Social effects of the speed of hummed sounds on human-computer interaction

Our research focuses on the nature of voice interaction and activation of psychological tendencies in humans by the power of prosody sounds. This study examines whether people's impressions and behaviours are affected by variations in the speed of hummed sounds. The sounds consist of just prosodic components similar to continuous humming on the open vowel /a/ or /o/ without any language information. In interaction between individuals as well as among animals, temporal structures including voice speed or duration contribute rhythmic interaction and are closely connected to the participants' dynamics of mental or emotional states. We think that this phenomenon can be applied to human-computer interaction, even through the variation in temporal structures of hummed sounds used to reduce the influence of content or meaning in language. Our interactive system mimics the prosodic features of the human voice by using humming-only sounds under three different voice speed conditions: (a) faster, (b) normal, and (c) slower than the original speaker. We examine whether the variation in the sound's speed gives rise to both psychological and behavioural influences in the relationship between the computer and the subject through interaction. Subjects tend to prefer a computer with a normal or faster speaking rate to that with a slower rate on both usefulness and familiarity. Moreover, the speech rate of the subjects changed inversely to the variation in a computer's hummed sounds. This study demonstrates the importance of temporal structure and emphasizes the need for an investigation of the fundamentals at work in interaction. (C) 2003 Elsevier Ltd. All rights reserved.