2015 How speech rate shapes perception

Speech can be delivered at different rates and, as a consequence, listeners have to normalize the incoming speech signal for the rate at which it was produced. This perceptual process, known as rate normalization, is contrastive in nature: for instance, the perception of an ambiguous Dutch vowel in between short /ɑ/ and long /a:/ is biased towards hearing long /a:/ when preceded by a fast sentence context.

Rate normalization has (primarily) been explained in terms of durational contrast: the ambiguous vowel is perceived as longer because it has a relatively long duration compared to the preceding shorter vowels in the fast context. In this presentation, novel experimental data will be presented that challenge this account of durational contrast by (1) demonstrating that it is the contextual rate, not duration, that elicits rate normalization; and (2) suggesting that vowel categorization is sensitive to the phase of the contextual rhythm.

In order to explain these new findings, a neurobiologically plausible account of rate normalization is proposed involving neural entrainment of endogenous brain oscillations to the speech rate of the spoken signal.