Mere-exposure effect

Based on Wikipedia: Mere-exposure effect

The Strange Power of Showing Up

In 1968, a professor at Oregon State University conducted one of the strangest classroom experiments in the history of psychology. Charles Goetzinger had a student attend his class every day wearing nothing but a large black bag. Only the student's feet were visible. The bag-clad figure would simply sit on a table at the back of the room, session after session, saying nothing.

At first, the other students were hostile. Who was this weirdo? What was going on? But something remarkable happened over the following weeks. The hostility softened into curiosity. And then curiosity warmed into something that could only be described as friendship. By the end of the experiment, students had developed genuine fondness for the mysterious black bag in the corner of their classroom.

This bizarre outcome perfectly illustrated a psychological principle that shapes far more of our lives than we realize: the mere-exposure effect. Put simply, we tend to like things more just because we've seen them before. Not because they're objectively better. Not because we've learned anything new about them. Simply because they're familiar.

Familiarity Breeds Fondness

The scientist most responsible for establishing this effect was Robert Zajonc, a Polish-born American psychologist whose name is pronounced "ZY-unts." Before he ever ran a laboratory experiment, Zajonc made a crucial observation about how all organisms respond to new things.

When any creature encounters something unfamiliar, its first response is fear and avoidance. This makes evolutionary sense. Unknown things might be dangerous. But here's what Zajonc noticed: each subsequent encounter with that same thing produces a little less fear and a little more interest. Eventually, after enough exposures, the once-frightening novelty becomes something the organism actually seeks out.

Think about the first time you heard a song that later became one of your favorites. Chances are, you didn't love it immediately. Maybe you thought it was okay, or even slightly annoying. But something made you hear it again—perhaps the radio, a friend's playlist, or the algorithm of a streaming service. And somewhere around the third or fourth or tenth listen, something clicked. The song transformed from noise into pleasure.

This isn't just your imagination. Research has found that people generally like songs more after hearing them a few times. The melody becomes easier to follow. The hooks become anticipated pleasures rather than surprises. The familiarity itself becomes a source of comfort.

The Experiments That Proved It

In the nineteen sixties, Zajonc ran a series of experiments that established the mere-exposure effect as a genuine psychological phenomenon. His approach was elegantly simple: show people various stimuli repeatedly, then ask how much they like them.

He started with language itself. Zajonc analyzed how often different words appeared in written English and found something striking: words with positive meanings were used far more frequently than their negative counterparts. We say "good" more than "bad," "happy" more than "sad." Was this because positive things are more common in life? Or because the mere frequency of these words had colored our feelings about them?

To test this, Zajonc moved to stimuli that had no pre-existing meaning: Chinese characters shown to people who couldn't read Chinese, nonsense words that sounded like nothing in particular, random geometric shapes. He would show some of these stimuli many times and others only once or twice. Then he'd ask participants to rate how much they liked each one.

The results were consistent and striking. The stimuli people had seen more frequently were rated as more likeable, more pleasant, more positive. This held true even when participants couldn't consciously remember which items they'd seen before. The effect was operating below the level of awareness.

One particularly clever experiment tested this with Chinese characters. Participants were shown some characters briefly, then told that all the characters represented adjectives. When asked whether each character meant something positive or negative, they consistently rated the familiar characters as more positive—even though the characters were selected at random and had no actual positive or negative meanings.

But here's where it gets even more interesting. In a variation of this experiment, participants weren't asked about the characters at all. Instead, they were simply asked to describe their mood after viewing them. Those who had been repeatedly exposed to certain characters reported feeling happier than those who hadn't. The mere exposure hadn't just changed their opinions about the stimuli—it had actually improved their emotional state.

Before You Can Even Think

Perhaps the most radical claim Zajonc made was this: the mere-exposure effect doesn't require thought at all. In fact, it may work best when we're not thinking.

To test this, he used a device called a tachistoscope, which can flash images for incredibly brief durations—so brief that viewers can't consciously perceive what they've seen. When asked whether they'd seen an image, participants responded at chance levels, essentially guessing. They had no conscious awareness of the exposure.

Yet even these subliminal exposures produced the mere-exposure effect. People still preferred the images they'd been unknowingly shown. The preference was forming beneath the threshold of consciousness.

This led Zajonc to propose what he called the affective primacy hypothesis. "Affective" refers to feelings and emotions, and "primacy" means coming first. The hypothesis suggests that our emotional reactions to things—our likes and dislikes—occur before our thinking kicks in, not after. We feel first, then think. And often, our thinking simply serves to justify what we already feel.

