Interpersonal coordination of body movement, psychological state, and identity referential processing

Abstract

Interpersonal coordination is universally observed in human activities. It occurs via diverse communication media such as motion, emotion and speech, and it is constrained by individual characteristics and social factors. This thesis consists of three studies to investigate how people coordinate bodily movements, mental states and perceptual processes. In Study 1 (Chapter 2), a real-world task was employed to study whether individual permanent traits and social impressions shaped walking synchrony. Participants were paired up to walk and chat in a natural environment, while their steps were recorded by motion sensors attached above ankles. The walking step synchrony was calculated among paired walkers. We found evidence of modulation in step synchronization from age, gender, and autistic traits in pairs who met for the first time. Although the effect varied across contexts, female pairs, and pairs of higher age and of lower autistic tendency, exhibited a higher synchronization ratio than male pairs, and pairs of lower age and of higher autistic tendency. A higher first impression rating between a pair led to a significantly higher step synchronization, and the pairs of higher walking synchronization enjoyed slightly greater social benefits than pairs of lower walking synchrony. Our results indicate that walking synchrony is a form of social communication. In Study 2 (Chapter 3), we investigated behavioral and neural correlates of shared mental state in interpersonal flow. Flow is an optimal experience while one fully indulges in an activity while feeling pleasurable and achieving peak performance (“in the zone”). Shared flow experience is often observed in group activities. However, the dynamics between members in interpersonal flow is rarely explored. A hyperscanning EEG paradigm using a dual-player music game was developed to evoke interpersonal flow. In addition to subjective reports, we used suppressed neural response to irrelevant auditory stimulus as an objective index to quantify flow. Compared with non-flow and non-interpersonal conditions, interpersonal flow evoked inter-brain functional connectivity between areas of sensory processing, attentional control, emotion and self-referential processing, indicating shared cognitive and emotional states between two players. In Study 3 (Chapter 4), we explored how perception of self and other was altered by social interaction. Neutral information enjoys beneficial processing when associated with self or significant others. The role of social context in identity-referential saliency is rarely studied. We investigated whether a newly met partner received a processing advantage in joint perceptual matching tasks. The partner was co-acting the task together with participants (Experiment 1), or physically present without verbal communication (Experiment 2), or absent (Experiment 3). Intriguingly, trials related to a partner were responded to more accurately and more quickly than those related to a stranger except in Experiment 3. Overall, referential saliency toward a newly met partner could be quickly established without prior familiarity, and physical presence was a critical contributor. The study demonstrated that social interaction evoked coordination of perception and created saliency toward others’ identity. In sum, this thesis expands a comprehensive perspective on how people coordinate behaviorally and neurally in multiple activities, and provides insights on ecological methodology for interpersonal coordination research.