Publications by authors named "Shevrin H"

Freud proposes that in unconscious processing, logical connections are also (heavily) based upon phonological similarities. Repressed concerns, for example, would also be expressed by way of phonologic ambiguity. In order to investigate a possible unconscious influence of phonological similarity, 31 participants were submitted to a tachistoscopic subliminal priming experiment, with prime and target presented at 1 ms.

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Primary and secondary processes are the foundational axes of the Freudian mental apparatus: one horizontally as a tendency to associate, the primary process, and one vertically as the ability for perspective taking, the secondary process. Primary process mentation is not only supposed to be dominant in the unconscious but also, for example, in dreams. The present study tests the hypothesis that the mental activity during REM-sleep has more characteristics of the primary process, while during non-REM-sleep more secondary process operations take place.

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How can perceptual consciousness be indexed in humans? Recent work with ERPs suggests that P3b, a relatively late component, may be a neural correlate of consciousness (NCC). This proposal dovetails with currently prevailing cognitive theory regarding the nature of conscious versus unconscious processes, which holds that the latter are simple and very brief, whereas consciousness is ostensibly required for more durable, complex cognitive processing. Using a P3b oddball paradigm, we instead show that P3b and even later, related slow wave activity occur under rigorously subliminal conditions.

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While showing unconscious influences on complex decisions is indeed difficult, relevant awareness in relatively simpler subliminal paradigms is more easily assessed. Utilizing objective detection (vs. more typical identification or classification) tasks to assess awareness overcomes longstanding residual methodological problems, and prior work using such methods (e.

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Our approach is based on a tri-partite method of integrating psychodynamic hypotheses, cognitive subliminal processes, and psychophysiological alpha power measures. We present ten social phobic subjects with three individually selected groups of words representing unconscious conflict, conscious symptom experience, and Osgood Semantic negative valence words used as a control word group. The unconscious conflict and conscious symptom words, presented subliminally and supraliminally, act as primes preceding the conscious symptom and control words presented as supraliminal targets.

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Whether or not affect can be unconscious remains controversial. Research claiming to demonstrate unconscious affect fails to establish clearly unconscious stimulus conditions. The few investigations that have established unconscious conditions fail to rule out conscious affect changes.

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In earlier publications, experimental evidence was provided for the existence of the primary vs. secondary process mental organization posited by Freud. A well-established cognitive categorization test based on attributional and relational similarity was found to map on to primary and secondary principles of mental organization respectively, thus offering the opportunity to test hypotheses drawn from psychoanalytic theory independent of the clinical situation.

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Although the veridicality of unconscious perception is increasingly accepted, core issues remain unresolved [Jack, A., & Shallice, T. (2001).

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Unconscious perceptual effects remain controversial because it is hard to rule out alternative conscious perception explanations for them. We present a novel methodological framework, stressing the centrality of specifying the single-process conscious perception model (i.e.

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Controversy exists about whether associative learning occurs without awareness. In an earlier study using subthreshold (subliminal) stimuli, we reported evidence that such learning could occur as measured by event-related brain potentials [ERP; Cons. Cognit.

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Analysis of event-related potentials (ERPs) using signal processing tools has become extremely widespread in recent years. Nonstationary signal processing tools such as wavelets and time-frequency distributions have proven to be especially effective in characterizing the transient phenomena encountered in event-related potentials. In this paper, we focus on the analysis of event-related potentials collected during a psychological experiment where two groups of subjects, spider phobics and snake phobics, are shown the same set of stimulus: A blank stimulus, a neutral stimulus and a spider stimulus.

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Current theories of emotion suggest that threat-related stimuli are first processed via an automatically engaged neural mechanism, which occurs outside conscious awareness. This mechanism operates in conjunction with a slower and more comprehensive process that allows a detailed evaluation of the potentially harmful stimulus (LeDoux, 1998). We drew on the Halgren and Marinkovic (1995) model to examine these processes using event-related potentials (ERPs) within a backward masking paradigm.

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Earlier work has provided experimental evidence for the existence of the primary and secondary process mental organization posited by Freud and has demonstrated that primary process effects are the more active unconsciously (Brakel et al. 2000). Primary and secondary processes were assessed by a categorization test in which qualitatively different principles could be used.

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In previous research Libet (1966) discovered that a critical time period for neural activation is necessary in order for a stimulus to become conscious. This necessary time period varies from subject to subject. In this current study, six subjects for whom the time for neural activation of consciousness had been previously determined were administered a battery of psychological tests on the basis of which ratings were made of degree of repressiveness.

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A series of studies is reviewed strongly suggesting that event-related potentials (ERPs) may provide markers for unconscious processes. In one study it was shown that, although smaller in amplitude by a least a factor of four, ERPs to subliminal stimuli have a similar component structure to ERPs to supraliminal stimuli. In another study, it was shown that an oddball P300 could be obtained for subliminal stimuli.

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This experiment provides brain event-related potential (ERP) evidence for differential processing of visually presented pleasant and unpleasant affectively valent words (mood adjectives) for both supraliminal (40 ms) and subliminal (unmasked, 1 ms) stimulus durations. Unpleasant words elicited a more positive amplitude than pleasant words in both durations. ERP components (P1, N1, P2, P3, and a late positive potential; LP) were measured at six electrode sites (F3, F4, P3, P4, CzPz, Oz).

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Objective: To provide evidence that a P300 component can be elicited by subliminal stimuli in an oddball paradigm.

Methods: The words LEFT and RIGHT were presented in a frequent-rare ratio (80-20%), counterbalanced between subjects. Stimuli were presented at the objective detection threshold (d'=0, via unmasked 1 ms presentations), a stringent measure for detecting any conscious perception.

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The authors report on two experiments designed to test an important feature of the primary process: unconscious categorisation by attributes rather than by relations. These experiments were designed to provide support, independently of the clinical situation, for the presupposition of a psychological unconscious and for the presupposition that unconscious mentation is organised along primary-process lines. Their results were encouraging.

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This study investigated the predictive validity of facial electromyograms (EMGs) in a subliminal conditioning paradigm. Two schematic faces (pleasant; CS- and unpleasant; CS+), were presented to eight right-handed males during supraliminal pre- and postconditioning phases. Subliminal conditioning consisted of 36 energy-masked presentations of each face pairing the CS+ with an aversive shock 800 ms poststimulus.

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Using a classical conditioning technique, this study investigated whether nonconscious associative learning could be indexed by event-related brain activity (ERP). There were three phases. In a preconditioning baseline phase, pleasant and unpleasant facial schematics were presented in awareness (suprathreshold).

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