A subliminal message is a signal or message embedded in another object, designed to pass below the normal limits of perception. These messages are indiscernible by the conscious mind, but allegedly affect the subconscious or deeper mind. Subliminal techniques have occasionally been used in advertising and propaganda; the purpose, effectiveness and frequency of such techniques is debated.


E.W. Scripture published in 1898 The New Psychology, which described the basic principles of subliminal messages. In 1900, Knight Dunlap, an American professor of psychology, flashed an "imperceptible shadow" to subjects while showing them a Müller-Lyer illusion containing two lines with pointed arrows at both ends which create an illusion of different lengths. Dunlap claimed that the shadow influenced his subjects subliminally in their judgment of the lengths of the lines. Although these results were not verified, American psychologist Harry Levi Hollingworth reported in an advertising textbook that such subliminal messages could be used by advertisers.

During World War II, the tachistoscope, an instrument which projects pictures for an extremely brief period, was used to train soldiers to recognize enemy airplanes. Today the tachistoscope is used to increase reading speed or to test sight.

In 1957, market researcher James Vicary claimed that quickly flashing messages on a movie screen, in Fort Lee, New Jersey, had influenced people to purchase more food and drinks. Vicary coined the term subliminal advertising and formed the Subliminal Projection Company based on a six-week test. Vicary claimed that during the presentation of the movie Picnic he used a tachistoscope to project the words "Drink Coca-Cola" and "Hungry? Eat popcorn" for 1/3000 of a second at five-second intervals. Vicary asserted that during the test, sales of popcorn and Coke in that New Jersey theater increased 57.8 percent and 18.1 percent respectively.

Vicary's claims were promoted in Vance Packard's book The Hidden Persuaders, and led to a public outcry, and to many conspiracy theories of governments and cults using the technique to their advantage. The practice of subliminal advertising was subsequently banned in the United Kingdom and Australia, and by American networks and the National Association of Broadcasters in 1958.

But in 1958, Vicary conducted a television test in which he flashed the message "telephone now" hundreds of times during a Canadian Broadcasting Corporation program, and found no increase in telephone calls. In 1962, Vicary admitted that he fabricated his claim, the story itself being a marketing ploy. Efforts to replicate the results of Vicary's reports have never resulted in success.

In 1973, commercials in the United States and Canada for the game Hûsker Dû? flashed the message "Get it". During the same year, Wilson Bryan Key's book Subliminal Seduction claimed that subliminal techniques were widely used in advertising. Public concern was sufficient to cause the FCC to hold hearings in 1974. The hearings resulted in an FCC policy statement stating that subliminal advertising was "contrary to the public interest" and "intended to be deceptive". Subliminal advertising was also banned in Canada following the broadcasting of Hûsker Dû? ads there.

A study conducted by the United Nations concluded that "the cultural implications of subliminal indoctrination is a major threat to human rights throughout the world."

In 1985, Dr. Joe Stuessy testified to the United States Senate at the Parents Music Resource Center hearings that:
The message [of a piece of heavy metal music] may also be covert or subliminal. Sometimes subaudible tracks are mixed in underneath other, louder tracks. These are heard by the subconscious but not the conscious mind. Sometimes the messages are audible but are backwards, called backmasking. There is disagreement among experts regarding the effectiveness of subliminals. We need more research on that.

Stuessy's written testimony stated that:

Some messages are presented to the listener backwards. While listening to a normal forward message (often somewhat nonsensical), one is simultaneously being treated to a back-wards message (in other words, the lyric sounds like one set of words going forward, and a different set of words going backwards). Some experts believe that while the conscious mind is absorbing the forward lyric, the subconscious is working overtime to decipher the backwards message.


Subconscious stimulus by single words is well established to be modestly effective in changing human behavior or emotions. However there is no strong evidence that messages in advertising can or have been used effectively.

Perception of subliminal messages is a type of subconscious cognition. Unlike unconscious tasks such as attending to one signal in a noisy environment while keeping track of other signals (e.g., listening to one voice out of many in a crowded room) and automatic tasks such as breathing, subliminal message cognition cannot be done consciously.

An important question about subliminal perception is: How much of the message is perceived? That is, is the whole message sensed and fully digested, or are only its main and simpler features? There are at least two schools of thought about this. One of them argues that only the simpler features of unconscious signals could be perceived. The second school of thought argues that unconscious cognition is comprehensive and that much more is perceived than can be verbalized.

Proponents of the power of subliminal messages claim they gain influence or power from the fact that they circumvent the critical functions of the conscious mind, and therefore subliminal suggestions are potentially more powerful than ordinary suggestions. This route to influence or persuasion would be akin to auto-suggestion or hypnosis, wherein the subject is encouraged to be (or somehow induced to be) relaxed so that suggestions are directed to deeper (more gullible) parts of the mind; some observers have suggested that the unconscious mind is incapable of critical refusal of hypnotic or subliminal suggestions.

