Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perceptual Distortion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1990

The effects of varying fins in Müller-Lyer and Holding illusions.

Five experiments were conducted to determine how distortion of spatial position induced by unidirectional Müller-Lyer fins varied as a function of angle and length of fins. Research employing Cornsweet's staircase method yielded ambiguous results, but psychophysical methods of magnitude estimation, paired comparisons, and production showed conclusively that distortions of position are affected by angle and length of fins in a manner similar to that found in distortions of length. It was concluded that similar strategies are employed in processing attributes of length and position and that a theory based on averaging of attributes within an attentional field describes the performance of real observers.

Adult↗
PubMed1991

Disturbed body image in patients with eating disorders.

OBJECTIVE: The authors attempt to answer the question of whether patients with eating disorders experience more distortions in body image than do individuals without eating disorders. METHOD: The study group was composed of 214 women out of 230 patients consecutively admitted to an inpatient eating disorders program. Twelve men and four patients with atypical eating disorders were excluded from study. The 214 patients were divided into three groups: 87 with anorexia nervosa alone, 72 with anorexia and bulimia nervosa, and 55 with bulimia nervosa alone. The comparison group was composed of 61 women drawn from 125 consecutive participants in a survey of university students. Fifty-six men were dropped from the comparison group, along with eight women who fulfilled diagnostic criteria for eating disorders. Each subject used a three-dimensional measure to rate her body size and stated her desired body size at seven points: left biceps, left calf, left thigh, waist, abdomen, hips, and bust. The subjects' measurements at each of these points were taken. Distortion in body image was calculated as the subject's perceived body size divided by her actual body size. All subjects were also given a battery of tests of intelligence, skill, and memory. RESULTS: All three patient groups differed significantly from the comparison group in distortions in body image. Most but not all patients with eating disorders had distortions in their body image. CONCLUSIONS: If replicated, these findings would suggest that the diagnostic criteria regarding disturbance of body image for both anorexia and bulimia need to be revised.

Anorexia Nervosa↗
PubMed2002

Effects of geometric distortions on face-recognition performance.

The importance of 'configural' processing for face recognition is now well established, but it remains unclear precisely what it entails. Through four experiments we attempted to clarify the nature of configural processing by investigating the effects of various affine transformations on the recognition of familiar faces. Experiment 1 showed that recognition was markedly impaired by inversion of faces, somewhat impaired by shearing or horizontally stretching them, but unaffected by vertical stretching of faces to twice their normal height. In experiment 2 we investigated vertical and horizontal stretching in more detail, and found no effects of either transformation. Two further experiments were performed to determine whether participants were recognising stretched faces by using configural information. Experiment 3 showed that nonglobal vertical stretching of faces (stretching either the top or the bottom half while leaving the remainder undistorted) impaired recognition, implying that configural information from the stretched part of the face was influencing the process of recognition--ie that configural processing involves global facial properties. In experiment 4 we examined the effects of Gaussian blurring on recognition of undistorted and vertically stretched faces. Faces remained recognisable even when they were both stretched and blurred, implying that participants were basing their judgments on configural information from these stimuli, rather than resorting to some strategy based on local featural details. The tolerance of spatial distortions in human face recognition suggests that the configural information used as a basis for face recognition is unlikely to involve information about the absolute position of facial features relative to each other, at least not in any simple way.

Adult↗
PubMed1999

Selective horizontal dysmetropsia following prestriate lesion.

We describe a patient (P.S.) who, following a right prestriate lesion, reported that objects in the left visual field appeared distorted and smaller than those on the right. Other aspects of visual processing were remarkably unaffected. We carried out a series of size comparison tests using simple or complex stimuli and requiring different types of behavioural responses. We found that P.S. significantly underestimated the size of stimuli presented in her left visual field. When comparison tasks involved stimuli placed along the vertical axis or in the right visual field, P.S. performed well. The vertical and horizontal components of size distortion were found to be differentially affected. We conclude that size processing may be dissociated from other aspects of visual processing, such as form or colour processing, and depends critically on part of the occipital, prestriate areas (Brodmann areas 18-19).

Aged↗
PubMedDate not supplied

A conceptual model of factors contributing to the development of muscle dysmorphia.

Muscle dysmorphia is a recently described subcategory of Body Dysmorphic Disorder. It is most prevalent in males and has a number of cognitive, behavioral, socioenviornmental, emotional, and psychological factors that influence its expression. An etiological model describing these influences is presented for evaluation. Nine variables (body mass, media influences, ideal body internalization, low self-esteem, body dissatisfaction, health locus of control, negative affect, perfectionism, and body distortion) were identified through the use of extant literature on muscle dysmorphia and through extrapolation from literature involving women and eating disorders. The functional relationships among these variables are described and implications of the model are discussed.

