Long-term effects of congenital hearing impairment on language performance in adults

Aim
The aim of this study was to examine long-term effects of moderate to severe congenital hearing impairment (MSCHI) at an age when language development is completed, i.e., in adults.

Method
We studied language performance in Dutch in 10 normal-hearing (NH) adults and 20 adults with MSCHI, using analysis of elicited language samples on morphosyntactic correctness and syntactic complexity.

Results
The data show long-term effects of MSCHI in the domain of morphosyntax: MSCHI may lead to a persisting lower level of mastery of the determiner use constraint and a lower level of performance in using bound morphemes and adverbs, compared to NH adults. In the MSCHI group, morphosyntactic correctness is related to degree of congenital hearing impairment, and not to age. For syntactic complexity, no group differences were found.

Conclusion
The study results give a language-specific description of aspects at risk when language is acquired with an inferior auditory input. MSCHI especially may lead to problems in the use of low salient bound and free morphemes, as well as to problems with aspects of the language that are relatively complex. Thus, the consequences of MSCHI may remain after language development is completed.