Prosodic adaptation in human

State-of-the-art speech recognizers are trained on predominantly normal speech and have difficulties handling either exceedingly slow and hyperarticulated or fast and sloppy speech. Explicitly instructing users on how to speak, however, can make the human–computer interaction stilted and unnatural. If it is possible to affect users’ speaking rate while maintaining the naturalness of the dialogue, this could prove useful in the development of future human–computer interfaces. Users could thus be subtly influenced to adapt their speech to better match the current capabilities of the system, so that errors can be reduced and the overall quality of the human–computer interaction is improved. At the same time, speakers are allowed to express themselves freely and naturally. In this article, we investigate whether people adapt their speech as they interact with an animated character in a simulated spoken dialogue system. A user experiment involving 16 subjects was performed to examine whether people who speak with a simulated dialogue system adapt their speaking rate to that of the system. The experiment confirmed that the users adapted to the speaking rate of the system, and no subjects afterwards seemed to be aware they had been affected in this way. Another finding was that speakers varied their speaking rate substantially in the course of the dialogue. In particular, problematic sequences where subjects had to repeat or rephrase the same utterance several times elicited slower speech.