The mere exposure effect.
You like people more just by seeing them.

In 1968, psychologist Robert Zajonc published a paper with a simple but unsettling thesis: mere repeated exposure to a stimulus is sufficient to enhance your attitude toward it. He called it the mere exposure effect.

He demonstrated it first with nonsense syllables, then with Chinese characters shown to people who couldn't read Chinese, then with photographs of strangers. In every case, the more often people were shown something — even subliminally, without awareness — the more they rated it positively. No interaction required. No reason given. Just repetition.

The effect holds for faces, music, words, shapes, and — most relevant to social life — for people. The more you encounter someone, the more you tend to like them. Not because they've earned it. Not because you've had meaningful exchanges. Simply because they've become familiar.

Why the brain treats familiarity as safety

The underlying mechanism is threat detection. The brain continuously scans for danger, and unfamiliar stimuli register as potential threats until proven otherwise. Each time you encounter something without incident, your threat response dials down slightly and something like comfort takes its place.

With people, this translates directly to warmth. The stranger in your office who you walk past every morning becomes someone you nod to, then someone you say good morning to, then someone you genuinely like — without any conscious decision being made.

How often do you need to see someone?

Zajonc's original research suggested the effect plateaus around 10–20 exposures, with the steepest gains in the first few encounters. Later research has found the optimal range to be somewhere between 10 and 30 exposures — beyond that, the returns diminish and can even reverse if the repeated exposure feels forced or unwanted.

The proximity connection

This is why proximity matters so much in friendship formation. Dozens of studies on college dorms, workplaces, and neighborhoods have found the same thing: the people who end up as your friends are overwhelmingly the people who were geographically close to you — not the most interesting, or the most compatible, but simply the most accessible.

In one classic study, students were randomly assigned to dorm rooms. A year later, they were most likely to be friends with the people whose rooms were physically closest to theirs — not because of any shared interests, but because proximity created the exposures that generated liking.

What changes when you know this

Once you understand the mere exposure effect, you can stop waiting for lightning-bolt connection and start engineering proximity instead. If there's someone you'd like to know better, the most reliable strategy isn't a brilliant conversation — it's simply showing up in the same contexts repeatedly.

This is what makes social routines so valuable. The gym class you take every Tuesday. The coffee place you stop at before work. The neighborhood bar where you're a regular. These aren't just habits — they're exposure engines, quietly building familiarity with a consistent cast of people around you.

The flip side: absence degrades familiarity

The effect works in reverse, too. When you stop seeing someone, familiarity fades, and with it, some of the warmth. This is one of the reasons friendships that feel solid can erode faster than expected when life circumstances change — a move, a new job, a different routine.

You don't need a falling out to lose a friend. You just need the exposures to stop. The relationship doesn't collapse; it gradually becomes unfamiliar. And unfamiliar, to a brain that runs on pattern recognition, quietly becomes distant.