Lexical effects on spoken word recognition by pediatric cochlear implant users.

OBJECTIVE: The purposes of this study were 1) to examine the effect of lexical characteristics on the spoken word recognition performance of children who use a multichannel cochlear implant (CI), and 2) to compare their performance on lexically controlled word lists with their performance on a traditional test of word recognition, the PB-K.
DESIGN: In two different experiments, 14 to 19 pediatric CI users who demonstrated at least some open-set speech recognition served as subjects. Based on computational analyses, word lists were constructed to allow systematic examination of the effects of word frequency, lexical density (i.e., the number of phonemically similar words, or neighbors), and word length. The subjects' performance on these new tests and the PB-K also was compared.
RESULTS: The percentage of words correctly identified was significantly higher for lexically "easy" words (high frequency words with few neighbors) than for "hard" words (low frequency words with many neighbors), but there was no lexical effect on phoneme recognition scores. Word recognition performance was consistently higher on the lexically controlled lists than on the PB-K. In addition, word recognition was better for multisyllabic than for momosyllabic stimuli.
CONCLUSIONS: These results demonstrate that pediatric cochlear implant users are sensitive to the acoustic-phonetic similarities among words, that they organize words into similarity neighborhoods in long-term memory, and they use this structural information in recognizing isolated words. The results further suggest that the PB-K underestimates these subjects' spoken words recognition.