What is love? What science says happens in the brain

Love is a strong bond of care and attachment to another person, made of several linked states rather than one feeling: desire, an intense focus on one person, and the calmer attachment that can last decades. Philosophers have named its kinds since ancient Greece. Brain research adds that early romantic love runs largely on the reward and motivation systems, and that lasting bonds draw on systems for attachment as well.

In short

• The Greeks split love into kinds, such as eros (desire), philia (friendship) and agape (selfless love), and the split still helps.
• Brain scans of people newly in love show the reward system at work, which is why early love can feel more like a craving than a mood.
• Long-term love isn't simply passion that faded: some long-married couples show the same reward activity plus activity in regions linked to attachment.

What kinds of love did the Greeks name?

Ancient Greek had several words where English has one. The Stanford Encyclopedia of Philosophy sets out the three that philosophers discuss most, and the British writer C. S. Lewis added a fourth in The Four Loves (1960):

Word	What it names	Example
Eros	Passionate desire, often sexual, drawn by the other person's qualities	Falling for someone
Philia	Friendly affection between equals, also for family or a community	A lifelong friendship
Agape	Love that doesn't depend on the other's merits; in Christian writing, God's love for people	Loving a stranger in need
Storge	Familiar, family affection that grows from closeness over time	A parent and child

The split matters because the kinds behave differently. Eros responds to what is attractive in someone. Agape is meant to love regardless. A full answer to "what is love" has to cover a crush, a friendship and a parent's devotion, and the science below mostly studies the first and the last.

What happens in the brain when you fall in love?

Early romantic love looks less like an emotion and more like a drive, a state of wanting focused on one person. That was the conclusion of a 2005 study in the Journal of Neurophysiology by Arthur Aron, Helen Fisher, Lucy Brown and colleagues. They scanned 17 young adults who had been intensely in love for between 1 and 17 months while each looked at a photo of their beloved and of a familiar acquaintance.

The beloved's face activated the right ventral tegmental area, a small region deep in the brain that makes dopamine, and the caudate nucleus, part of the reward system. The more intense a person's reported passion, the stronger the activity in part of the caudate. Aron described romantic love, as the American Physiological Society reported, as "a motivation or goal-oriented state that leads to various specific emotions, such as euphoria or anxiety": feelings that follow from wanting someone. A 2011 study of 18 Chinese students in love found the same reward regions active, a sign that the pattern isn't limited to one culture.

This fits what new love feels like: hard-to-stop thoughts about one person, energy, and a pull to be near them. The reward system is the same broad circuitry involved in pursuing food and other rewards, which is why the language of craving fits early love so well. It is also why Fisher proposed that love has three overlapping systems: lust (sex drive), attraction (focused romantic love) and attachment (the long-term bond).

What keeps people together?

The bond that lasts depends on chemistry studied most closely in a small rodent. Prairie voles usually pair for life, unlike most mammals, which made them the main animal for studying how bonds form. A 2023 review by Sara Blumenthal and Larry Young sets out what the experiments found: mating releases oxytocin and vasopressin, two hormones that also act as brain messengers, and they work together with dopamine to link a partner with reward. Blocking oxytocin receptors in key reward regions stopped female voles from forming the usual preference for their partner after mating, and knocking down a vasopressin receptor in another reward region, the ventral pallidum, also impaired that preference.

Humans are harder to study, since nobody blocks their hormones to see whether a marriage holds. The human evidence is indirect: brain scans, studies where people inhale oxytocin, and genetic variants in the oxytocin and vasopressin receptors that are linked, modestly, to how people rate their relationships. The reviewers stress that human bonds are also shaped by culture, personal history and experience in ways a vole's are not.

Psychology adds a second strand. Attachment theory, developed by John Bowlby for the bond between infants and caregivers, was extended to adult romance by Cindy Hazan and Phillip Shaver in 1987. It proposes that the patterns people learn early, secure or anxious or avoidant, shape how they love as adults. It connects to a broader claim in psychology that belonging is a basic need, the third level of Maslow's hierarchy.

Does love fade over time?

For many couples the passion settles, but it doesn't have to vanish. In a study published in 2012, Bianca Acevedo and colleagues scanned 17 people married for an average of 21.4 years who said they were still intensely in love. Looking at their partner's face activated the same dopamine-rich reward regions as in new lovers, and also regions linked to attachment and pair-bonding. The sample was small and chosen for unusually lasting passion, so it shows what is possible, not what is typical.

The psychologist Robert Sternberg offered a way to describe that change in his triangular theory of love, published in 1986. Love, he proposed, mixes three parts: intimacy (closeness), passion (desire) and commitment (the decision to stay). Each mix has a name.

Intimacy	Passion	Commitment	Sternberg's name
Yes	No	No	Liking
No	Yes	No	Infatuation
No	No	Yes	Empty love
Yes	Yes	No	Romantic love
Yes	No	Yes	Companionate love
No	Yes	Yes	Fatuous love
Yes	Yes	Yes	Consummate love

A worked example shows how one relationship moves through the table. In month two, a couple has strong passion and growing intimacy but no commitment yet: romantic love. In year three they move in together and plan a future, adding commitment: consummate love. By year twenty, if passion has quieted while closeness and commitment remain, they sit at companionate love, which many long-married people describe as the deepest kind. The long-married couples in Acevedo's study were the ones who had kept all three corners.

Still argued

Whether love is best called an emotion, a drive or a commitment is still argued by philosophers and psychologists alike, and the answer may differ for its different kinds. Brain imaging has its own limits. The studies scan small groups, often 17 or 18 people, mostly young and in Western or Westernized settings, and seeing a region light up shows where activity rises, not what the experience is. Critics caution that "love is dopamine" mistakes one measured ingredient for the whole.

So what is love, in the end?

No single chemical or brain region is love. The brain uses dopamine for wanting, oxytocin and vasopressin for bonding, and its thinking regions for the choices that keep a relationship going, and people experience the mix as one thing. Philosophy names the kinds and asks what love owes the beloved. Science shows how the body carries it out. Both describe something that changes over a life: from the pull of a new face to the steadier attachment of people who have chosen each other for years.

Check yourself

• Without looking back: why did Aron and his colleagues describe early romantic love as a drive rather than an emotion?
• What did the prairie vole experiments show about oxytocin and vasopressin, and why can't the same tests be run in people?
• Using Sternberg's three parts, how would you describe the difference between romantic and companionate love?

Sources

• Love — Bennett Helm, Stanford Encyclopedia of Philosophy, revised 2021
• Love may be a lateralized brain function, like speech — American Physiological Society, via ScienceDaily, 2005
• Neural correlates of long-term intense romantic love — Acevedo, Aron, Fisher and Brown, Social Cognitive and Affective Neuroscience, 2012
• The neurobiology of love and pair bonding from human and animal perspectives — Blumenthal and Young, Biology, 2023
• Reward and motivation systems: a brain mapping study of early-stage intense romantic love in Chinese participants — Xu et al., Human Brain Mapping, 2011
• Triangular theory of love — Wikipedia