The reliability of ear advantage and attentional capacity in dichotic listening
Date
1981
Authors
Clark, Campbell McGillivrary
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Abstract
The main theoretical assertion of the study was that neuropsychological research has concentrated primarily on the experimental model of enquiry. It was argued that due to the questions of interest and environmental constraints, the individual differences approach is probably more appropriate than the experimental approach for the development of neuropsychological theory. Therefore, a commonly used and accepted neuropsychological test, the dichotic listening task, was examined in terms of an individual differences model. The dichotic listening technique has been used extensively to infer speech dominance or more generally, cerebral asymmetries of function. Competing stimuli (eg., words) are presented simultaneously to each ear and the subject repeats what was presented. After a series of trials, the number of correct responses for the respective ears are counted and compared. If one ear is superior in performance, then it is argued that the contralateral hemisphere mediates that function (eg., language). With respect to the dichotic listening task, it was argued that the test may measure two aspects of cognitive processing, namely ear preference and attentional capacity. Moreover, it was shown that traditional measures of ear preference are confounded with overall accuracy or attentional capacity. The current study employed a measure of ear advantage which is independent of accuracy.
Second, the published papers concerning the reliability of dichotic listening tasks were reviewed. All of the reviewed studies used a confounded measure of ear preference while none of the studies examined all aspects of reliability or used experimental procedures consistent with the individual differences model. Therefore, the current study examined the internal consistency of dichotic items, the test/retest reliability of dichotic tapes and the parallel form reliability of two different dichotic tapes for the attentional capacity and ear preference variables. Sampling and experimental procedures were consistent with the individual differences approach. The test/retest period was one week. The findings suggest that both the attentional capacity and ear preference variables can be measured reliably. However, the absolute value of the attentional capacity is tape dependent and improves over time. The absolute value of the ear advantage variable did not change over tapes or sessions. In contrast to the experimental studies which suggest a right ear advantage is typical, the majority of subjects in the study did not exhibit an ear advantage. Finally, on the second session, a significant inverse relationship between ear preference and attentional capacity was found. Specifically, the greater ear advantage, the lower the attentional capacity. Such a finding may provide insight into changes in subject processing strategies. In conclusion, it was argued that the individual differences approach is necessary for development of a comprehensive theory of neuropsychology. By concentrating on findings from the experimental model, a rather biased model of brain processes has developed. For example, the results of the current study clearly contradict the assertion that most individuals do exhibit an ear advantage. Finally, the position was presented that only by closer examination of the statistical properties of the data set, can more generic theories be developed.