Description:The principal way in which we are social beings, in contrast to individuals, is through talk. This work examines brief listener responses to shed light on one of the central features of this human togetherness: the listener. Seemingly unobtrusive response tokens such as "yeah", "mm hm", "okay" and "mm" are examined and are actually found to be complex. One objective of this work is to survey the major distinctions between some backchannels, namely those that can be characterized as response tokens: continuers, acknowledgement tokens, newsmarkers and change-of-activity tokens.