Perceptual organization in schizophrenia.

A report of numerosity task was used in 2 experiments to examine the effect of inherent stimulus organization on the report accuracy of 2 S groups. Ss in each experiment were 10 schizophrenics and 10 drug abusing inpatients (controls). In both experiments, displays containing from zero to 6 lines were presented tachistoscopically. In Exp I, the lines appeared either alone or with noise elements (circles). When the lines appeared alone, schizophrenics and controls performed comparably. Their report accuracy decreased with increases in the number of lines. In the noise condition, the level of performance dropped only for schizophrenics. In Exp II, the stimulus arrays did not contain noise elements. Ss were given the task of reporting all the lines they saw. The perceptual organization of the arrays was manipulated by varying the similarity and proximity of the line elements. The performance of controls deteriorated as the organization of the arrays became more complex; schizophrenics were not affected by the organization. In fact, their average performance was significantly better than that of controls. Results of the 2 experiments are interpreted as evidence that schizophrenics' perceptual deficit lies in a failure to organize information at an early stage in processing. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization and schizotypy.

The preattentive visual information processing of hypothetically psychosis-prone college Ss was evaluated using 3 different paradigms: target detection (n?=?57), visual suffix effect (n?=?57), and configural superiority effect (n?=?68). It was hypothesized that anhedonic Ss would show the same perceptual organization deficits reported in process schizophrenics and that perceptual aberration-magical ideation Ss and depressed Ss would perform similarly to control Ss. In each study, anhedonics performed similarly to each comparison group, even though there was adequate power to detect performance differences if they existed. A framework for understanding the visual information-processing deficits of schizophrenics and high-risk Ss is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of two-dimensional patterns.

The perceptual organization of image patterns is considered from 2 standpoints. First, a theoretical framework is presented from which computational models of perceptual organization can be constructed and tested. Second, a specific computational model for perceptual organization of line images is described. In this model, input images are first processed by a dense array of neurons that have properties consistent with recent analyses of single-neuron responses in primary visual cortex. Then, complex image structure is discovered by interleaved pattern-matching and grouping processes constrained by a generalized uniqueness principle. A series of 3-pattern grouping experiments was performed to test a restricted version of the model and to estimate critical parameters. Using the estimated parameters, an extended version of the model was tested by generating predictions for a series of "textbook" perceptual organization demonstrations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization and precategorical acoustic storage.

Current views of precategorical acoustic storage (PAS) have been largely based on differences in the level of recall of terminal list items as a function of input modality and on experiments in which various types of suffixes are added to unstructured auditory lists. Experiments with grouped lists reveal that PAS can make a far more extensive contribution to serial recall. A series of four experiments investigated grouping effects in relation to existing accounts of consolidation, attentional selection, and auditory masking in PAS. Grouping effects obtained with very brief intralist pauses were inconsistent with the consolidation and masking hypotheses. Contrary to the attentional hypothesis, nontemporal grouping by voice or by spatial location was found to be as effective as grouping by extended pauses. When nontemporal methods of grouping were combined with intralist pauses, the two sets of grouping cues were no better than one, suggesting that list segmentation by pauses and by item attributes must be explained in terms of a single process. These results are discussed in the context of previous research that implies the existence of an auditory store with a capacity greater than previously attributed to PAS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization and intelligence: A further study.

This experiment was a replication of that of Krech and Calvin (Levels of perceptual organization and cognition. J. abnorm. soc. Psychol., 1953, 48, 394-400) using modified techniques. The correlation previously reported by Krech and Calvin between intelligence and perception, did not obtain upon replication. The data confirmed their finding that progression over trials was usually from low to high perceptual organization, but did not show a correlation between perception and stimulus-exposure time from 0.01 to 1.00 second. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization in schizophrenia: The processing of symmetrical configurations.

The hypothesis that the perceptual organization dysfunction of patients with poor premorbid schizophrenia is due to a deficit in global visual sensory store processing was tested by assessing their ability to process symmetrical configurations that develop early and have strong prepotent structures. Two same–different judgment tasks in which performance varies as a function of the symmetrical organization and task demands were administered to participants with good and poor premorbid schizophrenia, those with mood disorders, and normal controls. Like the other groups, poor premorbid schizophrenics' latency and error response patterns closely paralleled the a priori model of adequate processing. The results support their competence in perceptually processing symmetrical configurations and disconfirm the hypothesis that their input deficiencies represent a general deficiency in all forms of perceptual organization. The implications for specifying their early input dysfunction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual false recognition in Alzheimer's disease.

