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Results for “Perceptual Distortion”

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At least 991 records · Page 55Linked to original sources
PubMed1977

Awareness of body dimensions during pregnancy: an analogue study.

Two alternative explanations of the body-image abnormality in anorexia nervosa patients are outlined: namely, the 'abnormal sensitivity' and 'adaptational failure' hypotheses. Evidence relating to these 2 conflicting hypotheses was obtained from body-perception measurements carried out on groups of pregnant women. In the first study 40 pregnant women, at approximately 4 month's duration, were found to overestimate their bodily dimensions, albeit to a lesser extent than the previously tested group of anorexia nervosa patients (Slade & Russell, 1973a). When they were subdivided on the basis of a history of weight change over the previous 12 months, the 'stable weight' subgroup was found to overestimate significantly more than the 'weight gain' and 'weight loss' subgroups. In a second study 16 of the original group of pregnant women were retested at approximately 8 month's duration. Although their weight and bodily dimensions had increased on retesting, their tendency to overestimate was found to be significantly reduced. It was concluded that the phenomenon of body-image disorder is not specific to anorexia nervosa, extending not only to patients with obesity and to some normal women, but also to women during pregnancy. Moreover, the 'abnormal sensitivity' hypothesis was considered to fit these and other recently accumulated data better than the alternative 'adaptational failure' hypothesis. Some of the theoretical and clinical implications of these findings are discussed.

Adolescent↗
PubMed2003

The detection of intentional contingencies in simple animations in patients with delusions of persecution.

BACKGROUND: It has been proposed that delusions of persecution are caused by the tendency to over-attribute malevolent intentions to other people's actions. One aspect of intention attribution is detecting contingencies between an agent's actions and intentions. Here, we used simplified stimuli to test the hypothesis that patients with persecutory delusions over-attribute contingency to agents' movements. METHOD: Short animations were presented to three groups of subjects: (1) schizophrenic patients; (2) patients with affective disorders; and (3) normal control subjects. Patients were divided on the basis of the presence or absence of delusions of persecution. Participants watched four types of film featuring two shapes. In half the films one shape's movement was contingent on the other shape. Contingency was either 'intentional': one shape moved when it 'saw' another shape; or 'mechanical': one shape was launched by the other shape. Subjects were asked to rate the strength of the relationship between the movement of the shapes. RESULTS: Normal control subjects and patients without delusions of persecution rated the relationship between the movement of the shapes as stronger in both mechanical and intentional contingent conditions than in non-contingent conditions. In contrast, there was no significant difference between the ratings of patients with delusions of persecution for the conditions in which movement was animate. Patients with delusions of persecution perceived contingency when there was none in the animate non-contingent condition. CONCLUSIONS: The results suggest that delusions of persecution may be associated with the over-attribution of contingency to the actions of agents.

Adult↗
PubMed2006

Theory of Mind (ToM) and counterfactuality deficits in schizophrenia: misperception or misinterpretation?

BACKGROUND: Theory of Mind (ToM) refers to the ability to infer another person's mental state based upon interactional information. ToM deficits have been suggested to underlie crucial aspects of social interaction failure in disorders such as autism and schizophrenia, although the development of paradigms for demonstrating such deficits remains an ongoing area of research. Recent studies have explored the use of sarcasm perception, in which subjects must infer an individual's sincerity or lack thereof, as a 'real-life' index of ToM ability, and as an index of functioning of specific right hemispheric structures. Sarcastic detection ability has not previously been studied in schizophrenia, although patients have been shown to have deficits in ability to decode emotional information from speech ('affective prosody'). METHOD: Twenty-two schizophrenia patients and 17 control subjects were tested on their ability to detect sarcasm from spoken speech as well as measures of affective prosody and basic pitch perception. RESULTS: Despite normal overall intelligence, patients performed substantially worse than controls in ability to detect sarcasm (d=2.2), showing both decreased sensitivity (A') in detection of sincerity versus sarcasm and an increased bias (B'') toward sincerity. Correlations across groups revealed significant relationships between impairments in sarcasm recognition, affective prosody and basic pitch perception. CONCLUSIONS: These findings demonstrate substantial deficits in ability to infer an internal subjective state based upon vocal modulation among subjects with schizophrenia. Deficits were related to, but were significantly more severe than, more general forms of prosodic and sensorial misperception, and are consistent with both right hemispheric and 'bottom-up' theories of the disorder.

Adult↗
PubMed1999

Timing and characteristics of perceptual attenuation by transcranial stimulation: a study using magnetic cortical stimulation and somatosensory-evoked potentials.

