R. Harter Kraft

Hemispheric asymmetries during six- to eight- year-olds performance of piagetian conservation and reading tasks☆

Abstract To investigate childrens hemispheric processing, their EEGs were recorded and alpha asymmetries were computed for each task or subtask. Piagetian conservation and reading tasks shifted from greater right-hemispheric processing during encoding of information to greater left-hemispheric processing during retrieval and verbal/logical expression of the information, which suggests interhemispheric processing within these tasks. Conserving responses and high reading scores were related to greater interhemispheric or bilateral processing during information retrieval. It is suggested that Piagetian Conservation tasks are behavioral measurements of interhemispheric integration and that progression through Piagetian stages may parallel cortical myelin development.

The effect of sex, laterality and familial handedness on intellectual abilities

This study assessed the relationship of sex, familial handedness and laterality to the intellectual abilities of 116 right-handed 12-14-yr-old subjects. Verbal scores were predicted by an interaction between familial handedness and the subjects own laterality. A strong right ear advantage for verbal stimuli and a large lateral difference between the ear advantage for verbal and nonverbal stimuli predicted high Verbal Intelligence scores for the strong right hand-eye preference subjects with family histories of dextrality. Conversely, attenuated ear advantage scores for verbal stimuli predicted high Verbal Intelligence scores for the strong right hand-eye familial sinistral subjects. Although the results were less consistent for Performance Intelligence scores, they were significantly and positively related to assessed hand-eye preference, and a significant interaction between familial handedness and the subjects own laterality was observed for the Object Assembly subtest. A strong left ear advantage for nonverbal stimuli predicted high scores for the strong right-preference familial dextral subjects and attenuated ear advantage for nonverbal stimuli predicted high scores for the strong right-preference familial sinistral subjects.

RELATIONSHIP OF EAR SPECIALIZATION TO DEGREE OF TASK DIFFICULTY, SEX, AND LATERAL PREFERENCE

Children in Grades 2 and 6 nested in age, sex, and lateral-preference groups were administered two dichotic listening tests (digit and environmental sound). There was a right-ear advantage for verbal stimuli which did not increase with age, supporting the invariance models of the development of verbal laterality past 5 to 6 years of age. The percentage of left-ear accuracy for verbal stimuli relative to the right ear decreased with task difficulty. Girls were more accurate than boys when recalling verbal stimuli and the older boys were more accurate than the other children when identifying environmental sounds. In recalling nonverbal stimuli, boys showed a left-ear advantage and out-performed girls, who showed a right-ear advantage. The sex difference in ear advantage increased with task difficulty. There was an over-all increase in accuracy with age when identifying both verbal and nonverbal stimuli with the exception of the ambidextrous children, who demonstrated low accuracy scores for the environmental sound stimuli across age groups.

Sex-related differences in cognition: Development during early childhood

Abstract Fifty-five right-handed children from right-handed families between 2- and 5-years-of-age were individually administered two batteries of hand preference, verbal and spatial measures with a six month interval separating administrations. Early between-sex differences in production and comprehension abilities were revealed. Girls outscored boys on measures of verbal fluency and graphic reproduction of shapes. Boys outscored girls on a measure of verbal comprehension. Within-sex differences between comprehension and production abilities were also apparent. At both administrations, boys scored significantly higher on verbal tests of knowledge, comprehension and reasoning than on measures requiring oral or manual production. Girls showed the reverse pattern. By the second administration, however, the high production/low comprehension pattern was only significant for girls consistently demonstrating high degrees of right-hand preference across testing times. Significant between-sex differences in these comprehension versus production ability patterns ranged between 1/2 to 11/6 standard deviations in magnitude and accounted for 8–10% of the variance in childrens ability difference scores. These results are interpreted as support for a biological basis of early sex-related cognitive differences and Kimuras (1983) model of sex differences in the organization of the left hemisphere.

Laterality and School Achievement: Interactions between Familial Handedness and Assessed Laterality

179 8- to 12-yr.-old children received hand-preference, eye-preference, dichotic (digits and nonverbal sounds) tests, and the Wide Range Achievement Test. These data and those from previous studies suggest that brain organization for receptive language laterality can be predicted by familial handedness in conjunction with assessed hand-eye preference. A model of optimum functional ear laterality patterns within a given brain organization is advanced. For example, the “typical” pattern of a right-ear (left-hemisphere) advantage for verbal stimuli was associated with high achievement scores only for right-handed individuals with a family history of dextrality.

