THINKING CRITICALLY Can Subliminal Messages Change Your Behavior

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The Scope of Consciousness
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Source: Schacter et al. (1991).
FIGURE
4.2
Stimuli Used in a Priming
Experiment
Look at these figures and decide, as quickly as you can,
whether each can actually exist. Priming studies show that this task
would be easier for figures you have seen
in the past, even if you don’t recall seeing
them. How did you do? The correct answers appear on page 141.
doing
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Tutorial: Priming
visual awareness—a condition known as blindsight (Ro et al., 2004; Weiskrantz, 2004).
So though patients say they see nothing, if forced to guess, they can still locate visual
targets, identify the direction of moving images, reach for objects, name the color of
lights, and even discriminate happy from fearful faces (Morris et al., 2001). The same
blindsight phenomenon has recently been created in visually normal volunteers using
magnetic brain stimulation to temporarily disable the primary visual cortex (Boyer,
Harrison, & Ro, 2005; Jolij & Lamme, 2005).
Research on priming also demonstrates mental processing without awareness (e.g.,
Naccache et al., 2005). In a typical priming study, people tend to respond faster or more
accurately to stimuli they have seen before. This is true even when they cannot consciously recall having seen those stimuli (Arndt et al., 1997; Bar & Biederman, 1998;
Kouider & Dupoux, 2005). In one study, for example, people looked at figures like those
in Figure 4.2. They had to decide which figures could actually exist in three-dimensional
space and which could not. The participants were better at classifying pictures they had
seen before, even when they could not remember having seen them (Schacter et al.,
1991).
There is even evidence that some of the decisions and choices we make in everyday
life may be guided to some extent by mental processes that occur without our awareness (Dijksterhuis et al., 2006; Myers, 2004). For example, your “lucky” choice of the
fastest moving supermarket checkout line might seem to have been based on nothing
more than a “hunch,” a “gut feeling,” or intuition, but previous visits to that store might
have given you useful information about the various clerks that you didn’t know you
had (Adolphs et al., 2005). In a laboratory study that supports this notion, people
watched videotaped television commercials while the changing stock prices of fictional
companies “crawled” across the bottom of the screen. Later, these people were asked to
choose which of these companies they liked best. They couldn’t recall anything they
had seen about the companies’ stock, so they had to make their choice on the basis of
their “gut reaction” to the company names. Nevertheless, their choices were not random; they more often chose companies whose stock prices had been rising rather than
those whose stock had been falling (Betch et al., 2003).
T
T H I N K I N G C R I T I C A L LY
he research we have described suggests
that we don’t always have to be aware of
Can Subliminal Messages
information in order for it to affect us
(Hassin, Uleman, & Bargh, 2004), but how
Change Your Behavior?
strong can this influence be? In 1957, an
adman named James Vicary claimed that a
New Jersey theater flashed messages such as “buy popcorn” and “drink Coke” on a
movie screen, too briefly to be noticed, while customers watched the movie Picnic.
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Chapter 4 Consciousness
He said that these messages caused a 15 percent rise in sales of Coca-Cola and a 58
percent increase in popcorn sales. Can messages perceived at a subliminal level—that
is, below conscious awareness—act as a form of “mind control”?” Many people seem
to think so. Each year, they spend millions of dollars on audiotapes, CDs, and videos
whose subliminal messages are supposed to help people lose weight, raise self-esteem,
quit smoking, make more money, or achieve other goals.
■ What am I being asked to believe or accept?
Two types of claims have been made about subliminal stimuli. The more general one
is that subliminal stimuli can influence our behavior. The second, more specific claim
is that subliminal stimuli provide an effective means of changing people’s buying habits,
political opinions, self-confidence, and other complex attitudes and behaviors, with or
without their awareness or consent.
■ Is there evidence available to support the claim?
Evidence that subliminal messages can affect conscious judgments comes in part from
laboratory studies that present visual stimuli too briefly to be perceived consciously. In
one such study, participants saw slides showing people performing ordinary acts such
as washing dishes. Unknown to the participants, each slide was preceded by a subliminal exposure to a photo of “positive” stimuli (such as a child playing) or “negative”
stimuli (such as a monster). Later, participants rated the people on the visible slides as
more likable, polite, friendly, successful, and reputable when their images had been preceded by a positive subliminal photo (Krosnick et al., 1992). The subliminal photos not
only affected participants’ liking of the people they saw but also shaped beliefs about
their personalities.
In another study, participants were exposed to subliminal presentations of slides
showing snakes, spiders, flowers, and mushrooms. Even though the slides were impossible to perceive at a conscious level, participants who were afraid of snakes or spiders
showed physiological arousal (and reported feeling fear) in response to slides of snakes
and spiders (Öhman & Soares, 1994).
The results of studies such as these support the notion that subliminal information
can have an impact on judgments and emotion, but they say little or nothing about
the value of subliminal tapes for achieving self-help goals. In fact, no laboratory evidence exists to support the effectiveness of these tapes. Their promoters offer only the
reports of satisfied customers.
■ Can that evidence be interpreted another way?
Many claims for subliminal advertising—including the New Jersey movie theater case—
have turned out to be publicity stunts using phony data (Haberstroh, 1995; Pratkanis,
1992). And testimonials from satisfied customers could be biased by what these people
would like to believe about the subliminal tapes they bought. In one study designed to
test this possibility, half the participants were told that they would be listening to tapes
containing subliminal messages for improving memory. The rest were told that the subliminal messages would promote self-esteem. However, half the participants in the
memory group actually got self-esteem messages, and half of the self-esteem group
actually got memory messages. Regardless of which version they received, participants
who thought they had heard memory enhancement messages reported improved memory; those who thought they had received self-esteem messages said their self-esteem
had improved (Pratkanis, Eskenazi, & Greenwald, 1994). In other words, the effects of
the tapes were determined by the listeners’ expectations, not by the tapes’ subliminal
content. These results suggest that customers’ reports about the value of subliminal selfhelp tapes may reflect placebo effects based on optimistic expectations rather than the
effects of subliminal messages.