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PubMed1978

Pictorial depth and related constancy effects as a function of recognition.

It is argued that while pictorial cues must be fundamental in the perception of an extended ground plane in daily life (and, by definition, in the perception of depth in pictures), the traditional pictorial cues such as perspective or texture gradients are neither a necessary nor a sufficient basis for it. That they are not necessary was shown by experiments in which such cues were eliminated from pictures representing a scene in depth. Illusory size perception based on localization of objects in depth in such pictures nonetheless occurred. That they are not sufficient was shown by experiments in which photographs of grassy fields did not yield impressions of depth or related size illusions when conditions were such that the scene was not recognized. Once recognized, however, these same pictures did yield such perceptions. It is suggested that a critical step in perceiving depth based on pictorial information is recognition of the scene.

Art↗
PubMed1978

Body awareness in anorexia nervosa: disturbances in "body image" and "satiety".

Patients with anorexia nervosa have been shown previously to display distortions in body image perception. Bruch has postulated that these disturbances as well as disturbances in interoception are meaningfully related to the development of the syndrome. We hypothesized that disturbances in body image, as measured by a distorting photograph technique, and interoception, as measured by a satiety-aversion to sucrose test, should be demonstrable in anorexic patients vs. normal controls. Furthermore, these disturbances should be modifiable by external cues (looking at one's image in a mirror and ingesting isocaloric "high" and "low" calorie connotation meals). We also hypothesized that body image and interoceptive disturbances would be interrelated in the same individuals. Results indicated that patients with anorexia nervosa (N = 26) differed from normal controls (N = 16) in overestimating their body sizes (p = 0.06) and in failing to develop an aversion to the sucrose tastes (p less than 0.001). However, neither viewing one's image in a mirror nor ingesting both "high and "low" calorie connotation meals altered body size perception. Intrasubject body size estimates were very stable from week to week for the anorexic subjects (r = +0.75, p less than 0.001) but less for the controls (r = +0.45, p less than 0.05). The data revealed that overestimation of body size was closely related to the failure to develop an aversion to sucrose tastes in anorexic patients.

Adult↗
PubMed1978

Effect of perspective and slant on perception of apparent size and distance.

An experiement was performed to re-examine the role of linear perspective and floor slant on apparent size and distance scales. Misleading perspective cues did not alter the observers' apparent distance scales but did influence the absolute magnitude of distance judgments; floor slant exerted little influence on apparent distance scales or the absolute magnitude of distance judgments. Neither perspective nor slant manipulation reliably affected apparent size scales or exerted more than a minor influence on the absolute magnitude of size judgments.

Cues↗
PubMed1991

Body-image marking. Validity of body-width estimates as operational measures of body image.

The relation of image-marking estimates of body width (IM) to actual widths, to other indices of body-size perception, and to measures of body satisfaction were examined using data obtained in a nonclinical sample of 200 women. The results of regression and correlational analyses were as follows: (a) actual widths accounted for only a small proportion of the variance in IM estimates, (b) the variance in IM estimates remaining after actual width was accounted for was not meaningfully related to other body-image indices, and (c) actual widths were more highly correlated with other body-image indices than were differences between estimated and actual widths (IM estimate-actual width). The current results suggest that most of the variance in IM estimates is error variance. Possible methodological confounds, which may bias women's estimates of body widths in the direction of overestimation, are discussed.

Adult↗
PubMed1979

[The role of the pupil's size in the perception of other persons].

Studies by Hess (1975) show that the pupil serves as a source of information in perception of the emotional state of another person. Large pupils are interpreted in a positive sense. Basing on the results of Hess, the hypothesis that pupil size does not become a relevant variable in person perception until after puberty, was formed. The following result would be interpreted as supporting the hypothesis: since girls reach puberty before boys, more girls should react to pupil size than boys of the same age. 121 students between the ages of 11 and 16 years judged in several statements which of two face photos of a teacher expressed a greater degree of positive attention and esteem towards the students. The two face photos were identical with the exception of pupil size. All age groups rated the photos with larger pupils more positively. Sex differences occurred in the ratings of the 11 to 12-year-olds. Some basic differences between this experiment and that of Hess are discussed.

Adolescent↗
PubMed1992

The effects of colour adaptation and stimulus size on white perception as a function of eccentricity in man.

