Subliminal Self-help Auditory Tapes:
An Empirical Test of Perceptual Consequences
TIMOTHY E. MOORE, Glendon College, York University
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 selfhelp 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.
While subliminal perception is a valid phenomenon, recent research has shown that it occurs only under
certain carefully controlled conditions. These include the establishment of individual thresholds for each
participant, a controlled viewing environment, focussed attention on the display area, and exclusion of
extraneous sources of stimulation. Most important, for the present purposes, is the finding that subliminal
perception is most appropriately defined as a situation in which there is a discrepancy between the viewers'
phenomenal experience, and their ability to discriminate between different stimulus states. Participants are
often sensitive to stimuli they claim not to have seen. When required to distinguish between two or more
stimuli, subjects can do so with some success, even while professing to be guessing (Holender, 1986). On the
other hand, there is little reliable evidence of semantic processing of stimuli which cannot be discriminated
(Cheesman & Merikle, 1984; 1986).
According to Merikle and Reingold (1992) the available evidence suggests that subliminal perception is not
perception in the absence of stimulus sensitivity. Rather, it occurs when subjective experience is at odds with
objective measures of signal detection. Such a perspective makes it possible to interpret and understand many
previous studies. In the past, investigators did not typically distinguish very carefully between subjective and
objective indicators of perception. Consequently somewhat mystical notions of supersensitive unconscious
perceptual processes abounded. Today there is consensus that subliminal perception consists of a dissociation
between an objective measure of perception and concurrent subjective awareness (Fowler, 1986; Greenwald,
1992a; Kihlstrom, 1987; Merikle, 1988).
This approach is an improvement over previous procedures that defined awareness exclusively in terms of
observers' (or listeners') self reports of awareness. Dixon (1981), for example, in an extensive review of
subliminal perception research, was content to accept introspective self reports as the defining criterion for
'awareness'. Critics have noted (e.g., Glucksberg, 1982; Merikle, 1983), that without the additional precision
afforded by signal detection methods, it is impossible to make much sense of the countless studies that have
relied on observers' self reports of their conscious experiences. Subjects may sometimes report a stimulus'
absence because of response bias or demand characteristics. Alternatively, some stimuli may be so weak that
they fall outside the range of subjects' sensory capabilities. The latter would, perforce, be "not consciously
seen", nor would they initiate any perceptual activity at all. In short, studies that define awareness only in
terms of self reports generate findings that shed little light on the topic of unconscious perception (Merikle,
1984). For the most part, research on subliminal auditory stimulation has not been sensitive to the distinction
between objective and subjective thresholds (e.g., Borgeat, Elie, & Chabot, 1985; Henley, 1975).
The weight of the evidence derived from signal detection methods shows that stimulus discriminability is a
necessary condition for semantic activation and attendant higher-level decision processes (Greenwald, 1992a).
It is the meaning of the message that is the critical aspect of the (presumed) signals on subliminal tapes.
Consequently, failure to discriminate meaning would preclude any effects attributable to the semantic content
of a phrase or message. With respect to subliminal tapes, Merikle (1988) showed that listeners were unable to
distinguish a subliminal tape from a placebo control in a forced-choice task. Such data are important for they
imply that no perceptual activity is triggered by the subliminal content of the tapes.
Because subliminal perception is defined as a lack of subjective confidence when participants are nevertheless
responding discriminatively, differential sensitivity to 2 different stimulus states is a necessary condition for
any influence from the meaning of those stimuli. If listeners are unable to discriminate between different
signals on a forced choice task, then the semantic activation (Stage 2 in Figure 1) necessary for inducing
motivational change can be all but ruled out.
METHOD
Subjects
The subjects were 53 undergraduates (27 males, 26 females) at York University's Glendon College.
Approximately half (22) were introductory psychology students who volunteered to participate. The remaining
subjects were recruited by means of notice-board postings, and paid $10 for their participation.
