Serial control of phonology in speech production

Abstract

The aim of this thesis is to further our understanding of the processes which control the sequencing of phonemes as we speak: this is an example of what is commonly known as the serial order problem. Such a process is apparent in normal speech and also from the existence of a class of speech errors known as sound movement errors, where sounds are anticipated (spoken too soon), perseverated (repeated again later), or exchanged (the sounds are transposed). I argue that this process is temporally governed, that is, the serial ordering mechanism is restricted to processing sounds that are close together in time. This is in conflict with frame-based accounts (e.g. Dell, 1986; Lapointe & Dell, 1979), serial buffer accounts (Shattuck-Hufnagel, 1979) and associative chaining theories (Wickelgren, 1969). An analysis of sound movement errors from Harley and MacAndrew's (1995) corpus shows how temporal processing bears on the production of speech sounds by the temporal constraint observed in the pattern of errors, and I suggest an appropriate computational model of this process. Specifically, I show how parallel temporal processing in an oscillator-based model can account for the movement of sounds in speech. Similar predictions were made by the model to the pattern of movement errors actually observed in speech error corpora. This has been demonstrated without recourse to an assumption of frame and slot structures. The OSCillator-based Associative REcall (OSCAR) model, on the other hand, is able to account for these effects and other positional effects, providing support for a temporal based theory of serial control