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Subliminal Perception of Pictures in the Right Hemisphere

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Abstract

We addressed the questions whether stimuli presented below the threshold of verbal awareness are nevertheless perceived and whether there are perceptual differences between the two cerebral hemispheres. Pictures of line drawn objects and animals were subliminally presented to each visual half-field for subsequent identification in a form as fragmented as possible. The performance of 40 healthy subjects was compared to that of 63 controls. Whereas identification performance after blank presentation in the experimental group did not differ from that of controls, identification in a significantly more fragmented form was achieved after the presentation of the complete picture. This effect, however, occurred only after subliminal stimulation in the left visual field, i.e., of the right hemisphere. Our results show that (i) pictures presented below the threshold of verbal awareness can be perceived, and (ii) that only the right hemisphere can perceive them and make use of the perception. It remains an open question whether this kind of hemispheric specialization represents a right hemisphere dominance for subliminal perception or reflects an inability of the left hemisphere to access and behaviorally use unaware percepts via fragmented picture identification, for which a right hemisphere advantage is known.

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... In the case of the above-mentioned 67-year-old professor with profound anterograde amnesia and more selective retrograde amnesia, Markowitsch and co-workers employed several testing paradigms tapping into priming, such as Gollin's Incomplete Pictures Test [137], Word Stem Completion, Sentence Completion, Phrase Completion, and procedural memory system (Mirror Image Reading). The obtained findings pointed to a non-uniformity of performance levels in these tasks. ...
... N.N.'s perceptual priming, tested with the incomplete picture task [137], was at the second presentation somewhat lower than that of students, average age 24 years, tested with a 24 h delay. ...
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Memory is not a unity, but is divided along a content axis and a time axis, respectively. Along the content dimension, five long-term memory systems are described, according to their hierarchical ontogenetic and phylogenetic organization. These memory systems are assumed to be accompanied by different levels of consciousness. While encoding is based on a hierarchical arrangement of memory systems from procedural to episodic-autobiographical memory, retrieval allows independence in the sense that no matter how information is encoded, it can be retrieved in any memory system. Thus, we illustrate the relations between various long-term memory systems by reviewing the spectrum of abnormalities in mnemonic processing that may arise in the dissociative amnesia-a condition that is usually characterized by a retrieval blockade of episodic-autobiographical memories and occurs in the context of psychological trauma, without evidence of brain damage on conventional structural imaging. Furthermore, we comment on the functions of implicit memories in guiding and even adaptively molding the behavior of patients with dissociative amnesia and preserving, in the absence of autonoetic consciousness, the so-called "internal coherence of life".
... These data are also in conformity with results emphasising the left hemisphere in detailed, analytic processing of faces and figures [55], and the right hemisphere in a more or-all-none global, immediate stimulus perception [45]. Krickl et al. [55] had presented figures and human faces to patients with damage to the right or left hemisphere. ...
... Henke et al. [45] studied the subliminal perception of human faces in normal subjects and found a right hemisphere advantage under conditions of very brief (40 ms), but repeated presentation. That processing in the left hemisphere is more analytic and in the right one is more global is also confirmed by fear conditioning, an in principal universal or general condition. ...
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Evidence for a differential involvement of the human left and right amygdala in emotional and cognitive behaviour is reviewed, with a particular emphasis on functional imaging results and case reports on patients with amygdalar damage. The available evidence allows one to conclude that there is definitely a hemisphere specific processing difference between the left and right amygdala. However, between studies the direction of the asymmetry is partly incongruent. In spite of this, the following tentative proposals are made: the left amygdala is more closely related to affective information encoding with a higher affinity to language and to detailed feature extraction, and the right amygdala to affective information retrieval with a higher affinity to pictorial or image-related material. Furthermore, the right amygdala may be more strongly engaged than the left one in a fast, shallow or gross analysis of affect-related information.
... The two hemispheres are also differentially sensitive to prior exposure with the right hemisphere benefiting more than the left. Specifically, Henke, Landis, and Markowitsch (1993) found that objects could be identified on the basis of fewer fragments after the right (but not the left) hemisphere had been exposed to the complete object. ...
