Effects of Stimulus Type and Response Condition

Dichotic listening refers to a binaural competing auditory recognition task in which listeners are asked to identify one or both stimuli. Most listeners exhibit a right ear advantage (REA) in which they can better identify stimuli presented to the right ear than the left ear. Dichotic speech recognition is included in test batteries assessing auditory processing in both children and adults. Recognition performance on dichotic listening tasks, however, varies according to the stimulus type, response condition and age of the listener. Determination of normal versus abnormal performance on a dichotic listening task is therefore dependent upon how it was measured and in what population. The purpose of the present study was to measure dichotic speech recognition using four common stimulus types and three common response conditions in the same group of listeners. Two groups participated: ten young adults with normal hearing (21-22 years) and seven older adults with bilateral sensorineural hearing loss (67-80 years). Four types of speech stimuli were used: (1) consonant-vowel syllables (CVs), (2) sentences, (3) digits, and (4) monosyllabic words. For each task listeners were asked to respond under three response conditions: (1) free recall, (2) directed-right, and (3) directed-left. Results revealed that the young adults exhibited smaller REA‟s and better overall performance on all stimulus types relative to older adults. Poorer overall performance for older adults is unsurprising given the presence of hearing loss; however, larger REA‟s likely reflect age-related deficits in auditory processing. In addition, recognition performance varied substantially across stimulus types for both age groups. Both young and older adults performed best for sentences and poorest for CV‟s. By measuring dichotic speech recognition across stimulus types in the same group of subjects, this study may prov