Scientists have their own models of love and attraction, formed independently and through different methods. Though there are likely many models, I will stick to the model of love defined by Helen Fisher.
Helen E. Fisher, PhD biological anthropologist, is a Senior Research Fellow, at The Kinsey Institute, Indiana University, and a Member of the Center For Human Evolutionary Studies in the Department of Anthropology at Rutgers University. She has written six books on the evolution, biology, and psychology of human sexuality, monogamy, adultery and divorce, gender differences in the brain, the neural chemistry of romantic love and attachment, human biologically-based personality styles, why we fall in love with one person rather than another, hooking up, friends with benefits, living together and other current trends, and the future of relationships – what she calls: slow love.
Fisher maintains that humans have evolved three emotional systems used in mammalian mating and reproduction: lust, attraction, and attachment. Not all mammals have all three emotional systems, but they exist in all human cultures studied.
Lust is also known as sex drive or libido, is the urge for sexual consummation. Lust is associated with estrogens and androgens, and with activity in the amygdala and hypothalamus.
Attraction is an emotional system which causes an individual to prefer courtship with specific other individuals. This saves on resources used for courting and provides a fitness benefit if the attraction is directed at mates who will produce more fit offspring. In humans, it is also known as passionate love, romantic love, and obsessive love. Attraction is associated with increased activity of dopamine and norepinephrine and decreased activity in serotonin in various parts of the brain. There is a long list of symptoms associated with attraction:
- The loved one takes on special meaning.
- An inability to love other individuals.
- Intrusive thinking about loved one.
- Tendency to focus only on the loved one’s positive qualities.
- Quickly changing psychophysiological responses including euphoria, sleeplessness, shyness, flushing, butterflies in the stomach, dilated pupils, accelerated breathing, and anxiety.
- Profound empathy and sexual desire for loved one.
In humans, attachment is also called companionate love. It’s basically the emotion which keeps long-term partners together. It’s associated with feelings of calm, security, and emotional union with the partner. Neurologically, it’s associated with oxytocin and vasopressin in certain parts of the brain.
In a TED Talk from 2006, Helen Fisher takes on a tricky topic – love – and explains its evolution, its biochemical foundations, and its social importance. She closes with a warning about the potential disaster inherent in antidepressant abuse.
“Love can start off with any of these three feelings,” Fisher maintains. “Some people have sex first and then fall in love. Some fall head over heels in love, then climb into bed. Some feel deeply attached to someone they have known for months or years; then circumstances change, they fall madly in love and have sex.” But the sex drive evolved to encourage you to seek a range of partners; romantic love evolved to enable you to focus your mating energy on just one at a time, and attachment evolved to enable you to feel deep union to this person long enough to rear your infants as a team.”
But these brain systems can be tricky. Having sex, Fisher says, can drive up dopamine in the brain and push you over the threshold toward falling in love. And with orgasm, you experience a flood of oxytocin and vasopressin – giving you feelings of attachment. “Casual sex isn’t always casual” Fisher reports, “it can trigger a host of powerful feelings.” In fact, Fisher believes that men and women often engage in “hooking up” to unconsciously trigger these feelings of romance and attachment.
What happens when you fall in love? Fisher says it begins when someone takes on “special meaning.” “The world has a new center,” Fisher says, “then you focus on him or her. Your beloved’s car is different from every other car in the parking lot, for example. People can list what they don’t like about their sweetheart, but they sweep these things aside and focus on what they adore. Intense energy, elation, mood swings, emotional dependence, separation anxiety, possessiveness, a pounding heart, and craving are all central to this madness. But most important is obsessive thinking.” As Fisher says, “Someone is camping in your head.”
Fisher and her colleagues have put over 75 people into a brain scanner (fMRI) to study the brain circuitry of romantic love: among them, 17 had just fallen madly in love; 15 had just been dumped; 17 reported they were still in love after an average of 21 years of marriage. One of her central ideas is that romantic love is a drive stronger than the sex drive. As she says, “After all, if you casually ask someone to go to bed with you and they refuse, you don’t slip into a depression, or commit suicide or homicide; but around the world people suffer terribly from rejection in love.”
Fisher also maintains that taking serotonin-enhancing antidepressants (SSRIs) can potentially dampen feelings of romantic love and attachment, as well as the sex drive.
Fisher has looked at marriage and divorce in over 80 societies, adultery in over 42 cultures, patterns of monogamy and desertion in birds and mammals, and gender differences in the brain and behavior. In her 2009 work, Why Him? Why Her?, she reported on four biologically-based personality styles, and using data on 28,000 people collected on the dating site Chemistry.com, she explores who you naturally are and why you are chemically drawn to some people rather than others. Today she is applying her understanding of brain chemistry and personality to business, specifically the neuroscience of leadership and innovation.
 Helen Fisher website.
 “Defining the Brain Systems of Lust, Romantic Attraction, and Attachment” Fisher, H.E., Aron, A., Mashek, D. et al. Arch Sex Behav (2002) 31: 413. Link to the article.