However, critics of the theory have suggested that the effect of subliminal messages would at best be no more than that of a glimpse of a billboard in the corner of an eye. Controlled experiments that attempt to demonstrate the influence of subliminal messages generally find little to no effect.
The book Mind Hacks by O'Reilly Press states that subliminal messages are effective in "priming" (putting a half-processed idea in the mind, leading to increased familiarity or a "tip of the tongue" situation where the idea is present but is not articulated until triggered). It also states that for this reason it has limited application in persuasion, and only slightly more use in advertising. The text states that additionally only one word or image is perceived subliminally most of the time, and that the primary way in which it can be used in advertising is by creating a familiarity with a product that has not been seen before, familiarity that could be misinterpreted as preference. The text references an experiment in which faces were flashed subliminally before the test subject rated a group of faces as to which were preferable—this experiment can be duplicated online, through the URL given in the book.

The Datalust.net community created a wiki book (now lost, though a (somewhat) improved wiki version is available here) based on informal research, proposing a technique by which subliminal messages could be used in conjunction with other techniques to improve cognitive function, among other things. This has not been tested in a strict experiment, however there is some anecdotal evidence supporting some of these claims, as documented in the book itself. It is useful to note that the original wiki version was lost when an accidental slip-up in an upgrade of the wiki software corrupted the database, and so the cache has not been updated since then, although the techniques have progressed. The initial creator of the technique gives his contact information in the book, and so interested parties can contact him for updated techniques and hypotheses.

In 2006, a study by Dr. Johan Karremans at the University of Nijmegen suggested that subliminal messaging may have an effect when the message is goal-relevant. In their experiments, half of the participants was subliminally primed with Lipton Ice (i.e., "Lipton Ice" was repeatedly flashed on a computer screen for 24 milliseconds), while the other half was primed with a control non-word. Subsequently, the prime positively influenced participants' choice for Lipton Ice over another soft drink, but only for participants who already were thirsty. Participants who were not thirsty were not influenced by the subliminal messages.

According to a 2007 study by Mathias Pessiglione et al. published in Science, subjects would exert more force on a hand grip in order to receive a portion of a British pound than they would exert for a pence, even when the duration of the display which indicated the payment type was short enough that subjects were not consciously aware of it.

In "The Secret Sales Pitch: An Overview of Subliminal Advertising," author/attorney August Bullock argues the case that subliminal messages do affect behavior and are commonly employed in media.

He proposes a theory he calls "The Ambiguity Principle," in which he maintains that carefully constructed ambiguities can be tools of subliminal persuasion. When a stimulus has two meanings, and one of the meanings resonates with a repressed emotion, the disturbing meaning is repressed the same way that the emotion is repressed. The repressed meaning influences the viewer on a subliminal or unconscious level.

For example, the cigarette slogan "If you got crushed in the clinch with your soft pack, try our hard pack" has two meanings. On the surface it says "Our cigarettes are better because they come in hard packages rather than soft ones." An alternate interpretation, however, is "If you are anxious about impotency, smoke our cigarettes to compensate." The secondary "impotency" interpretation is repressed because it is disturbing, just at the viewer's sexual apprehensions are likely repressed. The repressed meaning activates unconscious anxieties and induces consumption -- because people smoke more when they are uncomfortable.

If the ad directly challenged the viewer by proclaiming "You are impotent, aren't you?" the viewer would be offended and would avoid the product. Because the message is presented as a subliminal ambiguity, however, the viewer is influenced by the stimulus without becoming aware of it.

Bullock maintains there are three kinds of subliminal ambiguities: in the meaning of text, in the meaning of a picture, and in the form of an optical illusion (where, for example, ice cubes in a liquor ad might be interpreted as skulls or death images). In the cigarette ad discussed above, the backbone of a female model appears to have been airbrushed to resemble an erect phallus. Bullock maintains that modern media often contain these three forms of subliminal messages. He cites many authorities that corroborate his thesis. Bullock's work is extremely controversial and has been heatedly rebuffed by advertising establishment.

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Author's Bio: 

This definition is part of a series that covers the topic of Subliminal Messaging and Subliminal Learning. The Official Guide to Subliminal Messaging and Subliminal Learning is Bradley Thompson, one of the world's leading experts in the world of subliminal messaging. He is author of the best-selling books, “Developing your Own Subliminal-Studio”; “Be Psychic” and "Lucid Dreaming in Seven Days”. Bradley is also developer of the Subliminal Power tool, used by Olympic athletes and business leaders across the globe. Bradley runs his own weekly Self-Development Newsletter and continues to develop world-leading self-help tools. Some of Bradley's more recent contributions include Subliminal CDs; Instant Hypnosis downloads; The Absolute Secret and the Lucid Dreaming Kit Motivator software and more.

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