Perception of Dichotic and Monaural Verbal Material and Cerebral Dominance For Speech

Abstract

The primary purpose of the present investigation was to determine whether asymmetry between sides occurs in the recognition of verbal material under conditions of dichotic or monaural presentation of words. In the first experimental procedure, different filtered PB words (one to each ear) were presented simultaneously to 24 young adults with normal hearing, and the subject responded to both stimuli. In a second condition, the same filtered words were delivered simultaneously to each ear but the subject attended to only the word in one or the other ear. During the final presentation, the filtered words were delivered monaurally. Pair digits, as reported by Kimura (1961 a, 1961 b) were also presented simultaneously to each ear and the subject was instructed to respond to all the digits.

The results of both the simultaneous presentation of digits and filtered lists demonstrated that significantly more words were recognized from the right ear, contralateral to the dominant hemisphere for speech in this group, than from the left ear. But when the same filtered words were delivered monaurally, as in the Calearo & Antonelli (1963) investigation, the results were identical for each ear. The findings substantiated the suggestion by Kimura (1963) that when competition occurs between auditor pathways, ipsilateral and contralateral to the dominant hemisphere for speech, asymmetry between sides is observed.