This challenges a deeply held assumption about how human minds work. We like to believe we're rational creatures who gather information, weigh it carefully, and then form opinions. Zajonc argued the opposite: we form opinions quickly and unconsciously, then gather information to rationalize them.

As he put it, "preferences need no inferences."

The Chicken and the Tone

If the mere-exposure effect seems too human-centric, consider what happens with chickens. Researchers played tones of two different frequencies to chicken eggs—different groups of eggs heard different tones while the chicks were still developing inside their shells.

After the chicks hatched, the researchers played both tones to all of them. Each group of chicks consistently preferred the tone they had heard before hatching. They had developed a preference in the egg, before they had even entered the world, based on nothing more than familiarity.

This suggests the mere-exposure effect isn't some quirk of human psychology or cultural conditioning. It appears to be a fundamental feature of how nervous systems work. Familiar equals safe. Safe equals good. This logic is hardwired.

The Brain Behind the Effect

Neuroscience has provided some clues about where this effect originates. A key structure appears to be the amygdala, an almond-shaped region deep in the brain that processes emotional significance.

When researchers studied monkeys with damage to the amygdala, they found something revealing. These monkeys could still learn and remember perfectly well—their cognitive functions were intact. But their emotional responses were impaired. They had trouble developing the normal preferences that healthy monkeys showed.

The opposite pattern emerged when researchers studied monkeys with damage to the hippocampus, the brain structure crucial for forming new memories. These monkeys had significant cognitive impairments—they struggled to remember things. But their emotional responses remained fully functional. They could still develop preferences based on exposure.

This double dissociation—damage to the amygdala impairing emotion but not memory, damage to the hippocampus impairing memory but not emotion—supports Zajonc's claim that affect and cognition are separate systems. You can like something without being able to remember it, and you can remember something without having feelings about it.

Fluency and the Feeling of Ease

But why would repetition lead to liking? What's the mechanism?

The leading explanation involves something called perceptual fluency—how easily your brain can process a stimulus. When you encounter something familiar, your brain processes it more quickly and efficiently than something new. This ease of processing itself feels good.

Think about it this way. Recognizing a familiar face in a crowd requires less mental effort than scrutinizing an unfamiliar one. Reading a word you've seen many times is faster than puzzling out a new one. This fluency, this cognitive smoothness, appears to generate a small positive feeling that we then attribute to the thing itself.

We don't think "this is easy to process, therefore I feel slightly good, therefore I must like this thing." We just like it. The cognitive machinery works invisibly, and we experience only the output: a preference.

The Limits of Exposure

If familiarity breeds fondness, would infinite exposure breed infinite fondness? No. The effect has clear limits.

A comprehensive analysis of two hundred and eight experiments found that the mere-exposure effect typically reaches its maximum impact after somewhere between ten and twenty presentations. Beyond that, additional exposure often has no further positive effect—and may even start reducing liking.

You've probably experienced this with songs. A new track grows on you with each listen, becoming more enjoyable as it becomes more familiar. But there's a tipping point. Hear it too many times, and it becomes irritating. The hundredth repetition doesn't bring pleasure; it brings exhaustion.

This inverted U-shaped curve—liking increases with exposure up to a point, then decreases—has been documented for decades. The mere-exposure effect is real, but it's not unlimited.

The analysis also found some interesting variations. The effect is stronger when stimuli are unfamiliar to begin with and when they're presented briefly. It's weaker for children than adults. And curiously, introducing a delay between exposure and the measurement of liking actually strengthens the effect—as if the preference needs time to settle in.

There's also a dark side. When people already dislike something or someone, repeated exposure can make them dislike it even more. Familiarity doesn't always breed fondness. If the initial reaction is negative, repetition can amplify the negativity. The black bag experiment worked because students didn't start with strong negative feelings about bags. Had the bag initially represented something they hated, more exposure might have deepened their hostility.

Advertising and the Unconscious Consumer

The most obvious application of the mere-exposure effect is advertising. If people like things more simply from seeing them repeatedly, then the path to consumer preference seems clear: show them your product over and over.

And indeed, this works—to a point. Studies have shown that banner ads flashed repeatedly on computer screens are rated more favorably than ads shown less frequently. College students exposed to a "test" banner during a reading task liked that advertisement more than others, even though they weren't consciously paying attention to any of the ads.

This supports what advertisers have long believed: you don't need to persuade people with clever arguments. You don't need them to deeply engage with your message. Simple repetition creates a "memory trace" that unconsciously influences behavior. As one researcher put it, the approach tendencies created by mere exposure "may be preattitudinal"—they form before people have developed any conscious attitude about the brand at all.

But the research is more complicated than advertisers might hope. One study found that higher levels of media exposure were actually associated with lower reputations for companies, even when the coverage was mostly positive. How could more exposure hurt?

