The origin of much pseudoscience is cloudy, but with subliminal messaging, there are two primary sources for this belief, both known and both relatively contemporary.

The first culprit was market researcher James Vicary, who in 1957 claimed to have set up a modified movie projector and inserted into films furtive messages that appeared on the screen so briefly that they could not be seen or consciously registered by the mind. Flashing for just three-thousandths of a second were exhortations to drink Coke and eat popcorn. As a control, he did this for only some of the viewings, and he reported that when the messages were flashed, popcorn sales shot up 58 percent and Coke sales increased 18 percent.

Especially with the buttered snack, these numbers represented a significant uptick and could qualify as one of the first steps in the Scientific Method, observation. This caught the notice of Harcourt Assessment, a company that distributed educational and psychological tools and resources. The company asked Vicary if he would work with it and see if the experiment could be repeated under controlled conditions. He agreed, but none of the subsequent research showed any increase in sales based on the insertion of extremely fleeting stealth advertisements. About five years after his alleged one-person experiment, Vicary conceded he had made it up in an attempt to draw customers to his marketing firm.

This left a vacuum in the one-person field of subliminal messaging proponents, so in stepped Wilson Key. He authored Subliminal Seduction in 1974 and followed with two sequels. The gist of his work is that advertisers and other entities insert secret messages into media in order to subconsciously impact viewers’ actions and spending habits. Despite his belief in the potency of these techniques, Key is apparently not using them himself. Subliminal Seduction ranks 322,215^th on Amazon.

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Timothy Moore, acting on behalf of Skeptical Inquirer, read the book so you and I don’t have to. In his review, he wrote, “Key offers no scientific evidence to support the existence of subliminal images, nor does he provide any empirical documentation of their imputed effects.” Instead, Moore continued, Key is content to “cloak his claims in scientific jargon” in order to make them seem valid.

He fooled enough people that the FCC once issued an order decreeing that subliminal ads are “contrary to the public interest.” He also participated in subliminal messaging’s most prominent moment, the Judas Priest civil trial in 1990.

Key served as a pretrial witness for the plaintiff parents who asserted a secret message inserted in the Stained Class album encouraged listeners to commit suicide, a message that two teens, per the lawsuit, obeyed.

Beyond the bizarre business strategy of killing your customers, there was the issue of the supposed suicidal suggestion, “Do it.” This seems ridiculously vague. Even if “Do it” had been inserted, and then registered subconsciously by listeners, exactly what are they supposed to be doing? Eating popcorn and drinking Coke? Buying the next Judas Priest album? Playing ding dong ditch? There are a million actions listeners could undertake and be “doing it,” so it wouldn’t be limited to suicide. For that to be the case, the supposed message would need to be something like, “End it all,” “Embrace death,” or, consistent with the 1980s heavy metal panic, “Satan is calling you home.”

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Regarding his methodology, Key told the court, “Science is pretty much what you can get away with…and you can get away with a great deal.” I suppose points for honesty can be given here, but this admission speaks many non-subliminal volumes about the legitimacy of the technique.

One example of both Key’s pseudoscientific language and his fabrications is the claim that the unconscious mind picks up subliminal messages at light speed. Warp speed seems cool and it’s scientific, so Key piggybacks on this and tries to make subliminal messaging seem believable. But there is no reason to think that the messages, which are not light, would travel at warp speed. And according to neurological researcher Terence Hines, the fastest brain process travels at just 40 miles per hour.

While the Judas Priest trial was an exception, most supposed spoken subliminal messages are said to be for the consumers’ benefit. Whereas subliminal messages in the visual realm were allegedly used for unethical purposes, in the auditory arena, they were said to be for assisting in weight loss, enlarging breasts, increasing libido, tobacco cessation, and even ending constipation.

While the purpose is nobler, the evidence behind it is equally scant. The mechanism for how auditory subliminal messaging would work is even more problematic than how it would with visual cues. With video, it is possible to insert words for such a brief time that they are not registered by the eye or brain. That was done in the Harcourt Assessment testing. What was never observed was evidence that the subconscious picked it up and caused the viewer to act.

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But the auditory realm seems an even more unlikely avenue for this technique to work. Slowed down enough, a visual message would be perceived. But subliminal audio tapes feature messages below the human ear threshold with soothing music or nature sounds played over them. Moreover, the subliminal message is often accelerated or compressed so that even when its volume is increased enough to be heard, the message remains unintelligible.  

Finally, even if the message could somehow be perceived by the subconscious, there is no reason to believe this would lead to motivation. Most persons who pick up a subliminal message tape do so out of laziness, in hopes their problem will be fixed without effort. They want their issue alleviated by laying down and listening to pleasant sounds, not  by any effort on their part to reduce the number of cigarettes or doughnuts consumed.