Previous research has found that patients with probable Alzheimer's disease (AD) show lower levels of false recognition of semantic associates than do healthy older adults. To investigate whether this finding is attributable to semantic impairments in patients with AD, the authors examined false recognition of perceptually related novel objects with little semantic content in patients with AD and healthy older adults. By using corrected recognition scores to control for unrelated false alarms, it was found that patients with AD showed lower levels of both true and false recognition of novel objects than did older adults. These results suggest that the previous difference in false recognition of semantic associates observed between patients with AD and older adults is not entirely attributable to semantic memory deficits in patients with AD but may also involve poorly developed gist information in these patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of moving stimuli modulates the flash-lag effect.

When a visual stimulus is flashed at a given location the moment a second moving stimulus arrives at the same location, observers report the flashed stimulus as spatially lagging behind the moving stimulus (the flash-lag effect). The authors investigated whether the global configuration (perceptual organization) of the moving stimulus influences the magnitude of the flash-lag effect. The results indicate that a flash presented near the leading portion of a moving stimulus lags significantly more than a flash presented near the trailing portion. This result also holds for objects consisting of several elements that group to form a unitary percept of an object in motion. The present study demonstrates a novel interaction between the global configuration of moving objects and the representation of their spatial position and may provide a new and useful tool for the study of perceptual organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization in schizophrenia: utilization of the Gestalt principles

BACKGROUND: Allergen immunotherapy results in a number of changes in clinical, inflammatory, and immunologic parameters. However, the basis for the specificity of this form of therapy is unknown, especially in the context of changes in T- and B-lymphocyte function after desensitization to specific allergens. OBJECTIVE: This study was designed to determine the immunologic consequences of rush immunotherapy. METHODS: We studied 10 patients who had positive skin test responses to the house dust mite Dermatophagoides pteronyssinus (Dpt) and cat dander extract. Each received rush immunotherapy to mite, but not cat dander, over a 2- to 4-week period until maintenance was achieved. Patients were evaluated before and when maintenance was achieved for skin test and nasal reactivity to mite and cat dander; antibody levels to the allergen were monitored, as were lymphocyte proliferative responses and cytokine production. RESULTS: Rush immunotherapy to house dust mite resulted in a significant reduction in skin and nasal reactivity to mite allergen, but not to cat allergen, in 10 of 10 patients. This was accompanied by a rise in serum anti-Dpt IgE, whereas anti-cat IgE was not altered (7 of 7 patients). In seven of seven patients there was an increase in anti-Dpt IgG4 levels. T-cell proliferative responses to mite antigen were suppressed, and numbers of CD8+ T cells increased in frequency. There was a marked increase in interferon-gamma production, particularly by CD4+ T cells in 10 of 10 patients. The correlation between the increases in interferon-gamma production and the changes in cutaneous reactivity was highly significant. CONCLUSION: We show that rush immunotherapy is immunologically specific in eliciting changes in T- and B-cell responses to the desensitization antigen. The specificity and potential benefit of immunotherapy may be linked to the increase in interferon-gamma production by allergen-activated CD4+ T lymphocytes.     

Perceptual organization of behavior: A hierarchical control model of coordinated action.

Compared the behavior of 4 college students and 2 faculty members (including the present author) with a hierarchical control system model of behavioral organization. Ss varied the position of 2 control handles simultaneously to keep the distance constant between 2 pairs of lines. Three variations on this basic experiment that illustrate some fundamental properties of coordinated action showed (1) how independent actions, compensating for unpredictable and undetectable disturbances, can produce a single behavioral result; (2) how the ability to produce a particular result is maintained when the connection between action and result is changed; and (3) how 2 independent outputs can appear to be related as coordinative structures when one output disturbs a result being controlled by the other. The correlation between the behavior of Ss and the model in all experiments was typically on the order of .99. A detailed examination of the operation of the model demonstrated that actions are structured by perception, not by central commands or equations of constraint. (35 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perceptual bias for affective and nonaffective information in asymmetric Parkinson's disease.

