How Love Works


Only 3 percent of mammals (aside from humans) form "family" relationships like we do. See pictures of famous historical couples. LWA/Dann Tardif/Getty Images

There are plenty of one-liners in both the film and literary versions of the vampire story "Twilight" that are known to provoke eye rolls (even among fans). But one particular sentence from lead bloodsucker Edward Cullen seems to stick with viewers and readers: "You're like my own personal brand of heroin."

While Cullen's profession of love to his mortal soulmate, Bella Swan, might seem over the top in every way, he's not totally off the mark. As it turns out, like narcotics, love can absolutely be habit-forming and even compulsive. And if you've ever been in love, you've probably at least considered classifying the feeling as an addiction. And guess what: You were right. As it turns out, your gut feeling was right — scientists have spent decades discovering how the same chemical process at play in other kinds of addiction plays a role in why, when and how that takes place with addiction takes place when we fall in love.

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The truth is, love isn't simply a societal construct or a silly concept that's central to over-the-top epic romances and cheesy rom-coms. Love is a chemical state of mind that's part of our genes and influenced by our upbringing. Humans are wired for romance for many reasons, but in part because our DNA is driving us toward a path of becoming loving parents who care diligently for our helpless offspring (whether or not we choose to fulfill that destiny is of course another story, but our drive to love remains, regardless).

In this article, we'll find out what love really is and what happens in our bodies that makes us fall in love — and ensures we stay there. We'll also look at what attracts us to someone in the first place. Is it their pheromones, or do they just fit the right "love template?"

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If you've ever been in love, you've probably at least considered classifying the feeling as an addiction. And guess what? You were right. The same chemical process is taking place. Andia/Getty Images

Romantic love both exhilarates and motivates us. It is also critical to the continuation of our species. Without the attachment of romantic love, we would live in an entirely different society that more closely resembled some (but not all) of those social circles in the animal world. The chemicals that race around in our brain when we're in love serve several purposes, and the primary goal is the continuation of our species. Those chemicals are what make us want to form families and have children. Once we have children, those chemicals change to encourage us to stay together to raise those children. So in a sense, love really is a chemical addiction that occurs to keep us reproducing.

There's solid science to support the chemistry of love in all its forms. According to a 1997 paper entitled "Lust, Attraction, and Attachment in Mammalian Reproduction," by Dr. Helen Fisher from Rutgers University, romantic love can be broken down into three categories: lust, attraction and attachment. And depending on the type of love you're talking about, different bodily chemicals are involved.

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Lust, driven by the desire for sexual gratification, is primarily motivated by the production of sex hormones testosterone and estrogen thanks to the brain's hypothalamus. Attraction, although closely related, is something different; it hinges on the brain's reward system and is the reason why new relationships feel so insanely intoxicating. This form of love relies on other hypothalamus products: dopamine and norepinephrine, which induce giddy, energetic, euphoria. And attachment, the main factor in long-term relationships, is largely rooted in the hormones oxytocin (aka "the cuddle hormone") and vasopressin, which promote bonding.

­Regardless of the country or culture, romantic love plays an important part. While cultural differences in how that love is displayed vary greatly, the fact that romantic love exists is undisputed.

But let's get down to the nitty gritty. What is it that makes us fall in love with someone in the first place?

We all have a template for the ideal partner buried somewhere in our subconscious. It is this love map that decides which person in that crowded room catches our eye. But how is this template formed?

Appearance

Many researchers have speculated that we tend to go for potential members of the opposite sex who remind us of our parents. Some have even found that we tend to be attracted to those who remind us of ourselves. In fact, cognitive psychologist David Perrett, at the University of St. Andrews in Scotland, did an experiment in which he morphed a digitized photo of the subject's own face into a face of the opposite sex. Then, he had the subject select from a series of photos which one he or she found most attractive. According to Perrett, his subjects always preferred the morphed version of their own face (and they didn't recognize it as their own).

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Of course, there are plenty of other theories regarding why certain people are attracted to certain types of appearance and the implications "attractiveness" has on initial interest and romance. There are evolutionary explanations based on assumptions around reproductive capabilities, predilections for proportional features, and of course, personal preference. Several studies examining the role of attraction in online dating have found that not only are attractive individuals more likely to be contacted than unattractive individuals but that attractive individuals were more selective in who they chose to contact (maybe those takeaways are no-brainers for anyone who's ever swiped right or left on a dating app).

Personality

Like appearance, we tend to form preferences for those who remind us of our parents (or others close to us through childhood) because of their personality, sense of humor, likes and dislikes, etc. One study found that perceptions of physical attractiveness are influenced by positive personality traits, like honesty and helpfulness, and people who exhibit negative traits, like unfairness and rudeness, appear to be less physically attractive to observers.

