MEASURES OF AUDITORY-VISUAL INTEGRATION IN NONSENSE SYLLABLES AND SENTENCES

For all but the most profoundly hearing-impaired (HI) individuals, aud itory-visual (AV) speech has been shown consistently to afford more ac curate recognition than auditory (A) or visual (V) speech. However, th e amount of AV benefit achieved (i.e., the superiority of AV performan ce in relation to unimodal performance) can differ widely across HI in dividuals. To begin to explain these individual differences, several f actors need to be considered. The most obvious of these are deficient A and V speech recognition skills. However, large differences in indiv iduals' AV recognition scores persist even when unimodal skill levels are taken into account. These remaining differences might be attributa ble to differing efficiency in the operation of a perceptual process t hat integrates A and V speech information. There is at present no acce pted measure of the putative integration process. In this study, sever al possible integration measures are compared using both congruent and discrepant AV nonsense syllable and sentence recognition tasks. Corre lations were tested among the integration measures, and between each i ntegration measure and independent measures of AV benefit for nonsense syllables and sentences in noise. Integration measures derived from t ests using nonsense syllables were significantly correlated with each other; on these measures, HI subjects show generally high levels of in tegration ability. Integration measures derived from sentence recognit ion tests were also significantly correlated with each other, but were not significantly correlated with the measures derived from nonsense syllable tests. Similarly, the measures of AV benefit based on nonsens e syllable recognition tests were found not to be significantly correl ated with the benefit measures based on tests involving sentence mater ials. Finally, there were significant correlations between AV integrat ion and benefit measures derived from the same class of speech materia ls, but nonsignificant correlations between integration and benefit me asures derived from different classes of materials. These results sugg est that the perceptual processes underlying AV benefit and the integr ation of A and V speech information might not operate in the same way on nonsense syllable and sentence input. [S0001-4966(98)03510-3].