The Cargo Cult Science of Subliminal Persuasion   
Anthony R. Pratkanis
Skeptical Inquirer, Spring 1992
   
   Imagine that it is the late 1950s-a time just
after the Korean War, when terms like
brainwashing and mind control were on the
public's mind and films like the Manchurian
Candidate depicted the irresistible influence of
hypnotic trances. You and your friend are off
to see Picnic, one of the more popular films of
the day. However, the movie theater, located
in Fort Lee, New Jersey. is unlike any you have
been in before. Unbeknownst to you, the
projectors have been equipped with a special
device capable of flashing short phrases onto
the movie screen at such a rapid speed that you
are unaware that any messages have been
presented. During the film. you lean over to
your companion and whisper. "Gee. I'd love a
tub of buttered popcorn and a Coke right now."
To which he replies. "You're always hungry and
thirsty at movies, shhhhh." But after a few
moments he says, "You know, some Coke and
popcorn might not be a bad idea."
  A short time later you hear that you and
your friend weren't the only ones desiring
popcorn and Coke at the theater that day.
According to reports in newspapers and
magazines, James Vicary, an advertising expert,
had secretly flashed. at a third of a millisecond,
the words "Eat Popcorn" and "Drink Coke" onto
the movie screen. His studies, lasting six weeks,
involved thousands of moviegoing subjects who
received a subliminal message every five seconds
during the film. Vicary claimed an increase in
Coke sales of l8 percent and a rise in popcorn
sales of almost 58 percent. Upon reading their
newspapers, most people were outraged and
frightened by a technique so devilish that it
could bypass their conscious intellect
and beam subliminal commands
directly to their subconscious. (See
Moore, this issue, for a definition of
"subliminal.")
  In an article titled "Smudging the
Subconscious," Norman Cousins
(1957) captured similar feelings as he
pondered the true meaning of such a
device. As he put it, "If the device is
successful for putting over popcorn,
why not politicians or anything else?"
He wondered about the character of
people who would dream up a machine
to "break into the deepest and most
private parts of the human mind and
leave all sorts of scratchmarks."
Cousins concluded that the best
course of action would be "to take this
invention and everything connectcd
to it and attach it to the center of the
next nuclear explosive scheduled for
testing."
  Cousins's warnings were taken to
heart. The Federal Communications
Commission immediately investigated
the Vicary study and ruled that the
use of subliminal messages could re-
sult in the loss of a broadcast license.
The National Association of Broad-
casters prohibited the use of sublim-
inal advertising by its members.
Australia and Britain banned sublim-
inal advertising. A Nevada judge ruled
that subliminal communications are
not protected as free speech.
  The Vicary study also left an
enduring smudge on Americans' con-
sciousness-if not their subconscious.
As a teacher of social psychology and
a persuasion researcher, one of the
questions I am most frequently asked
is, "Do you know about the 'Eat
Popcorn/Drink Coke' study that they
did?" At cocktail parties. I am often
pulled aside and, in hushed tones, told
about the "Eat Popcorn/Drink Coke"
study. Indeed. my original interest in
subliminal persuasion was motivated
by an attempt to know how to respond
to such questions.
  Three public-opinion polls indicate
that the American public shares my
students' fascination with subliminal
influence (Haber 1959; Synodinos
1988; Zanot, Pincus. and Lamp 1983).
By 1958, just nine months after the
Vicary subliminal story first broke, 41
percent of survey respondents had
heard of subliminal advertising. This
figure climbed to 81 percent in the
early 1980s, with more than 68
percent of those aware of the term
believing that it was effective in selling
products. Most striking, the surveys
also revealed that many people learn
about subliminal influence through
the mass media and through courses
in high school and college.
  But there is a seamier side to the
"Eat Popcorn/Drink Coke-' study-
one that is rarely brought to public
attention. In a 1962 interview with
Advertising Age, James  Vicary
announced that the original study was
a fabrication intended to increase
customers for his failing marketing
business. The circumstantial evidence
suggests that this time Vicary was
telling the truth. Let me explain by
recounting the story of the "Eat
Popcorn/Drink Coke" study as best I
can, based on various accounts pub-
lished in academic journals and trade
magazines (see Advertising Research
Foundation 1958; "ARF Checks" 1958;
Danzig 1962; McConne11. Cutler, and
McNeil 7958; "Subliminal Ad" 1958;
"Subliminal Has- 1958; Weir 1984).