The likely explanation is that extensive exposure brings a large number of associations, and these associations tend to be mixed—some favorable, some unfavorable. A company nobody has heard of is a blank slate. A company everyone has heard of carries baggage, both good and bad.

This suggests the mere-exposure effect is most helpful when a company or product is genuinely new and unfamiliar to consumers. Getting your name out there matters most when no one knows your name. But there may not be an "optimal" level of exposure—just an initial boost from moving out of obscurity.

Choices Without Reasons

Perhaps the most profound implication of the mere-exposure effect is what it suggests about how we make decisions.

In one experiment, researchers made participants thirsty, then showed them either a happy face or an unpleasant face before offering them a beverage. Those who saw the happy face bought more beverages and were willing to pay more for them. Their choices were influenced by a fleeting emotional prime they weren't even aware of, not by any evaluation of the beverage itself.

Zajonc argued this is how many of our choices work. We like to think we make decisions based on careful analysis—weighing pros and cons, considering evidence, reasoning our way to conclusions. But more often, we decide first and rationalize later. We choose what we like, then construct reasons to justify the choice.

If preferences were truly based on rational evaluation of information, Zajonc pointed out, persuasion would be much easier than it actually is. You'd simply present people with the right facts, and they'd update their views accordingly. But anyone who has tried to change someone's mind about politics, religion, or their favorite sports team knows this isn't how it works. Our preferences are stubborn, resistant to evidence, and often formed by processes we're completely unaware of.

The Familiar Investor

The mere-exposure effect reaches far beyond advertising and music preferences. It shapes decisions with real financial consequences.

Stock traders, for instance, tend to invest disproportionately in domestic companies—simply because they're more familiar with them. This happens even when international markets offer similar or better alternatives based on objective financial metrics. The familiarity of hearing about a company, seeing its products, recognizing its name, creates a preference that has nothing to do with investment fundamentals.

Academic publishing shows a similar pattern. When researchers are surveyed about journal quality, they rate journals where they've previously published or served as reviewers dramatically higher than journals they haven't been involved with. The familiarity bias is so strong it distorts supposedly objective assessments of scholarly merit.

Even democracy isn't immune. Statistical analyses of voting patterns have found that a candidate's exposure—how often voters have seen or heard of them—has a strong effect on vote share, distinct from the popularity of their actual policies. Name recognition isn't just an advantage; it may be one of the most powerful advantages in politics.

When Exposure Backfires

Given the mere-exposure effect, a hopeful thought emerges: perhaps prejudice between social groups could be reduced simply by bringing them together. If people dislike what they don't know, wouldn't more exposure lead to more liking?

This idea, known as the contact hypothesis, has some support. Under the right conditions, increased contact between groups can reduce prejudice and improve relations.

But the mere-exposure research adds an important caveat. When groups already have negative attitudes toward each other, further exposure can actually increase hostility rather than reduce it. Familiarity amplifies whatever initial reaction existed. If that initial reaction was negative, repetition makes things worse, not better.

This means exposure alone isn't a solution to prejudice. The conditions of contact matter enormously. Forced interaction between hostile groups, without other interventions to shift attitudes, may deepen the conflict rather than resolve it.

The Warmth of the Known

Early in the study of this phenomenon, the psychologist Edward Titchener described what he called a "glow of warmth" that people feel in the presence of something familiar. That description has held up remarkably well.

The world is full of unknowns, and unknowns are potentially dangerous. When we encounter something we've seen before, something our brain can process fluently and easily, we experience a small but real feeling of comfort. This feeling isn't reasoned. It isn't justified by any evaluation. It simply arises from the machinery of perception doing what it evolved to do: favoring the known over the unknown.

This explains why we return to the same restaurants, the same vacation spots, the same songs, the same authors, the same comfortable routines—even when objectively better options might exist. The known carries a built-in advantage that novelty must overcome.

It also explains why change is hard, why new ideas face resistance, why the first reaction to anything unfamiliar is often skepticism or rejection. We're not necessarily close-minded. We're just wired to prefer what we've encountered before.

Understanding this doesn't make you immune to it. Even knowing about the mere-exposure effect, you'll still develop preferences based on familiarity. You'll still like songs more after hearing them a few times. You'll still trust brands you've seen before over brands you haven't.

But perhaps knowing about it offers something useful: a moment of pause before you conclude that your preference is based on merit. Maybe you don't like that candidate because of their policies. Maybe you don't prefer that product because it's superior. Maybe you just saw it first, or saw it more.

The black bag in the back of the classroom had no qualities that made it worthy of friendship. It was just there, day after day, until being there was enough.