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.

Longitudinal change of ear advantage for receptive language function in 2 1/2- 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 differences in schematic face encoding during dual-task performance with increasing levels of difficulty.

20 normal, right-handed, familial dextral men performed (a) unimanual finger tapping, (b) encoding of schematic faces at three levels of difficulty (3, 5, and 7 faces), (c) verbal production, (d) concurrent tapping and verbal production, and (e) concurrent tapping and face encoding. Subsequent recognition of faces was disrupted more by concurrent left-hand tapping than by concurrent right-hand tapping, supporting both the hypothesis that the right hemisphere mediates face encoding in adults and Kinsbourne and Hicks' (1978) "functional cerebral distance principle." Left- and right-hand tapping rate and variability were not asymmetrically affected by either verbal production or face encoding. While there was an increase in generalized interference effects on face encoding, the degree of asymmetry of the interference remained constant. In addition, as the difficulty of the memory task increased, variability of tapping rate decreased. This was discussed in terms of attention and automatic motor programming.

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.

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.

Lateral specialization and social-verbal development in preschool children.

Forty-two 2 1/2- to 5 1/2-year-old children's 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.

Lateral specialization and verbal/spatial ability in preschool children: age, sex and familial handedness differences.

One hundred and fifty-five preschool children between 2 1/2 and 5 1/2 yr of age were administered two dichotic tests (digit and nonverbal sound) and three Wechsler Intelligence subtests (vocabulary, geometric design and block design). The familial dextral (FD) children around 4 yr and older demonstrated a greater degree of absolute ear laterality than the FD children under 4 yr of age. There were also age-related changes in the relationship between children's ability scores and their ear laterality scores. For older FD children a greater right-ear advantage for verbal stimuli and a left-ear advantage for nonverbal stimuli was associated with higher vocabulary scores. Under 4 yr of age, however, a strong right-ear advantage for verbal stimuli was associated with relatively higher spatial than vocabulary ability. For these younger FD children, less marked laterality predicted higher vocabulary scores. It is hypothesized that a cortical organizational transition is occurring around 4 yr of age and that this transition involves a shift from reliance on subcortical to cortical mediation, accompanied by increasing callosally mediated inhibition and integration of hemispheric function. Furthermore, there were sex differences observed in the relationship between lateral specialization and spatial ability. As young as 2 1/2 yr of age, the FD boys' spatial ability scores were positively associated with having a left-ear advantage for nonverbal sound stimuli. The FD girls' spatial ability scores were not significantly related to their ear advantage scores for nonverbal sounds but were associated with their ear advantage scores for verbal stimuli. In addition, around 4 yr of age a shift was observed in the relationship between the boys' absolute laterality scores and the difference between their spatial and vocabulary ability scores which was not found for the girls' scores. It it suggested that the maturation of right hemispheric spatial mediation may be delayed or inhibited in girls.

A digital signal processing system for EEG frequency analysis.

This paper describes the digital signal processing work of a research project for studying children's cognitive processes by analyzing EEG signals during school-related tasks. The EEG being analyzed involves two homologous channels (left and right parietal area), and is recorded on magnetic tapes. The objective of the analysis is to determine if, by examining the alpha band of the ongoing EEG, different school tasks and correct vs incorrect responses can be detected. Analysis of alpha-band calls for the determination of signal power in the 7-12 Hz frequency band (adjusted for the age of the subjects) for each channel as well as correlation between the channels. A digital signal processing scheme implemented on an Apple II microcomputer was developed for such an analysis. The results obtained are discussed.

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 subject's 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 subject's 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.

The relationship between right-handed children's assessed and familial handedness and lateral specialization.

Eighty right-handed males (6-12 yr of age) stratified into age x degree of handedness x family history of handedness groups were administered three dichotic (digit, syllable, environmental sound) tests. Older subjects accurately identified more stimuli than the younger subjects across tasks. There were significantly laterality differences for both verbal and nonverbal stimuli between family history of handedness groups regardless of the subjects' age and degree of handedness. Those subjects with familial sinistrality had attenuated right-side advantage for verbal and non-verbal stimuli and decreased nonverbal accuracy scores compared to the familial dextral subjects who evidenced at right-ear (left hemisphere) advantage for verbal stimuli and a left-ear (right hemisphere) advantage for nonverbal.