backchannelling (n.)

A term used in PRAGMATICS and SOCIOLINGUISTICS, as part of the study of listener behavior in an INTERACTION, referring to the reactions given to a speaker by way of FEEDBACK. They include monosyllabic responses (mhm), short phrases (I guess so), utterance repetitions and sentence completions, as well as non-verbal cues (e.g. nodding, gaze variation).