Equipment
The tapes were played on two Panasonic model RX-FT500 stereo cassette players. The output from the players
was channeled to a stereo headset through a computer-controlled multiplexer. The multiplexer could feed
output to the headset from either player, but not from both simultaneously. A computer controlled the
multiplexer. Instructions and feedback were displayed on the computer monitor. The tone and volume controls
of each cassette player were fixed at identical settings for the duration of the testing. Output from each cassette
player (measured at each output jack with a volt meter) averaged 6 dB - a comfortable listening level.
Materials
This investigation required cassettes that were identical except for the their 'subliminal' content. Tapes whose
supraliminal content differed would permit listeners to distinguish one from the other independently of any
potential subliminal influences. Most tape companies produce tapes for a host of different therapeutic
purposes. Dozens of tapes from several different companies were purchased or borrowed, and three pairs of
tapes, each pair from a different company, were selected. Each pair appeared to contain identical supraliminal
content but different subliminal messages. The tape pairs,1 henceforth referred to as those from Company A,
B, or C contained subliminal messages for either weight loss or smoking cessation (Company A), memory or
self-confidence (Company B), and reading improvement or stress control (Company C). According to the
accompanying brochures, none of the three companies used production techniques that would make the
subliminal messages unintelligible. In other words, had the messages not been 'subliminal' they would have
been comprehensible.
Almost all of the dozens of tapes examined for this study shared a common format in that the only consciously
perceivable sounds on the tapes consisted of music, ocean waves, and the occasional bird cry. The tapes from
Company A, however, differed from the others in that speech-like sounds were sometimes noticeable. It was
therefore possible that participants listening to these tapes would respond discriminatively on the basis of
consciously perceivable words or phrases.
Procedure
Participants were tested individually in a quiet basement laboratory. Sound excluding headphones eliminated
any extraneous noises. Successive 5-second samples from two different tapes were presented, and subjects
were asked to identify their respective sources (i.e., "Was it tape A or tape B?"). Subjects were given a fairly
complete explanation about the purpose of the study. Recorded instructions to all participants included the
following information:
"You will be participating in research that investigates subliminal perception. We are studying peoples' ability
to make decisions about information that they may have received without any conscious awareness. To do so,
we are asking you to participate in an auditory discrimination test. What I mean by that is that you will be
asked to identify which of two different sound tracks you are hearing from one trial to the next. You will be
wearing ear phones. Five-second passages from one of two different cassette tapes will be transmitted on each
test trial. Your task is to determine which is which. The order of presentation is random. You will be informed
about the correctness of your choice after each trial by means of a message on the screen. The tapes will sound
similar, if not identical, to one another, but they differ in terms of the subliminal messages that each contains.
Thus, even though they sound similar, it is possible that they are discriminably different in some subtle way. If
so, you may be able to distinguish one from the other. Even if you are not sure which is which, please make a
decision on each trial".
After detailing the procedure, subjects were shown the packaging labels from the tapes, which included all the
affirmations claimed by the manufacturer to be present on the tapes2. This information remained available to
subjects throughout the testing. Before the discrimination trials began, subjects first listened to 10 seconds
from each tape while a message on the screen indicated which tape was being presented.
On each trial, subjects heard a 5-second sample from either of the two tapes. They indicated their decision as
to which tape they had heard by pressing one of two paddle buttons connected directly to the computer.
Immediate feedback as to the correctness of their decision was given via the CRT display. Approximately 2
seconds elapsed between feedback presentation and the onset of the next trial.
All subjects received 400 discrimination trials, presented in two blocks of 200 trials each. During each block,
both tapes played continuously, while the computer randomly selected 5-second segments3 from one tape or
the other. A different random order was used in each trial block for each subject. Blocks were separated by
approximately 3 minutes while the tapes were rewound. The 10-second sample was included at the beginning
of each block. At the end of each block, the computer printed a summary on the screen informing the subject
of the number of correct responses during that block.