  Advertisers, the FCC, and research
psychologists doubted Vicary's claims
from the beginning and demanded
proof. To meet these demands, Vicary
set up demonstrations of his machine.
Sometimes there were technical dif-
ficulties in getting the machine to
work. When the machine did work,
the audience felt little compulsion to
comply with subliminal commands,
prompting an FCC commissioner to
state, "I refuse to get excited about
it-I don't think it works" ("Subliminal
Has" 1958).
  In 1958, the Advertising Research
Foundation pressed Vicary to release
his data and a detailed description of
his procedures. They argued that it
had been more than a year since the
results were made public and yet there
had been no formal write-up of the
experiment, which was necessary to
evaluate the claims. To this day, there
has been no primary published
account of the study, and scientists
interested in replicating the results
must rely on accounts published in
such magazines as the Senior Scholastic
("Invisible Advertising" 1957), which,
although intended for junior-high
students, presents one of the most
detailed accounts of the original study.
  Pressures for a replication accu-
mulated. Henry Link, president of
Psychological Corporation, challenged
Vicary to a test under controlled
conditions and supervised by an
independent research firm. No change
occurred in the purchase of either
Coke or popcorn (Weir 1984). In one
of the more interesting attempted
replications, the Canadian Broadcast
Corporation, in 1958, subliminally
flashed the message "Phone Now" 352
times during a popular Sunday-night
television show called CIose-up
("Phone Now" 1958). Telephone
usage did not go up during that period.
Nobody called the station. When asked
to guess the message, viewers sent
close to five hundred letters, but not
one contained the correct answer.
However, almost half of the respond-
ents claimed to be hungry or thirsty
during the show. Apparently, they
guessed (incorrectly) that the message
was aimed at getting them to eat or
drink.
  Finally, in 1962 James Vicary
lamented that he had handled the
subliminal affair poorly. As he stated,
"Worse than the timing, though, was
the fact that we hadn't done any 
research, except what was needed for 
filing for a patent. I had only a minor
interest in the company and a small 
amount of data-too small to be 
meaningful. And what we had             
shouldn't have been used promotion-
ally" (Danzig1962). This is not exactly
an affirmation of a study that sup-
posedly ran for six weeks and involved 
thousands of subjects.
  My point in presenting the details 
of the Vicary study is twofold. First, 
the "Eat Popcorn/Drink Coke" affair
is not an isolated incident. The topic
of subliminal persuasion has attracted
the interest of Americans on at least
four separate occasions: at the turn    
of the century. in the 1950s, in the
1970s, and now in the late 1980s and
early 1990s. Each of these four flour-
ishings of subliminal persuasion show
a similar course of events. First,
someone claims to find an effect; next, 
others attempt to replicate that effect 
and fail; the original finding is then
criticized on methodological grounds;
nevertheless the original claim is
publicized and gains acceptance in lay 
audiences and the popular imagina- 
tion. Today we have reached a point
where one false effect from a previous
era is used to validate a false claim
from another. For example, I recently
had the occasion to ask a manufac-
turer of subliminal self-help audio-
tapes for evidence of his claim that
his tapes had therapeutic value. His
reply: "You are a psychologist. Don't
you know about the study they did
where they flashed Eat Popcorn and
Drink Coke' on the movie screen?"
  During the past few years. I have
been collecting published articles on
subliminal processes-research that
goes back over a hundred years
(Suslowa 1863) and includes more
than a hundred articles from the mass
media and more than two hundred
academic papers on the topic (Pratkan-
is and Greenwald 1988). In none of
these papers is there clear evidence in
support of the proposition that sub-
liminal messages influence behavior.
Many of the studies fail to find an
effect, and those that do either cannot
be reproduced or are fatally flawed on
one or more methodological grounds,
including: the failure to control for
subject expectancy and experimenter
bias effects, selective reporting of
positive over negative findings, lack
of appropriate control treatments,
internally inconsistent results, unre-
liable dependent measures, presenta-
tion of stimuli in a manner that is not
truly subliminal, and multiple exper-
imental confounds specific to each
study. As Moore (SI, this issue) points
out, there is considerable evidence for
subliminal perception or the detection
of information outside of self-reports
of awareness. However. subliminal
perception should not be confused
with subliminal persuasion or influ-
ence-motivating or changing behav-
ior-for which there is little good
evidence (see McConnell, Cutler, and
McNeil 1958; Moore 1982 and 1988).
