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Greenberg AC. Comment regarding Malik, et al.'s (1996) "The method of subliminal psychodynamic activation: do individual thresholds make a difference?". Percept Mot Skills 1997; 84:1024-6. [PMID: 9172219 DOI: 10.2466/pms.1997.84.3.1024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Researchers using the method of subliminal psychodynamic activation need to consider the neutrality of their control messages. Anagrams or numbers are recommended as even benign-sounding phrases can produce nonneutral effects.
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277
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de Houwer J, Hendrickx H, Baeyens F. Evaluative learning with "subliminally" presented stimuli. Conscious Cogn 1997; 6:87-107. [PMID: 9170563 DOI: 10.1006/ccog.1996.0281] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Evaluative learning refers to the change in the affective evaluation of a previously neutral stimulus (NS) that occurs after the stimulus has been associated with a second, positive or negative, affective stimulus (AS). Four experiments are reported in which the AS was presented very briefly. Significant evaluative learning was observed in participants who did not notice the presentation of the affective stimuli (ASi) (Experiment 2) or could not discriminate between the briefly presented positive and negative ASi when asked to do so (Experiment 3). In two other experiments (Experiments 1 and 4), no significant learning effect was obtained. A meta-analysis performed on the present and previously reported results (De Houwer, Baeyens, & Eelen, 1994) gave evidence for a small, though statistically reliable evaluative learning effect when ASi are presented "subliminally." This finding supports the hypothesis that evaluative associations can be learned implicitly.
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278
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Abstract
This research demonstrates that subliminally activated stereotypes can alter judgments about oneself and can change cognitive performance. In the first study, an intervention that activated positive stereotypes of aging without the participants' awareness tended to improve memory performance, memory self-efficacy, and views of aging in old individuals; in contrast, an intervention that activated negative stereotypes of aging tended to worsen memory performance, memory self-efficacy, and views of aging in old participants. A second study demonstrated that for the strong effects to emerge from the shifting stereotypes, the stereotypes must be important to one's self-image: Young individuals randomly assigned to the same conditions as the old participants in the first study did not exhibit any of the significant interactions that emerged among the old participants. This research highlights the potential for memory improvement in old individuals when the negative stereotypes of aging that dominate the American culture are shifted to more positive stereotypes.
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279
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Malik R, Paraherakis A, Joseph S, Ladd H. The method of subliminal psychodynamic activation: do individual thresholds make a difference? Percept Mot Skills 1996; 83:1235-42. [PMID: 9017738 DOI: 10.2466/pms.1996.83.3f.1235] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The present experiment investigated the effects of subliminal psychodynamic stimuli on anxiety as measured by heart rate. Following an anxiety-inducing task, male and female subjects were tachistoscopically shown, at their subjective thresholds, one of five subliminal stimuli, MOMMY AND I ARE ONE, DADDY AND I ARE ONE (symbiotic messages). MOMMY HAS LEFT ME (abandonment message), I AM HAPPY AND CALM (positively toned but nonsymbiotic phrase), or MYMMO NAD I REA ENO (control stimulus). It was hypothesized that men would exhibit a greater decrease in heart rate after exposure to the MOMMY stimulus than the control message. No definitive predictions were made for women. The abandonment phrase was expected to increase heart rate. A positively toned message was included to assess whether its effects would be comparable to those hypothesized for the MOMMY message. The results yielded no significant effects for stimulus or gender and so provided no support for the hypotheses.
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280
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Abstract
A "response window" technique is described and used to reliably demonstrate unconscious activation of meaning by subliminal (visually masked) words. Visually masked prime words were shown to influence judged meaning of following target words. This priming-effect marker was used to identify two additional markers of unconscious semantic activation: (i) the activation is very short-lived (the target word must occur within about 100 milliseconds of the subliminal prime); and (ii) unlike supraliminal prime-target pairs, a subliminal pair leaves no memory trace that can be observed in response to the next prime-target pair. Thus, unconscious semantic activation is shown to be a readily reproducible phenomenon but also very limited in the duration of its effect.