Objective: To relate lateralized impairments of visual perception in Parkinson's disease to asymmetries in the severity of motor symptoms. Method: Ten patients with worse left-sided motor symptoms (LPD), 15 with worse right-sided (RPD), and 13 healthy age-matched controls (all right-handed) viewed mirror-imaged pairs of emotional chimeric faces, (left side smiling, right neutral, and vice versa), of greyscales (strips whose luminance varied smoothly from black on the left to white on the right, and vice versa) and of gender chimeric faces (left side male, right female, and vice versa). Participants signaled which stimulus appeared happier, brighter, or more feminine, respectively, so showing which side received more attention. Results: For emotional chimeras, controls and LPD showed little bias, whereas RPD showed a strong bias to left hemispace (p = .018, r = .45). Across all patients, this bias was associated with severity of right-sided motor impairment (p = .018, r = .49). The bias was much weaker and insignificant for greyscales (p = .72, r = .14). For gender chimeras, RPD again showed a significantly greater left hemispace bias than did LPD (p = .037, r = .47), although neither patient group differed significantly from controls. Across all patients, this bias correlated with ratio of right-to-left symptom severity (p = .044, r = .48). Conclusions: The left hemispace bias in RPD is greater for facial than for luminance judgments, and is amplified for emotional judgments. Asymmetrical degeneration of the striatum, particularly involving the left side, appears to underlie this deficit in visual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preserved organization of semantic attributes in Alzheimer's disease.

This study investigated whether Alzheimer's disease (AD) disrupts the basic organization of the semantic attributes of concepts. Young and normal older Ss and AD patients were presented with a target concept followed by a stimulus word and were to decide whether the stimulus was related to the target. On those trials where it was, the stimulus was either a high-, medium-, or low-dominance attribute of the target. The higher the normative dominance, the more important the attribute to concept meaning. In all 3 S groups, decision time varied as a function of dominance. The higher the dominance, the faster the decision. Attribute dominance affected the performance of AD patients more than that of normal Ss. These results suggest that AD patients retain their knowledge of the relative importance that the different attributes of a concept have for concept meaning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual asymetries in audition.

Visual feature extraction has been investigated using search experiments. Targets that contain a feature not present in the distractors are easier to detect than if they do not, leading to search asymmetries. If sounds are decomposed into features in the auditory system, there might be asymmetries in analogous tasks. Six experiments investigating this are described. Strong asymmetries were identified, with frequency-modulated targets easier to detect among pure-tone distractors than vice versa and longer sounds easier to select from short distractors than the reverse. It is demonstrated that this asymmetry is not a result of peripheral limitations. In contrast, no asymmetries were observed between high- and low-frequency tones or between short 3-tone sequences differing only in their temporal structure. The results are discussed with reference to models of perceptual grouping and attention, the applicability of analogies between vision and audition, and possible physiological correlates. The paradigm provides a new way in which to investigate auditory feature extraction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual span in schizophrenia.

Administered a forced-choice letter recognition task to assess the span of apprehension of 30 schizophrenics (good premorbid paranoids, good premorbid nonparanoids, and poor premorbid nonparanoids) and 20 controls (hospitalized nonschizophrenics and penitentiary inmates). When the task required only that 1 target letter be detected, there were no significant differences between groups. When the target was presented in conjunction with varying numbers of irrelevant "noise" letters, however, the span of schizophrenics was significantly less than that of either control group. The span of schizophrenics reached an upper limit at a small display size (4 letters) and showed no further increase. The constructs of premorbid adjustment and paranoid status bore no relationship to the deficit. Measures of the trial-to-trial variability in number of elements processed and consistency of scanning path did not differentiate schizophrenics and controls. The number of irrelevant noise letters surrounding a target was found to have no influence on detection in either group. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual closure in schizophrenia.

