Preconscious processing of stimuli below the intensity or duration of the absolute threshold and therefore not eliciting conscious perception. It has been shown to occur for all sense modalities, and has been established experimentally by presenting stimuli of sufficiently low intensity or short duration as to be sub-threshold, and by masking. Alarm was raised about subliminal advertising by the best-selling book The Hidden Persuaders (1957) by the US journalist Vance (Oakley) Packard (1914–96) and the essay Brave New World Revisited (1959) by the English novelist and essayist Aldous (Leonard) Huxley (1894–1963). Packard referred to a newspaper report in The Times: ‘It cited the case of a cinema in New Jersey that it said was flashing ice-cream ads onto the screen during regular showings of film. These flashes of message were split-second, too short for people in the audience to recognize them consciously but still long enough to be absorbed unconsciously. A result, it reported, was a clear and otherwise unaccountable boost in ice-cream sales’ (pp. 42–3). In 1957 the New Yorker magazine (21 September, p. 21) and the Nation magazine (5 October, p. 206) reported that the motivational research practitioner James M(cDonald) Vicary (1915–77) had carried out an experiment in a New Jersey cinema in which the messages Drink Coca-Cola and Eat popcorn (not ice-cream) had been flashed subliminally on alternate evenings and the sales of these products during the intervals had reportedly risen by 18 per cent and 58 per cent respectively. However, Vicary admitted later that he had never actually carried out these experiments (Advertising Age, September 17, 1984, pp. 72–3, and October 15, 1984, p. 46); in any event, the reported exposure time of 1/3,000 second was far too short to produce subliminal perception, and attempts to replicate the effect have uniformly failed. Research has shown that subliminal messages have only limited power to influence behaviour, and ‘subliminal auditory tapes’ that are marketed as a means of boosting IQ or helping people to lose weight, give up smoking, or achieve other self-help goals have proved ineffective when studied objectively. Also called subception. See also Poetzl phenomenon.