An ELT Glossary : Backchannel language

Definition : The verbal signals given by a listener to indicate attention, surprise, interest etc but without the intention of "taking over" or participating equally in the discourse.  
Examples : "Really?" "Uh-huh", "Did you?" "That's amazing."

Backchannel cues can also be given non-verbally - eg by the listener nodding to show that s/he is following and interested.

Cross-cultural differences : The type of backchannel reaction used, the frequency of backchannels, and their position (ie while the speaker is still talking or when s/he pauses) may all differ from culture to culture, sometimes creating negative reactions in cross-cultural communication. For example, Cutrone (2014) studied the differences in backchannel language used by Americans and Japanese speakers and found that the Japanese used a greater number of backchannels than the Americans, of a shorter and more generic type, and often while the speaker was still talking. After talking to each other, they made comments on the other person's communicative style such as :

American speakerIt was difficult to know if he wanted to talk or what. I mean sometimes he would interrupt me with grunts or words I had just said, and I’d try to let him talk and he wouldn’t take it any further and we’d have these awkward silences. If that was supposed to be listening feedback, then it felt a little strange to me. Laughs are fine, but it was the other stuff that I didn’t really get. I guess I prefer the feedback after I’m done speaking and not during (my speech).

Japanese speakerMy partner’s reactions were much bigger than mine. I am not so comfortable giving such big ones as that.

References and Related Reading

Pino Cutrone on Japanese Learners' problems in intercultural communication