Gesture, Prosody and Information Structure Synchronisation in Turkish
Authors:   , Turk Olcay 
Published: December 2021

<p>This thesis investigates the synchronisation of gesture with prosody and information structure in Turkish. Speech and gesture have a close relationship in human communication, and they are tightly coordinated in production. Research has shown that gestural units are synchronised with prosodic units on a prominence-related micro level (i.e., pitch accents and gesture apexes), however these studies have largely been on a small number of languages of a similar prosodic type, not including Turkish, which has prominence-less prosodic words. It is known that both gesture and speech, through prosody, are hierarchically structured with nested phrasal constituents, but little is known about gesture-prosody synchronisation at this macro level. Even less is known about the timing relationships of gesture with information structure, which is also closely related to prosody. This thesis links gesture to information structure as a part of a three-way synchronisation relationship of gesture, prosody, and information structure.  Four participants were filmed in a narrative task, resulting in three hours of Turkish natural speech and gesture data. Selected sections were annotated for prosody using an adapted scheme for Turkish in the Autosegmental-Metrical framework, for information structure and for gesture. In total, there were over 20,000 annotations.  The synchronisation of gesture and speech units was systematically investigated at (1) the micro level, and (2) the macro level. At the micro level, this thesis asked which tones apexes are synchronised with, and whether this synchronisation depends on other prosodic and gestural features. It was found that gesture apexes were synchronised with pitch accents if there were pitch accents in the relevant prosodic phrases; if not, they were synchronised with low tones that marked the onsets of prosodic words. This synchronisation pattern was largely consistent across different prosodic and gestural contexts, although it was tighter in the nuclear area. These findings confirm prominence as a constraint on synchronisation with evidence of pitch accent-apex synchronisation. The findings also extend our knowledge of the typology of micro-level synchronisation to cases where prominence is locally absent showing that micro-level synchronisation also obeys the prosodic hierarchy.  At the macro level, the aim was to find the prosodic anchor for single gesture phrases while testing for the possible effects of prosodic, gestural and information structural contexts. The findings showed that there was no one-to-one synchronisation of single gesture phrases with single intermediate or intonational phrases. However, it was found that gesture phrases often spanned over multiple consecutive intermediate phrases, and the synchronisation of gesture phrase boundaries was with the boundaries of these intermediate phrase groupings. In addition, these groupings tended to be combinations of pre-nuclear and nuclear intermediate phrases constituting the default focus position in Turkish. This synchronisation behaviour over the focal domain implied that there might be another speech element governing the speech-gesture synchronisation which also informs prosody, i.e. information structure.  Based on this finding and a few other associations in the earlier studies, it was hypothesised that gesture is also informed by and synchronised with information structure. In order to test this hypothesis, it was investigated whether gesture phrases were synchronised with information structural units, i.e., topics, foci and background. The findings showed that gesture phrases tended to accompany discursively prominent foci over topics and background. However, gesture phrases did not show perfect synchronisation with any of these information structure units, although there was a systematic overlap in which foci and topics were contained within the duration of complete gesture phrases. Further investigations revealed that gesture phrase parts that bear apex related meaning provided a much better anchor for the synchronisation of information structure units. The preference for accompanying and synchronisation with the parts of gesture bearing gesturally prominent apical meaning also highlighted that prominence is a driving factor of synchronisation at the macro level as well as at the micro level.  This thesis has revealed pivotal links between gesture, prosody and information structure through a systematic investigation of synchronisation of these structures. The implications of these links have also been discussed within the thesis, and a model of speech and gesture production integrating synchronisation has been proposed. Overall, the thesis contributes to a deeper understanding of speech and gesture production, explaining how these interact during natural speech.</p>