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PubMed1998

Size perception by vision and kinesthesia.

When two sizes, one perceived by vision and the other by kinesthesia, are apparently equal, the physical relationship between them varies: The sizes may be equal, or the visual size may be larger than the kinesthetic size, or vice versa. In this study, the method of cross-modal matching and the method of magnitude production were used to explore the relationship between apparently equal sizes (5-40 cm) perceived by vision and by kinesthesia. The sizes were linear or circular, and the mode of standard presentation was visual, kinesthetic, or verbal. The size and the direction of the intermodal mismatch varied with the size of the standard. It was also found that an apparent length of movement varied with the direction of movement. In all conditions, the relationship between apparently equal visual and kinesthetic sizes was well approximated by a power function.

Adolescent↗
PubMed1996

Determinants of body size perceptions and dieting behavior in a multiethnic group of hospital staff women.

OBJECTIVE: This study was designed to identify determinants of body size perceptions and their relationship to dietary behavior in a multiethnic group of women. DESIGN: A single interview consisting of the Massara and Stunkard body image cards (1979) and questionnaires on sociocultural background, anthropometry, and dieting history were administered to volunteers from the staff of a hospital. SUBJECTS: The sample was a convenience sample of 186 women representing a range of staff positions recruited from Methodist Hospital in Brooklyn, NY; 174 completed the study. Data on 150 women are presented in this article. RESULTS: Height and weight-for-height were stronger predictors of accuracy of perceived body size than ethnicity. Tall, slight women were more likely to overestimate and short, heavy women were more likely to underestimate actual body size. Ethnicity had an interactive effect with height as taller European Americans were more likely to perceive their body size as larger than actual compared with Afro-Caribbeans and African Americans. Women with a history of dieting were more likely to overestimate their size and to view it as different from what is perceived as attractive to others. APPLICATIONS/CONCLUSIONS: Based on the results, we conclude that body size is a stronger predictor of accuracy of perceived body size than ethnicity; and dieters overestimate their body size and believe it to be heavier than their social group would prefer.

Black or African American↗
PubMed1985

The size illusion: visual and kinaesthetic information in size perception.

Earlier studies have shown the size of kinaesthetically presented two-dimensional movement patterns to be significantly overestimated. Whether this size overestimation is characteristic of the kinaesthetic system alone has not been established. Two experiments are reported which were designed to investigate size judgment made after kinaesthetic and visual pattern presentation and the effect of environmental cues on the perception of movement patterns. In experiment 1 patterns were presented kinaesthetically (experimenter guided hand movements around the outline of the pattern) or in combination with visual information given by a moving light (pinpoint light attached to the stylus which was moved around the pattern); visual and kinaesthetic cues were either congruent or conflicting with each other; and environmental cues were either present or absent. In experiment 2 static visual display was compared with visually traced pattern presentation, again with or without environmental cues. Overall the results showed that, regardless of experimental manipulation, in all cases where the information was given over time the subject perceived the pattern larger than reality. After static visual display, overestimation of size did not occur.

Adolescent↗
PubMed1998

A search for differences in size perception of near objects in young myopes corrected by either spectacles or contact lenses.

Accommodation and convergence demands are lower for a spectacle-corrected myope than for the same individual when corrected with contact lenses. Thus the impact of accommodative/convergence micropsia ought to be lower with the spectacle correction. A size-matching experiment which required myopic subjects (corrections up to -12.25 D) to match the sizes of each of four standard targets with a variable comparison target was therefore conducted. The standard targets were placed at four viewing distances: 3 m, I m, 0.5 m and 0.25 m. All standard targets subtended 2 degrees at the eye. The variable comparison target was situated at a fixed distance of 2 m and was generated on a visual display unit. Each of the eight subjects was shown one standard target at a time under binocular viewing conditions and was told to adjust the size of the comparison target until he/she felt that both targets were equal in linear size. Two sets of readings were taken: one when the subject's myopia was corrected with spectacles and one when corrected with contact lenses. No systematic difference in size perception was found between the spectacle and contact lens corrected cases, implying that the relatively small differences in accommodation and convergence demand did not significantly influence the size judgements.

Journal Article↗
PubMed1999

Size constancy and angular size matching in size perception of near objects.

