PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Form Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 685 records · Page 38Linked to original sources
PubMed1976

Implicit-shape constancy as a factor in pictorial perception.

Schoolboys from the Ivory Coast and from Kenya were tested on a simple task intended to detect the effect of implicit-shape constancy. The presence of such an effect was confirmed. Comparison of two Ivorean subsamples differing in their responses to a request to build a model of a depicted structure showed that those subjects who build flat (2D) models were less influenced by the implicit-shape constancy than those subjects who built three-dimensional structures. This confirms a postulated link between the implicit constancy and perception of pictorial depth.

Adolescent↗
PubMed1976

Constraints on classificatory skills in young children.

On three occasions over a one-year period 23 children aged 3-4 were asked to match target objects with other objects which were similar to the target in shape or in colour but not in both. A sequence of matches to each target was asked for. The structure of these sequences is examined for evidence of classifacatory abilities. Many subjects appear to be attempting (not always successfully) to follow a strategy of 'holding fast' to their original choice of matching criterion (colour or shape) on subsequent trials. The striking differences between performance after a first-trial colour-match and after a first-trial shape-match are described. It is argued that development during this period involves an increasing ability to ignore the more salient attribute (shape) when matching by colour. The general developmental significance is discussed.

Aptitude↗
PubMed1977

The influence of secondary depth cues on the understanding by Nigerian schoolboys of spatial relationships in pictures.

The ability of 105 Nigerian schoolboys to interpret pictures three-dimensionally was studied as a function of changing the number of depth cues on moving from monochrome photographs incorporating the effects of shadow, through fully cued line drawings, to line drawings containing only elevation cues. The experiment also investigated the effects of different amounts of previous formal training in technical drawing on performance in these tasks. The results showed a significant increase in performance as the number of depth cues increased above that contained in the minimum cued line drawings. However, the difference between the effects of fully cued line drawings and the photographs was not significant. Neither the main nor interaction effects relating to levels of formal training in technical drawing were significant.

Adolescent↗
PubMed1978

Factors influencing the response latencies of subnormal children in naming pictures.

The times taken to name 56 drawings of objects on five separate occasions were analysed for 21 ESN(M) and 21 ESN(S) children, matched for picture-naming vocabulary. The ESN(S) group not only had a higher mean response latency but also showed greater inter- and intra-subject variance. Nine objects were selected whose names have a Thorndike-Lorge language frequency of 50 words per million or greater, and nine others were selected with a frequency of less than 50 words per million. Each object was drawn in two ways, one giving a two-dimensional outline with the addition of important detail, the other drawing also incorporating cues indicating the depth of the object. An analysis of variance of the children's latencies in naming the selected 36 pictures of 18 objects over five trials indicated that the method of drawing had no effect upon naming latencies. Pictures with high-frequency names were named faster than those with lower frequency names, the ESN(S) group showing a greater rate of increase in naming latency for the lower frequency words than the ESN(M) children. Results were discussed in terms of the Oldfield and Lachman models of lexical memory storage and of the search processes required for the retrieval of names.

Adolescent↗
PubMed1988

Visual resolution of macaque retinal ganglion cells.

1. The visual resolving ability of different types of macaque retinal ganglion cells was estimated at different retinal eccentricities, by measuring the amplitude of modulated responses to black-white gratings of spatial frequencies near the resolution limit for each cell. 2. The resolving ability of tonic, spectrally opponent ganglion cells was usually similar to that of phasic, non-opponent ganglion cells at similar eccentricities, except that at eccentricities greater than 10 deg some tonic ganglion cells with remarkably high resolution (up to ca. 15 cycles/deg) were found. Our cell sample was limited within the central 2 deg of the visual field, however. 3. Only a small proportion of phasic ganglion cells showed an increase of mean firing level to gratings near the resolution limit. The maintained firing of tonic ganglion cells was higher than that of phasic ganglion cells. 4. With red-black or green-black gratings, the resolution of phasic ganglion cells was unaffected. For red or green on-centre ganglion cells, a marked deterioration of resolving ability occurred when the grating was of a colour to which a cell responded poorly (green-black gratings for red on-centre cells, and red-black gratings for green on-centre cells). A slight improvement in resolving ability occurred when the grating was of an excitatory colour. 5. For a sub-sample of cells, we compared resolution limit with centre size as determined from area-threshold curves. For both phasic and tonic ganglion cells, resolution limit (the period length just resolved) was about half the centre diameter, as is the case for cat ganglion cells. This implies that the centre sizes of phasic and tonic monkey ganglion cells are similar at most eccentricities. 6. We attempt to relate these results to primate retinal anatomy and visual resolution, determined behaviourally.

Action Potentials↗
PubMed2001

Representation of perceived object shape by the human lateral occipital complex.

The human lateral occipital complex (LOC) has been implicated in object recognition, but it is unknown whether this region represents low-level image features or perceived object shape. We used an event-related functional magnetic resonance imaging adaptation paradigm in which the response to pairs of successively presented stimuli is lower when they are identical than when they are different. Adaptation across a change between the two stimuli in a pair provides evidence for a common neural representation invariant to that change. We found adaptation in the LOC when perceived shape was identical but contours differed, but not when contours were identical but perceived shape differed. These data indicate that the LOC represents not simple image features, but rather higher level shape information.

Adaptation, Physiological↗
PubMed1975

Visual construction of color is digital.

When disparate shapes are flashed under the appropriate temporal and spatial conditions, the human visual system resolves their disparity smoothly and continuously. No equivalent supplementations are found for color, which the system resolves by abrupt transformation. Shape and color reveal themselves, contrary to some modern theorizing, as properties handled in different ways by the visual nervous system, continuous or analog for shape, abrupt or digital for color.

Color Perception↗
PubMed1976

Spatial frequency-contingent color aftereffects.

Two-dimensional Fourier analysis of checkerboards reveals that major components are at a 45 degree angle to the check edges. After adapting to chromatic checkerboards, subjects who viewed achromatic grating stimuli reported that complementary color aftereffects are aligned with spatial frequency components rather than with the edges in the pattern.

Adaptation, Ocular↗
PubMed1968

Pattern perception: integrating information presented in two modalities.

Subjects were required to organize and identify temporal patterns composed of either (i) two stimuli in one modality; (ii) two stimuli in each of two modalities, with the pattern alternately presented in the two modalities; or (iii) one stimulus in each of two modalities. Patterns (i) and (iii) are organized as structured patterns, but (ii) is organized by modality, not by pattern structure. When elements of a pattern appear in two modalities, the auditory-tactual combination produces the poorest performance.

Analysis of Variance↗