While they have yet to become as commonplace as climate control, subliminal stimuli play a large role in our consumerist culture, despite laws to the contrary. The most infamous and insidious example may be the early 1970s ads for "Hūsker Dū?," a children’s board game. Single frames that read "Get It" were inserted into the product’s commercial and the ensuing outrage spurred the FCC ban on subliminal ads. More recently, during an airing of the cooking competition "Iron Chef America" on the Food Network, a frame featuring the McDonald’s logo and its slogan "I’m Lovin' It" aired for 1/30th of a second. The Food Network claimed it was merely a technical error.

And these sinister clandestine messages are not confined to the airwaves. In 2007, the Ontario Lottery and Gaming Corp, the state administration that oversees Canadian casinos, forcibly removed almost 100 video slot machines from gaming floors across the city. The games were discovered by a news investigation to flash a "jackpot" signal for a fraction of a second during game play. Authorities were concerned that the brief visual, though too fast to be discerned by the human eye, would be sufficient to induce gamblers to keep feeding money into the machine beyond what their reason might dictate.

And of course, subtle subliminal come-ons can be found in a plethora of print ads and pictures: the curve of a woman’s breast, the hint of a lady’s sexual nethers and, of course, the ubiquitous and barely disguised word "sex." Even mundane watch ads almost always have the clock hands at 10 and 2, some say to insinuate legs spread open. The pleasure subtly suggested by these hidden erotic treasures will be associated in your unconscious mind with the product being advertised. Drink this beverage and you will get some sex.

After Vicary's experiment, scores of other psychologists, behaviorists and ad men by the bushel tried to repeat it themselves, with little or no success. Even Vicary himself would later be forced to declare that his original results had been blown out of proportion. Nowadays, some are convinced that effective subliminal messaging is a hoax as big as Orson Welles' "War of the Worlds" broadcast. The debunking site, Snopes.com, lists the Vicary experiment as a fraud and declares with certainty that "subliminal advertising doesn’t work."

But if this were true, if subliminal messaging were completely useless and had no effect, then why has the practice persisted for more than a century? And why would an authority of behavioral control as powerful as a Central Intelligence Agency commission say otherwise? Clearly subliminal messaging is a very real, powerful method of persuasion, capable of nudging you toward a behavior or desire you did not consciously select. To guard against subliminal messages requires constant vigilance; it may originate from any number of sources—including billboards, television, radio, stores and magazines.

And worst of all, you won’t even see it coming.