I. That two people genuinely present with each other show measurable physiological alignment

- Boukarras, S., et al. (2025). Interpersonal physiological synchrony during dyadic joint action is increased by task novelty and reduced by social anxiety. Psychophysiology. — Cardiac synchrony rises when a dyad attends to a shared challenge; social anxiety reduces it. - A systematic review and meta-analysis of interpersonal autonomic-nervous-system synchrony and its association with relationship and performance outcomes (Physiology & Behavior, 2021). [verify authors] — Synchrony is greater between friends than strangers in positive conditions; effects are real but heterogeneous. - Palumbo, R. V., et al. (2017). Interpersonal autonomic physiology: A systematic review of the literature. Personality and Social Psychology Review. [verify] — Foundational review of physiological "linkage" across relationships. - "Seeing each other matters: Visual contact enhances heart-rate-variability synchrony between interaction partners" (2026 preprint). [verify / preprint] — Mutual visual contact strengthens HRV synchrony. - Cardiac synchrony in parent–infant dyads during shared reading/play (SHER project; bioRxiv preprint). [verify / preprint] — Early relational synchrony and its enhancement through shared attention.