Love, Desire, and the Brain: What Keeps Couples Together in the Long Run

Whoever loves does not live alone. In every mind that opens itself to another person, three roommates share a flat: desire, infatuation and attachment. They keep different hours, have different tastes and, if brain research is to be believed, even their own chemistry. And they rarely agree.

The image is more than a pretty invention. In 2002 the anthropologist Helen Fisher, together with Arthur Aron and colleagues, described exactly this division into three: three separate but interconnected systems in the brain, one for sexual desire (Fisher calls it lust), one for romantic attraction to a particular person and one for long-term attachment. Anyone who wants to understand why so many relationships break up after the first rush, and why some still burn after decades, should get to know this shared flat.

I have written a book on the subject, Herzklopfen für die Ewigkeit (in German). This text covers its core, checked against the studies it draws on.

Meet the roommates

Desire is the most uncomplicated of the three and at the same time the least reliable. According to Fisher, it depends mainly on the sex hormones, the estrogens and androgens, and it is not particularly choosy: it evolved to get mating started with any suitable partner. It likes what is new and unknown, and a little distance. Routine bores it.

Infatuation is the loudest. It moves in when the spark flies, and from then on the flat is unrecognizable. It has only one person on its mind, sleeps little and sends messages at hours it later regrets. When Aron, Fisher and colleagues put people who had just fallen in love into a brain scanner in 2005 and showed them a photo of their beloved, the strongest responses came from dopamine-rich regions of the reward and motivation system, the same circuits involved in craving and addiction. That explains why the first weeks feel like a high and why you keep wanting more of this one person.

Attachment is the quietest. It moves in inconspicuously, often before anyone notices, makes tea, takes out the rubbish and makes sure you feel safe with the other person. Fisher links it mainly to the messengers oxytocin and vasopressin. Oxytocin is often trivialized as the cuddle hormone; glue would be the better word. In 2012 Ruth Feldman's research group measured oxytocin in the blood of sixty couples who had just fallen in love. It was markedly higher than in singles. Six months later it had not dropped in the couples who were still together. And the initial level already distinguished the couples who stayed together from those who separated during that time.

The loud roommate

Infatuation has a peculiarity that can be measured if you know what to look for. In 1999 the Italian psychiatrist Donatella Marazziti examined twenty people who had fallen in love within the previous six months and compared them with patients with obsessive-compulsive disorder and a control group. She measured the density of serotonin transporters on blood platelets. In the people in love it was as low as in the OCD patients and clearly lower than in the other participants.

This finding needs to be handled with care. It does not say that infatuation is an obsessive-compulsive disorder, nor that people in love lack serotonin. It says that both states match on one single measure. But anyone who has ever been in love knows the circling thoughts that go with it.

An example: Emma and Julian meet at a party, and from the next morning on Emma has a new roommate who gives her no peace. Emma reads every message from Julian three times and wonders why this time he used a full stop instead of a smiley. At work she can hardly concentrate. This is not a character flaw. Her brain is in a state of emergency, and it is meant to be, for long enough that two people stick together.

Why infatuation moves out again

A state of emergency cannot last forever. Anyone who lived for years the way Emma lives in these weeks would lose their job, neglect their friends and eventually burn out. So the loud roommate grows quieter, and at some point she packs her boxes. That is not a defect; it is the design.

This is exactly where a consequential misunderstanding begins. When infatuation moves out, many people think: the magic is gone, so he or she must not have been the one after all. They mistake the farewell party for the end of the shared flat. Yet the quiet roommate signed the lease long ago.

What she can become was shown by the neuroscientist Bianca Acevedo in 2012. She put ten women and seven men into the scanner who had been married for an average of 21.4 years and said they still loved their partner intensely. For comparison they saw photos of a close friend, a highly familiar acquaintance and a less familiar person. At the sight of the partner, the same dopamine-rich reward system responded as in people newly in love. In addition, regions known from attachment research became active, for instance from the bond between mother and child.