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281
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Taylor JG. Breakthrough to awareness: a preliminary neural network model of conscious and unconscious perception in word processing. BIOLOGICAL CYBERNETICS 1996; 75:59-72. [PMID: 8765655 DOI: 10.1007/bf00238740] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A neural network model is constructed to mimic the processing involved in semantic and working memory when subliminal effects are involved. These effects involve modifications of reaction time to later inputs, according to whether or not there has been conscious or unconscious processing of the earlier input. The model is constructed of two separate modules: one (a semantic memory module) allowing for processing at a semantic, but unconscious, level, and the other (a working memory module) for conscious experience. The latter module, although a replica of the earlier one, has different lateral connectivity and output function from the former. The model is shown to give a good fit to Marcel's data on the processing of polysemous words. Further tests are suggested for the model, and a possible cortical implementation suggested. The relevance of the model to recent approaches to consciousness is also explored.
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282
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Malik R, Krasney MS, Aldworth B, Ladd HW. Effects of subliminal symbiotic stimuli on anxiety reduction. Percept Mot Skills 1996; 82:771-84. [PMID: 8774013 DOI: 10.2466/pms.1996.82.3.771] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The present study assessed the effectiveness of subliminal psychodynamic stimuli in reducing anxiety. 50 male and 50 female college students were tachistoscopically exposed to one of five stimuli: MOMMY AND I ARE ONE, DADDY AND I ARE ONE, I AM HAPPY WITH MYSELF, ONE, or a control stimulus MYMMO NAD I REA ENO. It was hypothesized that men would show a significant decrease in anxiety to the MOMMY stimulus, while women were expected to respond favorably to either the MOMMY or DADDY stimulus, or to both. Results showed that the subliminal stimuli did not produce differential effects on anxiety. This finding did not support previous claims for subliminal psychodynamic activation that the stimulation of symbiotic fantasy with the maternal figure produces positive behavioral effects. Despite this negative finding women's response to the MOMMY message was predicted by measures of self-perception.
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283
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Harris JL, Salus D, Rerecich R, Larsen D. Distinguishing detection from identification in subliminal auditory perception: a review and critique of Merikle's study. THE JOURNAL OF GENERAL PSYCHOLOGY 1996; 123:41-50. [PMID: 8901209 DOI: 10.1080/00221309.1996.9921258] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Assertions made by Merikle (1988) regarding audio subliminal messages were tested. Seventeen participants were presented subliminal messages embedded in a white-noise cover, and three signal-to-noise (S/N) detection ratios were examined. Participants were asked to guess message presence and message content, to determine subjective/objective thresholds. Results showed that participants were unable to identify target words presented in this audio subliminal stimulus format beyond chance levels.
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284
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Frydman M. Subliminal manipulation of smoking. J Environ Pathol Toxicol Oncol 1996; 15:173-6. [PMID: 9216802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Subliminal advertising techniques have increased in usage and are commonly accepted, particularly regarding cigarette smoking. Considering the high cost of such subliminal methods, their use can be justified only by tangible results, measured by an increase in cigarette sales. The results of our studies confirm the physiological and psychological effects of subliminal stimulation that have already been reported in the specialized literature. Our research on smoking prevention led us to study the sophisticated advertising strategies used by the tobacco industry. We have shown that revealing the subliminal stimuli-at least the visual ones-is extremely useful for teenagers. The enlightened teenager becomes able to recognize the subliminal manipulation concealed in advertising, and the risk of becoming its victim. Such educational efforts have their merits, particularly at the school level.
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285
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Murphy ST, Monahan JL, Zajonc RB. Additivity of nonconscious affect: combined effects of priming and exposure. J Pers Soc Psychol 1995; 69:589-602. [PMID: 7473021 DOI: 10.1037/0022-3514.69.4.589] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Affect deriving from 2 independent sources--repeated exposure and affective priming--was induced, and the combined effects were examined. In each of 4 studies, participants were first shown 72 Chinese ideographs in which the frequency of exposure was varied (0, 1, or 3). In the second phase participants rated ideographs that were primed either positively, negatively, or not at all. The 4 studies were identical except that the exposure duration--suboptimal (4 ms) or optimal (1 s)--of both the initial exposure phase and the subsequent priming phase was orthogonally varied. Additivity of affect was obtained only when affective priming was suboptimal, suggesting that nonconscious affect is diffuse. Affect whose source was apparent was more constrained. Interestingly, increases in liking generated through repeated exposures did not differ as a function of exposure duration.
