Abstract
Models of speech production typically assume that control over the timing of speech movements is governed by the selection of higher-level linguistic units, such as segments or syllables. This study used real-time magnetic resonance imaging of the vocal tract to investigate the anticipatory movements speakers make prior to producing a vocal response. Two factors were varied: preparation (whether or not speakers had foreknowledge of the target response) and pre-response constraint (whether or not speakers were required to maintain a specific vocal tract posture prior to the response). In prepared responses, many speakers were observed to produce pre-response anticipatory movements with a variety of articulators, showing that that speech movements can be readily dissociated from higher-level linguistic units. Substantial variation was observed across speakers with regard to the articulators used for anticipatory posturing and the contexts in which anticipatory movements occurred. The findings of this study have important consequences for models of speech production and for our understanding of the normal range of variation in anticipatory speech behaviors.
Highlights
When we speak, we control the selection and execution of numerous articulatory movements
Pre-speech anticipatory posturing effects were observed minimally 300–500 ms prior to response initiation, which implies that pre-speech anticipatory movements occurred quite early relative to their associated targets. Taken together these results indicate that anticipatory movements dissociations are more closely associated with long-distance coarticulation than with local gestural overlap, and this entails that production models need two mechanisms for generating coarticulation: one that arises from temporally overlapping articulations, and one that arises from coactivation of motor plans
The main finding of the current study is that individual speech movements associated with a given linguistic unit can be produced well in advance of other movements associated with the same unit
Summary
We control the selection and execution of numerous articulatory movements. Current models of speech production assume that movement initiation is organized by higherlevel linguistic units, such as segments and/or syllables [1,2,3]. Recent studies suggest that speech movements associated with the same segment or syllable can be dissociated from each other [4,5]. This phenomenon may be prevalent immediately prior to the beginnings of utterances, when speakers can anticipate upcoming motor plans and are maintaining those plans in working memory. Little is currently known about the contexts in which pre-speech anticipatory movements can occur, as well as the vocal organs that may be PLOS ONE | DOI:10.1371/journal.pone.0146813. Little is currently known about the contexts in which pre-speech anticipatory movements can occur, as well as the vocal organs that may be PLOS ONE | DOI:10.1371/journal.pone.0146813 January 13, 2016
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