Internal speech functioning and speechreading in deafened and normal hearing adults.

The present study compared internal speech functioning in two groups of subjects: deafened and normal hearing adults. Internal speech functioning was assessed by means of either direct testing (i.e. rhyme-judgement tasks) or indirect testing (lexical access tests). No differences between the groups across tasks was obtained for speed. Neither was there any difference in accuracy level assessed by indirect tests. For direct testing the deafened group performed at a significantly lower level of accuracy. Accuracy was also correlated with the number of years that they had been deaf. It was concluded that one of the primary consequences of an acquired deafness is that the representational aspects of internal speech deteriorate over time, whereas the mechanical aspects remain relatively intact. Intercorrelations between accuracy level in direct testing and speechreading performance also suggest that speechreading ability declines. Clinical implications of the results are discussed.