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286
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Hida W, Okabe S, Miki H, Kikuchi Y, Kurosawa H, Takishima T, Shirato K. Submental stimulation and supraglottic resistance during mouth breathing. RESPIRATION PHYSIOLOGY 1995; 101:79-85. [PMID: 8525124 DOI: 10.1016/0034-5687(95)00011-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We studied submental stimulation on supraglottic resistance (Rsg) in 5 normals and 6 patients with obstructive sleep apnea. We then examined the most effective sites of stimulation in the submental regions, and the relationships between Rsg and stimulation frequency and voltage in the supine position. Inspiratory and expiratory Rsg's were obtained as the slope of the linear portion of the pressure-flow relation determined at zero flow. Before stimulation, inspiratory and expiratory Rsg's were 0.76 +/- 0.06 (means +/- SE) and 0.61 +/- 0.02 cmH2O.L-1.sec, respectively, in normals, and 1.04 +/- 0.20 and 0.92 +/- 0.29 cmH2O.L-1.sec, respectively, in patients. Stimulation in the proximal half submental region with surface electrodes 1 cm apart decreased inspiratory and expiratory Rsg's in patients, and inspiratory Rsg in normals. Inspiratory Rsg measured in this submental region showed a stimulation frequency-and voltage-dependency in both groups, but expiratory Rsg did not. These findings suggest that submental stimulation in the proximal half region widens the supraglottic airway during mouth breathing and probably involves the upper airway muscles.
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287
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van den Hout M, Tenney N, Huygens K, Merckelbach H, Kindt M. Responding to subliminal threat cues is related to trait anxiety and emotional vulnerability: a successful replication of Macleod and Hagan (1992). Behav Res Ther 1995; 33:451-4. [PMID: 7755532 DOI: 10.1016/0005-7967(94)00062-o] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Macleod and Hagan (1992) [Behaviour Research and Therapy, 30, 151-161] reported that threat-relevant interference on a masked Stroop task, where neutral and negative words cannot be consciously perceived, is positively correlated with trait anxiety and emotional vulnerability to stressful life events. Their findings were obtained from subjects who were currently stressed. The aim of the present study was to determine whether the Macleod and Hagan findings could be replicated in a sample that was not currently stressed. Using a sample of 32 volunteers, we found a significant correlation between trait anxiety and threat-relevant interference on a masked Stroop. Furthermore, it was found that the single best predictor of vulnerability to life stress was the interference on the masked Stroop. The findings of the present study correspond quite closely to those reported by Macleod and Hagan (1992).
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288
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Greenwald AG, Klinger MR, Schuh ES. Activation by marginally perceptible ("subliminal") stimuli: dissociation of unconscious from conscious cognition. J Exp Psychol Gen 1995; 124:22-42. [PMID: 7897340 DOI: 10.1037/0096-3445.124.1.22] [Citation(s) in RCA: 185] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Introduces a linear regression method for investigating unconscious cognition. For words that were obscured by simultaneous dichoptic masking, indirect effects (semantic priming) and direct effects (perceptual identification) were assessed in 20 experiments (total N = 2,026). When measures of both indirect and direct effects have rational zero points, a statistically significant intercept in the indirect-on-direct-measure regression shows that (a) the indirect effect occurred in the absence of the direct effect, and (b) unconscious cognition is involved. For a position discrimination task, but not for an evaluative decision task, indirect-on-direct regression showed the significant intercept effect. Although small in magnitude, this intercept effect provides the statistically most secure finding yet obtained of a much-sought and controversial data pattern--indirect effect with no direct effect. With one added assumption (which appears plausible for the present data), this pattern indicates that unconscious cognition is dissociated from (i.e., occurs separately from) conscious cognition.
