Effects of hypnotic suggestion on response to subliminal auditory cues
University of Florida, 1995
Virginia W. Sloan
Theoretical Framework and Supporting Research Is consciousness the meat of human existence, or is it merely the tip of the mental iceberg? The realm of non- conscious cognition has been a subject of animated philosophical, scientific and practical debate for many years. Whyte (1978) traces the concept of the unconscious back to the time of Descartes and Leibniz. In 1890, William James presented a series of arguments for and against the existence of unconscious mental processes. Freud identifies Bernheim’s demonstrations of post-hypnotically suggested behavior in 1889 and Breuer’s studies of hysteria in the early 1900s as the foundations for his theories of repression and unconscious ego defense mechanisms (Edmonston, 1986; Stross & Shevrin, 1969). Psychoanalytic theory secured for the unconscious mind an integral part in the birth of modern psychology, differentiating conscious from unconscious processes and imbuing the unconscious with substantial, mysterious powers to influence and shape behavior through dreams, defense mechanisms, instincts, wishes, and memories. Since the 1950s, the field of psychology has undergone several waves of skepticism (described well by Greenwald, 1992) during which theorists (stemming originally from behavior ists in the line of B.F. Skinner) dismissed the unconscious summarily as scientifically unverif iable, and researchers struggled to begin affirming and delineating the powers of the unconscious. In the 1960s, the information- processing theoretical framework for cognition popularized by cognitive psychology once again included both unconscious and conscious facets of processing, separated by the faculty of attention. In this framework, attention was viewed as the locus of conscious agency. Cognitive activation and the establishment and retrieval of memories were conceptualized as accomplishable through both unconscious and conscious routes (Greenwald, 1992; Loftus & Klinger, 1992). In the last guarter century, efforts to understand the nature and function of the non-conscious mind have led scientists down a variety of widely differing avenues of research. Among these are subliminal stimulation (including subliminal psychodynamic activation and subliminal semantic activation), psychophysics, selective attention (dichotic listening and dichoptic viewing), hypnosis, unconscious learning and memory research (such as subliminal mere exposure effects), as well as the burgeoning fields of neuropsychology and neuropsychophysiology. Two of these areas, subliminal stimulation and hypnosis, have been selected as the focus for this study. At this point in the 90s, it seems safe to say that a general (though definitely not unanimous) consensus has emerged in psychology throughout the world that some unconscious properties of the mind indeed exist and do influence both perception and behavior (Greenwald, 1992; Chertok, 1982; Caput i , 1884; Shevrin & Dickman, 1980; Meichenbaum & Gilmore, 1984; Kihlstrom et al , 1992). However, what the unconscious is, how “smart” it is or what its limits are, and how and to what extent it governs behavior and physiological processes are still major guestions for research exploration and dispute. Terminology has varied with research paradigms. “Implicit,” “non-conscious,” “subconscious,” “preconscious,” “subception” and “perception without awareness” are terms which have been favored by one or more researcher as replacements for the concept of “unconscious.” There is little consensus, but abundant sentiment, in the field as to the differences among these terms. As Whyte (1978) very aptly observes, “the trouble is not that they are ambiguous: … It is that we do not yet know the right definitions to use (p. 17).” This investigator favors the use of the word “non-conscious” as the clearest designation to include all of the above-listed concepts. However, the term “unconscious” is widely used throughout the field today with this broader application and, therefore, will be so used in this study, despite the risk of confusion with one of the more specific meanings given it by Freud, Kihlstrom and others.
