Falling in love

What it's like

One person, suddenly everywhere.

It usually isn't calm. Researchers who study teenagers in the early, intense stage of love list its main features as more arousal, persistent thoughts about the person, overwhelming joy, and working to be near them.

What people notice

• They're all you think about: In infatuated people, a brain signal of attention was stronger for words connected to the person they loved than for words connected to a friend, and they recalled more of those words afterwards.
• Hard to focus: People in love often say they can't concentrate on schoolwork. In the lab, their partner's face grabbed attention even when it had nothing to do with the task, yet their scores on the task didn't drop.
• Nervous: People who had fallen in love in the past six months had more cortisol, a stress hormone, than people who were single or in long relationships. The researchers read it as the stress and arousal of starting something new.
• Butterflies: Your stomach has its own electrical rhythm, and emotion moves it: in one experiment it rose during emotional film clips, in step with how stirred up people said they felt. That study used films, not crushes, so it's a clue about butterflies rather than proof.
• Wired, not tired: Teenagers who had just fallen in love logged fewer hours of sleep than other teenagers, yet rated their sleep as better and felt less sleepy and more focused in the day, with brighter moods morning and evening.

What's happening in the brain

A drive with one target. The model lights each part as you read.

The wanting

Seventeen people who were intensely in love looked at a photo of the person they loved, then at a photo of someone they simply knew. For the person they loved, two dopamine-rich areas tied to reward and motivation were more active: the ventral tegmental area and the caudate. A team in Beijing repeated the experiment with 18 people and found the same two areas.

That is why the researchers describe romantic love as mainly a motivation system rather than an emotion: a drive that focuses on one specific person, and one that is distinct from the sex drive. It fits how it feels. The mood can swing from joy to dread in an hour, and the same person sits at the centre of both.

More than reward

In another group of 17 people deeply in love, pictures of their partner, compared with pictures of friends, also activated the insula and the anterior cingulate.

The critic goes quiet

Some areas were less active while people looked at their partner: the amygdala, the posterior cingulate and parts of the right prefrontal cortex. The same researchers later described the quieted regions as ones tied to negative emotions and to judging other people, a network for critical social assessment being turned down.

What these studies can't tell you

Each scan study here had 17 or 18 people who described themselves as intensely in love, looking at a photo inside a scanner. They show which areas are busier, not what each area is doing. And they studied people already in love, not people with a new crush.

How long it lasts

The start is the loudest part.

What changes, and what doesn't

• The stress settles: When the people who had recently fallen in love were tested again 12 to 24 months later, their hormone levels no longer differed from anyone else's.
• The wanting can stay: In 17 people married an average of 21 years who said they were still intensely in love, their partner's face still activated the ventral tegmental area, as in new love, along with areas linked to attachment.
• A no doesn't switch it off: In 15 people who had recently been rejected but were still in love, a photo of the person who rejected them still activated the ventral tegmental area. This reward system is involved whether someone is happily or unhappily in love.

None of this tells you what to do about a crush. What it does suggest is a way to read the pull: strong wanting is how this system works in anyone, so it is information about what you want, not a verdict on the other person or on you. And if the low after a rejection isn't lifting, talk to someone you trust.

Check what you know

Three questions about falling in love.

• A friend says a crush is just an emotion, like being happy or sad. What did the scan researchers conclude? It's mainly a motivation system: a drive toward one person. Seeing the person activated reward and motivation areas, and the authors concluded that romantic love is primarily a motivation system rather than an emotion.
• You've slept less since you fell for someone, but you feel great. What did a study of teenagers find? That pattern: fewer hours of sleep, but less sleepiness and a better mood. Teenagers newly in love logged fewer hours of sleep, yet reported better sleep quality, less daytime sleepiness and more positive mood.
• Someone says nerves are a bad sign: if it were right, you'd feel calm. What does the hormone study suggest? Stress hormones run higher at the start, then settle. People who had fallen in love in the past six months had higher cortisol; 12 to 24 months later it was no different from anyone else's.