  My second reason for describing
the Vicary study in detail is that it
seems to me that our fascination with
subliminal persuasion is yet another
example of what Richard Feynman
(1985) called "cargo-cult science." For
Feynman, a cargo-cult science is one
that has all the trappings of science-
the illusion of objectivity, the appear-
ance of careful study, and the motions
of an experiment-but lacks one
important ingredient: skepticism, or a
leaning over backward to see if one
might be mistaken. The essence of
science is to doubt your own inter-
pretations and theories so that you
may improve upon them. This skep-
ticism is often missing in the inter-
pretation of studies claiming to find
subliminal influence. Our theories and
wishes for what we would like to think
the human mind is capable of doing
interferes with our ability to see what
it actually does.
  The cargo-cult nature of subliminal
research can be seen in some of the
first studies on the topic done at the
turn of the century. In 1900, Dunlap
reported a subliminal Muller-Lyer
illusion-a well-known illusion in
which a line is made to appear shorter
or longer depending on the direction
of angles placed at its ends. Dunlap
flashed an "imperceptible shadow" or
line to subliminally create this illusion.
He claimed that his subjects'judgment
of length was influenced by the
imperceptible shadows. However.
Dunlap's results could not be imme-
diately replicated by either Titchener
and Pyle (1907) or by Manro and
Washburn (1908). Nevertheless, this
inconsistency of findings did not stop
Hollingworth (1913) from discussing
the subliminal Muller-Lyer illusion in
his advertising textbook or from
drawing the conclusion that sublim-
inal influence is a powerful tool avail-
able to the advertiser.
  I contend that it was no accident
that subliminal influence was first
investigated in America at the turn of
the century. The goal of demonstrat-
ing the power of the subliminal mind
became an important one for many
people at that time. It was a time of
great religious interest, as illustrated
by academic books on the topic,
religious fervor among the populace,
and the further development of a
uniquely American phenomenon-
the spiritual self-help group. One such
movement, popular in intellectual
circles, was called "New Thought."
which counted William James among
its followers. The doctrine of New
Thought stated that the mind pos-
sesses an unlimited but hidden power
that could be tapped-if one knew
how-to bring about a wonderful,
happy life and to exact physical cures.
Given the rise of industrialization and
the anonymity of newly formed city
life, one can see how a doctrine of the
hidden power of the individual in the
face of realistic powerlessness would
be well received in some circles.
  The historian Robert Fuller (1982;
1986) traces the origins of New
Thought and similar movements to
early American interest in the teach-
ings of Franz Anton Mesmer. Fuller's
point is thst the powerful unconscious
became a replacement for religion's
"soul." Mesmer's doctrines contended
that each person possessed a hidden,
though strong, physical force, which
he termed animal magnetism. This
force could be controlled by the careful
alignment of magnets to effect per-
sonality changes and physical cures.
On one level, mesmerism can be
viewed as a secularization of the meta-
phor of spiritual humans that under-
lies witchcraft. Animal magnetism
replaced the soul, and good and bad
magnets replaced angels and devils
that could invade the body and affect
their will. Mesmerism was introduced
to America at the beginning of the
nineteenth century and, characteristic
of Yankee ingenuity, self-help move-
ments soon sprang up with the goal
of improving on Mesmer's original
magnet therapy; they did so by
developing the techniques of hypnot-
ism, seances, the healing practices of
Christian Science, positive thinking,
and the speaking cure.
  With the distance of a century, we
overlook the fact that many journals
of the nineteenth century were
devoted to archiving the progress of
mesmerism and with documenting the
influence of the unconscious on the
conscious. As Dunlap (1900) said in
the introduction to his article on the
subliminal Muller-Lyer illusion, "If
such an effect is produced, then we
have evidence for the belief that under
certain conditions things of which we
are not and can not become conscious
have their immediate effects upon
consciousness." In other words, we
would have one of the first scientific
demonstrations that the unconscious
can powerfully influence the con-
scious. A simple step perhaps, but
who knows what wonderful powers
of the human mind wait to be un-
leashed.
  As a postscript to the subliminal
Muller-Lyer affair. I should point out
that 30 years later Joseph Bressler-
a student of Hollingworth-was able
to reconcile the empirical differences
between Dunlap and his opponents.