... Likewise, identification times were faster for the fragments of previously seen objects. This is not particularly surprising; the results of many studies attest to the facilitory role of learning (Leeper, 1935), training (Gollin, 1960), past experience (Rock, 1975), perceptual priming (Snodgrass & Corwin, 1988), or priming on the identification of fragmented pictures (Danzinger & Salthouse, 1978;Henke et al., 1993;Parkin & Russo, 1990;Roediger & McDermott, 1993;Salthouse & Prill, 1988;Snodgrass & Feenan, 1990;Vokey, Baker, Hayman, & Jacoby, 1986;Whitfield & Elias, 1992;Whitfield, Elias, & Dore, 1991;Wippich et al., 1991). Our results, however, further show that a single 1-to 2-s episode of this sort also influences unsuccessful visual processing of identified objects as well. ...
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The authors investigated visual processing leading to object identification by manipulating the number of fragments and nature of the study. During the study, participants either named or drew objects in Experiment 1 and drew them all in Experiment 2. During the test, participants made an identification judgment at each of 6 different fragmentation levels for studied and new objects. Fewer fragments were needed to identify studied than unstudied objects. Reaction times were faster for studied than unstudied objects both at identification and at the preceding level. Event-related brain potentials (ERPs) to unidentified objects were characterized by a late negativity in contrast to a positivity to identified objects. ERPs to studied but not to new objects contained a smaller and later version of the identification positivity at level just prior to identification, which was not due to differential response confidence. Much covert visual analysis and even object identification may precede overt identification, depending on the nature of prior experience.
... In an Incomplete Pictures test (Henke et al., 1993; Kessler C.C. 110 92 103 100 109 et al., 1993) subjects see a fragmented picture and attempt to name the object represented. Additional pictures are presented, each one more complete than previous one in the ...
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... Specifically, Gazzaniga (1993) suggested that the left hemisphere is crucial for consciousness, and left dominance in response to conscious stimuli is reflected in the left-brain decoder. Nevertheless, some discrepancies were found from this theoretical perspective, and an opposite right lateralization was revealed for conscious awareness (Henke, Landis, & Markowitsch, 1993;Shevrin et al., 1996). ...
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... En marketing, plusieurs chercheurs ont abordé le thème de la spécialisation hémisphérique (Alwitt, 1985 ;Anand, Holbrook et Stephens, 1988 ;Hansen, 1981, Janiszewski, 1988Rothschild et alii, 1988 ;Rothschild et alii, 1986 ;Weinstein, Appel et Weinstein, 1980) et celui de la coopération hémisphérique (Janiszewski, 1993 ;Rothschild et Hyun, 1990). Comme dans les autres disciplines, l'idée d'une plus grande efficacité de l'hémisphère droit pour traiter les images et de l'hémisphère gauche pour traiter les mots reste dominante ; cet équilibre semblant respecté avec des stimuli non consciemment perçus (Henke, Landis and Markowitsch 1993). Ces travaux nous ont guidés dans les expérimentations présentées infra pour le choix des emplacements publicitaires. ...
... This is compatible with the notion that both the hemispheres are involved in visual consciousness, probably with peculiar aspects. Previous studies have emphasized the role of the left hemisphere for consciousness, whereas others have favored the right hemisphere (Galin, 1974;Kostandov and Arzumanov, 1977;Brandeis and Lehmann, 1986;Shevrin et al., 1992;Gazzaniga, 1993;Henke et al., 1993). In this framework, the left hemisphere may subserve sequential organization of percepts and linguistic elaboration, whereas the right one may subserve global visuo-spatial search and somatic perceptive processes, as revealed by well-known neurological syndromes such as neglect, visual extinction, prosopagnosia, etc. (Berti and Rizzolatti, 1992;Wallace, 1994;Baudena et al., 1995;Farah and Feinberg, 1997;De Renzi, 2000). ...
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... In particolare Gazzaniga (1993) ha sottolineato la centralità dell'emisfero sinistro nei processi di elaborazione conscia. Tuttavia, in alcuni casi sono state osservate discordanze nei risultati sperimentali, con una prevalenza emisferica destra per condizioni di stimolazione conscia (Henke, Landis eMarkowitsch, 1993). Nel presente contributo è previsto il monitoraggio degli effetti di asimmetria emisferica in relazione al tipo di stimolazione.Stimolazione subliminale. ...
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... After 15 min of interpolated activity, subjects were tested a second time. There were five fragmented versions each for 11 different objects, with the first object serving as a practice item (Henke, Landis, & Markowitsch, 1993). For the word-fragment-completion test, 40 eight-letter words were presented visually to the participants, and 40 other eight-letter words were read to the participants by the examiner. ...