Body Image↗
PubMed1999

Figural aftereffects in the perception of faces.

We examined figural aftereffects in images of human faces, for which changes in configuration are highly discriminable. Observers either matched or rated faces before or after viewing distorted images of faces. Prior adaptation strongly biases face perception by causing the original face to appear distorted in a direction opposite to the adapting distortion. Aftereffects transferred across different faces and were similar for upright or inverted faces, but were weaker when the adapting and test faces had different orientations (e.g., adapt inverted and test upright). Thus the aftereffects depend on which images are distorted, and not simply on the type of distortion introduced. We further show that the aftereffects are asymmetric, for adapting to the original face has little effect on the perception of a distorted face. This asymmetry suggests that adaptation may play an important normalizing role in face perception. Our results suggest that in normal viewing, figural aftereffects may strongly influence form perception and could provide a novel method for probing properties of human face perception.

Discrimination Learning↗
PubMed1997

Card-sort performance and syndromes of schizophrenia.

The performance of subgroups of schizophrenic patients on the Wisconsin Card Sort Test was investigated. Factor analyses of positive and negative symptom ratings confirmed that ratings described three groups similar to those reported by several other researchers. These symptom groups were labeled psychomotor poverty, cognitive disorganization, and reality distortion. Coaching and incentives resulted in significant improvement in the card-sort performance for patients characterized by symptoms of psychomotor poverty and reality distortion. Patients with symptoms of disorganization, however, had impaired ability to improve card-sort performance after coaching and incentives. Results indicate that symptoms of disorganization appear to differentiate learners from nonlearners on the Wisconsin Card Sorting Test and may be correlated with different underlying deficits.

Adult↗
PubMed1994

Cognitive distortions and psychiatric diagnosis in dually diagnosed adolescents.

OBJECTIVE: The purpose of this study was to examine the characteristics and patterns of cognitive distortions among psychiatrically hospitalized adolescents. METHOD: Measures of cognitive distortions, depression, and hopelessness were administered to 135 adolescents on two psychiatric inpatient units. Subjects were grouped according to their Axis I diagnoses: depression only, conduct disorder only, depression and substance abuse, conduct disorder and substance abuse, all three diagnoses, and none of the three diagnoses. RESULTS: Multivariate analyses of covariance indicated that differently diagnosed adolescents exhibited varying levels of cognitive distorting as measured by the Children's Negative Cognitive Errors Questionnaire (CNCEQ). In particular, adolescents with multiple Axis I diagnoses tended to score highest. On all but one of four CNCEQ subscales, the depression only group evidenced as much cognitive distortion as did the group with multiple diagnoses. However, each diagnostic grouping demonstrated its own somewhat distinct distortions based on CNCEQ subscales. CONCLUSIONS: Findings are discussed in terms of the utility of differentiating cognitive styles for subsequent treatment. It is suggested that disparate cognitive interventions could be matched with adolescents displaying particular problems.

Adolescent↗
PubMedDate not supplied

Effect of aging on visual shape distortion.

BACKGROUND: Individuals experience a visual illusion created by shape interaction: when two shapes are presented successively and briefly, the form of the second (test) shape appears distorted due to the form of the first (prime) shape; this shape interaction is called the shape distortion effect. While age-related deterioration in performance is found in various aspects of visual perception, the effect of aging on the shape distortion effect has not been evaluated. OBJECTIVE: The purpose of this study is to determine the effect of aging on the shape distortion effect. METHODS: We measured the perception of briefly presented elementary shapes and of the shape distortion effect in 29 healthy volunteers, with ages ranging from 18 to 83 years. For each shape interaction trial, a prime rectangle was presented (vertical or horizontal) for 45 ms, followed by an interstimulus interval for 135 ms, a test circle for 60 ms and finally a random dot mask for 300 ms. The test circle was presented in each quadrant of the visual field. The prime rectangle was flashed either at the same position as the test circle (0 degrees offset, intrahemifield) or 11 degrees apart, displaced horizontally in the opposite hemifield (11 degrees offset, interhemifield). In the elementary-shape trials, there was no prime, and the test shape was a circle or an ellipse. Using the method of adjustment, the percent elongation [(longer diameter - shorter diameter)/(shorter diameter) x100] of the reproduced ellipse was computed. RESULTS: The mean percent elongation in response to the elementary shapes did not vary with increasing age. The shape distortion effect decreased significantly with increasing age during both intra- and interhemifield conditions. The mean shape distortion effect was larger for the intrahemifield condition than for the interhemifield one. CONCLUSION: The shape distortion effect decreases with advancing age while the perception of elementary shapes does not. These results indicate a severer age-related dysfunction of the cerebral processing of shape interaction than that of elementary-shape perception.

