Anthony Pratkanis

Anthony R. Pratkanis was born in Portsmouth, Virginia, in 1957, graduated from Eastern Mennonite College in 1979, and took his doctorate at Ohio State University in 1984. He taught at Carnegie Mellon University before joining the University of California, Santa Cruz, in 1987, where he is now emeritus professor of psychology. His article "The Cargo-Cult Science of Subliminal Persuasion" appeared in the Spring 1992 issue of Skeptical Inquirer, at a moment when the 1957 "Eat Popcorn" cinema story was still, he said, the question students and readers most often put to him — and not long after a 1990 court case in which he appeared as an expert witness on alleged subliminal content in a Judas Priest recording.

In that 1992 article Pratkanis traced claims of subliminal influence back to 1900 and argued they kept following one course: an effect is claimed, attempts to replicate fail, the original finding is criticised on methodological grounds, and the claim spreads anyway. Reviewing a literature he and Anthony Greenwald had assembled — more than two hundred academic papers — he reported no clear evidence that subliminal messages influence behaviour, and catalogued the recurring defects: uncontrolled subject expectancy, selective reporting, unreliable measures, and stimuli not presented below awareness. The distinction he pressed matters more than the verdict: evidence for subliminal perception — detection of information outside conscious report — is considerable, while subliminal persuasion, the motivating of behaviour, had little good evidence. Borrowing Feynman's phrase, he called such research cargo-cult science: the trappings of experiment without the scepticism, the leaning over backward to see whether one might be mistaken. With Jay Eskenazi and Greenwald he then tested mass-market self-help tapes directly: volunteers listened daily for five weeks, some given tapes mislabelled so belief and content came apart. The tapes produced no measured change in self-esteem or memory, the three reported in 1994, while conviction tracked what listeners believed they had heard rather than what the tape contained — an illusory placebo effect, in their phrase. Earlier double-blind tests with Greenwald, Spangenberg and Eskenazi found the same.

The critique's reach is specific, and so is its limit. By his 1992 count, nine studies had tested subliminal self-help tapes and none found effects matching manufacturers' claims; what such experiments settle is the promise that hidden audio or flashed words change measurable behaviour. They settle nothing about perception outside awareness as such — Pratkanis explicitly allowed that subliminal perception is a real subject of study. He argued instead that the fascination carries a cost: attention to hidden magic diverts attention from overt influence — the advertising and sales persuasion an average person meets millions of times with little education about its methods, the subject he took up with Elliott Aronson in Age of Propaganda (W. H. Freeman, 1991; revised edition 2001).

What remains useful is a small methodological caution, not a lesson about hidden messages. The 1994 design pried apart two things that usually travel together: what a person believes they practised and what a test measured. Anyone keeping a record of mood, focus or progress meets the same entanglement — a difficult week credited to the wrong cause, an improvement counted before it is verified. Pratkanis's mislabelled tapes are a compact reminder to keep belief and measurement distinguishable in one's own notes; that is the whole of the connection.