A sceptic’s guide to subliminal advertising


Audiotapes promise to enlarge women’s breasts. A Republican TV attack ad aimed at candidate Al Gore briefly flashes the word “RATS” superimposed on Gore’s face. Judas Priest insert satanic messages in their music and a fan commits suicide as a result. Welcome to the world of subliminal messages. It sounds like something from the mind of a George Orwell or an Aldous Huxley. It does indeed seem like a terrifying prospect, but how real is the threat of subliminal manipulation?

The website dictionary.com define subliminal thus: existing or operating below the threshold of consciousness; being or employing stimuli insufficiently intense to produce a discrete sensation but often being or designed to be intense enough to influence the mental processes or the behaviour of the individual. Modern psychology accepts that much of our mental processing goes on outside of our immediate awareness—that our brains work on many tasks at once without monitoring them consciously. There is also an effect known as priming in which I mentioned in my post about Daniel Kahneman. This is when exposure to a stimulus influences a response to a later stimulus. Here is what I wrote:

“The most curious is an experiment by John Bargh, a psychologist at New York University. One group of college students were asked to arrange brief sentences including the words Florida, forgetful, bald, grey, or wrinkle. The other half were presented with none of these words. On completing their task, the students were told to walk down the corridor to another room. The experimenters recorded the time the students took to walk this short distance. Surprisingly, the students in the first group walked more slowly than those in the second group. This has been dubbed “the Florida effect.” The unconscious association of terms commonly associated with being old actually had an effect on the students’ walking pace.”

But when people think about subliminal messages they are describing something far more sinister.

The birth of subliminal advertising goes back to a 1957 experiment by a market researcher named James Vicary. During the showing of a film at Anew Jersey cinema the commands “Eat Popcorn” and “Drink Coca-Cola” were inserted into the movie. They only appeared for a single frame, allegedly long enough for the subconscious to pick up, but too short for the viewer to be aware of it. Nevertheless, they created an 18.1% increase in Coke sales and a 57.8% increase in popcorn sales. There is only one problem – it appears to have been a hoax. It certainly wasn’t scientifically rigorous; this was an experiment without a control group. However, the media lapped it up and Vance Packard popularized this view of the unconscious in his 1957 smash bestseller, The Hidden Persuaders. Packard believed Vicary’s tale hook, line and sinker. In 1962 Vicary apparently in 1962 that he’d made up the whole story in an effort to revive his failing consulting business.*

You would have though that this would have been the end of this story. But subliminal manipulation is one of those zombie ideas that just refuse to go away. Even though there was no evidence that it actually works, subliminal advertising has been banned for more than half a century in the USA. And in the 1970s with the paranoia about government and the whole Watergate business, the idea came back in the work of Wilson Bryan Key, who claimed that advertisers were using subliminal messaging of a very serious sexual nature in order to manipulate behaviour. Advertisers were conspiring to influence consumer choices by embedding blurred sexual images into television and magazine ads. Key argued that just one exposure to these camouflaged images could affect consumer choices weeks later. The Straight Dope website describes him thus:

This is a guy who also claims that every Ritz cracker has the word “sex” embedded on it 12 times on each side; that on April 21, 1986, Time magazine published a picture of Moammar Gadhafi with the word “kill” embedded on the face; and that once at a Howard Johnson’s he felt compelled to order fried clams, even though he hates fried clams, because (he later discovered) the place mat had a picture of fried clams containing subliminal images of an orgy including oral sex and bestiality with a donkey. This guy doesn’t have sex embedded in his pictures, he’s got sex embedded in the brain.

I came across these characters in a programme on BBC Radio 4 called Can You Spot the Hidden Message? What was great about the programme was that they then conducted an experiment on subliminal advertising on the following programme – The Infinite Monkey Cage. The experiment took place in a cinema-type environment. 98 volunteers were divided up into a test group and a control group. Each group were shown a three minute clip of Spooks, which was picked because it is full of fast cuts and moving camerawork. The test group were shown a video that contained the subliminal message, while the control group’s video contained no secret messages. The subliminal message chosen was Lipton, as in the famous brand of iced tea. Lipton was chosen for two reasons: it was reasonably familiar, but not generally a habitual choice, like Coca Cola, and it was seen as thirst-quenching. The members of the audience had been plied with crisps and nuts during the show. The participants were then asked whether they wanted to drink Lipton iced tea or mineral water.

The results showed no statistically significant effects. For all participants, a few more people in the test group picked Lipton, but not enough to be statistically significant. When they removed those who would have picked Lipton anyway, and those who dislike it and would never pick it, slightly more people in the control group picked Lipton, but this difference was not significant either. Here is a summary of the findings I found online:

Test group (all participants): 46% chose Lipton, 54% water

Control group (all participants) 37% Lipton, 63% water

Results refined to exclude those who would definitely have chosen Lipton, or who would definitely not have chosen it

Test group (refined) 53% Lipton, 47% water

Control group (refined) 61% Lipton, 39% water

This is just one study of course. This experiment has apparently been carried out successfully under laboratory conditions. But I remain sceptical. There may be some effects, but they do not appear to be very marked. It is extremely difficult to pull it off. If the flashes are too fast, they are not even subconsciously perceptible. If they are too slow, some people would notice them. The subliminal messages may influence choice immediately after the film, but it is hard to imagine them having a lasting effect on their drink purchases once they had left the cinema. What’s more, if any advertiser caught trying this for real, it would be a PR disaster. Advertisers do influence us, but their techniques are there for all to see. I hope I have been able to persuade you of the rather tenuous effect of subliminal advertising. Anyone for a Ritz?

* According to one website, this was all a massive cover-up:

In 1962 Vicary suddenly confesses that he fabricated the results of his experiment… Why would someone discredit himself in such a way and lose his dignity and credibility? It’s obvious that he was paid to do so by those who use subliminal messages to manipulate you. Remember the quote from “Usual Suspect” : The greatest trick the Devil ever pulled was convincing the world he didn’t exist… That’s exactly the trick they are trying to pull, I.E. convincing the world that subliminal technique does not work. And they did a pretty good job.”


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