Transcranial cortical magnetic stimulation (CMS) is a noninvasive, non-noxious procedure to induce perceptual attenuation when applied concomitant to sensory stimuli. To investigate the perceptual timing of simple stimulus features in the somatosensory modality, we applied right hemisphere CMS at different intervals following a stimulus delivered to the left hand. Different intervals between peripheral stimuli and CMS were defined according to the components of the somatosensory-evoked potentials (SEP), previously obtained in response to the same stimulus. Perceptual attenuation was maximal when CMS coincided with the primary cortical response (parietal N20 potential); conversely, perception of stimulus intensity was not modified when CMS was concomitant with the N200 and P300 potentials. Using small CMS intensities, a "perceptual dip" was observed when CMS arrived in coincidence with the N120 potential, a SEP response thought to be originated in part in the second somatic area. Our results support the view that both N200 and P300 are post-perceptual responses. The results also suggest that the cortical processes active during the N20 and N120 potentials may be essential for the conscious perception of somatosensory stimuli delivered to the hand.

Adult↗
PubMed2006

Geometrical structures of photographic and stereoscopic spaces.

Two experiments were conducted to investigate the geometrical structures of photographic and stereoscopic spaces. In Experiment 1, it was investigated how accurately photographic space reproduces real physical space, and the geometrical structure of photographic space was compared with that of visual space. As a result, the mapping function of distance between photographic and physical spaces (delta = ad(b)) shows that a and b range from 0.96-1.1 and 0.69-0.78. The mapping function of angle between photographic and physical spaces (phi = g phi(h)) shows that g and h range from 2.37-5.29 and 0.74-0.97. Further, photographic space has larger anisotropic property than visual space and photographic space may be hyperbolic. In Experiment 2, the geometrical structure of stereoscopic space was compared with that of visual space. It was found that stereoscopic space was almost the same as visual space.

Adolescent↗
PubMed2006

Visual distance estimation in static compared to moving virtual scenes.

Visual motion is used to control direction and speed of self-motion and time-to-contact with an obstacle. In earlier work, we found that human subjects can discriminate between the distances of different visually simulated self-motions in a virtual scene. Distance indication in terms of an exocentric interval adjustment task, however, revealed linear correlation between perceived and indicated distances but with a profound distance underestimation. One possible explanation for this underestimation is the perception of visual space in virtual environments. Humans perceive visual space in natural scenes as curved, and distances are increasingly underestimated with increasing distance from the observer. Such spatial compression may also exist in our virtual environment. We therefore surveyed perceived visual space in a static virtual scene. We asked observers to compare two horizontal depth intervals, similar to experiments performed in natural space. Subjects had to indicate the size of one depth interval relative to a second interval. Our observers perceived visual space in the virtual environment as compressed, similar to the perception found in natural scenes. However, the nonlinear depth function we found can not explain the observed distance underestimation of visual simulated self-motions in the same environment.

Adult↗
PubMed2006

Does energy expenditure affect the perception of egocentric distance? A failure to replicate experiment 1 of Proffitt, Stefanucci, Banton, and Epstein (2003).

In a series of recent studies, Proffitt and his colleagues have reported that the perceived distance to a target is influenced by the energy expenditure associated with any action, such as walking or throwing, for spanning the distance to the target. In particular, Proffitt, Stefanucci, Banton, and Epstein (2003) reported that wearing a heavy backpack caused verbal reports of distance to increase. We conducted a study to determine whether three responses dependent on perceived distance (verbal report of distance, blind walking, and estimates of object size) are influenced by the backpack manipulation. In two experiments, one involving a between-participants design and the other involving a within-participants design, we found that none of the three responses were influenced by the wearing of a heavy backpack.

Adolescent↗
PubMed2004

[Migrainous complex hallucinations in 10-year old patient--a case report and review].

OBJECTIVES: Considering a prevalence of three to ten percent migraine in children is not a rare disease. Visual auras as a characteristic of classical migraine are often described in literature. However, most of these are primary hallucinations, whilst descriptions of complex hallucinations are barely to find. As far as we know this work describes the youngest age, at which complex hallucinations occurred in migraine attacks. Reviewing the existing literature possible pathophysiologic mechanisms and differential diagnosis are discussed. METHODS: We introduce a case-report of a 10-year old-patient who reports a complex visual hallucination during a migraine attack. Symptoms, history and diagnostic measures are described. In differential diagnosis to a migrainous aura the "Alice-in-Wonderland-syndrome", "Lilliputian hallucinations", the basilar migraine and epilepsy are discussed. RESULTS: For complex hallucinations an analogical pathomechanism to primary hallucinations in migraine can be assumed. The great variety of the migrainous aura is pointed out.