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... Specifically, Gazzaniga (1993) suggested that the left hemisphere is crucial for consciousness because its dominance in response to conscious stimuli is reflected in the term of[??] left-brain decoder. Nevertheless, some discrepancies from this theoretical perspective have been observed , and an opposite, right lateralization indicated for conscious awareness (Brázdil et al., 2001; Henke, Landis, & Markowitsch, 1993). ...
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... We use a version of our own devising (Henke, Landis, & Markowitsch, 1993) consisting of 21 pictures of animals and objects. Each item is progressively fragmented in 10 steps from a complete to an extremely fragmented representation. ...
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Extensive neuropsychological testing is reported on a 30-year-old patient (TA) with amnesia persisting 3 1/2 years after a major whiplash injury. TA's brain was investigated repeatedly with static and dynamic imaging techniques (computed tomography, magnetic resonance imaging, positron emission tomography) without detecting signs indicative for her amnesia. This amnesia started immediately after the whiplash injury and made the former university student totally dependent on her mother's care and guidance. TA is disoriented with respect to time. She demonstrates a sharp border between superior knowledge of facts and episodes from the time prior to whiplash injury and no memories at all for the period after it. The amnesia is global and persistent in spite of superior intelligence. It is concluded that traumatic, stressful events can induce persistent memory blocks even in the absence of measurable brain injury. Furthermore, it is proposed that there are several stages of memory formation, and that both environmental and internal processes may block or interfere with a smooth information transfer. The consequence may be measurable as delayed amnesia.
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Extensive neuropsychological testing is reported on two chronic patients with combined temporopolar and prefrontal damage, dominantly left-hemispheric, and, as control, one chronic patient with bi-hemispheric prefrontal damage. The principal finding is that combined temporofrontal damage, but not substantial prefrontal damage alone, results in marked retrograde memory deficits while leaving intelligence and new learning relatively unimpaired. Although their general world knowledge was good, the temporopolar patients demonstrated retrograde memory impairments on several tests of past events and faces of previously famous people. With respect to retrograde autobiographical memory, one of the temporopolar patients was severely impaired and the other was judged to be moderately impaired. The control patient appeared to be normal. These results, together with corresponding data from related single case and dynamic imaging studies, strongly support a crucial role of the temporofrontal junction area in the ecphory of old memories.
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Each 15 patients with damage to the prefrontal cortex, the medial temporal lobe, or with Parkinson's disease were compared with each other and with two groups of education and age-matched, non-brain damaged control patients on a number of cognitive tests, with emphasis on measuring explicit and implicit memory functions. The tests covered intelligence, attention and concentration, executive functions, temporo-spatial memory, priming, procedural, episodic, and meta-memory. The results obtained deviate in a number of ways from assumptions frequently made. While medial temporal lobe damaged patients performed - as expected - poorest in all explicit memory tests, Parkinson patients, in the initial phase of illness manifestation, already had major amnestic problems. Some deficits were even seen in priming tests. Deficits in Parkinson patients may be enhanced by overly cautious reaction tendencies. Prefrontally damaged patients performed quite normal in a number of tests, however, they displayed problems in attention-related functions. Our results point to substantial differences in the cognitive behavior of prefrontals and Parkinson's and demonstrate that unilateral damage of medial temporal lobe structures may already have severe effects on memory. Furthermore, age can significantly influence cognitive performance, especially in combination with brain pathology.
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During the last decade increasing attention to a peculiar phenomenon of implicit perception (perception without awareness) has been paid in neurosciences. In addition to consciously perceived stimuli, there is a great amount of signals from without and within the subject which are perceived and processed without any reportable awareness (i.e. unconsciously). These events can nevertheless influence our experience, thought, and action under some conditions. Blindsight, covert recognition of faces in prosopagnosia or object and shapes in visual agnosia as well as unconscious perception in neglect and extinction represent rare neurological visual disorders where perception and consciousness are dissociated as a result of brain damage. Some analogy of such dissociation in healthy subjects could be subliminal perception; its study was recently started in the field of cognitive neurophysiology. Results of sporadic ERP, fMRI and PET studies complement clinical observations and together particularize neuroanatomical and neurophysiological substrate of implicit perception. So far it was proved that mechanism of unaware processing of visual stimuli in the human brain does not differ substantially from the aware processing at least from the electrophysiological viewpoint. The proof of significantly faster unaware information processing represents another distinctive feature of the visual perception without awareness. Based on the author's own experimental and clinical findings and comparing them with the results of the previously published studies, the crucial role of a large scale neural system for conscious experience of perception is suggested, distributed extensively among dorsal posterior association areas and the prefrontal cortex with the dominant role of the right hemisphere. This system can be considered as an interactive "gate" of consciousness regulating the access of consciousness to information as well as blocking transmission of too weak information into the awareness.
