Phonetic context effects in adult listeners with cochlear implants

Abstract

From previous studies it is known that normal-hearing (NH) listeners have the ability to compensate for the acoustic variability present in speech through context-dependent perception of speech sounds. One question of practical and theoretical interest is whether listeners with cochlear implants (CI) also show context-dependent speech perception. Because of the lack of spectral resolution in the input, the representation of speech for CI listeners may differ from NH listeners, which may interfere with perceptual compensation. In a test of this prediction, adult postlingually deafened CI listeners did not demonstrate the contrastive context effects elicited from NH listeners for either /da/–/ga/ targets and /al/–/ar/ contexts or V targets and /b—b/–/d—d/ contexts. In contrast, as predicted by the good temporal resolution of the CI signal, CI listeners showed normal effects of vowel length on preceding glide-stop categorization. CI simulations with NH listeners were also performed for some of these context effects. The results support the view that spectral content of contexts largely determines their effect on target sounds, and that phonetic content does not play an essential role. In addition, the findings predict that CI listeners will have particular difficulty with heavily coarticulated speech. [Work sponsored by NIH and NSF.]