Pheromones

The debated topic of human pheromones still carries some weight in the field of love research. The word "pheromone" comes from the Greek words pherein and hormone, meaning "excitement carrier."

In the animal world, pheromones are individual scent "prints" found in urine or sweat that dictate sexual behavior and attract the opposite sex. They help animals identify each other and choose a mate with an immune system different enough from their own to ensure healthy offspring. They have a special organ in their noses called the vomeronasal organ (VNO) that detects this odorless chemical.

The existence of human pheromones was discovered in 1986 by scientists at the Chemical Senses Center in Philadelphia and its counterpart in France. They found these chemicals in human sweat. A human VNO has also been found in some, but not all, people. Even if the VNO isn't present in all of us — and may not be working in those who do have it — there is still evidence that smell is an important aspect of love (note the booming perfume industry). An experiment was conducted where a group of females smelled the unwashed tee shirts of a group of sweaty males, and each had to select the one to whom she was most "attracted." Just like in the animal world, the majority of the females chose a shirt from the male whose immune system was the most different from their own.

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Chocolate may just be the world's favorite aphrodisiac. REDA&CO/Getty Images

Aphrodisiacs are, to some, considered to be more folklore than fact. Still, many people continue to believe in the love-inducing effects of certain foods, herbs and extracts. There are several common aphrodisiacs that may or may not have actual effects on your love life:

  • Asparagus: The vitamin E in this vegetable is said to stimulate sex hormones.
  • Chili peppers: Some researchers say that eating hot peppers makes us release endorphins, which might lead to "other things."
  • Chocolate: This favorite for Valentine's Day contains phenylethylamine, one of the chemicals your body produces naturally when you're in love.
  • Oysters: Oysters contain high levels of zinc, which reportedly increased the production of testosterone. Testosterone increases libido for both sexes.

Others include ginkgo, Spanish fly (dead beetle parts) and damiana.

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Most of these are supposed to create the desire for sex or improve male sexual ability rather than attract a mate. But, if you're stimulating hormones that make you more interested, then you're more likely to meet someone and fall in love. And, even if they don't actually work, some say that if you think it's going to work, you're halfway there.

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A couple kiss as snow falls during a winter storm in Times Square in New York on January 31, 2021. KENA BETANCUR/Getty Images

There are three distinct types or stages of "love":

  1. Lust, or erotic passion
  2. Attraction, or romantic passion
  3. Attachment, or commitment

When all three of these happen with the same person, you have a very strong bond. Sometimes, however, the one we lust after isn't the one we're actually in love with.

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Lust

When we're teenagers, just after puberty, estrogen and testosterone become active in our bodies for the first time and create the desire to experience "love." These desires, a.k.a. lust, play a big role both during puberty and throughout our lives.

According to an article by Lisa Diamond, entitled "Love and Sexual Desire" in the journal Current Directions in Psychological Science, lust and romantic love are two different things caused by different underlying substrates. Lust evolved for the purpose of sexual mating, while romantic love evolved because of the need for infant/child bonding. So even though we often experience lust for our romantic partner, sometimes we don't — and that's OK. Or, maybe we do, but we also lust after someone else. According to Diamond, that's normal.

As exologist John Money explains in Psychology Today, the line between love and lust in this way: "Love exists above the belt, lust below. Love is lyrical. Lust is lewd."

Pheromones, looks and our own learned predispositions for what we look for in a mate play an important role in whom we lust after, as well. Without lust, we might never find that special someone. But, while lust keeps us "looking around," it is our desire for romance that leads us to attraction.

Attraction

While the initial feelings may (or may not) come from lust, what happens next — if the relationship is to progress — is attraction. When attraction, or romantic passion, comes into play, we often lose our ability to think rationally — at least when it comes to the object of our attraction. The old saying "love is blind" is really accurate in this stage. We are often oblivious to any flaws our partner might have. We idealize them and can't get them off our minds. This overwhelming preoccupation and drive is part of our biology.

In this stage, couples spend many hours getting to know each other. If this attraction remains strong and is felt by both of them, then they usually enter the third stage: attachment.

The attachment, or commitment, stage of love is for the duration.
The attachment, or commitment, stage of love is for the duration.
Photo courtesy Morgue File

The attachment, or commitment, stage is love for the duration. You've passed fantasy love and are entering into real love. This stage of love has to be strong enough to withstand many problems and distractions. Studies by University of Minnesota researcher Ellen Berscheid and others have shown that the more we idealize the one we love, the stronger the relationship during the attachment stage.