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The author analyzed the role of consciousness in emotional face comprehension. The author recorded psychophysiological measures of event-related potentials (ERPs), elicited by supraliminal and subliminal stimuli when participants viewed emotional facial expressions of 4 emotions or neutral stimuli. The author analyzed an ERP emotion-specific effect (N200 peak variation; temporal interval was 180-300 ms poststimulus) in terms of peak amplitude and latency variables. The results indicated 4 important findings. First, there was an emotional-specific ERP deflection only for emotional stimuli, not for neutral stimuli. Second, the unaware information processing was quite similar to that of aware in terms of peak morphology, but not in terms of latency. In fact, unconscious stimulation produced a more delayed peak variation than did conscious stimulation. Third, valence of facial stimulus (positive or negative) was supraliminally and subliminally decoded because it was showed by differences of peak deflection between negative high arousing (fear and anger) and low arousing (happiness, sadness, and neutral) stimuli. Finally, the author found a more posterior distribution of ERP as a function of emotional content of the stimulus. Cortical lateralization (right or left) was not correlated to conscious or unconscious stimulation. The author discussed the functional significance of her results in terms of supraliminal and subliminal conditions.
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Examines some potential artifacts of design or execution of studies implying that central pattern masking may prevent awareness of perceptual products. Ss were 84 undergraduates. Three studies examined Ss' judgments of certain properties of masked words. Exps I and II replicated A. Marcel and K. Patterson's (1978) studies in demonstrating better-than-chance judgments about semantic properties of a word at target-mask intervals at which detection judgments and judgments of physical properties are at or near chance. However, a control "nonexperiment" in which no words are presented before the mask yielded a similar outcome. Exp IV examined the relative semantic relatedness, as assessed by naive judges, of masked-target/response pairs of randomly associated words and responses and of the type obtained by A. Allport (1977). Judges did not distinguish the 2 kinds of word pairs. Despite these negative findings, a final pair of experiments replicated Marcel's demonstration that masked words, no less than unmasked words, facilitate lexical decisions concerning subsequently presented semantically related words. Graphic and phonetic priming under mask and nomask conditions were also obtained. (37 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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In a recent study, McCauley, Parmelee, Sperber, and Carr (1980) reported results indicating that semantic priming had been produced by visual stimuli that were backward masked at durations too brief for greater than chance report. The conclusions drawn from such an experiment are critically dependent upon whether or not the primes were actually masked below the thresh-old for identification during priming trials. The three experiments reported here provide evidence that this requirement was not met. Rather, McCauley et al.’s (1980) methodology allowed for an uncontrolled increase in light adaptation during the actual testing of prime efficacy in the priming session. This increase in light adaptation reduced the effectiveness of the backward mask and resulted in an increase in prime visibility during priming trials. Thus, semantic priming probably occurred under conditions in which commensurate visual information was actually available.
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Previous research has found that repeated exposure to briefly presented visual stimuli can increase the positive affect for the stimuli without enhancing their recognition. Subjects could discriminate target and distractor shapes by affective preference in the absence of recognition memory. This study examined this phenomenon as a function of stimulus exposure duration. Over exposure durations of 0, 2, 8, 12, 24, and 48 ms, the functions for affect and recognition judgments exhibited different temporal dynamics. Target selection by affect was possible at very brief exposures and was influenced little by increasing durations; target selection by recognition required longer stimulus exposures and improved with increasing durations. Affective discrimination of stimuli that are not recognized is a reliable phenomenon, but it occurs only within a narrow band of time. This parametric study has specified the relationship between exposure duration and affect and recognition judgments and has located that temporal window.
