Secrets of lasting friendships are hiding in the brain

We all know the feeling. You meet someone new, trade a few words, and it feels like you’ve known them forever. With others, no matter how much time you spend together, the connection never comes. But why?

Researchers say the answer might be hidden in the brain. A new study shows that people whose brains respond in similar ways to the world are more likely to become friends later. Long before two strangers grab coffee or share stories, their brains may already be in sync.

People prefer like-minded company

Humans have always preferred like-minded company. Scientists call this tendency homophily – the pull toward people who look, act, or think like us. It explains why friends often share hobbies, values, or humor.

But a deeper question has nagged researchers for years. Do friendships create this similarity, or do people seek out those who already see the world the same way?

Carolyn Parkinson at the University of California, Los Angeles wanted to find out. She and her colleagues designed an experiment that started before friendships had a chance to form.

The brain predicts future friendships

The team recruited 41 graduate students. Just before classes began, and before anyone had a chance to build connections, each student entered a brain scanner.

Inside, they watched 14 short movie clips. The clips covered many styles and topics – documentaries, comedies, debates, food, sports, science.

The researchers tracked activity across 214 brain regions. Each student’s brain left a unique signature of how they paid attention, reacted, and interpreted what they saw. These “neural fingerprints” became the key to predicting future friendships.

Mapping friendships in the brain

Two months later, all 288 students in the program completed surveys asking who they spent free time with. They repeated the surveys six months after that. These results created a living map of friendships – who became close, who drifted apart, and who stayed distant.

When the researchers compared this map to the brain data, patterns emerged. Students who became friends eight months later had already shown more similar brain responses back at the start.

The strongest overlap appeared in the orbitofrontal cortex, a region linked to how we assign value and meaning.

First impressions aren’t enough

Interestingly, at the two-month mark, there was no big difference between the brains of friends and non-friends. That means early friendships may form out of convenience – living nearby, attending the same events, or sitting together in class.

But as time passes, people sort themselves out. Those with deeper neural similarities grow closer. Others drift away.

The study also revealed that people who became closer showed stronger alignment across 42 brain regions.

Many of these areas help us understand stories, focus attention, and imagine other people’s perspectives. It seems that lasting friendships may rely on how similarly two minds interpret the world.

Similar ways of thinking

These findings go beyond shared taste in movies or music. Even after accounting for whether students enjoyed the clips, the brain similarities held. That suggests something more fundamental at work.

“Sociodemographic factors, at least in terms of what we were able to measure here, just seem to explain part of the picture,” Carolyn Parkinson explained.

In other words, friendships aren’t just about being the same age or studying the same subject. They may be built on hidden compatibilities in thought.

When thinking lines up

The brain regions that mattered most belong to networks that knit together memories, beliefs, and emotions into a picture of what’s happening.

When two people’s brains line up in these areas, conversations flow more easily. Communication feels natural rather than forced.

“People whose thinking processes are more similar find it easier to get on. When they say something, they just know what the other is thinking because it is how they think themselves,” noted Robin Dunbar at the University of Oxford.

Friendship is deeper than background

The team checked whether similarities in gender, nationality, or academic background explained the brain overlap. These factors played a role, but they didn’t erase the effect.

Even after adjusting for such variables, people who grew closer showed distinct neural alignment. This means that the roots of friendship run deeper than surface similarities.

You might connect with someone from a different culture, age, or background if your minds process experiences in the same way. That connection could outlast friendships built only on proximity or circumstance.

Are friendships born or shaped?

For some scientists, these results confirm an old intuition. Dunbar, who wasn’t part of the study, sees the findings as expected.

“That like attracts like, rather than people thrown together by accidents draw closer in their traits. In other words, close friends are born, not made,” noted Dunbar.

But the story isn’t entirely one-sided. Life still shapes friendships. Initial bonds may form by chance. Over time, those built on deeper alignment endure, while others fade.

Both circumstance and compatibility matter, but this research shows that compatibility often wins out.

Hidden compass in our brains

What does this mean for everyday life? It suggests that our brains act like quiet compasses, pointing us toward the people who will eventually become close friends.

We may not be aware of it, but the ease we feel with some people could reflect deep similarities in how our minds process the world.

Friendship, then, is more than shared interests or happy accidents. It is also about shared rhythms of thought, hidden long before we realize it.

The study is published in the journal Nature Human Behaviour.

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