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289
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Mogg K, Bradley BP, Williams R. Attentional bias in anxiety and depression: the role of awareness. BRITISH JOURNAL OF CLINICAL PSYCHOLOGY 1995; 34:17-36. [PMID: 7757037 DOI: 10.1111/j.2044-8260.1995.tb01434.x] [Citation(s) in RCA: 400] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Attentional biases were assessed with a probe detection task in anxious (N = 17), depressed (N = 17) and normal control (N = 15) subjects. Word pairs were presented visually, with a dot probe following one word of each pair. Allocation of attention to the spatial position of the words was determined from response latencies to the probes. Half the word pairs were presented supraliminally, half subliminally. The anxious and depressed groups showed an attentional bias towards supraliminal negative words, in comparison with normal controls. The depressed group unexpectedly showed greater vigilance for supraliminal anxiety-relevant words than the anxious group. The anxious group shifted their attention towards the spatial location of negative words presented subliminally. The results support the hypothesis of an anxiety-related bias in preconscious processes.
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290
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Mitchell CW. Effects of subliminally presented auditory suggestions of itching on scratching behavior. Percept Mot Skills 1995; 80:87-96. [PMID: 7624224 DOI: 10.2466/pms.1995.80.1.87] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This study investigated effects of masked verbal suggestions of itching, utilizing a design closely analogous to commercially available subliminal audiotapes. Students participated in 1 of 3 groups (n = 21): an experimental group listened to an audiotape with music masking suggestions of itching, Control Group 1 listened to an audiotape with music only, and Control Group 2 listened to suggestions of itching presented supraliminally. Dependent variables included both behavioral and self-report measures of itching. There was no evidence of influence from subliminal suggestion; however, results assessing the influence of supraliminally presented suggestions were mixed for self-report and behavioral measures.
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291
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Senni C. [Basal stimulation: necessity and problems in the integration into care]. PFLEGE ZEITSCHRIFT 1994; 47:552-4. [PMID: 7952720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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292
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Colucci R, Musio C, Taddei-Ferretti C. EXPLAN--a programming language for complex visual stimuli presentation. INTERNATIONAL JOURNAL OF BIO-MEDICAL COMPUTING 1994; 37:29-39. [PMID: 7896435 DOI: 10.1016/0020-7101(94)90069-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Visual cognition research requires the flexible use of structured spatial patterns, characterized by various space and time parameters, which may be administered as visual stimuli. Dealing with this kind of study, we developed a special-purpose programming language and implemented a compiler to build executable programs. The language allows the presentation of stimuli, their space coordinates, persistency values, sequence, kinematic parameters, space-time proximity with other visual stimuli, determination of their modification according to external interaction, generation of subliminal stimuli, monitoring of different subject reactions, automatic reporting of stimulus presentation, and reaction monitoring. Such a language has been successfully utilized in a visual perception research.
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293
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294
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Abstract
The aims of this study were to determine whether stimuli which cannot be detected consciously may nevertheless influence subjects' choices, and whether such an effect is dependent upon stimulus quality and the cerebral hemisphere involved in processing. We subliminally presented words (associated with left hemisphere processing) and faces (associated with right hemisphere processing) to each visual half-field. Subsequently, subjects had to choose among six items. The performance of subjects was compared to that of controls to whom only blank stimuli were presented. Subjects chose the correct word or face significantly more often than controls. For words this effect was significant only when they were subliminally presented to the left hemisphere, whereas subliminal face processing was done by both hemispheres. Our results demonstrate that (i) subliminally presented stimuli influence subjects' choices and thus must have been perceived, and (ii) that cerebral dominance seems to play a role in subliminal perception.
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295
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Ruggieri V. A zoom lens before the eyes during imagery: individual differences and strange, unexpected responses. Percept Mot Skills 1994; 78:451-4. [PMID: 8022673 DOI: 10.2466/pms.1994.78.2.451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The research examined some aspects of an hypothetical involvement of the eyes in the process of imagery and the individual differences in the modulation of the imagery-perception interaction of 59 (7 male and 52 female) undergraduate students in psychology. The subjects were asked to image with open eyes and to project, looking through a zoom lens, the "mental" image onto a white screen. While the subject was imaging, the experimenter moved the lever of the zoom lens in the direction of an hypothetical enlargement. This movement evoked different classes of responses: 46% of the subjects had a loss, even if for a short time, of the image, 37% of the subjects observed a strange and unexpected enlargement of the mental image, 7% did not observe any change in imagery, and 10% had other responses. A psychophysiological discussion concerned the strange phenomena observed in this research that have not yet been explored enough.