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Some investigators have found that words previously associated with shock elicit electrodermal responses (EDRs) when presented in the nonattended channel of a dichotic listening task. The present experiment tested for this phenomenon while closely monitoring for shifts in attention to the nonattended channel. College student volunteers verbally shadowed a series of unrelated words presented to the attended channel while words made significant by previous association with shock (and semantically related words) were occasionally presented to the nonattended channel. Three principal findings were obtained. Fist, when EDRs were averaged across all trials and across all subjects, it was found that EDRs were elicited by the significant words presented in the nonattended channel. Second, for the subgroup of subjects that had the significant words presented to the right ear (activating the left cerebral hemisphere), it was found that EDRs were elicited by the significant words presented to the left ear (activating the right cerebral hemisphere), it was found that EDRs were elicited by the significant word seven on trials on which there were no apparent shifts in attention. The results of this study indicate the importance of closely controlling and monitoring for shifts in attention and suggest the potential importance of cerebral laterality in mediating EDRs to stimuli presented in a nonatttended channel.
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Experiments requiring the naming of bilaterally presented nouns, picturable nouns, consonant-vowel-consonant (CVC) nonwords, and line drawings are reported. In order to eliminate order of report strategies and facilitate comparison across experiments, the stimulus to be reported first was cued by underlining at presentation of each trial. Large right visual hemifield (RVF) superiorities were found to arise from both first and second reports for naming nouns and CVC nonwords. Drawings and picturable nouns, however, produced only a small RVF superiority arising entirely from subjects' second reports. It is proposed that hemispheric laterality effects for naming visually presented stimuli can arise from three principal sources, and the application of this model to existing studies is outlined.
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The effects of incidental stimuli, defined as visual stimuli not under verbal control, upon a selection task were observed as a function of feedback contingency. Ss judged letter pairs to be valid or invalid completions of preceding letter parts. During the presentation of the letter parts, the response pair or an alternative pair of letters was intermittently presented at a threshold value individually determined for each S. One group of Ss received a light feedback of performance contingent upon responding to the incidental stimuli; whereas a second group received a random noncontingent feedback. The results indicated: (a) both groups responded to the incidental stimuli; (b) feedback contingency had no effect on frequency of responding to the incidental stimuli; (c) frequency of responding to the incidental stimuli remained constant over 32 trials.
Article
In two experiments, no evidence for perception without awareness was found in a Stroop-priming task when the threshold for detecting color-word primes was measured reliably by a forced-choice procedure. Color words and color patches were either congruent or incongruent, and no priming occurred when the words were presented at the detection threshold. However, systematic increases in the level of detection for the primes led to correlated increases in the magnitude of priming. The results provide no support for recent claims that priming is a more sensitive indicator of perceptual processing than detection based upon verbal report. A resolution to the apparent discrepancy between the present results and previously reported findings is suggested.
Article
Studies of simultaneous detection and recognition were performed to test alternative models of the detection process, signal detection theory and low-threshold theory. Sensitivity in a detection experiment was independent of whether the type of signal (red or green light flash) was known in advance, because only one type of s trial was possible, or was unknown because either stimulus could occur. When a recognition judgment was added to either a binary or rating-scale detection response, Ss were able to report the nature of the stimulus at better than chance levels even when they indicated that the stimulus was not detected. Since such performance occurred when Ss used detection responses likely to have been given only in the nondetect state, the data lead to the rejection of low-threshold theory.
Article
The report attempts to delineate certain residual learning capacities of H.M., a young man who became amnesic in 1953 following a bilateral removal in the hippocampal zone. In addition to being able to acquire new motor skills (CORKIN [2]), this patient shows some evidence of perceptual learning. He also achieves some retention of very simple visual and tactual mazes in which the sequence of required turns is short enough to fit into his immediate memory span; even then, the rate of acquisition is extremely slow. These vestigial abilies, which have their occasional parallels in the patient's everyday life, are assessed against the background of his continuing profound amnesia for most on-going events, an amnesia that persists in spite of above-average intelligence and superior performance on many perceptual tasks.
Article
A consecutive series of sixty-five patients with unilateral cortical lesions was given three tests of visual recognition and one of immediate visual retention, together with the W.A.I.S. The right parietal group showed a deficit on all tests of visual perception. Test stimuli, which were both verbal and familiar, were graded in difficulty on a perceptual dimension, and discriminated between right and left hemisphere lesions. Evidence for some degree of differentiation of function within the right hemisphere is presented. The test of visual retention was associated with constructional impairment in the right hemisphere group, but not in the left hemisphere group. The relationship between perceptual disorders following right hemisphere lesions and visual object agnosia is discussed.