Accurate judgment of the relative sizes of near objects at various distances is important for a variety of occupational visual tasks. This study involved matching the apparent size of each of a series of standard targets, placed at distances between 0.2 and 3 m and all subtending 2 degrees at the eye, with a comparison target of similar geometry, but at a fixed distance of 2 m. Natural binocular viewing of the targets demanded exercise of accommodation and convergence in an environment rich in cues to target size and distance. As the available cues were reduced, judgements of the lateral dimensions of the targets were found to change gradually from those predominantly based on size constancy to those mainly based on angular size matching. These results are qualitatively very similar to those observed in past studies with more distant objects and emphasize the need to maintain adequate cues if linear size is to be judged accurately.

Accommodation, Ocular↗
PubMed1997

Sorority women's body size perceptions and their weight-related attitudes and behaviors.

Six hundred twenty-seven sorority women were surveyed to determine if sorority members constituted a subgroup of college women who may be at increased risk for disordered eating. The sorority members were administered Body Mass Index Silhouettes and the Eating Disorder Inventory. The findings indicated that these sorority women may have a greater fear of becoming fat, are more dissatisfied with their bodies, and are more weight preoccupied and concerned with dieting than are college women from previous studies. The findings also suggested that body size perceptions were distorted among both underweight and overweight women and that thin was the ideal body profile for the majority of the women. Although bulimia scores were higher for this population than for those reported in all but one of the previous studies, these differences were not significant. More research and innovative programs designed to address weight-related attitudes and behaviors among this population are called for.

Adolescent↗
PubMed1995

Distortion of size perception in visuospatial neglect.

BACKGROUND: A number of studies have shown that most patients with symptoms of unilateral (left-sided) visuospatial neglect make consistently rightward errors when attempting to bisect a horizontal line at its midpoint. One possible interpretation of this impairment is that such patients misperceive the left half of the line: that is, that they underestimate its extent relative to the right half. RESULTS: We have carried out direct tests for such a perceptual distortion in three neglect patients by asking them to make matching judgements on pairs of horizontal rectangles, vertical rectangles or nonsense shapes, of varying relative size, presented on a computer screen. We report here that all of the patients tested showed a significant and substantial relative underestimation of the horizontal extent or area of stimuli presented on the left side of their egocentric space. There was no such misperception of vertical extent. CONCLUSIONS: It is suggested that size perception may be partially determined by a representational system that is anatomically centred in the parieto-temporal region of the brain. The results are interpreted in terms of damage to this system in neglect patients.

Attention↗
PubMed1998

Relative size perception at a distance is best at eye level.

Relative size judgments were collected for two objects at 30.5 m and 23.8 from the observer in order to assess how performance depends on the relationship between the size of the objects and the eye level of the observer. In three experiments in an indoor hallway and in one experiment outdoors, accuracy was higher for objects in the neighborhood of eye level. We consider these results in the light of two hypotheses. One proposes that observers localize the horizon as a reference for judging relative size, and the other proposes that observers perceive the general neighborhood of the horizon and then employ a height-in-visual-field heuristic. The finding that relative size judgments are best around the horizon implies that information that is independent of distance perception is used in perceiving size.

Analysis of Variance↗
PubMed2003

A haptic size-contrast illusion affects size perception but not grasping.

Object features (e.g. size, shape and orientation) are relevant for recognition and identification, but also for the control of manual actions. Converging evidence suggests a dissociation between the visual systems that mediate object perception and object-directed action. Here we present evidence suggesting that a similar dissociation might exist in the haptic domain. We demonstrate that a haptic variation of a size-contrast illusion influences the perceived size of a target object, but not the degree to which the hand is opened when that object is the target of a grasping movement. This finding is consistent with the view that object perception is "scene-based" and takes into consideration not only the size of the target object but also the sizes of other nearby objects. In contrast, the control of object-directed action is primarily driven by the absolute size of the target object independent of the relative sizes of other objects in the environment, suggesting a "actor-based" frame of reference. The present findings suggest that dissociations between action and perception are not unique to the visual system, but might instead reflect a general organizational principle of sensory processing.

Adult↗
PubMed1999

A computer-graphic technique for the study of body size perception and body types.

We present a novel approach for measuring body size estimation in normal and eating-disordered women and men. Clinical categories of body types were used as prototypes. By comparing the subjective appearance of a person's body with prototypes, we can understand how different attributes of his or her body shape contribute to perception of body size. After lifelike random distortions have been applied to parts of their body image, individuals adjust their body shapes until they converge on their perceived veridical appearance. Exaggeration and minimization of particular body areas measured with respect to their true shape and with different prototypes can be expressed as numerical deviations. In this way, perceived body size and body attractiveness can be appraised during the course of diagnosis and treatment of eating disorders.

Body Constitution↗