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In 1957, an advertising executive from New Jersey announced that he had convinced moviegoers at a local theater to buy more popcorn using subliminal messaging. He claimed that 45,000 moviegoers were exposed to flashes of the words “Eat Popcorn” and “Drink Coca-Cola” on screen during a movie—with the words appearing and disappearing so quickly that viewers weren't even aware they were there.

And as a result, popcorn sales increased an average of 57.5% and Coke sales increased 18.1%. He got a lot of attention for this supposedly-scientific test, because those numbers are huge. It was every advertiser's perfect fantasy and every consumer's worst nightmare.

The idea that we could be constantly influenced by messages we don't even realize we're getting freaked people out. Except … the whole thing was a hoax. It turned out that there hadn't been an increase in popcorn or Coke sales at the theater in question.

And according to the theater manager, there hadn't been an experiment at all. But that hasn't stopped us from believing in the power of subliminal messages. Surveys from 1983, 1994, and 2004 show that about three-quarters of people who are familiar with subliminal messaging believe that companies use it — and a majority of those people think that it works.

Thankfully, research doesn't agree. Subliminal perception is for sure a thing. We definitely can react to a stimulus even when we can't consciously perceive it.

Which is different from superliminal perception—things that we do consciously perceive, even if we don't pay direct attention to them, like product placement. The line in between those two is known as the subjective threshold. Then, below that, there's the objective threshold—the level at which we don't perceive or react to the thing.

Subliminal perception research dates back to a book published in 1898, when a psychologist was looking to confirm the idea of a so-called “sub-waking self.” In a few experiments, he asked about two dozen participants to read numbers or letters on cards. But he held the cards so far away that they could only see a blur or small dot. When forced to choose, participants could usually distinguish between numbers and letters—they got it right around two-thirds of the time.

And they actually did better than chance at guessing exactly what was on each card. All of which suggested that they were perceiving the images on some level, even though they thought they were just guessing. A 1951 study in the journal Psychological Review found even clearer evidence by conditioning people to associate certain nonsense words with an electric shock.

Later, when the words were shown to them too briefly to be consciously seen, the researchers measured greater electrodermal activity for words associated with the shock. That's a slight change in how well skin conducts electricity, which is associated with sweating. In other words, even though subjects believed they hadn't seen anything, their bodies still anticipated the jolt.

So, we know subliminal perception is real. But subliminal advertising doesn't really work. Researchers have done plenty of studies, but no one seems to be able to show any real change in consumer behavior in response to subliminal ads.

For instance, a 1975 study in the journal Perceptual and Motor Skills flashed the words “Hershey's Chocolate” over a movie. But the researchers found that none of the 33 subjects given the message bought Hershey's in the ten days after the exposure. There's one exception, though.

A subliminal message can sort of work—but only if you're already motivated to follow it. A 2002 study of 81 undergraduates found that they did drink more water when subliminally primed with words like “dry” and “thirsty” — but if and only if they were already thirsty. If they weren't, the hidden messages didn't do anything.

In a follow-up experiment in the same study, 35 undergraduates were asked to pick between sports drinks described as “thirst-quenching” or “electrolyte-restoring”. They were only more likely to prefer the “thirst-quenching” drink if they were subliminally primed with thirst-related words and were already thirsty. So subliminal messages aren't going to make you do things you don't want to, but they might nudge you gently in a direction you're already headed.

It makes sense that subliminal messaging wouldn't drastically impact your behavior. The message is so subtle that it only has a subtle effect. Which is good, because subliminal advertising isn't technically illegal in the U.

S. While Australia and the U. K. have laws against it, the U.

S. doesn't forbid advertisers or networks from using it. That said, a 1979 Supreme Court case ruled that it isn't protected by the First Amendment. And the Federal Communications Commission's official stance is that it's misleading and shouldn't be used—and they reserve the right to yank the broadcasting license of anyone who does.

So nobody likes subliminal advertising; there just hasn't been that much effort put into stopping it. Probably because in the end, it isn't that useful. Advertisers don't really care about sneakily targeting people who are already motivated to buy their stuff—they'd rather invest in snagging new customers.

Thanks for watching this episode of SciShow Psych. If you want to learn about ways your mind can actually be hacked into buying things, check out our episode on how restaurants trick you into spending. [♩ OUTRO ].