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296
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Abstract
One hypothesis of traditional psychoanalytic theory holds that a cardinal aspect of the "natural" development of femininity involves the woman's substitution of the wish for a baby in place of her original wish for a penis. The current study modified and extended earlier research examining the validity of Freud's this "penis-baby" theory. College-aged women and men were presented with either subliminal or supraliminal auditory messages concerned with either pregnancy or penetration themes. Subjects' written responses to Holtzman ink-blots, obtained both before and after exposure to an auditory message, were content-coded for phallic imagery and sexual imagery. Consistent with Freud's speculations about the phallic significance of pregnancy for women, female subjects who were exposed to the subliminal pregnancy message produced significantly more phallic imagery responses to ink-blots than did women in any of the other experimental conditions (p < .01). The phallic imagery production of males did not vary significantly as a function of message condition. Implications of these findings are discussed in the context of modern revisions to Freud's psychology of women and the current psychoanalytic conceptualization of penis envy as a highly condensed mental product with many layers of meaning.
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297
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Hughes JA, Sanders LD, Dunne JA, Tarpey J, Vickers MD. Reducing smoking. The effect of suggestion during general anaesthesia on postoperative smoking habits. Anaesthesia 1994; 49:126-8. [PMID: 7864913 DOI: 10.1111/j.1365-2044.1994.tb03368.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In a double-blind randomised trial, 122 female smokers undergoing elective surgery were allocated to receive one of two prerecorded messages while fully anaesthetised. The active message was designed to encourage them to give up smoking whilst the control message was the same voice counting numbers. No patient could recall hearing the tape. Patients were asked about their postoperative smoking behaviour one month later. Significantly more of those who had received the active tape had stopped or reduced their smoking (p < 0.01). This would suggest a level of preconscious processing of information.
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298
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Smith TB. Effects of subliminal stimuli on unconscious processing of anxiety: an examination of implicit perception. Percept Mot Skills 1993; 77:899-904. [PMID: 8284173 DOI: 10.2466/pms.1993.77.3.899] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Researchers in cognitive psychology generally accept that information, including emotions, may be processed outside of awareness. Some have postulated that anxiety may be induced by stimuli presented below the level of detection, a process called implicit perception; however, conflicting findings as to the validity of subliminal stimuli in influencing anxiety have been reported over the past decade. In the present study, 39 subjects were exposed to either positive, negative, or neutral subliminal stimuli, and half the subjects were informed as to the type of stimuli they received. All subjects were monitored for frontalis muscle tension, a physiological indicator of anxiety, on an electromyograph (EMG). No significant effects of the exposure upon EMG recordings were noted. Awareness of the type of stimuli presented had a small but insignificant effect. These results, although tentative, when replicated would question the validity of subliminal visual presentation in altering emotive states.
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299
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Sylvester GP, Williams J, Achterberg C. Food and nutrition messages in film. A preliminary content analysis. Ann N Y Acad Sci 1993; 699:295-7. [PMID: 8267332 DOI: 10.1111/j.1749-6632.1993.tb18871.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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300
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Fudin R. Final comments on Hudesman, Page, and Rautiainen's (1992) subliminal psychodynamic activation experiment. Percept Mot Skills 1993; 77:367-70. [PMID: 8247655 DOI: 10.2466/pms.1993.77.2.367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Hudesman, et al.'s (1992) contention that their finding shows that subliminal psychodynamic activation (SPA) improved academic performance is questioned. That experiment lacked controls outlined by Fudin in 1986 which are needed to support the assumption that a positive SPA outcome is effected because the meaning of an entire experimental message is encoded. In 1993 Hudesman and Page argued that Gustafson and Källmén's 1991 results, obtained with such controls, indicated that the controls do not have to be used in subsequent SPA experiments. The 1990 results of Greenberg and of Kothera, Fudin, and Nicastro, however, do not support those of Gustafson and Källmén. From a different perspective, it is argued that good experimental controls are needed in all SPA experiments because they increase internal validity. Given that Hudesman, et al.'s subjects scored in a limited range on the mathematics portion of the 1978 CUNY Skills Assessment Test, the implication that their result can be generalized to all subjects is questioned.
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