The
theoretical potential for subliminal audio is not able to be
established from the published scientific data at this time.
Clearly, the published empirical data show that
subliminal audio influence is either extremely weak or non-existent. And most of the
theoretical rationales for the effect are questionable at best. By far, the
strongest effects found have been those attributed to the belief or expectation of the
listener that they were being influenced.
But ultimately, it is an empirical question, not a
theoretical one. The most interesting and exciting aspect of science is the
discovery of new effects that were not predicted by previous models.
Unfortunately, there is very little research on the
kind of masking techniques used in commercial subliminal audio tapes, perhaps a handful of
studies. For lack of interesting results, the putative effect has not been of
significant theoretical interest, except insofar as public concern has made it an
issue.
This is in striking contrast to the large amount of
data available on dichotic listening and tachistoscopic "subliminal"
techniques. The contrast makes it hard to believe the claims of a conspiracy to
suppress positive results.
Many experiments
performed to test the effectiveness of subliminal self-help tapes have failed to show any
useful effect, except that attributable to expectancy and
belief. (Beyerstein,1993).
Proponents of the tapes often claim that subliminal perception is a secret, that they have
the only technology that works, and that their special technology has not yet been
tested. (On the contrary, subliminal perception has been well studied:
see Controversy)
But what of the remarkable claims
for subliminal audiotapes and even backwards messages in music ?
In one of the few experiments which appeared to
show an interesting subliminal audio effect, Henley and Dixon ( 1974) examined
laterality differences as a contributing variable in auditory subliminal perception.
Masking their subliminal messages with music, they found that subjects in the experimental
groups reported cognition related to subliminal words significantly more often than
control subjects did. The experimental groups also discriminated between the subliminal
words and other words presented on a checklist.
The Henley and Dixon result was replicated by
Mykel and Daves (1979), once with
music as a mask, and once without music. The results without music were
equivocal, there were more hits in the subliminal group than the control, but not when
reports were grouped by "blind" judges.
This led researchers to suspect that the type of
music used as the mask might be influencing responses more than the subliminal
messages. Benes and colleagues (1990)
discovered that using mellow masking music produced more target imagery than frenetic
music, but that the imagery did not turn out to be related to the subliminal words
used. That is, the control group with music but no subliminal messages
produced more imagery for "water" and "family" words than did the
subliminal group !
These kind of results have unfortunately left
the field under-researched, providing the opportunity for advertisers to claim that the
research has not disproven their claims of effectiveness.
There is far less research into acoustic masking
for subliminal messages, because it has not
yet been found to be a reliable way of delivering subliminal stimuli.
Also, the practical difficulties of setting the appropriate
loudness threshold in a generic way, and getting sufficient fidelity on mass produced
audio tapes can be significant obstacles.
Finally, some proponents of audio subliminal influence
claim that the effect only seems to work when the recipient in a particular state of
mind. Hypnosis, for example, biases our information processing to favor non-salient
cues. There is no good research at this point to support or disconfirm this
claim. The visual subliminal effects do not appear to have this requirement, so it's
importance is questionable. It is likely, however, that whatever is perceived is
processed differently in different mindsets, and that this differs between subliminal and
supraliminal stimuli.
A reliable, useful form of audio subliminal delivery may someday
be available, or one may exist today and not yet be known through the published
literature, but these possibilities are difficult to evaluate and seem unlikely at
this point.
