 90 percent of birds form a long-term pair bond—because they have to," Fisher pointed out. "Somebody's got to sit on those eggs. That individual will starve to death unless they form a pair bond and rear the children as a team."

The closest relatives to humans in the animal kingdom, chimpanzees, do not form long-term monogamous relationships.

Personality is rooted, in part, in biology

Fisher came in contact with Match.com after receiving a phone call shortly before Christmas in 2005.

The company wanted her to meet the CEO and other senior executives to discuss her research.

She recalled the then CEO asking her why a person will fall in love with one person but not another.

Fisher replied that she didn't know the answer to that question.

Because she believes there's a significant biological basis to behaviour, she decided to conduct an investigation. And she told Match.com that she would report back with the results.

"When I went through all this academic literature—it took me a couple of years—[I found] there are a lot of systems in the brain," Fisher said. "But most of them keep the heart beating or the eyes blinking."

Only the dopamine, serotonin, testosterone, and estrogen systems were linked to personality traits—a whole constellation of traits, in fact.

She decided to create a questionnaire to determine the degree to which people expressed the traits in all four of these brain systems.

And she attached names to the four systems to reflect those personality constellations: directors (testosterone), negotiators (estrogen), builders (serotonin), and explorers (dopamine).

It became known as the Fisher Temperament Inventory.

Since it was created, more than 14 million people in dozens of countries have taken the questionnaire. And she said that it's the only personality test that's been scientifically proven.

"I had people take the questionnaire and then I put them in the brain scanner using functional magnetic resonance imaging," she explained, "and was able to show that those people who scored very high on the testosterone scale showed more activity in brain regions...linked to traits in testosterone."

The same was true in the three other constellations.

Helen Fisher has written several books based on her research, including, most recently, Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray. Gumtree.com

Narcissism linked to testosterone system

Romance or attachment junkies, who go searching for love from one person to another, tend to rank lower on the dopamine scale and higher on serotonin.

She also pointed to links between a passion for religion and the serotonin system, which is often associated with a more traditional outlook on the world.

Those who rank higher in dopamine—the explorers—are curious and energetic, sometimes even thrill seekers.

Directors are influenced by fetal testosterone and this constellation is associated with being good at math, computers, sports, and rules.

Negotiators, who are influenced by fetal estrogen, tend to be verbally adept, empathetic, and social creatures.

Fisher has since evolved the test into the NeuroColor Temperament Inventory, which can be used in workplaces to help managers and staff better understand one another and make use of their aptitudes.

Each of these brain systems has advantages, so companies might want to avoid focusing on hiring only one type of employee. But they can also be associated with some downsides.

"Narcissism has been linked with the testosterone system," Fisher noted. "Clinical depression has been linked with the estrogen system.

"I would think that accidents would be linked with the dopamine system," she continued. "And maybe religious zealots would be linked to the serotonin system.”

Fisher cautioned people not to think that they fall into one bucket or another.

"The only way to understand personality is to understand the full range of all the traits and where you fall on all the scales," she said.