Objectives: The purpose of this study is to identify factors predictive of successful English language outcomes in adolescents who received a cochlear implant (CI) between 2 and 5 yrs of age.
Design: All 112 participants had been part of a previous study examining English language outcomes at the age of 8 and 9 yrs with CIs. The participants were given a battery of language and verbal reasoning tests in their preferred communication mode along with measures of working memory (digit span) and verbal rehearsal speed (sentence repetition duration). The degree to which students' language performance was enhanced when sign was added to spoken language was estimated at both test sessions. Multiple linear regression analyses were used to document factors contributing to overall language outcomes.
Results: A substantial proportion of the adolescents obtained test scores within or above 1SD compared with hearing age-mates in the tests' normative samples: 71% on a verbal intelligence test, 68% on a measure of language content, 71% on receptive vocabulary, and 74% on expressive vocabulary. Improvement in verbal intelligence scores over an 8-yr interval exceeded expectation based on age-mates in the test's normative sample. Better English language outcomes were associated with shorter duration of deafness before cochlear implantation, higher nonverbal intelligence, higher family socioeconomic status, longer digit spans, and faster verbal rehearsal speed as measured by sentence repetition rate. Students whose current receptive vocabulary scores were not enhanced by the addition of signs also exhibited higher English language scores than those without sign enhancement; however, sign enhancement demonstrated in the elementary school years was not predictive of later high-school language skills.
Conclusions: Results of this study support the provision of CIs to children at the youngest age possible. In addition, it highlights the substantial role that cognition plays in later language outcomes. Although the students' use of sign to enhance language skills during the elementary years does not appear to have a negative impact on later language skills, students who continue to rely on sign to improve their vocabulary comprehension into high school typically exhibit poorer English language outcomes than students whose spoken language comprehension parallels or exceeds their comprehension of speech + sign. Overall, the language results obtained from these teenagers with more than 10 yrs of CI experience reflect substantial improvement over the verbal skills exhibited by adolescents with similar levels of hearing loss before the advent of CIs. These optimistic results were observed in teenagers who were among the first in the United States and Canada to receive a CI. We anticipate that the use of improved technology that is being initiated at even younger ages should lead to age-appropriate language levels in an even larger proportion of children with CIs.