Adult↗
PubMed1978

A visual system model and a new distortion measure in the context of image processing.

Underlying many techniques of image restortation, quantization, and enhancement is the mathematically convenient, but visually unsuitable distortion measure of squared difference in intensity. Squared-intensity differences has an indirect phenomenological correspondence in a model of the visual system. We have undertaken, therefore, an experiment that derives a new distortion measure from an acceptable visual system model and compares it in a fair test against squared difference in intensity in an image restoration task. We start with an eye-brain system model inferred from the works of current vision researchers, which consists of a bank of paralles spatial frequency channels and image detectors. From this model we derive a new distortion criterion that is related to changes in the per-channel detection probability and phase angle. The optimal linear (Wiener) filters for each distortion measure operate in turn on the same noisy incoherent images. The results show that the filter for the new distortion measures yields a superior restoration. It is more visually agrreable, more sharply detailed, and truer in contrast compared to the squared-difference filter, and impressive in its own right. Its mathematical properties suggest that significantly increased efficeincy in the storage or communication of images my be gained by its use.

Humans↗
PubMed2000

Relationship among body image, sex, and popularity of high school students.

Body dissatisfaction and attempts to lose weight are increasingly common among adolescents. Research has identified a number of factors significantly associated with body image, including sex, media, parental relationship, and puberty as well as weight and popularity. It was hypothesized that popular adolescents would have greater body dissatisfaction, more body distortion, and lower body esteem. From a rural high school 116 10th and 12th grade students were surveyed. Two teachers from the school also completed a Body Image Figure scale for each student. Subjects rated each grade member on a 5-point Likert-type scale, indicating how much they liked the classmate. A Social Preference rating (Popularity) was calculated for each subject from these ratings. Each subject also completed a Body Image Figure scale and Body Esteem scale. Body distortion was calculated by comparing the teachers' and a student's responses. Significant sex differences were found for scores on body satisfaction, distortion, and esteem, but none for popularity with distortion and body esteem. A relationship between popularity and body satisfaction was found, with the most popular adolescents reporting the least discrepancy between their ideal body image and their current body image. Popular adolescents are most satisfied with their body type.

Adolescent↗
PubMed1977

Children's response to their true and distorted mirror images.

In order to study the development of body image, 16 children aged 2 months to 8 years were tested to determine their levels of cognitive development on the basis of Piaget's theory, and their responses to their true and distorted mirror images. The study indicates a definite characteristic response by children according to their levels of cognitive development. This corresponds to infantile anxieties appropriate to the psychoanalytic theory of object relationships. The theoretical and clinical implications of the study are discussed.

Anxiety↗
PubMed2000

Probability ratings in claustrophobic patients and normal controls.

Forty-nine DSM-IV diagnosed claustrophobics and 49 sex- and age-matched community controls, without any current or past psychiatric disorder, were asked to estimate the probability that three types if events would occur if they were in the described situations. The events were claustrophobic, generally negative, and positive in nature. The results showed that claustrophobics significantly overestimated the probability of events they specifically feared, i.e. the claustrophobic events, while there was no difference between the groups regarding generally negative events and positive events. This finding remained when the higher scores for claustrophobics on the Claustrophobia scale and the Anxiety Sensitivity Index were covaried out. The conclusion that can be drawn is that claustrophobics' probability ratings are characterized by distortions that are specifically connected to anxiety-arousing events and not negative events in general. The hypothesis is proposed that this may be explained by an exaggerated use of simplified rules-of-thumb for probability estimations that build on availability in memory, simulation, and representativity.

Adult↗
PubMed1986

Age differences in depicting and perceiving tridimensionality in simple line drawings.

Twelve young adults (M = 21 years) and twelve elderly adults (M = 67 years) were asked to draw a solid cube. The depictions produced by elderly adults were rated by judges as less accurate than the depictions produced by young adults. Both age groups were also asked to evaluate cube drawings that were deliberately distorted in ways characteristic of the depictions produced by older adults. Compared to younger participants, the elderly were more likely to accept distorted drawings as accurate. Control tasks demonstrated that older adults were able to draw and evaluate simpler two-dimensional patterns on par with younger adults. Apparently the mental representation of tridimensional information deteriorates with age leading to deficits in both production and recognition.