We studied how much desaturating complementary colour had to be added to blue, green or red after homochromatic adaptation of short duration in order to perceive white or grey at eccentricities of 0-15 deg in the nasal visual field. The CIE 1931 (x,y) chromaticity coordinates corresponding to achromatic perception were subtracted from the chromaticity coordinates of blue, green and red in order to obtain the threshold differences (dx, dy) in chromaticity coordinates. When the stimulus size was constant at all visual field locations, the absolute values of dx and dy decreased with increasing eccentricity, which means that the desaturation threshold for white or grey perception was higher at the fovea than in the periphery. However, when the stimulus size was M-scaled magnifying its size with increasing eccentricity in inverse proportion to the lowest local sampling density of the human retina (cones and ganglion cells at eccentricities 0-10 and above 10 deg, respectively), dx and dy with blue became independent of visual field location except for the very centre of the fovea. However, M-scaling was unsuccessful with green and red. Although M-scaling with green reduced the change in dx and dy as a function of eccentricity, it had no effect on dx and dy with red colour.

Adaptation, Ocular↗
PubMed1988

Abnormal perception of food size in anorexia nervosa.

The hypothesis that patients with anorexia nervosa exaggerate the perceived size of food was tested. Video recordings of five items of food and four neutral objects of a similar size were made such that the size of each object increased steadily from half to twice its normal size. Each of the nine objects was placed on a ledge inside a dummy television screen next to the video screen, the food items alternating with the neutral objects, and 20 female patients with anorexia nervosa and 20 female controls matched for age were asked to adjust the size of the video recording to that of the real object. Although there was no overall difference in perceptual accuracy between patients and controls, both groups perceived the food items as being bigger than the neutral objects, the patients exaggerating the size of the food significantly more than the controls. These results imply that patients with anorexia might start eating more easily when admitted if their food were presented as small portions on large plates.

Adolescent↗
PubMed1990

Shape, size and relative space position perception in neglect patients.

Shape, size and relative position in space perception were tested in 17 right brain damaged (RBD) patients with neglect symptoms, 10 RBD patients without neglect and 11 controls. Simultaneous pair comparison task in free vision was used. Two arrangements of the visual display were used: side by side and top-bottom. Neglect patients' performance was comparable to RBD and controls in the shape and size test, but was below the other groups in the relative space position test. The selective failure of neglect patients in the position task did not depend on the spatial arrangement of the visual display, which may indicate a general perceptual deficit, rather than a deficit restricted to the neglect hemifield.

Aged↗
PubMed1989

Body-image disturbances in bulimia nervosa: influences of actual body size.

This study evaluated body-image distortion and ideal body-size preferences in 423 nonbulimic women and 108 bulimics. Analyses of covariance were utilized to compare the bulimic and nonbulimic groups on measures of current and ideal body size. Weight was used as a covariate to evaluate the influence of actual body size on perception of current body size and selection of ideal body size. Bulimics chose current body sizes that were significantly larger than those picked by nonbulimics regardless of actual body size. Bulimics also chose thinner ideal body sizes than did nonbulimics, regardless of actual body size. These results suggest that body-image distortion and extreme preference for thinness are a fundamental characteristic of bulimia nervosa. These results were discussed in terms of how perception of a large body size and preference for a very thin body size might interact to produce a high degree of dissatisfaction and overconcern with body size in bulimia nervosa.

Adult↗
PubMed1979

Accessing similarity and dimensional relations: effects of integrality and separability on the discovery of complex concepts.

A series of studies investigated how stimulus integrality and separability impact the cognitive accessibility of similarity and dimensional relations. A good deal of previous work has established that stimulus integrality and separability differentially determine perception; here, the question is whether they also have differential effects on conception. Are the principles that govern perception also principles that can be readily discovered in concept learning tasks? Is a similarity-based rule especially easy to abstract from integral stimuli and a dimensionally-based rule especially easy to abstract from separable stimuli? In Experiments 1 and 2, we measured the relative ease with which the two types of rules (similarity and dimensional) are discovered by adults with the two types of stimuli (integral and separable). In experiment 1, the two rules were made redundant and we asked which rule the subjects learned. In Experiment 2, one rule was made relevant and the other irrelevant, and we compared relative speeds of learning. The results from the studies led us to conclude (a) that dimensionally based rules are more accessible from separable than from integral stimuli; (b) that similarity-based rules are more accessible from integral than from separable stimul; and (c) that, in general, subjects have a bias to access dimensional relations in this type of task. Experiment 3 pursued an additional suggestion from Experiments 1 and 2 that the dimensional relations within integral stimuli are sometimes accessible, more so when larger interstimulus differences are encountered. In confirmation, Experiment 3 demonstrated that adult subjects are more successful in applying a dimensional rule to pairs of integral stimuli that differ by a small amount if they also have exposure to pairs of integral stimuli that differ by a large amount. In a later discussion, it was argued that such a finding is consistent with the notion that the "dimensions" of integral stimuli are merely arbitrary directions in the integral stimulus space, and some relevant pilot data to that effect were presented. Finally, Experiment 4 took up a developmental issue. Young children have sometimes produced perceptual responses governed by similarity relations when presented with stimuli that are separable for adults. Will they more readily access similarity-based or dimensionally-based relations from such stimuli in the concept learning tasks here? The results showed that both kindergarteners and fifth graders more readily access the dimensional relations. A final discussion integrated the findings from the several experiments, taking up the following issues: (a) the relation between the perception and the conception of stimulus relations and (b) the nonprimacy of the dimensional axes in the integral stimulus space.

