Background: Verbally based dichotic-listening experiments and reproduction-mediated response-selection
strategies have been used for over four decades to study perceptual/cognitive aspects
of auditory information processing and make inferences about hemispheric asymmetries
and language lateralization in the brain. Test procedures using dichotic digits have
also been used to assess for disorders of auditory processing. However, with this
application, limitations exist and paradigms need to be developed to improve specificity
of the diagnosis. Use of matched tasks in multiple sensory modalities is a logical
approach to address this issue. Herein, we use dichotic listening and dichoptic viewing
of visually presented digits for making this comparison.
Purpose: To evaluate methodological issues involved in using matched tasks of dichotic listening
and dichoptic viewing in normal adults.
Research Design: A multivariate assessment of the effects of modality (auditory vs. visual), digit-span length (1–3 pairs), response selection (recognition vs. reproduction), and ear/visual hemifield of presentation (left vs. right) on dichotic
and dichoptic digit perception.
Study Sample: Thirty adults (12 males, 18 females) ranging in age from 18 to 30 yr with normal
hearing sensitivity and normal or corrected-to-normal visual acuity.
Data Collection and Analysis: A computerized, custom-designed program was used for all data collection and analysis.
A four-way repeated measures analysis of variance (ANOVA) evaluated the effects of
modality, digit-span length, response selection, and ear/visual field of presentation.
Results: The ANOVA revealed that performances on dichotic listening and dichoptic viewing
tasks were dependent on complex interactions between modality, digit-span length,
response selection, and ear/visual hemifield of presentation. Correlation analysis
suggested a common effect on overall accuracy of performance but isolated only an
auditory factor for a laterality index.
Conclusions: The variables used in this experiment affected performances in the auditory modality
to a greater extent than in the visual modality. The right-ear advantage observed
in the dichotic-digits task was most evident when reproduction mediated response selection
was used in conjunction with three-digit pairs. This effect implies that factors such
as “speech related output mechanisms” and digit-span length (working memory) contribute
to laterality effects in dichotic listening performance with traditional paradigms.
Thus, the use of multiple-digit pairs to avoid ceiling effects and the application
of verbal reproduction as a means of response selection may accentuate the role of
nonperceptual factors in performance. Ideally, tests of perceptual abilities should
be relatively free of such effects.
Key Words
Auditory processing disorder - speech perception
