What every skeptic should know about subliminal persuasion

In this article, we restrict our discussion of subliminally presented stimuli to only those methods that are well supported by research evidence. Thus, audio self-help tapes with subliminal suggestions to "lose weight" or "be assertive" are not considered, nor are "backmasked" messages hidden in recorded music, or instances of messages embedded within pictures (such as the word "sex" airbrushed onto ice cubes or Ritz crackers). Research has shown convincingly that none of these methods is effective (Greenwald, Spangenberg, Pratkanis, and Eskenazi 1991; Moore 1982, 1988; Pratkanis 1992; Pratkanis and Greenwald 1988; Thorne and Himelstein 1984; Vokey and Read 1985). We focus instead on subliminal visual priming techniques, whereby stimuli are presented very quickly, and are typically followed immediately by a "pattern mask," such as a geometric shape or a series of random letters. This mask is intended to disrupt the individual's conscious processing of the stimuli - a bit like immersing pasta in cold water to halt the cooking process.(2)

Unconscious Processing: Out of Sight, But Not Out of Mind

Ask people to name a psychologist and there is disappointingly little variation in their answers. Virtually all of them name Sigmund Freud (with Dr. Joyce Brothers and TV'S Frasier Crane running a distant second and third). Many people might be surprised to learn, then, that contemporary psychology bears little resemblance, either in substance or in methodology, to the work of Freud (Stanovich 1992). That said, at least one idea often attributed to Freud - the unconscious - has made a comeback in contemporary cognitive and social psychology (Bornstein and Pittman 1992; Cohen and Schooler 1997; Erdelyi 1996; Greenwald 1992; Kihlstrom 1987; Uleman and Bargh 1989). Modern psychologists do not subscribe to all of Freud's notions regarding the unconscious; instead, the term refers simply to those mental processes that occur without conscious monitoring or guidance. Viewed in this way, the unconscious figures prominently in many contemporary psychological theories (Greenwald and Banaji 1995; Wegner 1994). For example, numerous studies have shown that some memories that cannot be recalled consciously may nevertheless exert influence on a variety of mental processes (Schacter 1987). Others have noted that stereotypes can be readily applied without any conscious effort or awareness (Gilbert and Hixon 1991; Spencer, Fein, Wolfe, Fong, and Dunn 1998). Indeed, stereotypes seem to be most readily applied at those times when one's conscious capacities are the most limited (Bodenhausen 1990; Bodenhausen and Lichtenstein 1987; Macrae, Milne, and Bodenhausen 1994).

Furthermore, the causal determinants of behavior - why we do what we do - can also be unavailable to conscious awareness. People are notoriously poor at articulating the true causes of their actions and recognizing the importance of critical causal stimuli (Nisbett and Wilson 1977). In one experiment, participants were given a sentence-completion task containing a number of words related to the elderly (e.g., old, wise, retired). Later, after the experiment had ostensibly ended, these individuals walked more slowly to the elevator than participants in a control group, as if they had internalized the concept of "elderly." None of them showed any recognition of their decreased walking speed or of the high frequency of words related to the elderly in the sentence-completion task (nor could the effect be attributed to other plausible alternative factors, such as depressed mood). The result, concluded the researchers, was a direct effect of unconscious processing on behavior (Bargh, Chen, and Burrows 1996).(3)