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Biomedical subjects

R T Solman

Publications and source records attributed to R T Solman.

10 recordsLinked to original sources
PubMed1991

Color-mediated contrast sensitivity in disabled readers.

Specific deficits in the processing of transient visual stimuli have been identified in reading-disabled children. It has been suggested that suitably chosen colored filters can assist reading-disabled children but this is controversial. In order to assess how colored lenses might assist a reading-disabled child, we compared contrast sensitivity judgments of 20 disabled readers with those made by 20 good readers of the same age. Contrast sensitivity thresholds were measured over a spatial frequency range of 0.4 to 12.8 cpd. Contrast sensitivity functions were recorded for each child under four different conditions. For each condition the child wore a spectacle frame with a colored filter which had been selected on the basis of the child's best and worst performances on a spatial location task (BEST and WORST), a neutral density optical filter (GRAY), and an untinted filter (CLEAR). The results showed that the best colored filter selected for each of the disabled readers dramatically reduced sensitivity as the spatial frequency moved into the range of printed material (i.e., sensitivity declined sharply from 0.4 to 12.8 cpd). In contrast, there was very little change in sensitivity for the good readers using their best filters. These provocative findings suggest that colored optical filters might improve transient-on-sustained inhibition in disabled readers. It is possible that individually designed filters will provide a way of mitigating the effects of weak transient processing in reading-disabled children. However, our results should not be interpreted as supporting the efficacy of prescribed, colored optical filters as a remediation technique for reading disability.

Child↗
PubMed1991

Colour-mediated grouping effects in good and disabled readers.

Specific deficits in the processing of transient visual stimuli have been identified in reading disabled children. It has, separately, been suggested that suitably chosen coloured lenses can be used to assist reading disabled children but this is controversial. To assess an hypothesis as to how coloured lenses might remediate visual processing, this study compared the visual perceptual grouping effects of eighteen disabled readers with those made by eighteen good readers of the same age. Perceptual grouping effects were obtained for each child under a normal condition and wearing blue, yellow, grey, red and green optical framed lenses. The results replicated previous work in demonstrating a larger grouping effect for the disabled readers, and it was suggested that this finding was consistent with the presence of a transient deficit in these children. Comparison of the grouping effects obtained using the coloured lenses showed that although there was no significant impact on the performances of the disabled readers, the blue lens significantly increased the size of the grouping effect for the good readers. The presence of the blue lens decreased the activity initiated by stimulation of the red and green cones relative to the level of activity initiated by blue cone stimulation. As blue cone initiated activity appears to play little part in the transfer of acuity information, the presence of the blue lens could depress performance in a normal visual system by decreasing the level of acuity information transfer (i.e., the information required for efficient selective attention sorting and minimizing the grouping effect).(ABSTRACT TRUNCATED AT 250 WORDS)

Color↗
PubMed1990

A stimulus control analysis of the picture-word problem in children who are mentally retarded: the blocking effect.

Conditioning to one member of a compound stimulus can be blocked by the presence of a second member to which the response was previously conditioned. This account of selective stimulus control can be used to explain the finding that pictures inhibit learning of written words if the relevant pictures and their verbal equivalents have been paired previously. We tested the blocking explanation of the picture-word problem with 8 mentally retarded students. Following baseline, each student was resented daily with four conditions in an alternating treatments design. In Condition A (blocking), a picture was presented alone and then was followed by the presentation of a picture and written word compound stimulus; in Condition B (blocking/control), a word was presented alone; in Condition C(blocking minimized), a word was enhanced in size and presented alone followed by the word and a picture; and, in Condition D (blocking minimized/control), the enhanced word was presented alone. Each stimulus was presented for 15 s. All students had the lowest percentage of words read correctly in the blocking condition, and all improved when blocking was minimized. Six of 8 students reached their highest percentage of words read correctly in the two control conditions when the words were presented as a single stimulus without pictures. These results indicate that pictures inhibit some students' learning of new words; this may be due to the blocking of conditioning to written words by prior conditioning to pictures.

Attention↗
PubMed1990

Spatial localization discrepancies: a visual deficiency in poor readers.

