Introduction: Interpersonal synchrony is a phenomenon occurring across a range of physiological processes during social interactions. While synchrony has been linked to various interpersonal and performance aspects, the mechanisms by which synchrony is established remain predominantly unclear. Our main aim of this study was to explore the impact of the visual system on physiological synchrony. We also incorporated a lie detection task as a performance measure into the study design. Methods: N=35 participants conducted the experiment in two different dyadic constellations. They completed two lie detection sequences per dyad, once while being able to see each other (VISION condition) and once while being separated by an opaque barrier (NO VISION condition). Heart rate variability (HRV) was recorded continuously and subsequently transformed to cross-wavelet power values for synchrony analysis for four distinct frequency ranges (0.5-0.25, 0.25-0.13, 0.13-0.06, 0.06-0.04 Hz). Results: Physiological synchrony was higher in the VISION than in the NO VISION condition for three of the four examined frequency ranges (0.5-0.25, 0.25-0.13, 0.13-0.06 Hz). No association could be established for the lowest frequency range (0.06-0.04 Hz). Lie detection did not differ significantly between the two conditions and on its own did not have a significant main effect on synchrony. In one frequency range a positive interaction between lie detection and condition emerged (0.25-0.13 Hz). Discussion: Results clearly demonstrate that the visual system plays a role in establishing physiological synchronisation. While no relation of lie detection with condition and synchrony on their own could be found, an interplay between lie detection and visual information on physiological synchrony could be observed in one frequency range. Our findings add to the literature describing physiological synchrony as a multifaceted phenomenon.

Interpersonal HRV synchrony is increasingly used as a marker of social connectedness, but whether frequency-specific dynamics exist has not been studied systematically. In fifty dyads (N = 100; mean age = 23.5 years, SD age = 5.43), we recorded continuous heart rates using two-channel ECG sensors across periods of social interaction and separation. Synchrony was quantified using cross-wavelet power (CWP) and decomposed into four frequency bands (2-4, 4-8, 8-16, and 16-24 seconds per cycle). Synchrony was lowest during separation, increased sharply upon a first encounter, and was strongest during social interactive phases. Coupling was greater in lower than higher frequencies, with high frequency (2-4 s) synchrony peaking at first encounter and declining thereafter, while lower frequency synchrony increased progressively across co-presence and interaction. Mean heart rate and high-frequency-HRV power positively predicted synchrony, while maximum heart rate predicted lower synchrony. These results suggest that interpersonal HRV synchrony is a phenomenon that changes dynamically across different frequency bands and time, with higher and lower frequency components exhibiting different sensitivities to social context. We suggest that CWP analysis can advance HRV research beyond the traditional low- and high-frequency dichotomy by revealing frequency-specific patterns of interpersonal autonomic coupling during social interactions.

While physiological stress responses have been well investigated in individuals, the effects of stress on interpersonal physiological processes have been studied less frequently. In the current study, we focused on how stress affects physiological synchrony (PS) – i.e., the alignment of physiological changes across individuals – an established phenomenon characterizing social interactions. We hypothesized that PS, specifically cardiac PS, would be altered in romantic couples if one of the partners was exposed to a standardized stressor. In a preregistered study, N = 75 couples (mean age = 22.66 ±2.99, 51% female) were separated upon arrival in the laboratory. In n = 38 dyads, one partner was exposed to a laboratory stressor while the other completed a non-stressful control task (stress dyads), in the other dyads both partners underwent the control paradigm (control dyads). Afterward, partners were reunited, completing a non-verbal synchronization, a walking, and a free interaction task. Partners rated their own and each others’ affect throughout the experiment. Compared to a non-interactive baseline, PS increased during the partners’ interaction. Cardiac synchrony related to parasympathetic nervous system (PNS) activity was lower in stress compared to control dyads. Further, participants were more accurate in estimating their partner’s emotional valence if their partner was non-stressed. Our findings indicate the disruption of especially PNS-related PS. This highlights that stress is not only an intra- but also interpersonal phenomenon whose effects on the interpersonal physiology of social interactions should be further investigated.