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Subliminal Advertising Made Me Do It February 13, 2007

Posted by Johan in Cognition.
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Psychological research on subliminal perception dates back to the late 19th century. In itself, the finding that stimuli that are not consciously perceived can affect subsequent behaviour did not arouse particular public interest or controversy. This changed in the 1950’s, when James Vickary famously reported increased soda and popcorn sales in a movie theatre, following subliminally presented messages endorsing those products during the course of a movie (Loudon & Della Bitta, 1993). While Vickary’s findings were soon discredited as irreplicable, there was great public concern over the possibility that advertisers could induce people to buy products with advertisements that people could not perceive, and thus not assess critically. This resulted in a number of policy decisions limiting the use of subliminal advertising. In popular books of the time, such as The hidden persuaders (Packard, 1981), originally released in 1957, Vickary’s findings were cited uncritically as evidence of the menacing effects of subliminal advertisements. Decades after the original controversy, Zanot et al (1983) found that in an American sample, almost half the participants knew of subliminal advertising, and out of those who knew about it, 68 percent believed it to be effective. Similar results have been obtained more recently (Rogers & Smith, 1993), which suggests that subliminal advertising remains a cause of public concern.

Yet, what is the empirical evidence that subliminal stimuli actually influence consumer behaviour? As we shall see, it is far from clear that subliminal advertising works.

It is important to make an initial distinction between subliminal communication and subliminal persuasion (De Fleur & Petranoff, 1959). Subliminal communication is a well-established psychological finding. For instance, participants were able to guess at better than chance levels which geometrical symbols had been presented subliminally while they watched a movie (De Fleur & Petranoff, 1959). In this task, there is no conflict between how the participants would normally act, and how they act following exposure to the subliminal stimulus. For subliminal persuasion to be effective, the message must do more than this: it must also persuade the participant to produce the desired behaviour.

The ability of advertisements to produce this persuasion effect was tested early on by De Fleur and Petranoff (1959). Two subliminal messages were broadcasted repeatedly on a local TV station: one advertising a certain product, and another advertising a TV programme, which would follow the movie that the subliminal messages had been inserted into. In addition to this, the effect of coupling the subliminal advertisement with a normal, explicit advertisement was tested. The results were a categorical failure of subliminal advertisement to create any discernable effect. Indeed, explicit advertisements actually fared better when presented without the subliminal message. Even the less demanding message, which simply asked participants to remain tuned to the TV station to watch the following programme, failed to produce any significant effects (De Fleur & Petranoff, 1959).

This failure to find an effect in naturalistic settings has not been unequivocally confirmed in the laboratory. Evidence from experiments indicates that participants prefer subliminally presented shapes and faces over previously unseen shapes and faces (Bornstein, Leone & Galley, 1987). In a mock debate between two confederates, participants would side more frequently with the confederate that they had previously been subliminally exposed to (Bornstein et al, 1987), indicating that in this case, subliminal exposure affected social behaviour (note, however, that this particular study has proved difficult to replicate). Likewise, coupling neutral photos of a person with pleasant or unpleasant subliminal stimuli affected participants’ subsequent ratings of the person (Krosnick, Betz, Jussim & Lynn, 1992). Taken together, these findings show that subliminal messages can affect both attitudes and behaviour, in contrast to the findings of De Fleur and Petranoff (1959). Why might these results conflict?

One factor that distinguishes the aforementioned laboratory studies from De Fleur and Petranoff’s (1959) naturalistic study is familiarity. The TV viewers were exposed to subliminal messages endorsing products and TV programmes that they were most likely already familiar with. By contrast, the experimental paradigm relies on stimuli that the participants have never seen before. The increasing appreciation that participants show for familiar stimuli is known as the mere exposure effect (Zajonc, 1968), and as Bornstein et al (1987) found, it extends to subliminal stimuli. It is conceivable that the mere exposure effect is the mechanism that enables subliminal persuasion. Indeed, subliminal stimuli tend to be too simple to offer any arguments, which would limit the efficacy of other forms of persuasion, but not necessarily the mere exposure effect. As shall be shown next, the known limitations of the mere exposure effect may offer some explanation for the differences between the results of naturalistic and laboratory studies on subliminal persuasion.