The concept of closure has been more frequently investigated using normal Ss than psychotic patients. The present study utilizes schizophrenics and compares their performance with a comparable group of hospitalized nonpsychotic Ss. Taylor's (1960) test of closure was used. Tendency to closure tended to be lower for the schizophrenics than for the nonschizophrenics, with schizophrenics on drugs (and, hence, manifesting a greater degree of personality disorganization than the other schizophrenic Ss) showing no tendency towards closure. The results are related to 2 theories of schizophrenia, one which involves a deficit in the energizing or arousal systems in the brain, and the other, an inability to maintain a set in the way normal Ss do. From Psyc Abstracts 36:04:4JQ31S. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): II. Vocal signals.

Operant conditioning and multidimensional scaling procedures were used to study auditory perception of complex sounds in the budgerigar. In a same–different discrimination task, budgerigars learned to discriminate among natural vocal signals. Multidimensional scaling procedures were used to arrange these complex acoustic stimuli in a two-dimensional space reflecting perceptual organization. Results show that budgerigars group vocal stimuli according to functional and acoustical categories. Studies with only contact calls show that birds also make within-category discriminations. The acoustic cues in contact calls most salient to budgerigars appear to be quite complex. There is a suggestion that the sex of the signaler may also be encoded in these calls. The results from budgerigars were compared with the results from humans tested on some of the same sets of complex sounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): I. Pure tones.

A new combination of operant conditioning and psychophysical scaling procedures was used to study auditory perception in a small bird. In a same–different discrimination task, budgerigars learned to discriminate among pure tones that varied along one or more acoustic dimensions. Response latencies were used to generate a matrix of interstimulus similarities. Multidimensional scaling procedures were used to arrange these acoustic stimuli in a multidimensional space that supposedly reflects the bird's perceptual organization. For tones that varied in intensity, duration and frequency simultaneously, budgerigars were much more sensitive to frequency changes. From a set of tones that varied only in intensity, it was possible to calculate the growth of loudness with intensity for the budgerigar. For tones that varied only in frequency, budgerigars showed evidence of an "acoustic fovea" for frequency change in the spectral region of 2–4 kHz. Budgerigars and humans also differed in their perceptual grouping of tone sequences that rise, fall, or remain constant in pitch. Surprisingly, budgerigars were much less responsive to pitch contour than were humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): III. Contact calls.

We trained budgerigars by operant conditioning to discriminate among a set of contact calls in a same–different task and analyzed response latencies from this task by using multidimensional-scaling (MDS) and cluster-analysis procedures. Humans listened to the same calls and indicated the similarity between pairs of calls by a direct rating procedure. An MDS program ({sindscal}) was used to arrange these complex acoustic stimuli in multidimensional space reflecting perceptual organization. Multiple regression techniques were used to identify the acoustic characteristics of contact calls that were correlated with the peceptual dimensions obtained from MDS. A number of spectral characteristics (e.g., peak frequency, rate of frequency modulation, and concentration of spectral energy) emerged as important for both budgerigars and humans, but the relative salience of these cues differed for the two species. Additional tests with two groups of budgerigars—cagemates and noncagemates—showed that experience with calls can change the salience of various acoustic characteristics used for perceptual organization and individual recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual organization of complex auditory sequences: Effect of number of simultaneous subsequences and frequency separation.

Previous findings on streaming are generalized to sequences composed of more than 2 subsequences. A new paradigm identified whether listeners perceive complex sequences as a single unit (integrative listening) or segregate them into 2 (or more) perceptual units (stream segregation). Listeners heard 2 complex sequences, each composed of 1, 2, 3, or 4 subsequences. Their task was to detect a temporal irregularity within 1 subsequence. In Experiment 1, the smallest frequency separation under which listeners were able to focus on 1 subsequence was unaffected by the number of co-occurring subsequences; nonfocused sounds were not perceptually organized into streams. In Experiment 2, detection improved progressively, not abruptly, as the frequency separation between subsequences increased from 0.25 to 6 auditory filters. The authors propose a model of perceptual organization of complex auditory sequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual defense revisited.

"In the present study the following hypothesis was submitted to experimental test: Subjects predisposed to use the mechanism of repression in conjunction with a given conflict will, when confronted subliminally with a conflict-relevant stimulus, show defensive behavior directly traceable to the perceptual process itself… ." The results of this study show that "with selective verbal report, familiarity, set, and antecedent conditions all controlled, an avoidance response directly traceable to the perceptual process was obtained." (PsycINFO Database Record (c) 2010 APA, all rights reserved)