Involvement of the speech production system in prediction during comprehension: an articulatory imaging investigation
Drake, Eleanor Katherine Elizabeth
This thesis investigates the effects in speech production of prediction during speech comprehension. The topic is raised by recent theoretical models of speech comprehension, which suggest a more integrated role for speech production and comprehension mechanisms than has previously been posited. The thesis is specifically concerned with the suggestion that during speech comprehension upcoming input is simulated with reference to the listener’s own speech production system by way of efference copy. Throughout this thesis the approach taken is to investigate whether representations elicited during comprehension impact speech production. The representations of interest are those generated endogenously by the listener during prediction of upcoming input. We investigate whether predictions are represented at a form level within the listener’s speech production system. We first present an overview of the relevant literature. We then present details of a picture word interference study undertaken to confirm that the item set employed elicits typical phonological effects within a conventional paradigm in which the competing representation is perceptually available. The main body of the thesis presents evidence concerning the nature of representations arising during prediction, specifically their effect on speech output. We first present evidence from picture naming vocal response latencies. We then complement and extend this with evidence from articulatory imaging, allowing an examination of pre-acoustic aspects of speech production. To investigate effects on speech production as a dynamic motor-activity we employ the Delta method, developed to quantify articulatory variability from EPG and ultrasound recordings. We apply this technique to ultrasound data acquired during mid-sagittal imaging of the tongue and extend the approach to allow us to explore the time-course of articulation during the acoustic response latency period. We investigate whether prediction of another’s speech evokes articulatorily specified activation within the listener’s speech production system The findings presented in this thesis suggest that representations evoked as predictions during speech comprehension do affect speech motor output. However, we found no evidence to suggest that predictions are represented in an articulatorily specified manner. We discuss this conclusion with reference to models of speech production-perception that implicate efference copies in the generation of predictions during speech comprehension.
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