Article
Discusses 2 independent ongoing research programs investigating the relationship between psychopathology and unconscious libidinal and aggressive wishes. In the 1st program conducted by the author (see record 1971-31262-001) laboratory experiments using a "subliminal psychodynamic activation"with 39 groups of from 26-8 clinical Ss supported the hypothesis that presentation (tachistoscopic) of wish-related stimuli (vs presentation of neutral stimuli) affected the level of manifest psychopathology. Additional support came from 16 experiments (using a similar design) with over 400 persons with primary process ego pathology, depression, homosexuality, or stuttering: subliminal exposure of stimuli led to intensification of pathology on a variety of psychological tests. Another series of studies with over 200 Ss led to decreased primary process ego pathology in schizophrenics by reducing conflict through activating a fantasy of symbiotic gratification. The 2nd major research program was developed by J. Reyher (1958 and 1967) and his associates and used hypnotic suggestion with "normal" college students to confirm that activation of aggressive and subliminal mental contents can stimulate pathology. Overall results illustrate theory validation by converging operations and pose a substantive challenge to critics of psychoanalytic theory. (2 p ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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The question is explored of the location of consciousness in the human brain. The author's own studies of defects of consciousness as the result of the splitting of the corpus callosum are described and disorders of consciousness associated with damage to other specific areas of the brain, are reviewed. A circuit spanning the brain is described which stretches from the parietal lobe at one side to the parietal lobe at the other and includes the splenium of the corpus callosum. The medial banks of the hemispheres, the callosal as well as the cingulate areas, are also thought to be involved.
Article
Although a systematic cognitive neuropsychology of awareness has not yet emerged, a number of phenomena reported in the literature provide an empirical basis for developing it. The present discussion focusses on two such phenomena: implicit knowledge, which refers to knowledge that is expressed in task performance unintentionally and with little phenomenal awareness; and anosognosia, which refers to unawareness of neuropsychological deficits. Two types of theoretical accounts of these phenomena are discussed. A first order theoretical account entails postulating damage to, or disconnection of, a system or process that generates awareness across multiple domains. A second-order account does not postulate disruption of a cross-domain awareness mechanism, but instead appeals to difficulties in gaining access to particular kinds of domain-specific information that are associated with aware expressions of knowledge in individual domains. Instances of first- and second-order accounts are illustrated with examples from studies of memory and amnesia. The relation between implicit knowledge and anosognosia is also discussed.
Article
Event-related potentials (ERPs) are recordings of the electric field which the brain produces in fixed time-relation to an event. ERPs open a time and space window onto covert steps of brain information processing which need not be accompanied by overt behavior or private experiences. ERPs are the only noninvasive method which resolves the dynamic pattern of events in the human brain down to the millisecond range. Early ERP components are valuable tools in clinical testing of the afferent sensory systems in the absence of anamnestic or clinical pathology. Later components (e.g. the 'P300') index intermediate, covert steps of information processing and have clarified the time course and the contingencies of processes in attention, decisions and language. ERP waveshapes show electric potential differences between two recording points. Conventional analysis often ignores the fact that there is no unique voltage amplitude or signal latency for a single point, and interprets ambiguous results. Although important insights have emerged with such strategies, full utilization of ERP data requires unambiguous ERP assessment and converging evidence from neuropsychological and cognitive experimentation. Sequences of field distribution maps offer an unbiased display of ERP data. Spatial analysis yields unambiguous values for further comprehensive assessment, and should precede analysis over time. Examples of spatial analysis have shown that different ERP field configurations follow the presentation of noun and verb meaning of homophone words; that the ERP effects to subjective contours resemble those to attention in time course and topography; that the 'cognitive' P300 component reflects the specific stimulus location; and that subliminal information influences the configuration of late ERP fields.
Article
The P300 component of the evoked potential was recorded over both hemispheres in order to study interhemispheric differences in the process of perception of subliminal verbal stimuli. The stimuli--subliminal words, neutral and emotional--were presented at random to the left or right visual fields. In response to an unrecognized emotional word, the amplitude of P300 wave increased diffusely over both hemispheres as compared to that to a neutral word, with no changes in interhemispheric differences. The interhemispheric difference changed considerably in the presence of an 'unaccountable' emotion caused by a subliminal word. This suggests a unilateral activation of the right hemisphere and a predominant role of this hemisphere in the cortical organization of the unconscious function 'unaccountable' emotion.
