18.7: The Validity Effect and Mere Exposure

Validity Effect

Researchers have found that the mere repetition of a claim will lead many of the people who hear it to think that it is more likely to be true (than they would have if they hadn’t heard it before). This is called the validity effect: mere repetition makes the claim seem more likely to be true or more “valid.” This effect occurs with true statements, false statements, and statements that involve expressions of attitudes.

In experiments on the validity effect, subjects are often asked to rate the likelihood that a series of sentences (e.g., “Over 22% of the countries in the United Nations are in Africa”) are true. In a later session, they are asked to perform the same task, but with a partially overlapping set of sentences. On average, sentences encountered in the first session receive higher rankings; subjects are more inclined to think they are true, simply because they have encountered them before. We seem to tend to believe what we hear.

Since the validity effect can lead people to believe certain things without giving them any thought whatsoever, it is not surprising that it is exploited in propaganda, advertising, and related endeavors. If a company has enough money to run ads over and over, we will hear their claims about their product over and over. In many cases, this will strengthen our tendency to believe those claims. The validity effect may also account for some of the biases and stereotypes people have. If you hear over and over how redheads are hot tempered, this will increase your tendency to believe it (especially if you don’t interact much with redheads).

Mere Exposure

There is an old saying that familiarity breeds contempt. The more you see of someone, the more flaws you notice, and you wind up thinking less of them. But in many cases, this old saying is wrong. The more people are exposed to something (that they don’t already dislike), the more they tend to like it. They don’t need to interact with it, or hear it discussed. The mere exposure to the stimulus, without anything else happening at all, is enough to make them like it more.

In a standard experiment people (who don’t know Chinese) were exposed to several Chinese characters. Later they were shown a larger set of characters that included the ones they saw earlier, as well as some new ones. The more previous exposures subjects had to one of the characters, the more they liked it the second time around. Similar results have been obtained for many other sorts of stimuli. For example, in one study, subjects were first shown pictures of men’s faces. The more times subjects saw a picture, the more they thought they would like the person. Advertisers know about this.Not only can repeating their claims make them seem more valid (the validity effect), simply exposing us to the name or a picture of their product can give us a comfortable sense of familiarity that translates into a purchase when we go to the store.

Subliminal Mere Exposure

The mere exposure effect also occurs when people don’t remember that they had previously encountered the stimulus. It even works, up to a point, when they were previously presented with a stimulus but weren’t aware of it. Even when figures are flashed on a computer screen for a very brief time, too fast for subjects to be aware of them, the subjects will later show a preference for these figures over ones they haven’t been exposed to previously.

In these cases, the exposure is said to be subliminal; ‘sub’ means under and ‘liminal’ means consciously detectable, so something subliminal is something that can’t be detected consciously (something supraliminal is something that can be). Are we susceptible to the subliminal influences of others? Can people manipulate our thoughts and actions by sending subtle, subliminal messages? In 1957, it was widely reported that a marketing group had conducted an experiment in a New Jersey movie theater. According to the story, messages like “Eat popcorn” and “Buy a soda” had been flashed on the screen, but so briefly that people in the audience weren’t aware of them. And, the story continued, sales of popcorn rose by 58% and those of soda by over 15%.

No one wants to have their thoughts and actions manipulated by other people in this way, but fortunately there is no evidence that this story is true, or that others can manipulate our thoughts and actions in such dramatic ways. We certainly are influenced by people’s body language and tone of voice in ways we may not realize. But there is no evidence that advertisers or the manufacturers of “subliminal self-help” tapes can manipulate our thoughts and actions in any major ways.