Psychologists at the University of Texas in Austin have come to the same conclusion. They found that idealization appears to keep people together and keep them happier in marriage. "Usually, this is a matter of one person putting a good spin on the partner, seeing the partner as more responsive than he or she really is," said Ted Huston, the study's lead investigator. "People who do that tend to stay in relationships longer than those who can't or don't."

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Playing a key role in this stage are oxytocin, vasopressin and endorphins, which are released when having sex (more on this later).

Let's find out more about the chemistry of love.

There are a lot of chemicals, hormones and neurotransmitters racing around your brain and body when you're falling in love.
There are a lot of chemicals, hormones and neurotransmitters racing around your brain and body when you're falling in love.
Photo courtesy Morgue File

There are a lot of chemicals racing around your brain and body when you're falling in love, as well as when you're engaged in a long-term commitment. Over the years, researchers have amassed an impressive array of evidence detailing the roles of various hormones, neurotransmitters, and more that play integral roles in our love-based relationships.

Two of those hormones, estrogen and testosterone, play a role in our sex drive. These are the two chemicals that drive lust or sexual desire. And while testosterone has historically been thought of as a "male" hormone, it's present in males and females and is responsible for boosting the libido in everyone, regardless of their biological sex.

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There are a lot of chemicals racing around your brain and body when you're in love. Researchers are gradually learning more and more about the roles they play both when we are falling in love and when we're in long-term relationships. Of course, estrogen and testosterone play a role in sex drive. Without them, we might never venture into the "real love" arena.

That initial giddy feeling that comes with a new crush or potential love affair is often characterized by a racing heart, flushed skin and sweaty palms. Researchers say this is due to the dopamine, norepinephrine and phenylethylamine released by the body. Dopamine is thought to be the "pleasure chemical," producing a feeling of bliss. Norepinephrine is similar to adrenaline and produces the racing heart and excitement.

According to Helen Fisher, a well-known love researcher and an anthropologist at Rutgers University, together these two chemicals produce elation, intense energy, sleeplessness, craving, loss of appetite and focused attention. She also says, "The human body releases the cocktail of love rapture only when certain conditions are met and ... men more readily produce it than women, because of their more visual nature."

In 2013, Fisher presented research at the Being Human conference that indicated that several brain chemicals, including dopamine and testosterone, play a role in a person's drive toward romance, sex and other rewards. She suggested that the precise balance of these chemicals could shape a person's personality and influence the type of people they're attracted to. While people with "active" dopamine systems tended to be reward-driven and impulsive, curious, energetic and mentally flexible. These people appeared to be attracted to people similar to themselves. People with more active serotonin systems tended to be conscientious rule followers who also leaned toward similar-minded partners.

But two groups of people seemed to be drawn to their opposites: highly analytical and competitive testosterone-dominant people who were often attracted to the "high-estrogen and oxytocin" types who tended to be nurturing, empathic and introspective. And the attraction went both ways.

Researchers have also used are using functional magnetic resonance imaging (fMRI) to watch people's brains when they look at a photograph of their object of affection. According to Fisher, what they see in those scans during that "crazed, can't-think-of-anything-but stage of romance" — the attraction stage — is the biological drive to focus on one person. The scans showed increased blood flow in areas of the brain with high concentrations of receptors for dopamine — associated with states of euphoria, craving and addiction. High levels of dopamine are also associated with norepinephrine, which heightens attention, short-term memory, hyperactivity, sleeplessness and goal-oriented behavior. In other words, couples in this stage of love focus intently on the relationship and often on little else.

Another possible explanation for the intense focus and idealizing view that occurs in the attraction stage comes from researchers at University College London. They discovered that people in love have lower levels of serotonin and also that neural circuits associated with the way we assess others are suppressed. These lower serotonin levels are the same as those found in people with obsessive-compulsive disorders, possibly explaining why those in love "obsess" about their partner.

When it comes to matters of sex (often an important piece of the romantic love puzzle), a hormone called oxytocin plays a major role. Oxytocin is released, which helps bond the relationship plays a critical role in everything from childbirth to breastfeeding, but it's also a crucial bonding component in sexual activity, erection, ejaculation, orgasm and more.

According to researchers at the University of California, San Francisco, the hormone oxytocin has been shown to be "associated with the ability to maintain healthy interpersonal relationships and healthy psychological boundaries with other people." When it is released during orgasm, oxytocin helps initiate an emotional bond — the more sex, the greater the bond.

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Oxytocin has also been shown to play a role in fidelity: One study found that men in monogamous relationships who were administered oxytocin maintained a greater distance between themselves and attractive females than men who received placebos and men who were not in relationships. Oxytocin is also associated with mother/infant bonding, uterine contractions during labor in childbirth, and the "let down" reflex necessary for breastfeeding.