RESULTS
Twenty-one subjects were tested on the pair of tapes from Company A, and 16 subjects for each of the pairs
from Companies B and C. The male/female breakdown for the three groups was 12/9, 7/9, and 8/8
respectively. For companies B and C, tapes within each pair were identical with respect to tone, speed,
volume, and supraliminal content. Consequently, better than chance identification accuracy would indicate that
subjects were responding discriminatively to the subliminal content, thereby providing evidence for subliminal
perception. One could theoretically expect above chance performance on Company A tapes if listeners had
been able to exploit the non-subliminal information contained in the audible portions of the speech signal.
Although Company A claims that the listener "will not consciously hear any spoken words on the tapes", most
participants indicated that they heard what sounded like an electronically modified voice at different times
during the testing. Single words or phrases were reported by a minority of listeners. For example, the phrase
'stop smoking' and the word 'eating' were each reported four times. No detectable speech sounds were reported
for participants who listened to tapes from Companies B or C.
A group mean of 100 represents a chance level of accuracy for each block. The data were analyzed in a
3(Group) × 2(Sex) × 2(Blocks) analysis of variance. There were no main effects and no interactions (F's < 1 in
all cases)4. Independent 1-tail t-tests also failed to approach significance. The Group × Block means are shown
in Figure 2. The overall mean was 100.2. Means for males and females were 100.02 and 100.37, respectively.
The overall mean for Block 1 was 99.66, and for Block 2 100.72. There was no hint of discriminative
sensitivity for any of the 3 pairs of tapes. Under the null hypothesis, one would expect participants' total
discrimination scores to be randomly distributed around an aggregate mean of 200. Inspection of individual
performances showed that 27 subjects obtained scores below the mean and 25 above (one subject's score was
exactly 200). The aggregate mean for all subjects was 200.4, with a standard deviation of 10.4.
DISCUSSION
Inasmuch as reliable evidence for subliminal perception has only been found under conditions that permit
stimulus discriminability, the tapes tested here did not meet this minimal condition for demonstrating
subliminal perception. Because the sample of tapes used in this study may not have been representative of all
commercially marketed self-help tapes, the preceding conclusion may not apply to the entire population of
such devices. It is noteworthy, however, that one of the pairs of tapes contained a 'subliminal' signal that was
often detectable and occasionally intelligible. Subjects were nevertheless unable to make the necessary
discrimination. It is important to emphasize that even if the tapes had been found to contain discriminable
messages, it would not follow that those messages would have any motivational impact. The failure of these
materials to provide subjects with sufficient information to permit discrimination makes it most improbable
that there could be any behavioural consequences.
An advocate of the effectiveness of the tapes might argue that the preceding test is irrelevant because
participants were not using the tapes under typical conditions, nor were they motivated to change the
behaviours the tapes were designed to remedy. The intended therapeutic effects, how-ever, are purportedly
brought about by the perception (albeit unconscious) of specific affirmations contained on the tapes. If the
subliminal content induces the requisite semantic activity, then respondents should be able to exploit that
information when engaged in a forced-choice task. If, after 400 trials (with feedback on each trial),
respondents are nevertheless at chance in distinguishing one tape from the other, it is a reasonable inference
that the messages did not trigger any perceptual activity - conscious or otherwise.
Placebo Effects
The preceding analysis has addressed the question of empirical evidence for the claim that subliminal speech
signals on self-help audio tapes are agents of therapeutic change. It is not unusual for people to experience (or
imagine) positive effects after participating in some therapeutic exercise. Responsible clinicians, however, are
interested in trying to isolate active therapeutic ingredients (Stricker, 1992) – over and above whatever
changes might be attributable to expectancy effects (Ross & Olson, 1981). Otherwise, rabbits' feet could be
marketed as therapeutic aids.
