Emotion(al) Contagion is the automatic mirroring of motor and expressive and physiological aspects of other’s expressions, usually considered in the domain of infants’ smiles, laughter, cries, etc..
a.k.a. affective sharing
a.k.a. vicarious emotional arousal
Decety J., & Meyer, M. (2008). From emotion resonance to empathic understanding: A social developmental neuroscience account. Development and Psychopathology 20, 1053-1080. doi:10.1017/S0954579408000503