Vasopressin, an antidiuretic hormone, is another chemical that has been associated with the formation of long-term, monogamous relationships. Fisher believes that oxytocin and vasopressin interfere with the dopamine and norepinephrine pathways, which might explain why passionate love fades as attachment grows. But passionate love doesn't necessarily have to burn out, either. According to a study published in the journal Social Cognitive and Affective Neuroscience, the fMRI brain scans of long-term married individuals and individuals who had recently fallen in love revealed both groups demonstrated similar activity in specific brain regions. Researchers focused on one brain region specifically: the dopamine-rich ventral tegmental area (VTA) and concluded that "for some individuals, the reward-value associated with a long-term partner may be sustained, similar to new love, but also involves brain systems implicated in attachment and pair-bonding." One potential factor that contributed to the enduring passion of the long-married individuals? Sex (duh). Participants in long-term romantic love reported high sexual frequency, which is associated with activation of another part of the brain called the posterior hippocampus.

Endorphins, the body's natural painkillers, also play a key role in long-term relationships. They produce a general sense of well-being, including feeling soothed, peaceful and secure. Like dopamine and norepinephrine, endorphins are released during sex; they are also released during physical contact, exercise and other activities. According to Michel Odent of London's Primal Health Research Center, endorphins induce a "drug-like dependency." High endorphin levels are released during exercise, fear, love, music, chocolate eating, laughter, sex, orgasm, etc. Increased levels of endorphin inhibits pain in the body and reduced levels of endorphin inhibits positive feelings.

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What is it that causes some couples to make it for the long haul? Dave Simpson / Getty Images

What about when that euphoric feeling is gone? According to Ted Huston at the University of Texas, the speed at which courtship progresses often determines the ultimate success of the relationship. What they found was that the longer the courtship, the stronger the long-term relationship.

The feelings of passionate love, however, do lose their strength over time. Studies have shown that passionate love fades quickly and is nearly gone after two or three years. The chemicals responsible for "that lovin' feeling" (adrenaline, dopamine, norepinephrine, phenylethylamine, etc.) dwindle. Suddenly your lover has faults. Why has he or she changed, you may wonder. Actually, your partner probably hasn't changed at all; it's just that you're now able to see him or her rationally, rather than through the blinding hormones of infatuation and passionate love. At this stage, the relationship is either strong enough to endure, or the relationship ends.

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One study examined the fading of love through the lens of "self expansion," the concept that people have a fundamental motive to expand their sense of self through the formation of close relationships. While new romantic partners tend to continuously learn new things about each other early on in their relationships (which generates passion for one another), over time, "self-expansion opportunities diminish and less passion is generated." Researchers concluded that people in long-term relationships reported lower levels of self-expansion in their relationships than people who had been with partners for shorter periods of time and "while self-expansion is not a panacea that will cure all relationship ills, it is one of the more promising keys to enhancing positive affect between long-term partners who seem to have grown bored."

If the relationship can advance, then other chemicals kick in. Endorphins, for example, are still providing a sense of well-being and security. Additionally, oxytocin is still released when you're having sex, producing feelings of satisfaction and attachment. Vasopressin also continues to play a role in attachment.

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Voles mate for life and form family relatioships like humans do. Eye Ubiquitous/Getty Images

Only three percent of mammals (aside from the human species) form "family" relationships like we do. The prairie vole is one such animal. This vole mates for life and prefers spending time with its mate over spending time with any other voles. Voles even go to the extreme of avoiding voles of the opposite sex.

When they have offspring, the couple works together to care for them. They spend hours grooming each other and just hanging out together. Studies have been done to try to determine the chemical makeup that might explain why the prairie vole forms this lifelong, monogamous relationship when its very close relative, the montane vole, does not.

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According to studies by Larry Young, a social attachment researcher at Emory University, what happens is that when the prairie vole mates, like humans, the hormones oxytocin and vasopressin are released. Because the prairie vole has the needed receptors in its brain for these hormones in the regions responsible for reward and reinforcement, it forms a bond with its mate. That bond is for that particular vole based on its smell — sort of like an imprint. As further reinforcement, dopamine is also released in the brain's reward center when they have sex, making the experience enjoyable and ensuring that they want to do it again. And because of the oxytocin and vasopressin, they want to have sex with the same vole.

Because the montane vole does not have receptors for oxytocin or vasopressin in its brain, those chemicals have no effect, and they continue with their one-night stands. Other than those receptors, the two vole species are almost entirely the same in their physical makeup.

Originally Published: Feb 12, 2005

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