In human language there seems to be a direct link between perception and action for back-channel feedback, that is, the grunts and other acknowledgments produced by a listener in a conversation. In particular, in Japanese, detection of a low pitch region in the speaker's utterance often cues the listener to produce back-channel feedback. This fact has been exploited in a system that can interact with unsuspecting speakers and appear to converse, in real time. This finding suggests that Brooks' 1991a, 1991b methodology for the study and synthesis of physical behavior is relevant also for social behavior. If so, then real-time responsiveness, rather than better phoneme recognition,is a top priorityfor the construction of spoken language systems and for the scientific study of language.