Adult↗
PubMed1991

The interaction of oculomotor cues and stimulus size in stereoscopic death constancy.

In the natural world, observers perceive an object to have a relatively fixed size and depth over a wide range of distances. Retinal image size and binocular disparity are to some extent scaled with distance to give observers a measure of size constancy. The angle of convergence of the two eyes and their accommodative states are one source of scaling information, but even at close range this must be supplemented by other cues. We have investigated how angular size and oculomotor state interact in the perception of size and depth at different distances. Computer-generated images of planar and stereoscopically simulated 3-D surfaces covered with an irregular blobby texture were viewed on a computer monitor. The monitor rested on a movable sled running on rails within a darkened tunnel. An observer looking into the tunnel could see nothing but the simulated surface so that oculomotor signals provided the major potential cues to the distance of the image. Observers estimated the height of the surface, their distance from it, or the stereoscopically simulated depth within it over viewing distances which ranged from 45 cm to 130 cm. The angular width of the images lay between 2 deg and 10 deg. Estimates of the magnitude of a constant simulated depth dropped with increasing viewing distance when surfaces were of constant angular size. But with surfaces of constant physical size, estimates were more nearly independent of viewing distance. At any one distance, depths appeared to be greater, the smaller the angular size of the image. With most observers, the influence of angular size on perceived depth grew with increasing viewing distance. These findings suggest that there are two components to scaling. One is independent of angular size and related to viewing distance. The second component is related to angular size, and the weighting accorded to it grows with viewing distance. Control experiments indicate that in the tunnel, oculomotor state provides the principal cue to viewing distance. Thus, the contribution of oculomotor signals to depth scaling is gradually supplanted by other cues as viewing distance grows. Binocular estimates of the heights and distances of planar surfaces of different sizes revealed that angular size and viewing distance interact in a similar way to determine perceived size and perceived distance.

Adult↗
PubMed1990

Size constancy at birth: newborn infants' responses to retinal and real size.

Two experiments are described whose aim was to investigate whether perception of size at birth is determined solely by proximal (retinal) stimulation, or whether newborn babies have the ability to perceive an object's real size across changes in distance. In Experiment 1, preferential looking between pairs of stimuli which varied in real size and viewing distance was found to be solely determined by retinal size, suggesting that changes to proximal stimulation can have profound effects on newborns' looking behavior. However, in Experiment 2 newborns were desensitized to changes in distance (and retinal size) during familiarization trials, and subsequently strongly preferred a different sized object to the familiar one, suggesting that the real size had been perceived as constant across the familiarization trials. These results confirm Granrud's (1987) findings that size constancy is present at birth.

Attention↗
PubMed1992

Color appearance across the retina: effects of a white surround.

Hue and saturation scaling was used to measure the appearance of spectral lights as a function of stimulus size at loci spaced across the horizontal meridian. At a given locus, each hue (red, yellow, green, and blue) grew as a function of stimulus size to some asymptotic value. Growth functions fitted to the hue data were used to derive the sizes of perceptive fields of the hue mechanisms. We had previously investigated the size scales of these fields by using stimuli presented on a dark background: Field sizes for all mechanisms increased with eccentricity, this increase was greater on the temporal than on the nasal retina, and the retinal size scales of the different hue mechanisms were not the same. We now report the results of repeating the study with stimuli embedded in a white surround rather than in darkness. The main effects of the white surround were as follows: Sizes of perceptive fields of all mechanisms were smaller everywhere than with the dark surround. For small fields, stimuli appeared everywhere more saturated with the white surround, but larger stimuli appeared less saturated.

Adolescent↗
PubMed1992

Choosing specifiers: an evaluation of the basic tasks model of graphical perception.

Effect sizes obtained from 39 experiments were used to evaluate the predictions of the basic tasks model of graphical efficacy. This model predicts that performance will be attenuated with graphical displays as a function of the particular specifier, or visual dimension, used to code data values. In this review the basic tasks model predicted performance more accurately than did Tufte's data-ink principle. In addition, variability in effect sizes across studies revealed that the model was more successful at predicting performance in local (focusing) tasks than in global information synthesis tasks. Furthermore, the model was better at predicting performance in tasks requiring the use of physically present rather than remembered graphs. Further differences in effect sizes resulted from variability in the exact specifiers used in experimental graphs. Minimal differences were obtained among graphs that used position, length, or angle as specifiers. However, graphs that used area or volume to represent quantitative values were associated with consistently worse performance than found with other formats.

Attention↗