Modeling spoken word recognition performance by pediatric cochlear implant users using feature identification

Abstract

Objective: Computational simulations were carried out to evaluate the appropriateness of several psycholinguistic theories of spoken word recognition for children who use cochlear implants. These models also investigate the interrelations of commonly used measures of closed-set and open-set tests of speech perception.

Design: A software simulation of phoneme recognition performance was developed that uses feature identification scores as input. Two simulations of lexical access were developed. In one, early phoneme decisions are used in a lexical search to find the best matching candidate. In the second, phoneme decisions are made only when lexical access occurs. Simulated phoneme and word identification performance was then applied to behavioral data from the Phonetically Balanced Kindergarten test and Lexical Neighborhood Test of open-set word recognition. Simulations of performance were evaluated for children with prelingual sensorineural hearing loss who use cochlear implants with the MPEAK or SPEAK coding strategies.

Results: Open-set word recognition performance can be successfully predicted using feature identification scores. In addition, we observed no qualitative differences in performance between children using MPEAK and SPEAK, suggesting that both groups of children process spoken words similarly despite differences in input. Word recognition ability was best predicted in the model in which phoneme decisions were delayed until lexical access.

Conclusions: Closed-set feature identification and open-set word recognition focus on different, but related, levels of language processing. Additional insight for clinical intervention may be achieved by collecting both types of data. The most successful model of performance is consistent with current psycholinguistic theories of spoken word recognition. Thus it appears that the cognitive process of spoken word recognition is fundamentally the same for pediatric cochlear implant users and children and adults with normal hearing.

Figure 1

Comparison of word (top panel) and phoneme (bottom panel) performance on the LNT easy word list. The MPEAK users are shown on the left; the SPEAK users are shown on the right. Error bars indicate a 95% confidence interval for the mean.

Figure 2

Comparison of word (top panel) and phoneme (bottom panel) performance on the LNT hard word list. The MPEAK users are shown on the left; the SPEAK users are shown on the right. Error bars indicate a 95% confidence interval for the mean.

Figure 3

Comparison of word (top panel) and phoneme (bottom panel) performance on the PBK. The MPEAK users are shown on the left; the SPEAK users are shown on the right. Error bars indicate a 95% confidence interval for the mean.