Psychological and Brain Sciences Brown Bag Seminar: Joe Toscano, Villanova University
Going Forward, Looking Back: Sensitivity to Bottom-Up Input and Top-Down Information during Speech Processing
Joe Toscano, Ph.D., Assistant Professor, Department of Psychology, Villanova University
Abstract: Debates about the nature of human listeners' ability to recognize speech have centered on (1) their sensitivity to bottom-up differences in the speech signal (e.g. whether speech sounds are categorically perceived or not) and (2) whether these processes are influenced by top-down information (e.g. via predictive coding or through other types of feedback). However, these debates have proven difficult to resolve. I will argue for a way forward to resolve these debates and, more importantly, to address new questions about the processes involved in spoken word recognition. That way forward is to take a more nuanced look at the earliest stages of perceptual processing, in real time, during spoken language comprehension. In particular, I will present work that uses the event-related brain potential (ERP) technique and fast diffuse optical imaging to investigate online processing of speech sounds and spoken words. These experiments allow us to address questions about the nature of early perceptual representations for speech and how they interact with higher-level language processing. Results from these experiments reveal that top-down lexical information feeds back to influence early speech perception, that listeners rapidly integrate the incoming speech stream with higher-level linguistic representations, and that representations spanning multiple levels of linguistic organization are active simultaneously. Overall, the results suggest a radical rethinking of the processes involved in language comprehension, requiring us to develop models that are more flexible in the representations used to process spoken language.