The Control of Serial Order in Speech Production (Syllable, Motor Rhythm).

Abstract

This dissertation concerns the manner in which speech segments are produced in an appropriate serial order. The ordering of segments is a classic issue, both in the study of speech production and behavior more generally. The issue arises because the elementary segments of behavior lack an intrinsic order. The models that have been advanced to account for speech production can be categorized into three groups depending on how they h and le the issue of serial order. These groups are hierarchical coding, element-to-position coding, and element-to-element coding. Two experiments are reported that attempt to test which of the above three coding systems is used to control the ordering of syllables in speech production. The experiments employed a modified choice reaction time procedure in which a subject had to produce one of two polysyllabic utterances on comm and . Three measures of performance on the utterance were used: latency, duration and accuracy. The subject was instructed to prepare to say one of the utterances, but had to occasionally switch and say the other utterance, depending on which of two response-signals occurred. Performance on the produced utterance was studied as a function of its relationship, in terms of syllable order, to the prepared utterance. By observing how the ordering relations between the two utterances influenced ease of performance, I drew inferences about how syllable order is controlled. The principle finding of the experiments is that switching utterances is easiest when the two utterances share pairings of syllables (e.g., BEE BAY BAH BOO and BAH BOO BEE BAY). Overlap of this kinds leads to shorter reaction times, shorter durations and fewer errors than overlap in terms of shared syllable positions (e.g., BEE BAY BAH BOO and BAH BAY BEE BOO), shared syllable-to-syllable associations (e.g., BEE BAY BAH BOO and BAY BAH BOO BEE), or no overlap at all (BEE BAY BAH BOO and BAH BEE BOO BAY). These results indicate that at some phase of speech production, hierarchical processes are used to control syllable order. The discussion of these results explores the possibility that the hierarchical structure controlling syllable order is related to the rhythmic organization of speech. In addition, factors influencing the control of serial order at different levels of speech are outlined.