Longitudinal Change of Ear Advantage for Receptive Language Function in 2½ - to 9-Year-Old Children

In Study I, 24 children at the average ages of 41.1 and 46.1 mo. were presented dichotic digits while another 27 children were tested at average ages of 40.0, 49.6, and 54.6 mo. In Study II, 40 children were tested at average ages of 50.7 and again at 91.8 mo. No significant change in right-ear advantage (REA) appeared across 4- or 9-mo. intervals; however, significant increases were found over the 14-mo. (Study I) and 41-mo. (Study II) intervals. There were no significant effects of sex or phenotypic or family history of handedness.

Lateral specialization and social-verbal development in preschool children

Forty-two 2 1/2- to 5 1/2-year-old childrens social and verbal behaviors were observed during free play in a preschool. A test measuring lateral specialization of verbal function and a standardized psychometric test of verbal ability were also administered. Analysis of variance indicated that the right ear (left hemisphere) is predominant in processing verbal stimuli in children as young as 2 1/2. Multiple regression analyses revealed significant relations between the right ear accuracy score for dichotically presented verbal stimuli and both psychometrically measured verbal ability and a social-verbal factor score derived from play behavior. After the increase related to age was statistically partialled out from both verbal ability and social-verbal scores, verbal expression, length of verbal utterances, time spent in conversation, and peer social interactions increased and parallel play decreased as a function of right ear (left hemisphere) accuracy for verbal stimuli. The relationship between left ear (right hemisphere) accuracy scores for verbal stimuli and social-verbal behavior, however, was not linear. Very high and very low levels of left ear recall predicted an increase in the frequency of parallel play and low social-verbal behavior while moderate levels of left ear accuracy scores predicted the reverse.

Reading comprehension performance and laterality: Evidence for concurrent validity of dichotic, dichhaptic and EEG laterality measures

EEGs were recorded while 55 boys read and answered questions about passages. Concurrent validity between parietal alpha ratios obtained from these recordings and dichotic/dichhaptic scores supports their utility as measures of lateral processing. The evidence was particularly strong between right hand advantage for dichhaptically presented sequential patterns and left hemispheric activity while answering. Results also indicate that coefficients for dichotically presented digits and alpha ratios during silent reading are indices of receptive laterality and measure the deployment of lateral structures rather than degree of structural laterality. This supports a dynamic rather than static model of lateral processing during receptive language.

Stability and Ear Advantage for Dichotically Presented Environmental Sound Stimuli: Development during Early Childhood

55 right-handed children with no family history of left-handedness received two dichotic presentations of environmental sounds. The mean test-retest interval was 9 days. Raw accuracy scores yielded acceptable temporal stability (rs>.72). The expected consistent left-ear advantage for environmental sound stimuli was only evident in younger and less mature children. Five- and 6-yr.-old children, particularly those with strong right-hand preferences, had a right-ear advantage for the stimuli. Their computed laterality coefficients showed low and nonsignificant test-retest reliabilities, however. Three- and 4-yr.-old children, particularly those with weak hand preferences, had a left-ear advantage for the same stimuli. Of the 3- and 4-yr.-old children who did not have strong right-hand preferences, 92% demonstrated consistent ear advantages across testing sessions and their laterality coefficient test-retest correlations were significant. In contrast, only 47% of the strongly right-handed 3- and 4-yr.-old children and 71% of the strongly right-handed 5- and 6-yr.-old children had consistent ear advantages for the same stimuli. It is suggested that the 3- and 4-yr.-old children processed these stimuli according to endogenous, stimulus-specific brain mechanisms and that learned processing strategies overrode these mechanisms for the 5-and 6-yr.-old children.

LATERALITY AND SPELLING ACHIEVEMENT: A REPLICATION FAILED

49 right-handed boys (24 familial dextral and 25 familial sinistral) were tested. Analysis did not support expected differences in familial handedness between ear-laterality scores or in the relationship between ear laterality and spelling achievement.