Functional brain asymmetry and dichotically-stimulated ear preference in musicians and nonmusicians
Date
1976
Authors
Johnson, Peter R. (Peter Richard)
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Abstract
A left ear-right hemisphere superiority in the recognition of dichotically-presented melody segments has often been demonstrated in the general adult population. More recently a right ear-left hemisphere superiority has been shown by musicians in a similar monaural task. Both findings can be explained by current ideas on functional brain asymmetry and the co-operative roles of the cerebral hemispheres. Gestalt synthesis appears to be the main task of the right hemisphere, while phonological analysis seems to be the specialty of its counterpart.
This cortical organization is thought to apply only to right-handed people. Studies of left-handers have produced equivocal results, due partly to errors in definition and measurement. However, groups of left-handed subjects often fail to match the homogeneity of groups of right-handers, in terms of their scores on dichotic listening tasks, suggesting the presence of two, or more, distinct sub-groups within the former population. It has been difficult to find simple external behaviours which distinguish between the proposed sub-groups in terms of their cortical organization.
The purpose of the present study was fourfold. First, it was to replicate the finding of a left ear superiority for dichotically-presented musical stimuli in the general adult population. Second, it was to extend the finding of a right ear superiority in musicians to include a dichotic listening task, and third, to investigate the previously described lack of asymmetry, using a reliably measured group of left-handed people. Finally, it was decided to test the hypothesis that the left hemisphere becomes more active in this task as a person's musical ability increases.
The subjects were 64 human adults with no evidence of hearing loss, who were assigned to one of four groups. These were Right-handed Musicians, Left-handed Musicians, Right-handed Nonmusicians and Left-handed Nonmusicians. There were 16 subjects in each group.
Each subject was presented with a series of melody recognition tasks. On each trial, there was a short dichotic presentation of violin melody segments which was followed by a 5-second interval and the presentation of a binaural recognition foil. The subject's task was to decide if he had just heard the recognition foil, and, if so, to which ear had it been presented.
The results were largely as predicted. Musicians demonstrated a right ear superiority for this task, while nonmusicians performed better with the left ear. The difference between these groups was largely due to a higher right ear score for musicians, implying the increased activity of the left hemisphere. The left-handed subjects, musicians or nonmusicians, showed considerably less ear asymmetry than the right-handers. However, as a group, their scores were more heterogeneous, emphasizing the need for a meaningful sub-division of these subjects.
The results suggest that the development of lateralization for music may parallel that for language. A holistic appreciation of music seems to be carried out mainly in the right hemisphere, but when the stimuli are to be meaning fully partitioned, a left hemisphere analyzing mechanism becomes active.