Digit span and other WISC-R scores in the diagnosis of dyslexia in children.

The examination of subtest scores on the Wechsler Intelligence Scale is needed to provide confirmatory evidence for various subtest categorizations as there is no consensus about what patterns might be diagnostically useful. The present study supports the use of the ACID/AVID profiles (Arithmetic, Coding or Vocabulary, Information, and Digit Span) as elements in the diagnosis of dyslexia. WISC-R scores from 44 subjects were analyzed for specific subtest patterns of scores which might separate dyslexic individuals from the WISC-R standardization group. Perhaps some WISC-R ACID/AVID profile pattern analyses may be valid in the diagnosis of a stringently defined population of learning disabled individuals such as dyslexic children.

Contrast sensitivity differences between proficient and disabled readers using colored lenses.

Colored overlays or lenses (e.g., Irlen lenses) have been used in attempts to remediate reading difficulties. The present study included four middle-socioeconomic status (SES) adults and four middle-SES children with reading disabilities as well as an equal number of nondisabled readers of the same age groups and SES. Examined were (a) the relationship of wavelength (lens color) to visual grating performance, (b) the effect of reading disability on performance with each lens-color/luminosity-grating combination, (c) group performances on a visual detection task with the clear and chromatic lenses, and (d) peripheral retinal brightness thresholds. The spatial frequency of the gratings (and not the lens color) permitted subjects with reading disabilities to be differentiated from the proficient readers. Subjects with reading disabilities displayed significantly lower contrast sensitivity when tested with sine-wave gratings, as well as displaying higher brightness thresholds in the peripheral retina.

The social misperception syndrome in children with learning disabilities: social causes versus neurological variables.

Family shortcomings or other intrinsic psychological deficits are frequently viewed as contributing factors to the social misperceptiveness frequently seen in children with learning disabilities. This article attempts to synthesize research defining the social problems of some children with learning disabilities. Particularly emphasized is the role of communication skills deficits. Breakthroughs in neurophysiology negate, to a large extent, traditional emphases on family dysfunction, school failure, or personality distrubances as primary causes of the social problems of some children with LD. Advances in vision and language research allow departure from the social paradigm of the "misperceptive syndrome" to consider constitutionally based hypotheses of neural dysfunction. Neural aberrations are viewed as triggering deficient language processing, which in turn may lead to unsatisfactory social interactions. Several correlates and characteristics of family, school, and environmental systems are discussed in the context of their impact on personality development and on changes in the life adjustments of both children and adults with learning disabilities.

Reply to Stuart and Lovegrove's question, "visual processing deficits in dyslexia: receptors or neural mechanisms?".

Recently Stuart and Lovegrove questioned the receptor hypothesis of Grosser and Spafford which these authors used to account for the findings that dyslexic individuals have superior peripheral color discrimination to normal readers but also have poorer peripheral brightness discrimination than normal readers. Stuart and Lovegrove hypothesized that dyslexics instead have an impaired transient visual system. The receptor hypothesis is an attempt by Grosser and Spafford to link the functioning of the rods and cones to transient and sustained visual system functioning in a more specific manner than has been tried heretofore by suggesting that, while the parvocellular system is almost entirely fed by cones, both kinds of receptors drive magnocellular cells (but with the rapid onset of early transient system responding being due to the highly light sensitive rods). The rods are proposed to be the receptors initiating the rapid onset of responding in the magnocellular, transient pathway. In dyslexic individuals, they maintain, there are relatively fewer rods to provide for the rapid onset of transient system responses, resulting in a diminished capacity of the transient system to inhibit sustained system activity (as occurs with normal readers). Their receptor hypothesis supplements the concept of transient-vs-sustained system differences.

Light sensitivity in peripheral retinal fields of dyslexic and proficient readers.

This present study furthers research on perceptual differences between dyslexics and normal readers which is contrary to the current linguistic approaches to this problem. Specifically, thresholds of light intensity for small retinal areas were examined. As hypothesized, the peripheral retinas of proficient readers evidenced lower thresholds than the peripheral retinas of dyslexic readers. These results are consistent with Grosser and Spafford's previous research which showed that dyslexics were better able to detect colors with their peripheral retinas than proficient readers. This research lends support to the premise that dyslexics' retinas have unusually high cone density in the periphery. Additional research is warranted to improve both diagnosis and treatment of dyslexia.

Wechsler Digit Span subtest: diagnostic usefulness with dyslexic children.

The current study supports Levinson's contention (1988) that the diagnosis of dyslexia cannot be based solely on neurophysiological evidence but must be made in conjunction with reading and educational test scores. Contrary to much current research, in the present study specific WISC-R profiles are identified within a stringently defined subgroup of 57 9- to 12-yr-old dyslexic children. Well-defined subtest scatter can differentiate dyslexics from proficient readers. In particular, the Digit Span subtest, which is not routinely administered by psychologists or included in computing Verbal IQ, can be considered an important component of a diagnostic battery. Unexpectedly, Coding emerged with Digit Span as a third factor in a principal component analysis; statistically significant sex differences appeared on the Coding task. Findings appear to confirm the phonological encoding deficiencies displayed by dyslexics on the Digit Span subtest. This study strongly supports consideration of WISC-R subtest differences, along with correlated factors, neurophysiological and perceptual evidence, when diagnosing dyslexic children. Cross-validation is planned.

Perceptual evidence for an anomalous distribution of rods and cones in the retinas of dyslexics: a new hypothesis.

The present study tested the hypothesis that from the ability of dyslexics to read peripheral letters one may infer the presence of cones, those visual receptors specialized for acuity, in the peripheral retina. The cones are also the receptors for color discriminations. The method of retinal perimetry was used to map color-sensitive zones of the retina for 14 dyslexic and 14 control subjects. A statistically significant difference showed that the 14 dyslexics reported colors at more peripheral positions than did the 14 normal readers. These data are consistent with the premise that dyslexics have an anomalous distribution of retinal receptors. These findings perhaps may help to explain the erratic eye movements of some dyslexics. It is suggested that retinal perimetry might be one component of a diagnostic battery for the differential diagnosis of dyslexics.