Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SIZE PERCEPTION”

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 469 records · Page 26Linked to original sources
PubMed1978

[Neurons of the rabbit visual cortex with simple and complex visual fields].

The receptive filelds of orientation-selective neurons were studied in the rabbit visual cortex. Two mechanisms of the selectivity were found: the mutual inhibition between on- and off-regions of the receptive field (simple type) and the orientation-dependent inhibition within the uniform region of the receptive field. The non-selective neurons could exhibit the lateral inhibition within the uniform region of the receptive field also. It is supposed that both "simple" and "complex" cells originate from the non-selective units.

Animals↗
PubMed1978

Infant recognition of the invariant form of objects.

The developing ability to abstract and recognize the invariant form of an object was studied in 6- to 9-month-old infants. It was found that 9-month-olds were capable of recognizing the invariant form of objects. They demonstrated this ability by differentiating a variation of a familiarized object from a configurationally novel object after a period of familiarization involving other variations of the familiar object. The forms of some objects were more difficult to recognize than others, but recognition of the more difficult forms was enhanced by allowing simultaneous comparison of variations during familiarization. 6-month-olds, on the other hand, did not demonstrate recognition of the invariant form of the experimental objects.

Child Development↗
PubMedDate not supplied

[Analysis of concrete and abstract cues as a function of different hemispheres in the white rat].

In experiments on 92 Wistar albino rats performed by the motor alimentary method of conditioning, the following models were used: reflexes to relation, transfer of conditioned reflexes and invariant recognition of visual images. Functional elimination of the cerebral cortex was achieved by means of spreading depression. It was shown that in a rat population, reflexes to rather wide relations of areas of geometrical figures or lengths of straight lines are equally disturbed after elimination of the right or the left hemisphere. In conditioned reflexes to relation of areas of some other geometrical figures or of their multitudes, as well as in finer reflexes to relation of lines lengths, elimination of the right hemisphere disturbs predominantly the analysis of concrete stimuli characteristics, while elimination of the left hemisphere disturbs analysis of abstract characteristics. The transfer of conditioned reflexes to other geometrical figures is predominantly disturbed following the inactivation of the left hemisphere. Invariant recognition of visual images is more affected following the elimination of the left hemisphere than that of the right one. It has been suggested that the animals' right hemisphere analyses in the main concrete characteristics of the stimuli, while the left one--their abstract characteristics.

Animals↗
PubMed1982

Echo perception of shape and texture by sighted subjects.

Experienced blind subjects have previously demonstrated good echo perception of size and distance and some echo-discrimination of shapes and textures. In three experiments untrained sighted subjects also proved able to echo-detect and recognize three simple shapes and to recognize fabric and wooden but not carpet and Plexiglas discs at significantly above chance levels. Some improvement occurred over the first few trials but little thereafter, suggesting that this sort of echo perception requires very little training. A blind subject exhibited over-all accuracy comparable to those of sighted subjects. There were, however, interesting differences between the blind subject and the sighted subjects in echo perception of specific stimuli and in approach to the task.

Adolescent↗
PubMed1975

Dark adaptation and short-wavelength backgrounds decrease perceived size.

The effects of background luminance, contrast, and background wavelength on the perceived size of small line figures were studied at mesopic levels of light adaptation. Perceived size diminished at low levels of background luminance. The effect disappeared at high levels of luminance. Perceived size of luminous circles increased as a logarithmic function of background luminance when the background intensity did not exceed 25 td(1). The strength of the size effect decreased as a function of circle diameter from 0-125 to 2 deg of visual angle(2). Perceived size of small luminous circles, subtending less than 0-5 deg, also increased as a function of contrast at low values of contrast but at very high values of contrast there was a decrease in perceived size. Background luminance had the same effect on the perceived size of circles as on the perceived size of spatial cycles in gratings. Control experiments led to the conclusion that dark adaptation is the primary source of the size effects. The main evidence for this conclusion was obtained from a demonstration that the same background luminance produced either an increase or a decrease in perceived size, depending on the adaptational state of the eye. It was also found that a shift from cone vision to rod vision contributes to the effects, for a stimulus looked smaller on a short-wavelength background than on a long-wavelength background. The size effects can be predicted from the changes of receptive-field properties of single neurones under corresponding conditions of stimulation, if it is assumed that the perception of size is mediated by size-specific channels formed of single neurones. Stimulation that leads to an activation of small receptive fields appears to indicate to the brain the presence of small retinal images. If small receptive fields are experimentally made responsive to larger retinal images, an underestimation of size results.