Adolescent↗
PubMed2006

Body-size perception, body-esteem, and parenting history in college women reporting a history of child abuse.

This study investigated the relations among physical, emotional, and sexual abuse up to adolescence and subsequent perception of body size, detection of changes in body size, and body-esteem. The role of parenting history in abused participants was also examined. 38 college undergraduate women, half of whom had been abused, reported instances of abuse, childhood parenting history, and current body-esteem. A recently developed software program of Gardner and Boice was used to present a series of distorted frontal profiles of each participant's own body for the women to rate as being too wide or too thin. A psychophysical procedure called adaptive probit estimation was used to measure the amount of over- and underestimation of these ratings and whether these changes were statistically significant. Analysis showed abused participants had distorted perceptions of body size, although the direction of the distortion was not consistent. There was no difference in detection of changes in body size. Abused and nonabused participants differed on measures of body-esteem and on ratings of most parenting experiences, including experiences with both mothers and fathers.

Adolescent↗
PubMed1999

Perfectionism and depression symptom severity in major depressive disorder.

In recent years it has been recognized that perfectionism is a multidimensional construct and two Multidimensional Perfectionism Scales have been developed and investigated in relative isolation [Frost, R.O., Marten, P., Lahart, C., & Rosenblate, R. (1990). The dimensions of perfectionism. Cognitive Therapy and Research, 14, 449-468; Hewitt, P.L., & Flett, G.L. (1991). Perfectionism in the self and social contexts: Conceptualization, assessment and association with psychopathology. Journal of Personality and Social Psychology, 60, 456-470]. The present study sought to evaluate the association between various dimensions of perfectionism, higher-order personality dimensions, and self and observer rated depressive symptoms in a group of 145 patients with major depressive disorder. Only three of ten perfectionism dimensions (socially prescribed perfectionism, concern over mistakes and self-criticism) displayed medium to large correlations with depressive symptoms, especially self-report symptoms reflecting depressive cognitive distortions. The results are discussed in relation to the specificity of perfectionism dimensions to depression, adaptive versus maladaptive aspects of perfectionism, and in the context of previous research, much of which has relied on college student samples.

Adult↗
PubMed2001

Electrically evoked otoacoustic emissions from the chicken ear.

The outer hair cell electromotile response is believed to underlie the sharp tuning and exquisite sensitivity of the mammalian inner ear, and contribute to the production of electrically evoked otoacoustic emissions (EEOAEs) and sound-evoked otoacoustic emissions (OAEs). Avian ears are also sharply tuned, extremely sensitive and generate spontaneous and sound-evoked OAEs, but avian hair cells do not exhibit somatic electromotility. However, stereocilia bundle movements have been observed in avian and amphibian hair cells suggesting that EEOAEs might arise from electrically evoked bundle movements. Here, we demonstrate for the first time that AC current applied to the round window of the chicken evokes EEOAE of up to 18 dB SPL. The EEOAE produces a bandpass response with maximum amplitude in the 1000-3000 Hz range; the response drops off rapidly above 4000 Hz and below 500 Hz. The impulse response to current pulses is characterized by a large peak sometimes followed by a damped oscillation with a frequency around 2000 Hz. EEOAEs decreased significantly after anoxia and paraformaldehyde damage of the cochlea. Kanamycin-induced hair cell loss also caused a significant reduction in EEOAE and distortion product OAE; these emissions showed only a small recovery at long recovery times, when most hair cells should have regenerated. These results suggest that the EEOAE has a biological origin in the cochlea, which could presumably involve electrically evoked stereocilia bundle movements.

Animals↗
PubMed1978

Spatially rearranged vision and REM sleep: a lack of effect.

An observation first made in our laboratory was responsible for focusing our attention upon an apparent increase in REM sleep in relation to altered visual experiences during the day. This finding was consistent with certain information-processing theories of REM sleep function and seemed to offer experimental support for them. Therefore, we proceeded to conduct a series of closely related experiments, designed to investigate further the possible REM-augmenting effects of spatially rearranged vision. Although our first two experiments seemed to support the original observation, subsequent, more carefully designed experiments, did not. The combined results from all of our experiments forced us to conclude that there is no consistent effect of distorted daytime vision on the amount or percentage of REM sleep. REM latency, or the number of rapid eye movements during REM periods. We suggest that future research on the topic employ experiments specifically designed to explore relationships between personality variables and a subject's REM sleep response to altered sensory input.

Adult↗