In this paper, we investigate the prosody and functions of interruptions in natural dialogue, and the role of interruption-initiated actions in spoken dialogue systems. The specific forms of prosody are both an indicator of cagnitive state and a reflöection of negotiation strategies to mutually guide a dialogue, with pitch and amplitude values signaling the degree of concordance with the current topic. These prosodic forms are potentially usable in spoken dialogue systems to provide intelligent responding systems that are responsive to homan motivations in dialogues.