Synchrony as a measure of conversation difficulty: Movement coherence increases with background noise level and complexity in dyads and triads

Hadley, Lauren V and Ward, Jamie A. 2021. Synchrony as a measure of conversation difficulty: Movement coherence increases with background noise level and complexity in dyads and triads. PLoS ONE, 16(10), e0258247. ISSN 1932-6203 [Article]

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Abstract or Description

When people interact, they fall into synchrony. This synchrony has been demonstrated in a range of contexts, from walking or playing music together to holding a conversation, and has been linked to prosocial outcomes such as development of rapport and efficiency of cooperation. While the basis of synchrony remains unclear, several studies have found synchrony to increase when an interaction is made challenging, potentially providing a means of facilitating interaction. Here we focus on head movement during free conversation. As verbal information is obscured when conversing over background noise, we investigate whether synchrony is greater in high vs low levels of noise, as well as addressing the effect of background noise complexity. Participants held a series of conversations with unfamiliar interlocutors while seated in a lab, and the background noise level changed every 15-30s between 54, 60, 66, 72, and 78 dB. We report measures of head movement synchrony recorded via high-resolution motion tracking at the extreme noise levels (i.e., 54 vs 78 dB) in dyads (n=15) and triads (n=11). In both the dyads and the triads, we report increased movement coherence in high compared to low level speech-shaped noise. Furthermore, in triads we compare behaviour in speech-shaped noise vs multi-talker babble, and find greater movement coherence in the more complex babble condition. Key synchrony differences fall in the 0.2-0.5 Hz frequency bands, and are discussed in terms of their correspondence to talkers’ average utterance durations. Additional synchrony differences occur at higher frequencies in the triads only (i.e., >5 Hz), which may relate to synchrony of backchannel cues (as multiple individuals were listening and responding to the same talker). Not only do these studies replicate prior work indicating interlocutors’ increased reliance on behavioural synchrony as task difficulty increases, but they demonstrate these effects using multiple difficulty manipulations and across different sized interaction groups.

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Copyright: © 2021 Hadley, Ward. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: Dyad data is available as supplementary information here: Triad data is available in the Open Science Framework repository:

Funding: LVH was supported by the Medical Research Council [grant number MR/S003576/1]; the Chief Scientist Office of the Scottish Government; and a UKRI Future Leaders Fellowship [grant number MR/T041471/1]. JAW was funded by the Leverhulme Trust through a British Academy, Royal Academy of Engineering and Royal Society APEX award [grant number APX\R1\201093].


Synchrony; conversation; nonverbal behaviour; speech in noise; group size

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22 September 2021Accepted
5 October 2021Published

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Date Deposited:

04 Oct 2021 13:01

Last Modified:

16 Oct 2021 03:47

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Yes, this version has been peer-reviewed.


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