At 10:39 AM 9/13/00 -0400, Michael Sylvester wrote:
>do subliminal perceptual techniques influence behavior?
Well, it depends what you mean by "subliminal," and it depends what you mean
by "behavior."
What seems clear is that words that are flashed for very brief periods and
then are
over-written, or "masked," can have subsequent effects in some
situations. For example,
if the word is presented fast enough that the participant cannot reliably
report whether
or not a word was presented (termed a "subjective" threshold), that masked
word will
often facilitate response to a subsequent, normally presented word that is
related in meaning
to it (e.g., "CAT" masked at subjective threshold can still prime "DOG").
Turns out, though, that if you present words at subjective threshold, and
then ask the
participant to make a forced choice between which of two words was the
masked word,
participants can do this with better than chance accuracy. So, there is a
gray area of
perception wherein people will report not being aware of a stimulus but
they still can make
conscious decisions based on the stimulus. So, you may ask, what if you
present a
masked stimulus even faster, fast enough that people are now no better at
chance in
determining what word they saw (termed an "objective" threshold)? Here,
the data are
more mixed. Some investigations find significant priming, and most
don't. I think the
jury is still out, but it's not too promising.
In any case, even if there were significant priming for objective-threshold
masked primes,
we know from plain ol' semantic priming research, where words are all
presented normally,
that the priming effect typically cannot survive even ONE intervening item
(e.g., CAT will
typically not prime DOG if an unrelated word like JAR appears between
them). So, it's highly
unlikely that a subliminally presented visual stimulus would have much
long-term effect on a
person's behavior (Vicary's 1957 claim about "Drink Coke" and "Eat Popcorn"
messages
increasing theater-goers consumer behavior was later determined to be a
hoax, and unreplicable).
Indeed, Vokey & Read (1985, American Psychologist) present an entertaining,
easy read
on their research on analogues of subliminal ads and satanic messages in
rock music, and
the short story is that there are no effects. I highly recommend
it. Also, Pratkanis, Greenwald,
and colleageus did a much-cited study (I don't have the reference handy) on
subliminal auditory
self-help tapes. Although these tapes did nothing (by objective measures)
for memory or
self-esteem, they elicited a false placebo effect such that subjects
believed their memory or
self-esteem had improved. Similar results have been found by numerous
other investigators.
For a quick media take on the science of subliminal ads, see:
http://www.abcnews.go.com/sections/science/DailyNews/subliminal000912.html
And for a link to the actual Bush ad that I assume prompted Michael's
question, see:
http://www.abcnews.go.com/sections/politics/DailyNews/gopad0000912.html
Best,
Mike
************************************************
Michael J. Kane
Department of Psychology
P.O. Box 26164
University of North Carolina at Greensboro
Greensboro, NC 27402-6164
email: [EMAIL PROTECTED]
phone: 336-256-1022
fax: 336-334-5066