Within the area of subliminal perception, one goal of the methodological rigor which has evolved over the past two decades has been to achieve a demonstrable separation of conscious influences from capacities ascribed to the unconscious. Problematically, research paradigms have adopted differing definitions of what unconscious cognition is. Some (e.g., selective attention, subliminal psychodynamic activation, dichoptic viewing, dichotic listening, and subliminal affective conditioning) have defined the domain of the unconscious as any cognition which is outside of attention , or, in other words, which is registered by the mind but unattended. This research explores the level of analysis and memory residues produced by such stimuli. Other lines of research (e.g., subliminal semantic activation, implicit memory and perception, and memory illusions) have defined the unconscious more liberally as cognition which cannot be validly verbally described or reported . Reguiring the ability to verbally acknowledge and report experience which is labeled conscious reduces controversy over the boundary between attention and awareness. This definition is useful for research on the ways in which cognition and action are influenced by events which were experienced but not remembered (Greenwald, 1992). Since the 1950s, commercial advertisers, movies, and rock music groups have aroused public interest in the unconscious effect of subliminal messages on behavior and the potential for invasion of personal privacy. Numerous reports have reached the press of movie theaters flashing subliminal messages to increase sales of refreshments , department stores playing subliminal messages to reduce shoplifting, and companies using subliminal sexual stimuli to increase the impact of their magazine and television advertisements. These sensational claims and the public curiosity they provoked provided additional impetus to psychologists in search of answers to the relevant questions (George & Jennings, 1975). In the mid-1980s an auditory subliminal technique called “backmasking,” purportedly used by the rock group Judas Priest to convey satanic messages, was implicated in the suicide of two teenagers (Loftus & Klinger, 1992). At the time, there was little evidence available to support or deny the validity of these claims, but several studies done since then have failed to support the alleged ability to process or act upon backmasked messages (Vokey & Read, 1985; Swart & Morgan, 1992). The popularity of subliminal self-help auditory tapes has been the most recent focus for consumer-motivated research testing the mind’s capacity to absorb and respond to subliminal messages (Merikle & Skanes, 1992; Swingle, 1992). Most of the work on subliminal perception has dealt with visual stimuli. Research on subliminal perception initially approached the investigation of the boundaries of consciousness and of what is registered outside of them by testing the psychophysiological limits of human perception and trying to establish a methodology by which it could be agreed that the mind was indeed receiving messages of which it was not consciously aware. Cheesman and Merikle (1984, 1986) introduced a fundamental distinction between subjective and objective thresholds for conscious perception, which has been adopted in subsequent experimentation. The objective threshold was defined as a level of stimulus presentation at which forced-choice responding indicates no more than chance level (50%) accuracy in perception, whereas the subjective threshold is a level of greater energy at which subjects report (or claim) awareness of stimulus presence at chance level of accuracy. A large volume of evidence today indicates that the body does register stimuli of which it does not have any conscious awareness, through visual, auditory and tactile modes. Subliminal processing of simple stimuli has been reliably and consistently reported through all three sensory modes, as well as by measuring evoked potentials within the brain, at levels between the subjective and objective threshold. However, conclusions about subliminal analysis of stimuli presented in the area below the objective threshold and of more complex (multiword or multipicture) stimuli continue to be controversial (Cheesman & Merikle, 1984; Fisher, 1975; Holender, 1986a, 1986b; Merikle & Skanes , 1992). Indeed, Greenwald (1992) argues in his overview of research on subliminal cognition that the capacity of the unconscious mind to analyze and process stimuli appears to be “severely limited.” He proposes a “two-word challenge” to the field, defying researchers to demonstrate that attentionless cognition can, in fact, extract meaning from a two-word (or more) sequence. Probably the best known field of subliminal research has been subliminal psychodynamic activation (SPA) , spearheaded by Silverman (For a comprehensive review of these findings, refer to Silverman, 1983, or Weinberger & Hardaway, 1990). For the most part, these studies have involved subliminal visual stimuli presented tachistoscopically for periods of only a few seconds, (e.g., eight 4-millisecond flashes at 5-second intervals). Numerous studies have shown that certain psychodynamically oriented messages (most commonly “Mommy and I are one.”), although outside the realm of reportable consciousness, have temporary measurable effects on behavioral factors, such as academic performance, anxiety level, stuttering, homosexual orientation, and schizophrenic organization. The same messages have been shown to lose their effect when presented at supraliminal intensities. The theoretical significance of these findings with respect to psychoanalytic theory and unconscious processing has been intensely debated (Balay & Shevrin, 1988; Balay et al., 1989; Fudin & Benjamin, 1991; Moore, 1989; Weinberger, 1989). It has been argued that the auditory mode of subliminal communication is more amenable to clinical adaptation than the visual because it can so easily be reproduced in the form of a portable audiotape and does not require such focused attention or refined machinery (Swingle, 1992; Urban, 1992). However, there is still a great deal of disagreement as to the complexity and duration of auditory messages which can be absorbed subliminally and how frequently and rapidly they should be repeated, for what length of time (Cacioppo & Petty, 1979; Merikle & Skanes, 1992). Whether it is more effective to present a clear stimulus below the auditory threshold of intensity or a masked stimulus below the threshold of discriminability is also unresolved (Miller, 1991; Mitchell, 1992; Urban, 1992, 1993). As with visual stimuli, it appears that auditory stimuli presented at a subliminal level have a greater effect than those presented at a supraliminal level, although the reasons for this are not fully understood (Borgeat et al., 1985; Zenhausern & Hansen, 1974). Swingle (1992) presents a body of research indicating that subliminal auditory messages as long as a full sentence can be effective therapeutic tools when used as part of a taped self-help regimen. However, several other studies done to test self-help tapes prepared commercially or for research purposes concluded that they had no therapeutic effect beyond that of placebo upon the targeted behavior (Merikle, 1988; Mitchell, 1992; Russell et al., 1991). Urban (1992, 1993) argues convincingly that the field must develop a standardized methodology, suggesting that difficulties in replicating and confirming the effectiveness of subliminal auditory stimulation stem from the dissimilarity of protocols and methods, which leaves it unclear whether the subliminal message was presented in such a way as to be effectively received by the subject.