Psychology
You unconsciously copy the body language of whoever you're talking to
Tanya Chartrand and John Bargh had participants chat with a partner (actually a researcher) who deliberately rubbed their face or shook their foot during the conversation. Participants mirrored these exact mannerisms without noticing, and rated the interactions as smoother when their partner had mimicked them back. We unconsciously copy posture, gestures and expressions as a kind of social glue.