Social and nonsocial synchrony are interrelated and romantically attractive

Romantic bonding is a crucial aspect of human life, yet the underlying mechanisms remain largely unknown. While physical attributes and resources influence attraction, recent research suggests that dynamic interactive features, such as synchrony, also play a significant role. Synchrony, the temporal matching of rhythms in physiology or behavior, has been observed across various domains and is consistently linked to social cooperation and satisfaction. However, the relationship between social and nonsocial synchrony, and whether individual differences in synchrony influence attractiveness, are open questions. This study aims to address these questions by examining whether experimentally manipulated synchrony influences attraction ratings and whether individual differences in social and nonsocial synchrony predict romantic attractiveness.

Existing literature demonstrates a strong correlation between physiological synchrony and romantic/sexual attraction. Studies have shown synchrony across various measures, including neural function, arousal, heart rate, hormones, and behavior. In addition to adult relationships, synchrony plays a vital role in parent-infant bonding and attachment. While social and nonsocial synchrony have been studied independently, the potential shared mechanisms and their connection to individual differences in attractiveness remain unexplored. Research suggests a link between sensorimotor synchronization (nonsocial) and social function, prompting the hypothesis that social interaction abilities stem from general sensorimotor integration processes.

The study employed two experiments: **Online Experiment:** 144 participants (76 women) aged 18-30 watched videos of actors interacting with either high or low synchrony (manipulated through directorial instructions). Participants then rated the actors' attractiveness and perceived attraction between them. Electrodermal activity (EDA) was measured to confirm synchrony levels in the videos. **Speed-Dating Experiment:** 48 participants (24 men, 24 women) aged 19-28 engaged in four 5-minute speed dates. EDA was measured using Empatica E4 wristbands. Participants rated their initial and post-date interest in each partner. Following the dates, participants completed a paced finger-tapping task to assess sensorimotor synchrony. Individual electrodermal synchrony scores, romantic attractiveness scores, and sensorimotor synchrony scores were calculated by averaging across dates or task blocks. Statistical analyses included repeated measures MANOVA for the online experiment, multilevel models and Bayesian analyses for examining the impact of initial interest on synchrony, and Pearson and Spearman correlations to assess the relationships between different synchrony measures and attractiveness.

**Online Experiment:** Inducing synchrony significantly increased attraction scores. Compared to the low-synchrony condition, the high-synchrony interaction increased both the attractiveness scores of the actors and the perceived attraction between them. **Speed-Dating Experiment:** * Individual scores of social and nonsocial synchrony were significantly correlated (Pearson r = 0.494, p = 0.008). * Individuals with higher electrodermal synchrony scores were rated as more attractive (Spearman r = 0.413, p = 0.005). * Initial interest did not significantly predict electrodermal synchrony during the date. The Bayesian analysis provided moderate support for the null hypothesis, indicating a non-reliable correlation. The study identified 'Super Synchronizers' – individuals who consistently demonstrate high synchrony regardless of the task or partner. These individuals were also rated as more attractive.

The findings support the hypothesis that synchrony plays a crucial role in eliciting romantic attraction. The positive correlation between social and nonsocial synchrony suggests a domain-general mechanism underlying the ability to synchronize, possibly related to anticipatory processes and learning. The attractiveness of Super Synchronizers further supports the importance of synchrony as an individual trait. The lack of correlation between initial interest and subsequent synchrony suggests that synchrony may elicit attraction rather than being a consequence of it. The results align with several possible mechanisms: improved physiological regulation in partners, better cue detection and adaptive interaction, and signaling of greater cognitive aptitude.

This research demonstrates a significant association between synchrony (both social and nonsocial) and romantic attractiveness. The identification of Super Synchronizers highlights the potential for synchrony as a stable individual trait. Future research should explore the longitudinal stability of synchrony, its underlying neural mechanisms, and its role in various relationship contexts, including homosexual relationships. Investigating causal effects of synchrony on romantic feelings and long-term relationship outcomes is also important.

The study's causal inferences are limited. While the experiments suggest that synchrony may elicit attraction, it does not definitively establish causality. Longitudinal studies are needed to determine the temporal stability of synchrony as a trait. The generalizability of findings is also limited to heterosexual participants; future research should include individuals from diverse sexual orientations. Furthermore, while the manipulation of synchrony in the online study was successful, the ecological validity of this method should be further investigated.