popular media about the effects of âbackmasking.â Oates (1991), however, does not confine his claims to negative messages purportedly heard when popular ...
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Running head: Effect of reverse speech on priming
A Test of the Affect of Reverse Speech on Priming David Kreiner, Nicole Altis, and Carla Voss
CENTRAL MISSOURI STATE UNIVERSITY
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ABSTRACT
Previous research (Vokey and Read, 1985) has indicated that listeners cannot consciously recognize backward messages, but that some information can be obtained from reversed speech. If, as David Oates (1991) has claimed, reverse speech has a powerful influence on language processing, we should be able to measure a reliable priming effect from reversed messages. 60 undergraduate students listened to short messages which were presented either backward or forward. Immediately after listening to each message, subjects responded in a lexical decision task to a visually word which had either been present in the preceding message or had not been present. No priming affect was found for backward messages, although there was significant priming from forward messages. The results are not consistent with an effect of reverse speech on word processing.
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Introduction Our study wanted to test claims about the effects of reversed speech. David Oates (1991) has claimed that backward messages are encoded in normal speech and that this constitutes a second, covert mode of communication in addition to the “overt” mode of forward speech. This is a recent version of longstanding claims made in the popular media about the effects of “backmasking.” Oates (1991), however, does not confine his claims to negative messages purportedly heard when popular musical recordings are played backwards, but articulates a startling theory suggesting that reverse speech is a normal part of human communication. Oates claims that these backward messages in speech are not rarities but are normally encoded in everyday speech. According to Oates’ theory, backward messages can reveal unconscious memories and motives, and this information is communicated unconsciously to listeners. Bryne et. al (2000) point out that “there is a potential for harm” with some of Oates’ claims. For example, Oates suggests that expert witnesses trained in interpreting reversed messages could testify as to the unconscious motives of a defendant. If Oates’ theory is not correct, this could potentially lead juries to the wrong verdicts. Byrne and Normand also point out that Oates suggests that graduates of his training program will be prepared to perform therapy. It might be argued that Oates’ claims should simply be dismissed, given that they are potentially dangerous and that the claims appear to be implausible . However, we concur with Byrne and Normand (2000) that claims such as these can and should be tested empirically.
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METHOD Participants Sixty students attending CMSU volunteered to participate. Students received extra credit in Psychology courses in exchange for their participation. Materials Twenty messages which Oates has claimed exist in reversed speech samples were obtained from the Reverse Speech Enterprise’s website, http://www.reversespeech.com. We selected messages which appeared to have some emotional content but which were not overly offensive. Each message was digitally recorded by a female. Reversed versions of each message were created using SoundEditTM 16 software. The messages range in duration from 726 to 1852 ms with a mean duration of 1380 ms (SD = 285). For twelve of the twenty messages, a content word from the message was selected for use in the lexical decision task. For the remaining eight messages, a pseudoword was constructed by replacing two letters in the content word for each message. An additional 4 messages were recorded and used for practice trials. The number of real word trials was greater than the number of pseudoword trials as a result of the limited number of stimuli that met our criteria of being emotional but not overly offensive. It was necessary for the number of word trials to be a multiple of four so that we could create four stimulus lists to counterbalance the items across forward and backward conditions as well as across priming and control trials. Although participants encountered more words than non-words, the small total number of trials letters in the center of the screen. Because the messages varied in
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Results Priming is computed for each participant by subtracting mean reaction time on priming trials from mean reaction time on control trials. Only times for correct responses are included. Data is excluded for 3 additional subjects who havefewer than 2 out of 3 correct trials for any of the four groups of real word trials, yielding a total of 60 participants for all of the results reported below. The mean number of errors out of 20 trials is .93 (SD = 1.10). For forward messages, the mean priming is 97 ms (SD = 201); for backward messages, the mean priming was 10 ms (SD = 359). Single-sample t-tests were conducted to determine whether the amount of priming was significant for forward or backward messages. Forward message priming is significantly different from zero, t(59) = 3.74, p < .001, r2 = .19, but backward message priming is not, t(59) = 0.22, p > .05, r2 = .00. Mean reaction times are shown in Chart 1. The number of errors is not significantly correlated with overall reaction times, r(58) = -.02, p > .05. Total number of errors is not significantly correlated with the amount of priming from backward messages, r(58) = -.14, p > .05. However, participants who make more errors tend to show less priming from forward messages, r(58) = -.36, p < .01.
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Conclusions There is no indication that backward messages cause priming. The amount of backward priming is not statistically significant and the effect size is 0. It is unlikely that the lack of a backward message priming effect was due to low power or to poor sensitivity of the research method, as the same method, using the same stimuli, produced a clear priming effect with forward messages. It is also difficult to argue that the stimuli used were not realistic or emotional enough to elicit a priming effect if one existed, as we used messages which Oates, a proponent of reverse speech, claimed to find in natural speech samples. The variability of reaction times within conditions is quite large. This is likely a result of the fact that there were only three trials within each condition for each participant. Despite these large standard deviations, there is still a significant priming effect from the forward messages. It should be noted that a repetition priming paradigm was used in the current study; the same word to which participants responded in the lexical decision task was contained in the backward or forward message. Another approach could be to use a semantic priming paradigm in which participants respond to a word that is semantically related to the word in the message (e.g., wolf and dog). We chose to use the repetition priming approach for several reasons. First, we wanted to use a method which would provide a high probability of detecting an effect of backward speech if such an effect existed. Repetition priming tends to produce large effects, and these effects have been found even when participants claim that they have not recognized the word (Stark and McClelland, 2001). This is important, because Oates claims that we process
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References Oates, D.J. (1991). Reverse speech: Hidden messages in human communication. Indianapolis, IN: Knowledge Systems. Begg, I.M., Needham, D.R. and Bookbinder, M. (1993). Do Backward Messages Unconsciously Affect Listeners? No. Canadian Journal of Experimental Psychology, 47, 1-14. Byrne, Thomas., & Normand, Michael. (2000). The demon-haunted sentence: A skeptical analysis of reverse speech. Skeptical Inquirer, 46-49. Cowan N., Leavitt L.A., Massaro D.W., & Kent R.D. (1982). A fluent backward talker. Journal of Speech and Hearing Research, 25, 48-53. J. Grainger, M.N. Van Kang., & J. Segui, (2001). Cross-modal repetition priming of heterographic homophones. Memory & Cognition, 29, 53-61. Jacoby & Kelley (1992). A process-dissociation framework for investigating unconscious influences: Freudian slips, projective tests, subliminal perception, and signal detection theory. Current Directions in Psychological Science, 1, 174-179. Stark, C.E.L., & McClelland, J.L. (April, 2000). Repetition priming of words, pseudowords, and nonwords. Journal Of Experimental Psychology: Learning, Memory, And Cognition, 26. Swart, L.C., & Morgan, C.L. (1992). Effects of subliminal backward-recorded messages on attitudes. Perceptual -and - Motor – Skills, 1107-1113. Vokey, J.R., & Read, J.D. (1985). Subliminal messages: Between the devil and the media. American Psychologist, 40, 1231-1239.
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Chart 1 Mean Reaction Times (ms) on Lexical Decision Task (Standard Deviations in Parentheses)
Word Type Priming
Control
Pseudo
1220(333) 1302(460)
1317(344) 1312(361)
1563(542) 1617(638)
Message Type
Forward Backward
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0 forward priming
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