In his seminal paper on the mere exposure effect, Zajonc wrote:

“[...] in all of these experiments a pattern of results emerges showing that the frequency manipulation has more pronounced attitude effects for stimuli that are novel, unfamiliar, or unusual than for familiar stimuli.” (1968, p. 18)

Thus, under the assumption that the mere exposure effect enables subliminal persuasion, it is not surprising that novel stimuli, such as those used in the experimental paradigm, generate effects, while familiar stimuli, such as those used in the study by De Fleur and Petranoff (1959), do not. Thus, subliminal persuasion is only likely to be effective for novel stimuli, which limits its usefulness for advertising purposes.

Despite this limitation, one paper offers evidence that subliminal persuasion may sometimes offer a unique advantage over explicit persuasion. In a first experiment, Weisbuch, Mackie and Garcia-Marques (2003) assessed their participants’ agreement with a persuasive message, which was attributed to a person whose photo had previously been primed explicitly or subliminally to the experimental groups. It was found that the experimental groups agreed more strongly with the message than a control group that had not been exposed to the photo, but there was no significant difference between the explicit and the subliminal exposure groups (Weisbuch et al, 2003). In a second experiment, the same procedure was followed, except in this case, participants were given a chance to correct for prior exposure: they were simply asked if they had seen the person in the photo before. This caused the explicit exposure group’s agreement scores to drop to the control group’s level, but interestingly, the subliminal exposure group appeared unaffected by this: their agreement levels were now significantly higher than both the explicit exposure group and the control group (Weisbuch et al, 2003). This implies that subliminal exposure can prevent participants from critically evaluating their reasons for agreeing with a message (Weisbuch et al, 2003). Because the subliminal exposure group were unaware of their prior exposure, they could not correct for the biasing effects of it. This inability to correct for prior exposure could prove beneficial for advertising purposes.
The notion that the mere exposure effect could underlie subliminal persuasion has implications that need to be tested. For instance, because the mere exposure effect operates by familiarity alone, the quality of the subliminally presented argument should not matter, so supposing that arguments differing in quality can be presented briefly enough to be perceived subliminally, a weak argument containing the advertised message should have the same effect as a strong argument containing the advertised message.

References
Bornstein, R.F., Leone, D.R., & Galley, D.J. (1987). The Generalizability of Subliminal Mere Exposure Effects: Influence of Stimuli Perceived Without Awareness on Social Behaviour. Journal of Personality and Social Psychology, 53, 1070-1079.
De Fleur, M.L., & Petranoff, R.M. (1959). A Televised Test of Subliminal Persuasion. The Public Opinion Quarterly, 23, 168-180.

Krosnick, J.A., Betz, A.L., Jussim, L.J., & Lynn, A.R. (1992). Subliminal Conditioning of Attitudes. Personality and Social Psychology Bulletin, 18, 152-162.

Loudon, D.L., & Della Bitta, A.J. (1993). Consumer behavior. Singapore: McGraw-Hill.

Packard, V. (1981). The hidden persuaders. London: Penguin.

Rogers, M., & Smith, K.H. (1993). Public Perceptions of Subliminal Advertising: Why Practitioners Shouldn’t Ignore this Issue. Journal of Advertising Research, 33, 10-18.

Weisbuch, M., Mackie, D.M., & Garcia-Marques, T. (2003). Prior Source Evidence and Persuasion: Further Evidence for Misattributional Processes. Personality and Social Psychology Bulletin, 29, 691-700.

Zajonc, R.B. (1968). Attitudinal Effects of Mere Exposure. Journal of Personality and Social Psychology Monograph Supplement, 9 (2, Part 2), 1-27.

Zanot, E.J., Pincus, J.D., & Lamp, E.J. (1983). Public Perceptions of Subliminal Advertising. Journal of Advertising, 12, 39-45.

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