Individual Differences in Effectiveness of Cochlear Implants in Prelingually Deaf Children: Some New Process Measures of Performance

The “efficacy” of cochlear implants in deaf children has been firmly established in the literature. However, the “effectiveness” of cochlear implants varies widely and is influenced by demographic and experiential factors. Several “key” findings suggest new directions for research on central auditory factors that underlie the effectiveness of cochlear implants. First, there are enormous individual differences in both adults and children on audiological outcome measures. Some patients show large increases in speech perception scores after implantation whereas others display only modest gains on standardized tests. Second, age of implantation and length of deafness affect all outcome measures. Children implanted at younger ages do better than children implanted at older ages and children who have been deaf for shorter periods of time do better than children who have been deaf for longer periods of time. Third, communication mode affects outcome measures. Children from “oral-only” environments do much better on standardized tests that assess phonological processing skills than children who use “total communication.” Fourth, there are no preimplant predictors of outcome performance in young children. The underlying perceptual, cognitive and linguistic abilities and skills “emerge” after implantation and improve over time. Finally, there are no significant differences in audiological outcome measures among current implant devices or processing strategies. Taken together, this overall pattern of results suggests that higher-level central cognitive processes such as perception, attention, learning and memory may play important roles in explaining the enormous individual differences observed among users of cochlear implants. Investigations of the content and flow of information in the central nervous system and interactions between sensory input and stored knowledge may provide new insights into individual differences. Knowledge about the underlying basis of individual differences may also help in developing new intervention strategies to improve the effectiveness of cochlear implants in children who show relatively poor development of oral/aural language skills.