Word recognition and phonetic perception by adult cochlear implant users: An examination of /d/–/t/

Abstract

Speech perception by cochlear implant users is marked by large individual differences in word recognition accuracy. The aim of the present study was to examine whether these individual differences in speech understanding are correlated with measures of phonetic sensitivity and categorization. Thirty adult post-lingually deafened cochlear implant patients, who were heterogeneous in terms of their implants and processing strategies, were tested in four experiments. Experiments 1 and 2 tested open-set word recognition and forced-choice consonant recognition for words and syllables spoken by ten different talkers. Experiments 3 and 4 tested forced-choice phoneme identification and discrimination along a synthetic /d/–/t/ continuum. The results demonstrated that open-set word recognition accuracy was highly correlated with the location of sensitivity peaks along the /d/–/t/ continuum; word recognition accuracy was higher for cochlear implant users who had sensitivity peaks near the typical /d/–/t/ category boundary location of normal-hearing individuals. In contrast, word recognition accuracy was unrelated to mean levels of discrimination performance or to measures of phoneme identification. The results suggest that at least some aspects of the common phonetic perceptual phenomena found in normal-hearing listeners have a functional role in speech understanding via cochlear implants.