Article
An investigation is reported of the ability of normal subjects and patients with right-hemisphere lesions to identify 3-D shadow images of common objects from different viewpoints. Object recognition thresholds were measured in terms of angle of rotation (through the horizontal or vertical axis) required for correct identification. Effects of axial rotation were very variable and no evidence was found of a typical recognition threshold function relating angle of view to object identification. Although the right-hemisphere-lesion group was consistently and significantly worse than the control group, no qualitative differences between the groups were observed. The findings are discussed in relation to Marr's theory that the geometry of a 3-D shape is derived from axial information, and it is argued that the data reported are more consistent with a distinctive-features model of object recognition.
Article
Replicated F. N. Dyer and L. J. Severance's study which showed that reliable Stroop-like delays of color naming could be generated by presenting incongruent color names in black ink just before nonword color patches, except that the interfering or facilitating words were presented at subthreshold exposure durations. 6 male undergraduates were Ss. The negative results found with these subliminal word stimuli raise serious doubts about the ability of meaningful stimuli to produce subliminal effects. Findings are discussed in relation to previous subliminal research.
Article
Evaluates the major criticisms of the "New Look" in perception. It is shown that the criticisms, including the logical paradox, homunculus, frequency, expectancy-set, and various response bias positions, are conceptually flawed or empirically incomplete. A reformulation of the phenomenon is presented which conceives of the perceptual defense-vigilance effect as a special instance of selectivity in cognitive processing. It is argued that selectivity-and therefore perceptual defense and perceptual vigilance-is a multiprocess complex of phenomena under central regulative control. Selectivity-and consequently defensive selectivity-is brought into play through varied mechanisms at multiple loci of the information-processing sequence. Thus, selectivity is pervasive throughout the cognitive continuum, from input to output, and no single site is likely to provide exhaustive explanation of any substantial selective phenomenon. (4 p ref)
Article
On each trial, 1 of 3 stimulus events occurred: presentation of (1) a 500-cps signal added to a sample of white noise; (2) an 1100-cps signal added to the noise; or (3) no signal added to the noise. 3 women and 1 man with normal hearing served as Ss. In the detection-recognition condition, each S reported whether a signal occurred (detection) and which of the 2 signals it was (recognition). Ss' criteria for a YES response were manipulated through instructions. The functions of primary concern were those relating the proportion of correct recognition responses to the proportion of YES responses on signal + noise trials, p(YESIS). The ability of Ss to detect the signals when they were not required to make the recognition response was measured in the detection condition. The proportion of correct recognition responses on trials on which the detection response was NO, p(CINO), was above chance at all detection criteria. Data contradict the predictions made by a threshold model adapted to the detection recognition situation. The proportion of correct recognition responses on all signal trials, whether the detection response was YES or NO, p(C), was unaffected by changes in criterion. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Because the nature of the input is one of the most important variables in determining how the brain will process information, findings from tachistoscopic studies aimed at assessing hemispheric lateralization of functions are examined in terms of the characteristics of the incoming information either available or required for processing. The basic features of tachistoscopic experiments are analyzed with a special emphasis on methodology. Variables determining the quality of the input are investigated as a function of the properties of the human visual system. Exposure duration, luminance, retinal eccentricity, and stimulus size all contribute to the efficiency of the hemispheres and interact in complex ways in the emergence of visual-field superiorities. Task demands are also examined in terms of the information necessary for efficient processing. The present review suggests that in tachistoscopic experiments, the factors determining the quality of the input must be controlled if this technique is to prove a reliable source of information for assessing hemispheric asymmetries. (5 p ref)
Article
When two pictures of common objects were presented sequentially, the second was named more quickly if both were members of the same semantic category. This semantic priming effect occurred only when both pictures went directly to the left hemisphere. If the target or prime stimulus was presented to the left visual field--right hemisphere, no priming effect was observed. These results suggest that semantic category information is activated and used by the left hemisphere of the brain.