In two studies, we compared the size of the spatial discrepancies made by young, good and poor readers when locating patterns in space. In the first study, each child was asked to point to the location of a briefly displayed pattern in a 7 x 7 matrix, and the discrepancy between the target's location and the child's response was recorded. The pattern was either a shape or a letter, and the target appeared at nine distances from the middle of the display. The discrepancies made by both groups of children increased with eccentricity, but the rate of increase was significantly greater for the poor readers. The second study required that two temporally and spatially separated target patterns be located on each trial. The discrepancies between their positions and the positions specified by the children were recorded for each target as a function of its eccentricity, and the results for both targets were similar to those obtained in the first study. That is, the discrepancies made by both groups of children increased with eccentricity, but the rate of increase was significantly greater for the poor readers. It was argued that the results of both studies are consistent with the hypothesis that poor readers are handicapped by a low-level processing or perceptual deficiency in the visual encoding system.

Achievement↗
PubMed1977

Evidence that focal processing involves a build-up of a visual object.

Subjects were required to make one of three judgements when presented with a tachistoscopically displayed letter, and the PEST procedure was used to obtain point estimates of the stimulus exposure time required to yield a 50 per cent (corrected for chance) level of accuracy. The judgements were ordered in terms of the information required, and on the assumption that pattern recognition involves the build-up of an appropriate visual object (Neisser, 1967), it was predicted that as the visual representation required to make a judgement increased in detail, the exposure time required would also increase. The results showed that stimulus exposure time increased as subjects located at one of four positions, classified as angular or circular, and identified a letter from the set F,T,O,Q. The type of information required to make these judgements, changed from the figure-ground discrimination needed for location, to the detailed level of representation needed for identification. Therefore, the results supported the prediction and were taken as evidence that pattern recognition involves the build-up of a visual object. The judgements location, classification, and identification were also made on a letter from the set F,f,Q,q, but in this case the classification judgement required subjects to name the letter independent of its case. The results showed that naming was just as difficult as identifying and this suggested that the level of representation required to name the letter was the same as that required to identify it.

Attention↗
PubMed1976

Influence of selection difficulty on the time required for icon formation.

By increasing the number of display items and the physical similarity between the target and the irreveland items it was possible to vary the difficulty of target selection in a visual-search task. The results showed that the accuracy with which the target was located declined as target selection became more difficult. On the other hand, estimates of the cumulative probability and the probability distributions of times necessary to form the icon indicated that these times were not influenced by changes in the difficulty of the task. The latter result supports Neisser's suggestion that the information processing carried out during the first stage analysis can be attributed to the action of a distinct cognitive mechanism.

Analysis of Variance↗
PubMed1975

Is construction reserved for the target during visual search?

This study was designed to examine the possibility, that where there is high similarity between irrelevant and target letters, the irrelevant letter will be constructed to sudents each attended a 1-hr. experimental session in which they searched 25 lists, followed by a recognition test. The lists were made up from the upper case letters of the alphabet, and during the recognition test each S was required to indicate how many times each of the irrelevant letters had appeared on the final list searched. Analysis of variance showed a significant recognition frequency effect. The results indicated Neisser's (1967) view, that during visual search construction is reserved for the target, may require modification.

Cognition↗
PubMed1975

Influence of similarity between target and irrelevant items on visual information processing.

6 undergraduate subjects searched circular stimulus displays of upper case letters of the alphabet for a pre-specified single target letter. The displays were given a masked exposure of 100 msec, and contained 1, 5, 11, or 17 irrelevant items which were either similar or dissimilar in shape to the target. It was anticipated that these conditions would provide a test of Neisser's (1967) notion of attention. The results, which showed that similarity, numbers and their interaction were significant, could not be explained by wholly serial or parallel models of information processing as they failed to account for the interaction. To explain the interaction it was necessary to consider processing by preattention and focal attention.

Adolescent↗
PubMed1975

Effect of target separation on selective attention.

A visual search task, in which subjects searched circular stimulus displays for two instances of a prespecified target, was used to investigate the effects of target-separation on accuracy. When a comparison was made of the total number of targets correctly located at each separation, no significant differences were found, and this suggested that, within the range of separations (maximum of 2.53 degrees) examined, the selective processing of the relevant items was not influenced by the distance separating them. Also, assuming that the redundancy of target items increased the probability of a target being perceived, the differences between the number of first targets correctly located and the number correct in a single target condition, were in the predicted direction. However, they failed to reach significance.

Attention↗