In a couple like Maria and Thomas, married for 25 years, infatuation has never quite moved out; she drops by regularly. But the house now belongs to attachment. Two qualifications belong here. Acevedo selected couples who described themselves as intensely in love, so not every long-term couple. And the scanner shows activity; it does not measure dopamine. But the study refutes the assumption that passion inevitably dies out after twenty years.

What attachment achieves in everyday life is shown by another study. In 2006 the psychologist James Coan put married women into the scanner and told them they might receive electric shocks. When they held their husband's hand, the threat regions of their brain responded less than when they held a stranger's hand or no hand at all. The effect was strongest in the women who described their marriage as particularly good. In a good relationship, then, the partner is not just someone you like. He has become part of your own stress regulation.

Trouble in the flat: attachment versus desire

And this is where it gets tricky, because the quiet roommate and desire do not get along very well. The couples therapist Esther Perel described this in Mating in Captivity: love seeks closeness, security and reliability. Desire needs a little distance, something unknown, the sense that the other person is not completely and constantly available. The cosier attachment makes the flat, the more often desire yawns.

This raises the question almost every long-term couple knows and hardly any asks out loud: how do you desire someone you have just done your tax return with? Fisher's model gives a sober answer. Because the three systems are separate, they do not automatically move in step. You can love someone deeply and still feel little desire for them. That is nothing to be ashamed of and no proof that something is wrong. That is how the flat is built. Once you know this, you stop blaming desire for yawning and start asking what might wake it up again. More on that shortly.

The lodger in the basement: core beliefs

Sometimes the shared flat fails not because of the three roommates but because of someone nobody invited. If biology lays down this architecture in all of us, why do so many couples fail to use it? My answer as a therapist: the hardware is there; the fault usually lies in the software. In beliefs about love that we bring with us, often from childhood or from earlier hurts, and that run in the background like a lodger who has lived in the basement for years.

Markus, for instance, learned early that people leave. Somewhere inside him is the sentence: in the end I will be left anyway. As long as infatuation is loud, nobody hears the lodger. As soon as it quiets down and real closeness develops, he comes up the stairs. Markus starts finding fault with his partner, withdraws, picks fights. From the outside it looks like disinterest. From the inside it is protection: if I end it myself, nobody can leave me.

Patterns like these do not dissolve through a resolution in front of the mirror. Markus first needs help to recognize them at all, and then ways to calm the fear at the moment it arises. In my book I describe, among other things, tapping techniques from so-called energy psychology, such as EFT (Emotional Freedom Techniques). Not to be confused with Emotionally Focused Therapy, which shares the abbreviation and is an independent couples therapy approach developed by Leslie Greenberg and Sue Johnson; it is not what this self-help example refers to. I know how esoteric tapping sounds to many people, so here is the state of research: a 2016 meta-analysis by Morgan Clond evaluated 14 randomized trials with a total of 658 participants and found a marked reduction in anxiety, also in comparison with the control groups. It also noted, however, that there are too few comparisons with established treatments such as cognitive behavioral therapy. How tapping works has not been conclusively explained. One plausible explanation: you expose yourself to the fear in your mind while calming your body at the same time. You do not need to talk about meridians for that.

When the smoke alarm goes off: body first, then words

Every shared flat has a smoke alarm, and in some it is set too sensitively. Then it no longer tells burnt toast from a house fire, and the pan left on the stove sets off the same alarm as a real threat.

Every relationship guide says: talk to each other. I-statements, active listening. That is right, but it has a precondition that is often overlooked. You have to be in a state in which words can get through at all.

Remember your last big argument. Your pulse races, your view narrows, every sentence from the other person sounds like an attack. The neuroscientist Amy Arnsten has reviewed how even mild, uncontrollable stress rapidly and markedly impairs the prefrontal cortex, the region responsible for reflection, perspective-taking and self-control. This is not due to a lack of blood flow but to signalling pathways that stress triggers in the nerve cells themselves. A textbook-perfect I-statement then reaches no one. Nobody gives a lecture on fire safety while the smoke alarm is screaming either.

That is why I consider two tools underrated.