Beta Rhythm↗
PubMed2001

Intractable depression or psychosis.

OBJECTIVE: Some patients with treatment resistant depression may have a difficult to recognize and therefore untreated thought disorder. Even a subtle disorder may significantly impact patients' lives. This case illustrates a mechanism for identifying and treating this subgroup of patients. METHOD: The treatment of a 67-year-old female with intractable depression is described. RESULTS: The Rorschach Exner Comprehensive System identified the presence of a thought disorder with four out of five conditions positive on the Schizophrenia Index and five out of seven conditions positive on the Depression Index. Low-dose risperidone was added to the patient's medications with excellent results. Post-testing indicated that the Schizophrenia and Depression Indices were no longer positive. CONCLUSION: A subgroup of patients with intractable depression may have an underlying thought disorder that can be identified with the Rorschach and successfully treated with low-dose antipsychotic medication.

Aged↗
PubMed2002

Children's recognition of caricatures.

This study examined children's and adults' perception and recognition of facial stimuli that were either systematically exaggerated (caricatures) or de-exaggerated (anticaricatures) relative to a norm face. The results showed that all age groups perceived caricatures as the most distinctive versions of a face and anticaricatures as the least distinctive, although the effect was smallest for 6-year-olds. In general, caricatures were identified as quickly as the veridical faces and faster than the anticaricatures. Across all age groups, participants' familiarity with the stimulus faces interacted with degree of caricature to determine speed of processing as well as choice of best likeness. The results are discussed in relation to the idea that distinctiveness information in a face is represented in relation to a norm.

Caricatures as Topic↗
PubMed1993

Anhedonia and premorbid competence in young, nonpsychotic psychiatric inpatients.

Earlier studies have demonstrated a significant relation between scores on the Physical Anhedonia Scale--but not on the Perceptual Aberration Scale--and premorbid social adjustment in schizophrenics (Chapman, Chapman, & Raulin, 1976, 1978; Schuck, Leventhal, Rothstein, & Irizarry, 1984). A similar relation between scores on these 2 scales and interpersonal competence in college students has also been noted (Beckfield, 1985; Haberman, Chapman, Numbers, & McFall, 1979; Numbers & Chapman, 1982). The present study extends this work by examining the relation of premorbid adjustment to scores on these 2 scales among young, nonpsychotic psychiatric inpatients. Consistent with the earlier findings, anhedonic Ss had poorer premorbid social competence when compared with nonanhedonic Ss, whereas no relation was found between scores on perceptual aberration and premorbid social competence.

Adolescent↗
PubMed1993

An appraisal of cognitive therapy.

This review describes the development of cognitive therapy (CT) for depression in the 1960s and 1970s and its application to diverse clinical populations. The question of how CT works, in terms of both active therapeutic ingredients and mechanisms of change within the individual, is addressed. The limitations of CT are discussed, as well as recent developments and modifications of the therapy that have evolved in response to these perceived limitations and that bring it closer to other therapy approaches. The review concludes with some directions for future research.

Adaptation, Psychological↗
PubMed1993

Cognitive therapy of anxiety disorders.

A review of studies of cognitive-behavioral therapy (CBT) for generalized anxiety disorder, panic disorder with and without agoraphobia, and social phobia indicates that CBT is consistently more effective than waiting-list and placebo control groups. In general, CBT has proved more beneficial than supportive therapy as well. Comparisons with active behavioral treatments provide more variable results. Converging evidence suggests that cognitive change may be a strong predictor of treatment outcome, but that such change may be produced by a number of therapeutic approaches. Pretest-posttest change with CBT is depicted in meta-analytic summary form for each disorder.

Agoraphobia↗
PubMed1993

Group cognitive-behavioral therapy and group interpersonal psychotherapy for the nonpurging bulimic individual: a controlled comparison.

This study evaluated the effectiveness of group cognitive-behavioral treatment (CBT) and group interpersonal psychotherapy (IPT) for binge eating. Fifty-six women with nonpurging bulimia were randomly assigned to 1 of 3 groups: CBT, IPT, or a wait-list control (WL). Treatment was administered in small groups that met for 16 weekly sessions. At posttreatment, both group CBT and group IPT treatment conditions showed significant improvement in reducing binge eating, whereas the WL condition did not. Binge eating remained significantly below baseline levels for both treatment conditions at 6-month and 1-year follow-ups. These data support the central role of both eating behavior and interpersonal factors in the understanding and treatment of bulimia.

Adult↗
PubMed1997

Misinterpretation of body sensations in panic disorder.

Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic.

Adult↗