Speech and Hearing Sciences ETDs

Publication Date

7-10-1974

Abstract

Previous research has established that when two speech signals are presented dichotically, normal listeners tend to report those stimuli presented to the right ear more accurately than those presented to the left. This has generally been interpreted as reflecting the primacy of contralateral auditory pathways and left hemisphere dominance for language function. Although many dimensions of the dichotic listening procedure have been subjected to experimental manipulation, little attention has been directed toward the investigation of performance differences between males and females or the reliability with which listeners perform. The present study was designed to examine these two areas more closely, using a greater number of performance measures and a larger sample than those routinely employed in previous studies. Twenty-five male and 25 female adults with normal and symmetrical hearing and no history of brain pathology served as subjects. All were native speakers of English and right-handed. Test stimuli consisted of 30 pairs of natural speech CV syllables representing all possible combinations of PA, TA, KA, BA, DA, and GA. Each subject was tested twice, the second session held approximately one month after the first. Stimuli and test conditions were identical for both sessions. Subject performance was analyzed on the basis of the following measures: Right ear correct, left ear correct, total correct, R-L difference, percent of correct, percent of error, single correct-right ear, single correct-left ear, double correct, and neither correct. For each measure, the mean scores of males, females, and combined groups were submitted to analysis by t-test to determine appropriate mean differences. Test-retest reliability was examined using the Pearson product-moment correlation. The results of the present study may be summarized as follows:

1. A right-ear advantage was found for males, females, and combined groups.

2. Significant differences in performance were found between males and females.

3. Test-retest performance was related, but varied as a function of the measure used and subject sex.

The results of the present investigation argue strongly for a cautious interpretation of dichotic listening results. The distinction between male and female performance is clearly justified, but may be obscured by the method of analysis used. Test-retest performance is somewhat related, but variability is far too great to justify assessment on the basis of a single test. In addition, listener reliability varies as a function of the measure used and the sex of the listener. These results may be interpreted as evidence of the lability of an individual's response to dichotic stimulation. This interpretation seems particularly poignant when considered in conjunction with the many ambiguities and contradictions that exist within the literature. Not only do results differ from laboratory to laboratory, but within the same experimental setting as well. The practical implications of the incongruities demonstrated by this study and others are that performance on a dichotic listening task may be reflecting something more than the neural organization underlying central auditory processing. Were this not the case, it seems unlikely that variations of the magnitude reported here and elsewhere would exist. It is hypothesized, therefore, that one or more factors are contributing to performance on a dichotic listening task. Whether these factors are related to listening strategies, sex-linked differences, cultural biases, cognitive approaches to the task, or other variables affecting performance is not presently known. These investigations must yet be performed.

Degree Name

Speech-Language Pathology

Level of Degree

Masters

Department Name

Speech and Hearing Sciences

First Committee Member (Chair)

William John Ryan

Second Committee Member

Max McClellan

Third Committee Member

David Joe Draper

Fourth Committee Member

Richard Baxter Hood

Language

English

Document Type

Thesis

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