Emotional Contagion

The tendency to automatically mimic and synchronize facial expressions, vocalizations, postures, and movements with that of another person and, consequently, to converge emotionally. An emotion process involving nonverbal communication that in part, explains empathy. See also susceptibility to emotional contagion.

Reference:

Hatfield, E., Cacioppo, J. & Rapson, R.L. (1992). Emotional contagion. In Clark, M.S. (Ed.), Review of personality and social psychology: Vol. 14. Emotion and Social Behavior. Newbury Park, CA: Sage.