When I first heard of the mere-exposure effect, I thought it was named after someone named Mere. But no, it was discovered in 1968 by social psychologist Robert Zajonc, and mere simply means mere, as in a mere coincidence or mere chance.

The mere-exposure effect says that people tend to develop a preference for things they have been repeatedly exposed to. Merely seeing, tasting, or hearing something again and again is enough to make us have positive feelings about it. That doesn’t mean we can’t be charmed by something or someone and take an instant liking to them. But overall, we prefer things we’re familiar with.

We like certain foods because we’ve eaten them time and again. And we don’t like certain foods because we tried them once, turned up our noses, and never ate them again. It could be we didn’t develop a taste for them because we didn’t give the mere-exposure effect a chance to kick in.

Certain songs get stuck in our heads and our hearts, not because they are good songs, but because we’ve heard them 300 times. We buy certain products because we’ve seen 3,000 commercials for them. We like certain celebrities because everywhere we look, we see their faces. And the list goes ever on.

Is there any scientific evidence that the mere-exposure effect is real? Oh, my, yes. Studies abound.

In one, three women visited a college class. One sat in on the class 15 times; another, ten times; and another, five times. None of the women interacted with any of the other students or the professor. They just attended the class and left when it was over.

At the end of the term, the students were shown pictures of four women and asked to fill out questionnaires rating their positive or negative reactions to each one. The picture of the woman who had sat in 15 times got favorable impressions from most students. The one who visited ten, less so. The one who visited five times, even less so. And a fourth woman who had never visited the class at all, received the least favorable reactions.

In another study, college students were asked to taste some unfamiliar fruit juices. Some were tasted 20 times, some ten times, some five, and some zero.

After the tasting phase of the experiment, the students rated each of the juices. It should come as no surprise that the more a juice had been tasted, the higher its rating.

A third study had people evaluate a dozen websites. Home pages that were similar in design to well-known sites were rated as more pleasing and easier to use than those with unfamiliar designs.

Product placement in movies, repeated plays of songs on the radio, the same faces on covers of magazines in the checkout line, and fast food sandwiches on billboards are all efforts to force familiarity on us.

If the mere-exposure effect teaches us anything, it’s to be careful what we allow ourselves to be repeatedly exposed to. Good or bad, we’ll come to like it.