Subliminal self-help auditory tapes: an empirical test of perceptual consequences (Appraisal of claims of subliminal effects of commercially available tapes)

Canadian Journal of Behavioural Science, Jan 1995 by Moore, Timothy E

Abstract

This article provides an appraisal of the claims of subliminal effects that are alleged to result from commercially available subliminal auditory tapes. Research is described whose purpose was to empirically investigate whether the tapes in question are capable - in principle - of initiating the perceptual activities that are a necessary and logical prerequisite for higher order processes implicated in therapeutic benefits.

Fifty - three subjects listened to pairs of subliminal tapes which contained ostensibly different subliminal messages, but which were otherwise identical. Participants were required to distinguish one tape from the other. After 400 trials on a forced - choice discrimination task, subjects' performance was indistinguishable from chance. These data indicate that the tapes tested do not appear to meet the minimum condition necessary for demonstrating subliminal perception, thereby obviating any possible therapeutic consequences.

In September of 1957 legal and ethical concerns were expressed regarding allegations that movie audiences were being surreptitiously controlled by invisible messages exhorting them to "Drink Coca - Cola" and "Eat popcorn". According to the New Yorker, minds had been "broken and entered" (Moore, 1982). More than three decades later, claims of covert subliminal manipulation persist. Television commercials, magazine ads, and book stores promote subliminal tapes that promise to induce dramatic improvements in mental and psychological health. These devices are widely advertised as being able to produce many desirable effects, including weight loss, memory enhancement, and improvement of sexual function.

Reviewers have been skeptical that subliminal self - help audio tapes have any genuine utility for enhancing human performance (Eich & Hyman, 1991; The British Psychological Society, 1992). Merikle and Skanes (1992) conducted an empirical evaluation of subliminal weight loss tapes and found no evidence that the tapes were effective in modifying behaviour. Other studies have obtained similar results (Greenwald, 1992b; Greenwald, Spangenberg, Pratkanis, & Eskenazi, 1991). The study to be described here suggests that there could never be any therapeutic benefits from such devices because they do not appear to contain a signal that is capable of triggering any perceptual activity - conscious or otherwise.

Moore (1991; 1992b) suggested that there is a chain of effects assumed to result from subliminal auditory tapes (see Figure 1).

This model assumes that success at any particular stage in the sequence is a logical and necessary precondition for achievements at any successive stage. Stage 1 entails a consideration of the nature of the signal prior to its being rendered subliminal. Because there are no grounds for supposing that an unintelligible signal could become comprehensible as a result of its subliminality, the absence of an intelligible signal at Stage 1 would obviate the possibility of semantic activation, let alone any therapeutic changes. Some tape companies purport to produce a subliminal speech signal whose presentation rate clearly exceeds the established parameters for the comprehension of compressed or accelerated speech (Heiman, Leo, Leighbody, & Bowler, 1986; King & Behnke, 1989). Other companies engage in multi - track recording of the 'subliminal' messages, resulting in "over a million [subliminal] messages on a one - hour cassette" (e.g., Alphasonics International, 1990). Since the signal produced by such procedures would be unintelligible even if it were clearly audible (cf. Miller, 1947), masking that signal would not enhance its comprehensibility.

In order for therapeutic results to occur, the relevant semantic content of the message would have to achieve some sort of internal representation (Stage 2). A critical assumption underlying claims of therapeutic influence is that 'subliminally' perceived messages are semantically processed. Weight loss tapes, for example, contain affirmations having to do with eating restraint, whereas smoking cessation tapes contain assertions about abstinence from cigarettes. The semantic content of the subliminal messages is different in each case, and it is this semantic content that is responsible for influencing the motivations of the user.

Motivational change (Stage 3) is usually inferred from behavioural change, and has not been measured directly in any studies to date. An altered motivational state is an explicit assumption of all subliminal auditory self - help tapes. A related assumption is that a subliminally presented directive is more therapeutically influential than would be a supraliminal version of the same directive. This assumption may be a consequence of confusing unconscious perceptual processes with the psychodynamic unconscious (cf. Eagle, 1987; Moore, 1992a).

Behavioural change (Stage 4) has been the focus of the majority of studies that have investigated the efficacy of subliminal self - help tapes. Greenwald (1992b) reviewed 16 experimental double - blind tests, none of which found any evidence of therapeutic utility.