Dark Adaptation↗
PubMed1987

A comparison of perceptive and receptive fields in man and monkey.

We have measured the perceptive field, the psychophysical correlate of the physiologically determined receptive field, in man and monkey. Measurements were made using the Hermann grid illusion and the Westheimer paradigm. The following results were found: First, in both man and monkey, the size of perceptive fields and field centers increases from the fovea to the periphery. As with receptive fields, this increase is first rapid and then more gradual; and it is more pronounced on the temporal than on the nasal side of the retina. Second, monkey and human perceptive field centers are approximately the same size. But total perceptive fields (i.e., centers plus surrounds) tend to be smaller in monkeys. Third, in monkey, psychophysically measured perceptive field centers are about the same size as neurophysiologically measured receptive field centers. And as these, they are larger, by a factor 1.3-2, than histologically measured dendritic fields. These findings strongly indicate that in monkey all three measurements refer to the same underlying retinal mechanism. The same relationship is assumed to hold in man.

Animals↗
PubMed1978

The effect of exposure time upon perceived size.

An experiment whereby a standard filled circle is exposed for 100-1000 msec on the tachistoscope for ten subjects. Each is asked to choose a comparison circle, which appears to be the same size, out of a series of eleven filled circles of various angular subtenses larger and smaller than the standard filled circle in the tachistoscope. The results indicate that exposure time has a role in the perception of size.

Adult↗
PubMed1993

The familiar-size cue to distance and stereoscopic depth perception.

The role of the familiar-size cue to distance in stereoscopic depth perception was examined in two experiments. In experiment 1 subjects judged the depth of a binocularly viewed interval, the far point of which was defined by either a familiar or an unfamiliar object, and in experiment 2 subjects adjusted the depth of the interval so that its extent appeared equal to the length of a vertical reference extent positioned on the surface of the object. Although familiar size influenced depth estimates (experiment 1) it did not influence matching judgments (experiment 2). The findings are discussed with reference to the issue of the nature of the familiar-size effects on judgments of stereoscopic depth.

Depth Perception↗
PubMed1986

Human ocular vergence movements induced by changing size and disparity.

Human subjects viewed an electronically generated bright square. Horizontal movements of the two eyes were recorded with the scleral coil method. The dynamic properties of vergence movements induced by movement of the bright square were investigated for the following three kinds of stimulus motion: (a) both the size and the binocular disparity of the square changed together, in such a way as to exactly mimic the retinal image changes produced by a real object's motion in depth; (b) the changing-size component in (a) was present with no disparity component; (c) the changing-disparity component in (a) was present with no size component. The gain and phase of the ocular vergence responses to these three stimuli were computed. Ocular vergence movements were induced by changing size in all five subjects. Responses during binocular viewing were higher and less variable than responses during monocular viewing. Size oscillations induced ocular vergence oscillations with a phase lead of up to 65 deg relative to target size for frequencies of stimulation below 1.0 Hz. Vergence oscillation amplitudes were of the order of 10 min of arc and maximal for frequencies of 0.4-0.7 Hz. Ocular vergence movements were not induced by changes in target size in one dimension nor by flickering a stationary square. Ocular vergence movements induced by size changes were entirely transient with no sustained component: vergence responses to disparity were sustained. When the stimulus combined size change with disparity change in the ratio characteristic of a real moving object, vergence tracking was more accurate and less noisy than when the eyes were stimulated with the disparity component alone. The ocular vergence response induced by the combination of size change with disparity change was accurately predicted by linearly adding the vergence response produced by the size change alone to the vergence response produced by the disparity change alone: combined stimulation produced no evidence of non-linear interaction between responses to size change and to disparity change. The properties of vergence responses induced by changing size and by changing disparity showed several close correlations with the corresponding data on psychophysical sensitivity for motion-in-depth sensation. We suggest that responses to changing size contribute to the accuracy with which ocular vergence tracks real objects moving in depth.

Adult↗