A developmental study of ear asymmetry in children

Research in the area of neuropsychology and child development suggests that the human brain undergoes a process of lateralization in which cognitive, speech and motor functions become "dominant" in one of the hemispheres. Further ivestigation suggest that this process occurs at a different rate for different individuals and could have an effect on their learning abilities. Such views are consistent with recent theories of "developmental dyslexia" and other disabilities attributed to a neurological or maturational lag. The present study was undertaken to determine the effects of several independent variables on ear asymmetry in children. Ear asymmetry has been used as a measure of hemispheric lateralization by many researchers. Specifically, a dichotic listening procedure (simultaneous auditory stimulation) was used to determine the effects of sex, age, socioeconomic status and intelligence on childrens' ear asymmetry scores. Eighty-four children were used as subjects. They were divided into three age groups (5-3-ll) and further grouped by sex and socioeconomic status. A dichotic listening task and the Peabody Picture Vocabulary Test were individually administered to each child. The results of the study indicated that age was the only significant variable for right ear scores (F=4.88; p < .05). There was no significant variable for left ear scores. Furthermore, a stepwise regression analysis indicated that age was the best and only significant predictor of right ear scores. Conversely, IQ was the best predictor of left ear scores. Also important was the finding that the difference between the right and left ear scores were significant for all age groups and that the difference became larger with age. This increased ear asymmetry with age was partly attributed to the use of dichotic tapes of different complexity with different age groups.