Subliminal: from the Latin for "beneath the threshold." First described by psychologists around the turn of the last century and coming into widespread use in the late 50s (a theater operator falsely claimed that brief flashes of "Hungry? Eat popcorn!" drove concessions sales through the roof), subliminal messages were outlawed after they appeared in a 1973 commercial for a Danish memory game called HÅ«sker DÅ«? ("do you remember?"). Flashes of the message "Get it!" prompted complaints from viewers, and the FCC responded by saying that subliminal ads were "contrary to the public interest" and "intended to be deceptive."
Five years later, the FCC specifically okayed one instance of subliminal "advertising," in a Wichita, Kansas TV news report about the BTK killer's 1978 killing of Nancy Fox, whose glasses were found lying near her body. The message included the text "Now call the chief" and a drawing of a pair of glasses, which the police apparently hoped would stir up some remorseful emotion in the killer, were he watching. Certainly the only known instance of police trying to subliminally hypnotize a killer into turning himself in -- and it didn't work.
There are few modern instances of blatant subliminal advertising, but critics claim that McDonald's has used the practice, specifically during a 2007 broadcast of Iron Chef America. You be the judge:
A Food Network spokesperson claims the one-frame McDonald's logo was just a glitch, but critics aren't so sure.
It can't be a coincidence: in the 1943 Merrie Melodies cartoon "Wise Quacking Duck," Daffy is shown spinning a coin, which for one frame, on one side of the coin, reads "BUY BONDS." (YouTube examples were available until recently, but were taken down recently.)
The film Fight Club features several subliminal flashes of the Tyler Durden character before he actually shows up; as he's an imaginary character, it's only fitting. In Tyler's job as a projectionist, he claims to insert pornographic subliminals into the films he shows, and sure enough, right before the end of the movie there's a prominent flash of a penis.
The jury is still out on how much effect subliminal messages, be they visual or aural, have on the human mind. Can a 1/24th of a second image make you want to buy popcorn? Can a Judas Priest song played backwards make you want to worship Satan? What do you think?