Article
An approach to the relationships between conscious perception and nonconscious perceptual processes is outlined. Its basis is the rejection of the assumption that phenomenal experience is identical to or is a direct reflection of representations yielded by perceptual processes. Nonconscious perceptual processes automatically redescribe sensory data into every representational form and to the highest levels of description available to the organism. Such processes (a) provide records of each resultant representation, (b) produce perceptual hypotheses in different domains, (c) activate related structures, and (d) affect analog aspects of actions. Conscious perception requires a constructive act whereby perceptual hypotheses are matched against information recovered from records, and serves to structure and synthesize that information recovered from different domains. These processes are related to three aspects of phenomenal experience: awareness, unity of percepts, and selectivity. Consciousness is seen as an attempt to make sense of as much data as possible at the most functionally useful level. Explication of the approach consists of (a) discussion of differences between conscious and nonconscious representations and processes; (b) exposition of the characteristics of the process of recovery; (c) a theory of central visual masking as a consequence of temporal and spatial parsing involved in recovery, wherein masking is seen as an aspect of the structural nature of consciousness whose goal is event perception, and does not affect nonconscious perceptual processing; (d) an interpretation of various clinical neuropsychological and normal phenomena in terms of limitations and impairments in the processes of recovery and synthesis; (e) reinterpretation of several perceptual phenomena in terms of the recovery of information and of how nonconscious processes precede and affect consciousness.
Article
Five experiments are presented which explore the relation of masking to consciousness and visual word processing. In Experiment 1 a single word or blank field was followed by a pattern mask. Subjects had to make one of three decisions: Did anything precede the mask? To which of two probe words was what preceded the mask more similar graphically? To which of two probe words was it more similar semantically? As word-mask stimulus onset asynchrony (SOA) was reduced, subjects reached chance performance on the detection, graphic, and semantic decisions in that order. In Experiment 2, subjects again had to choose which of two words was more similar either graphically or semantically to a nondetectable masked word, but the forced-choice stimuli now covaried negatively on graphic and semantic similarity. Subjects were now unable to choose selectively on each dimension, suggesting that their ability to choose in Experiment 1 was passively rather than intentionally mediated. In Experiment 3 subjects had to make manual identification responses to color patches which were either accompanied or preceded by words masked to prevent awareness. Color-congruent words facilitated reaction time (RT), color-incongruent words delayed RT. Experiment 4 used a lexical decision task where a trial consisted of the critical letter string following another not requiring a response. When both were words they were either semantically associated or not. The first letter string was either left unmasked, energy masked monoptically, or pattern masked dichoptically to prevent awareness. The effect of association was equal in the unmasked and pattern masked cases, but absent with energy masking. In Experiment 5 repeating a word-plus-mask (where the SOA precluded detection) from 1 to 20 times (a) increased the association effect on a subsequent lexical decision, but had no effect on (b) detectability or (c) the semantic relatedness of forced guesses of the masked word. It is proposed that central pattern masking has little effect on visual processing itself (while peripheral energy masking does), but affects availability of records of the results of those processes to consciousness. Perceptual processing itself is unconscious and automatically proceeds to all levels of analysis and redescription available to the perceiver. The general importance of these findings is to cast doubt on the paradigm assumption that representations yielded by perceptual analysis are identical to and directly reflected by phenomenal percepts.
Article
Experimental approaches to discrimination, performance and learning without awareness (consciousness) are surveyed. Methodological and definitional problems are emphasized. Equating awareness with verbal reports is criticized and it is shown that individual variations exist in the range between chance guesses and confidence thresholds. Better than chance discrimination will of necessity occur below an absolute threshold defined in terms of a 50% reacting point. The GSR is no more accurate than verbal reports below the threshold, while above it the GSR does not achieve 100% accuracy. A multiple concurrent response model with both responses independently but imperfectly correlated with the stimulus is proposed. The assumption of subliminal discrimination is not required. From Psyc Abstracts 36:01:3CH79E.
Article
In order to investigate the role of prior cognitive organization on receptivity to minimal stimulation, 2 cognitive structures of Ss' initial impressions of a neutral face were created. Then Ss redescribed their impressions of the constantly visible neutral face while 2 additional faces, 1 Happy and 1 Sad, were superimposed below Ss' detection threshold. The results showed that a cognitive structure in which the elements are relatively undifferentiated and nonlogically related significantly facilitates the influence of minimal stimuli. When Ss' initial impressions were organized into a more differentiated, logical structure, however, minimal stimuli tended not to be incorporated. The major findings are consistent with psychoanalytic notions about the role of primary and secondary thought processes and sensitivity to minimal stimulation. (20 ref.)