Bressler (1931) found that as the
subliminal angles increased in inten-
sity-that is, as they approached the
threshold of awareness-the illusion
was more likely to be seen. This
finding, along with many others,
served as the basis for concluding that
there is no absolute threshold of
awareness-it can vary as a function
of individual and situational factors-
and led to the hypothesis that, on
some trials, subjects could see enough
of the stimulus to improve their
guessing at what might be there. (See
also Holender 1986 and Cheesman
and Merikle's 1985 distinction
between objective and subjective
thresholds.)
   Other manifestations of "sub-
liminal-mania" illustrate additional
aspects of a cargo-cult science. In the
early 1970s, during the third wave of
popular interest in subliminal persua-
sion, the best-selling author Wilson
Bryan Key (1973; 1976; 1980; 1989)
advanced the cargo-cult science of
subliminal seduction in two ways. (See
also Creed 1987.) First, Key argued
that subliminal techniques were not
just limited to television and movies.
Cleverly hidden messages aimed at
inducing sexual arousal are claimed to
be embedded in the photographs of
print advertisements. Key found the
word sex printed on everything from
Ritz crackers to the ice cubes in a
Gilbey Gin ad. Second, Key was
successful in linking the concept of
subliminal persuasion to the issues
of his day. The 1970s were a period
of distrust by Americans of their
government. businesses, and institu-
tions. Key claimed that big advertisers
and big government dre in a conspir-
acy to control our minds using sublim-
inal implants.
   The legacy of Key's cargo-cult
science is yet with us. I often ask my
students at the University of Califor-
nia, Santa Cruz, if they have heard
of the term subliminal persuasion and,
if so, where. Almost all have heard
of the term and about half report
finding out about it in high school.
Many received an assignment from
their teachers to go to the library and
look through magazine ads for sub-
liminal implants.
   These teachers miss an opportu-
nity to teach science instead of cargo-
cult science. Key (1973) reports a
study where more than a thousand
subjects were shown the Gilbey Gin
ad that supposedly contained the word
sex embedded in ice cubes. Sixty-two
percent of the subjects reported
feeling "aroused," "romantic." "sensu-
ous." Instead of assuming that Key
was right and sending students out
to find subliminals, a science educator
would encourage a student to ask,
"But where is the control group in the
Gilbey Gin ad study? Perhaps an even
higher percentage would report feel-
ing sexy if the subliminal "sex" was
removed-perhaps the same, perhaps
less. One just doesn't know.
   Now in the late 198Os and early
1990s, we see a fourth wave of
interest in subliminal influence. Entre-
preneurs have created a $50-million-
plus industry offering subliminal self-
help audio- and video-tapes designed
to improve everything from self-
esteem to memory, to employee and
customer relations, to sexual respon-
siveness, and-perhaps most contro-
versial-to overcoming the effects of
family and sexual abuse (Natale1988).
The tapes work, according to one
manufacturer, because "subliminal
messages bypass the conscious mind,
and imprint directly on the subcon-
scious mind, where they create the
basis for the kind of life you want."
Part of the popularity of such tapes
no doubt springs from the tenets of
New Age. Like its predecessor New
Thought, New Age also postulates a
powerful hidden force in the human
personality that can be controlled for
the good, not by magnets. but by
crystals, and can be redirected with
subliminal commands.
   Accusations concerning the sinis-
ter use of subliminal persuasion
continue as well. In the summer of
1990, the rock band Judas Priest was
placed on trial for allegedly recording.
in one of their songs, the subliminal
implant "Do it." This message sup-
posedly caused the suicide deaths of
Ray Belknap and James Vance.
   What is the evidence that sublim-
inal influence, despite not working in
the 1900s, 1950s, and 1970s, is now
effective in the 1990s? Tape company
representatives are likely to provide
you with a rather lengthy list of
"studies" demonstrating their claims.
Don't be fooled. The studies on these
lists fall into two camps-those done
by the tape companies and for which
full write-ups are often not available,
and those that have titles that sound
as if they apply to subliminal influence,
but really don't. For example. one
company lists many subliminal-
perception studies to support its
claims. It is a leap of faith to see how
a lexical priming study provides
evidence that a subliminal self-help
tape will cure insomnia or help over-
come the trauma of being raped.
