The cognitive architecture of degraded speech intelligibility.

Accurate speech understanding is crucial in everyday life. Yet, speech is often degraded by a variety of talker and environmental factors, which listeners must overcome. In this online experiment, we assess how degraded speech intelligibility is supported by "elemental" cognitive processes. Eighty-nine healthy adults listened to spoken sentences degraded in five ways and reported the words that they heard. In addition, they completed the Reading Span and N-back tasks to assess working memory capacity (WM), as well as a short version of Raven's Advanced Progressive Matrices to assess fluid reasoning ability. In bivariate correlational analyses, all cognitive test scores predicted degraded speech intelligibility. However, multivariate and dominance analyses revealed that the test of fluid reasoning was the most important predictor of intelligibility. These results may undermine the assumption that WM, as measured by the Reading Span and other tasks, is the primary cognitive construct supporting degraded speech intelligibility.