Paying attention to speaking rate

Variability in speaking rate results in a many-to-many mapping between acoustic properties in speech and the linguistic interpretation of an utterance. In order to recognize the phonetic structure of an utterance, listeners must calibrate their phonetic decisions against the rate at which the speech was produced. This process of rate normalization is fast and effective allowing listeners to maintain phonetic constancy in spite of changes in speaking rate. Most of the research on rate normalization has investigated the sources of information used by listeners to determine the speaking rate. There is an assumption in much of this research that the normalization process is a passive, automatized filtering process that strips the effects of rate variation away from the signal prior to recognition. The study starts from a different perspective by assuming that speech perception is carried out by an active perceptual process that is specifically needed to address the lack of invariance problem (Nusbaum and Henly). This perspective predicts that increased variability from any source, including rate variability, should increase the cognitive load during speech perception. The results support this prediction.