Sadly, the trick of claiming that
something that has nothing to do with
subliminal influence really does prove
the effectiveness Or subliminal influ-
ence goes back to the turn of the
century. In the first footnote to their
article describing a failure to replicate
Dunlap's subliminal Muller-Lyer
effect, Titchener and Pyle (1907) state:
"Dunlap finds a parallel to his own
results in the experiments of Pierce
and Jastrow on small difference of
sensations. There is. however, no
resemblance whatever between the
two investigations." In a cargo-cult
science, any evidence-even irrelevant
facts-is of use and considered
valuable.
   Recently, there have been a num-
ber of studies that directly tested the
effectiveness of subliminal self-help
tapes. I conducted one such study in
Santa Cruz with my colleagues Jay
Eskenazi and Anthony Greenwald
(Pratkanis, Eskenazi, and Greenwald
1990). We used mass-marketed audio-
tapes with subliminal messages
designed to improve either self-
esteem or memory abilities. Both
types of tapes contained the same
supraliminal content-various pieces
of classical music. However, they
differed in their subliminal content.
According to the manufacturer, the
self-esteem tapes contained subliminal
messages like "I have high self-worth
and high self-esteem." The memory
tape contained subliminal messages
like "My ability to remember and recall
is increasing daily."
   Using public posters and ads placed
in local newspapers, we recruited
volunteers who appeared most inter-
ested in the value and potential of
subliminal self-help therapies (and
who were probably similar to those
likely to buy such tapes). On the first
day of the study, we asked our
volunteers to complete three different
self-esteem and three different
memory measures. Next they ran-
domly received their subliminal tape,
but with an interesting twist. Half of
the tapes were mislabeled so that some
of the subjects received a memory
tape, but thought it was intended to
improve self-esteem, whereas others
received a self-esteem tape that had
been mislabeled as memory improve-
ment. (Of course half the subjects
received correctly labeled tapes.)
   The volunteers took their tapes
home and listened to them every day
for five weeks (the period suggested
by the manufacturer for maximum
effectiveness). During the listening
phase, we attempted to contact each
subject about once a week to encour-
age their daily listening. Only a
handful of subjects were unable to
complete the study, suggesting a high
level of motivation and interest in
subliminal therapy. After five weeks
of daily listening, they returned to the
laboratory and once again completed
self-esteem and memory tests and
were also asked to indicate if they
believed the tapes to be effective.
   The results: the subliminal tapes
produced no effect (improvement or
decrement) on either self-esteem or
memory. But our volunteers did not
believe this to be the case. Subjects
who thought they had listened to a
self-esteem tape (regardless of
whether they actually did or not) were
more likely to be convinced that their
self-esteem had improved, and those
who thought they had listened to a
memory tape were more likely to
believe that their memory had
improved as a result of listening to
the tape. We called this an illusory
placebo effect-placebo, because it
was based on expectations; illusory,
because it wasn't real. In sum, the
subliminal tapes did nothing to
improve self-esteem ar memory abil-
ities but, to some of our subjects, they
appeared to have an effect. As we put
it in the title of our report of this
study, "What you expect is what you
believe, but not necessarily what you
get."
   Our results are not a fluke. We
have since repeated our original study
twice using different tapes and have
yet to find an effect of subliminal
messages upon behavior as claimed by
the manufacturer (Greenwald, Span-
genberg, Pratkanis, and Eskenazi
1991). By combining our data from all
three studies, we gain the statistical
power to detect quite small effects.
Still, there is no evidence of a sub-
liminal effect consistent with the
manufacturers' claims.
   Other researchers are also finding
that subliminal self-help tapes are of
no benefit to the user. In a series of
three experiments, Auday, Mellett,
and Williams (1991) tested the effec-
tiveness of bogus and real subliminal
tapes designed either to improve
memory, reduce stress and anxiety. or
increase self-confidence. The sublim-
inal tapes proved ineffective on all
three fronts. Russell, Rowe, and
Smouse (1991) tested subliminal tapes
designed to improve academic
achievement and found the tapes
improved neither grade point average
nor final examination scores. Lenz
(1989) had 270 Los Angeles police
recruits listen for 24 weeks to music
with and without subliminal implants
designed to improve either knowledge
of the law or marksmanship. The
tapes did not improve either. In a
recent test, Merikle and Skanes (1991)
found that overweight subjects who
listened to subliminal weight-loss
tapes fpr five weeks showed no more weight loss than 
did control subjects. In sum, independent researchers have
conducted nine studies to evaluate the effectiveness of 
subliminal self-help tapes. All nine studies
failed to find an effect consistent with the manufacturers' claims.
