What Is the Mere Exposure Effect in Psychology?

Would you rather watch a new movie, or an old favorite? Would you rather try a dish you’ve never had at a restaurant, or stick with something you know you’ll like? According to psychologists, there’s a reason why we may prefer the familiar over the novel. Researchers studying the "mere exposure effect" have found that we often prefer things that we’ve seen before over things that are new.

Key Research

In 1968, social psychologist Robert Zajonc published a landmark paper on the mere exposure effect. Zajonc’s hypothesis was that simply being exposed to something on a repeated basis was enough to make people like that thing. According to Zajonc, people didn’t need to experience a reward or positive outcome while around the object—simply being exposed to the object would be enough to make people like it.

To test this, Zajonc had participants read words in a foreign language out loud. Zajonc varied how often participants read each word (up to 25 repetitions). Next, after reading the words, participants were asked to guess at the meaning of each word by filling out a rating scale (indicating how positive or negative they thought the meaning of the word was). He found that participants liked words that they had said more often, while words that participants hadn’t read at all were rated more negatively, and words that had been read 25 times were rated highest. Just the mere exposure to the word was enough to make participants like it more.

Example of the Mere Exposure Effect

One place where the mere exposure effect occurs is in advertising—in fact, in his original paper, Zajonc mentioned the importance of mere exposure to advertisers. The mere exposure effect explains why seeing the same advertisement multiple times could be more convincing than just seeing it once: that “as seen on TV” product may seem silly the first time you hear about it, but after seeing the ad a few more times, you start to think about buying the product yourself.

Of course, there’s a caveat here: the mere exposure effect doesn’t happen for things we initially dislike—so if you really hate that advertising jingle you just heard, hearing it more won’t cause you to feel inexplicably drawn to the product advertised.

When Does the Mere Exposure Effect Happen?

Since Zajonc’s initial study, numerous researchers have investigated the mere exposure effect. Researchers have found that our liking for a variety of things (including pictures, sounds, foods, and smells) can be increased with repeated exposure, suggesting that the mere exposure effect isn’t limited to just one of our senses. Additionally, researchers have found that the mere exposure effect occurs in studies with human research participants as well as in studies with non-human animals.

One of the most striking findings from this research is that people don’t even have to consciously notice the object in order for the mere exposure effect to occur. In one line of research, Zajonc and his colleagues tested what happened when participants were shown images subliminally. Images were flashed in front of participants for less than one second—quickly enough that the participants were unable to recognize which image they had been shown. The researchers found that participants liked the images better when they had previously seen them (compared to new images). Moreover, participants who were repeatedly shown the same set of images reported being in a more positive mood (compared to participants who only saw each image once). In other words, being subliminally shown a set of images was able to affect participants’ preferences and moods.

In a 2017 study, psychologist R. Matthew Montoya and colleagues conducted a meta-analysis on the mere exposure effect, an analysis combining the results of previous research studies—with a total of over 8,000 research participants. The researchers found that the mere exposure effect did indeed occur when participants were repeatedly exposed to images, but not when participants were repeatedly exposed to sounds (although the researchers point out that this may have had to do with the particular details of these studies, such as the types of sounds researchers used, and that some individual studies did find that the mere exposure effect occurs for sounds). Another key finding from this meta-analysis was that participants eventually started to like objects less after many repeated exposures. In other words, a smaller number of repeated exposures will make you like something more—but, if the repeated exposures continue, you could eventually get tired of it.

Explanations for the Mere Exposure Effect

In the decades since Zajonc published his paper on the mere exposure effect, researchers have suggested several theories to explain why the effect happens. Two of the leading theories are that mere exposure makes us feel less uncertain, and that it increases what psychologists call perceptual fluency.

Uncertainty Reduction

According to Zajonc and his colleagues, the mere exposure effect occurs because being repeatedly exposed to the same person, image, or object reduces the uncertainty we feel. According to this idea (based in evolutionary psychology), we’re primed to be cautious around new things, since they could be dangerous to us. However, when we see the same thing over and over and nothing bad happens, we start to realize that there’s nothing to be afraid of. In other words, the mere exposure effect occurs because we feel more positively about something familiar compared to something that is new (and potentially dangerous).

As an example of this, think of a neighbor you pass regularly in the hall, but haven’t stopped to talk to beyond exchanging brief pleasantries. Even though you don’t know anything substantial about this person, you probably have a positive impression of them—just because you’ve seen them regularly and you’ve never had a bad interaction.

Perceptual Fluency

The perceptual fluency perspective is based on the idea that, when we’ve seen something before, it’s easier for us to understand and interpret it. For example, think about the experience of watching a complex, experimental film. The first time you watch the film, you might find yourself struggling to keep track of what’s happening and who the characters are, and you may not enjoy the movie very much as a result. However, if you watch the movie a second time, the characters and plot will be more familiar to you: psychologists would say that you experienced more perceptual fluency on the second viewing.

According to this perspective, experiencing perceptual fluency puts us in a positive mood. However, we don’t necessarily realize that we’re in a good mood because we’re experiencing fluency: instead, we may simply assume that we’re in a good mood because we liked the thing we just saw. In other words, as a result of experiencing perceptual fluency, we may decide that we liked the movie more on the second viewing.

While psychologists are still debating what causes the mere exposure effect, it seems that having been previously exposed to something can change how we feel about it. And it may explain why, at least sometimes, we tend to prefer things that are already familiar to us.

Sources and Additional Reading

• Chenier, Troy & Winkielman, Piotr. “Mere Exposure Effect.” Encyclopedia of Social Psychology. Edited by Roy F. Baumeister and Kathleen D. Vohs, SAGE Publications, 2007, 556-558. http://dx.doi.org/10.4135/9781412956253.n332
• Montoya, R. M., Horton, R. S., Vevea, J. L., Citkowicz, M., & Lauber, E. A. (2017). A re-examination of the mere exposure effect: The influence of repeated exposure on recognition, familiarity, and liking. Psychological Bulletin, 143(5), 459-498. https://psycnet.apa.org/record/2017-10109-001
• Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of Personality and Social Psychology, 9(2.2), 1-27. https://psycnet.apa.org/record/1968-12019-001
• Zajonc, R. B. (2001). Mere exposure: A gateway to the subliminal. Current Directions in Psychological Science, 10(6), 224-228. https://doi.org/10.1111/1467-8721.00154