Lambert, Shapiro, and Bergin (1986) pointed out that in the context of psychotherapy, placebo effects should
not be regarded as trivial or irrelevant. On the contrary, many factors that are common to different types of
therapy may play an active role in therapeutic change. These factors include the elements of warmth, empathy,
encouragement, respect, attention, etc. The possible presence of a placebo effect is sometimes used as
validating evidence of subliminal effects (Urban, 1992). Psychotherapists, however, are more than mere
placebologists. There is no evidence whatsoever that subliminal messages on self-help tapes produce effects
that are incremental to those attributable to placebo effects (Auday, 1992; Greenwald, 1992b; Greenwald, et
al., 1991; Merikle & Skanes, 1992; Pratkanis, 1992; Russell, Rowe, & Smouse, 1991). Furthermore, the
impersonal nature of listening to a mass-produced tape would probably attenuate the operation of placebo
effects, evidence for which is mixed (Greenwald, et al., 1991; Merikle & Skanes, 1992). The data reported
here indicate that subliminal self-help tapes are not capable of initiating the perceptual activities that are a
necessary and logical prerequisite for higher order processes implicated in therapeutic benefits.
CONCLUSION
As Koshland (1991) has noted, the ultimate criterion for resolving a scientific controversy must be the data in
a well-run experiment. Several such experiments have consistently failed to find evidence supporting claims of
subliminal therapeutic influence (cf. Greenwald (1992b). The present study, in conjunction with Merikle's
(1988) strongly suggest that there are no perceptual consequences of listening to these devices.
According to Rosen (1993) psychological self-help is big business and many psychologists rush to market with
exaggerated product claims. Subliminal tapes appear to constitute a paradigmatic example. Not all proponents
of these devices are unabashed quacks, however advocates of the tapes are almost invariably associated with
their sale. Perhaps subsequent research will reveal some heretofore undiscovered therapeutic application of
subliminal stimulation to self-help therapy. Given our current understanding of unconscious cognition the
possibility seems very remote.
This paper is based, in part, on presentations delivered at the 99th annual convention of the American
Psychological Association, San Francisco, August 16, 1991, in G. M. Rosen (Chair), Self-Care: A symposium
on self-help therapies, and at the 100th annual convention of the American Psychological Association,
Washington, DC, August 15, 1992, in M. N. Eagle (Chair), Subliminal Influence: For Better or For Nought? I
am grateful to Carol Fowler, Tony Greenwald, Phil Merikle, John Swets, and Vicki Tartter for comments on a
previous draft. The research reported here was supported by grants from York University's Glendon College
Research Committee and from the Ministry of Consumer and Corporate Affairs, Canada. Steve Feinstein
provided valuable technical expertise. Correspondence concerning this article should be addressed to Timothy
Moore, Department of Psychology, Glendon College, York University, 2275 Bayview Ave., Toronto, Ont.,
Canada M4N 3M6. E-mail: [email protected]
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FOOTNOTES
1
Company A: Adventures in Learning, Inc., 1260 Hornby St., Vancouver, British Columbia, V6Z 1W2;
Company B: Mind Communications, 1844 Porter S.W., Grand Rapids, MI 49509; Company C: Midwest
Research, Inc., 3275 Martin Road, Walled Lake, MI 48088.
2
Affirmations were not available for Company C.
3
To insure that segments of 5-second duration were sufficient to permit discrimination between tape pairs, the
affirmations from Company A's tapes (weight loss and smoking cessation) were recorded supraliminally and
five participants were engaged in an identical discrimination task, except that they were now required to
distinguish between 'themes' (i.e., weight loss vs. smoking cessation) instead of between tapes. Discrimination
accuracy averaged 89%, with a range of 88 to 91.
4
Statistical power (1-tail) exceeded .9 for the detection of a difference between chance performance (µ = 100)
and a sample mean of 104. Inasmuch as performance could have (theoretically) reached 180, a mean of 104
should be regarded as a minuscule effect with little or no practical implications.
FIGURES
Figure 1: Model of effects attributed to subliminal auditory self-help tapes.
Figure 2: Mean number of correct
discriminations (Companies x Blocks).