John E. Obrzut

Effects of grade level and sex on the magnitude of the dichotic ear advantage.

Abstract The magnitude of the dichotic ear advantage was assessed in kindergarten, second, fourth, and sixth grade children. 40 subjects (20 male, 20 female) participated in each grade. The results of a 2 × 2 × 4 (sex, ear, grade level) analysis of variance revealed a significant right ear advantage but no effect according to sex or grade level. Consequently, it seems that the magnitude of a dichotic ear effect does not increase with age nor is it related to sex. The results are discussed as they pertain to the possibility that channel capacity may be related to the dichotic stimulus dimension used.

Development of Cerebral Dominance: Dichotic Listening Asymmetry in Normal and Learning-Disabled Children.

Abstract The magnitude of the dichotic right-ear advantage was assessed in 48 normal and 48 learning-disabled children representing an age range of approximately 5 years. All subjects were matched according to age, sex, and handedness. An analysis of results indicated a significant right-ear advantage in both the normal and learning-disabled children, but revealed no developmental trends for either group. Differences observed in the performance of the learning-disabled and normal children may reflect variability in selective attention rather than differences in the degree of cerebral lateralization. These results suggest a need for a reconceptualization of the causative factors affecting children with learning disorders and lend support to the notion that cerebral lateralization is not a developmental phenomenon.

Dichotic Listening and Bisensory Memory Skills in Qualitatively Diverse Dyslexic Readers

Dichotic listening and bisensory memory skills were investigated in 144 male middle-class second-grade (N=72) and fourth-grade (N=72) readers. Subjects were classified according to the Boder system, which distinguishes among normal and three types of dyslexic readers: dysphonetic (auditory dyslexic), dyseidetic (visual dyslexic), and alexic (combined). Results of the dichotic (recall of simultaneous auditory stimuli) and bisensory (recall of simultaneous visual and auditory stimuli) tasks indicated that normal and dyseidetic readers were able to attend, store, and retrieve stimuli at both grades and experimental rates of stimulus presentation better than alexic or dysphonetic readers. Ear asymmetry, as measured by dichotic right-ear advantage, did not discriminate normal from dyslexic groups. The greater task inability of the alexic and dysphonetic groups may be reflective of their difficulty in processing linguistic (left hemisphere) and spatial (right hemisphere) information that is basic to the reading process. The overall results suggest that remediation may be more difficult to implement with certain types of problem readers than with others.

Time sharing and dichotic listening asymmetry in normal and learning-disabled children

Abstract Time-sharing and dichotic listening techniques were used to examine cerebral lateralization for language function in 48 normal and 48 learning-disabled children. All subjects were matched according to age, sex, and handedness. An analysis of results indicated that both nornal and learning-disabled children demonstrated left hemisphere lateralization of language function on the time-sharing and dichotic listening tasks. However, no developmental trends were evident for either group. Differences observed in the performance of the normal and learning-disabled children may relate to how each group utilizes “verbal strategies” and processes simultaneous information in the left hemisphere. The results strongly question the notion that attributes learning disabilities to incomplete or delayed language lateralization and lend support to the notion that cerebral lateralization is not a developmental phenomena.

Neuropsychological assessment of learning disabilities: a discriminant analysis.

The neuropsychological test scores of 23 learning disabled children were compared with those of a matched population of normal children in the 9-1 to 13-1 age range. All children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R), a dichotic listening task involving both free and directed recall conditions, a handedness inventory, the Tactile Performance Test and the Category Test from the Halstead-Reitan Neuropsychological Test Battery. A multivariate analysis of variance resulted in a significant separation between groups (p less than .001) using these procedures. A stepwise discriminant function analysis revealed that both of the directed dichotic tasks contributed the most of all 13 measures to the significant group separation. In addition, other cognitive tasks found to discriminate normal from learning disabled children include general verbal processes, concept formation, and tactile memory. These findings suggest that the directed dichotic listening procedure and the WISC-R Verbal IQ measure are reasonably valuable clinical tools in the classification of learning disabilities.

Attentional deficit in learning-disabled children: Evidence from visual half-field asymmetries

The structural theory of cerebral lateralization has been typically used to explain hemispheric asymmetries. However, the attentional model of brain functioning may help resolve some of the inconsistent findings with groups of learning-disabled children. To test this hypothesis, a visual half-field paradigm for word recognition was employed in a group of 26 learning-disabled and 26 normal children matched for sex, chronological age, and handedness. Three experimental conditions (unilateral, cued unilateral, and bilateral) and two word error types (visually and acoustically confusable words) were analyzed. The results indicated that normals produced the expected RVHF superiority under all experimental conditions, but the learning-disabled produced the expected RVHF superiority only under the cued unilateral condition. Learning-disabled children also made significantly more visually and acoustically confusable errors than normals and unlike normal children increased the number of acoustic errors in the RVF under bilateral stimulation. These results provide evidence that learning-disabled children may process information inefficiently and have brain activation patterns that are more susceptible to attentional effects.

The Neurobiological and Neuropsychological Foundations of Learning Disabilities

This article focuses on the factors that have led to the current interest in the neuropsychology of learning disorders. The validity of the neuropsychological model is examined. Research regarding the neurobiological basis of learning disorders, cerebral asymmetries, and neuropsychological assessment battteries for learning disabilities are discussed.

Reconceptualizing Cerebral Dominance: Implications for Reading- and Learning-Disabled Children

Over the past several decades much has been written regarding the suspected relationship between cerebral lateralization for function and cognitive development. Most typically, the research in this area has attempted to relate poorly established lateral preferences to reading and learning disorders. Generally, these research efforts have been inconclusive in increasing our conceptual understanding of this relationship. However, recent research employing more direct measures of central functional asymmetry suggests that a reconceptualization of the notion of cerebral dominance may be in order. A rationale for this reconceptualization is provided and the implications for children with learning disorders is discussed.

Training school psychologists in neuropsychological assessment: Current practices and trends ☆

Abstract Directors of school psychology programs at the Masters, sixth-year and doctoral levels were surveyed as to their programs degree of emphasis in neuropsychological screening and assessment. Despite variability according to program level, directors identified a need for training in these areas. This was particularly evident at the doctoral level, where greater flexibility exists in designing a students program of studies. The results of this survey support the notion that training in neuropsychological screening and assessment techniques is appropriate in the preparation of specialists in the area of school psychology.

An Investigation of the Dial as a Pre-Kindergarten Screening Instrument1

This study investigated the validity of the Developmental Indicators for the Assessment of Learning (DIAL) for the prediction of school success. Fifty-three kindergarten children ranging in age from 55 months to 71 months were pre-screened with the DIAL five months prior to school entrance and then administered the Slosson Intelligence Test (SIT), Metropolitan Readiness Test (MRT), and a Progress Report form during the end of the academic year. Canonical correlations and stepwise multiple linear regression analyses indicated that the DIAL Communications subtest was the most valid single predictor of school success as determined by the composite MRT. The DIAL Concepts subtest was the only significant predictor of Progress Report composite score. Implications of these results are discussed in terms of preschool screening programs and the use of the DIAL.