The first is a deliberate pause. Not the icy silence used to punish the other person; that is one of the most destructive patterns known to couples research. But an agreed interruption: we stop now, we will come back to it. John Gottman, who observed couples in the lab for decades, recommends at least twenty minutes when someone is emotionally flooded. That is how long, by his observations, the body needs to calm down. It is important to name a time to resume, so that the pause does not feel like a retreat, and not to use the time to gather arguments.

The second is touch. In 2007 the psychologist Beate Ditzen put 67 women through a standardized stress test: a speech and mental arithmetic in front of a strict panel. Beforehand they spent ten minutes with their partner. Some received a neck and shoulder massage from him, others words of encouragement, and a third group had no contact. After the touch, the rise in the stress hormone cortisol and in heart rate was markedly smaller. Encouraging words alone did not help. This fits Coan's findings on the partner's hand. A calm, undemanding touch tells the nervous system something words cannot say in that moment: you are safe. How this works biologically, though, is more complicated than the popular formula "touch releases oxytocin, and oxytocin blocks cortisol". Of all studies, in Ditzen's the oxytocin in the blood did not differ between the groups. That does not change the result.

Only once the body has calmed down does the conversation stand a chance. You have to go through the body to hand the steering wheel back to the mind. Some couples therefore sit down briefly before a difficult conversation, take three deep breaths together and tell each other: we are solving a problem together now, we are not defeating each other. It sounds trivial. It is an attempt to calm the smoke alarm before it goes off.

Getting desire back in from the balcony

That leaves the question most couples are preoccupied with after a few years: how do you keep this alive for ten, twenty, thirty years, between work, bills and full laundry baskets?

For Sara and Alex, another example couple, married for ten years, that point has come: infatuation moved out long ago, desire mostly sits bored on the balcony, and the living room is ruled by logistics. Who picks up the kids, who does the shopping. The two decide not to wait for the next stroke of luck. Five minutes a day in which they do not talk about logistics or the children, but about what has been on their minds and what made them happy. And one evening a week on which they do something they have never done before. A salsa class, for example, in which they step on each other's feet and embarrass themselves a little.

That sounds like project management, and this objection almost always comes up. But structure here is the opposite of rigidity. It removes the worry about whether you will find time for each other at all, and so creates the space in which you can let go again.

Why it has to be something new, rather than a cosy film night on the sofa, is something Arthur Aron investigated in a series of studies. In 1993 he and Charlotte Reissman and Michael Bergen divided 53 married couples into groups for ten weeks: some spent an hour and a half each week doing something they themselves found exciting, others something pleasant, and a third group nothing special. Marital satisfaction rose more with the exciting activities than with the pleasant ones. In 2000 Aron showed in the lab that even a seven-minute unfamiliar, slightly exciting task that a couple tackles together increases the experienced quality of the relationship, measured by questionnaires and by video recordings of conversations. Hormones, incidentally, were not measured in these studies. Aron's explanation is psychological: new things expand the self, and whoever experiences this expansion with their partner connects the good feeling with them.

Perel reports that people often feel most drawn to their partner precisely when they experience them from a little distance: when the partner is completely in their element, or when they see that other people are drawn to them. In the salsa class Sara sees her husband for a moment in a way she does not see him at home. That small distance is exactly what desire needs. What Sara and Alex are doing is trying to have both: a reliable framework that attachment loves, and within it, deliberately, something unknown that brings desire back in from the balcony.

And sometimes something very small is enough. In 2010 the psychologist Sara Algoe showed that everyday gratitude works like a booster shot for relationships: whoever notices their partner's kindness on a given day and feels grateful for it feels more connected to them the next day.

What remains

Love is not a studio flat. Infatuation moves in, makes noise and moves out again, and it has to. Attachment stays, and in some couples it still regularly invites infatuation over for dinner after decades. Desire is the moodiest of all: it does not stay of its own accord, but it comes back when you offer it something new. Whether the shared flat holds depends less on chance than on the lodger in the basement, on the way we argue and on the willingness to try new things together.

I would like to end with a question that also closes the podcast. If the people we love most become, over time, part of how we react to stress, how we calm down and what we experience as safe: what are your relationships making of you right now?

This text is no substitute for couples therapy or psychotherapy. If conflicts in your relationship frighten you or violence is involved, please seek professional support.

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