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 cognitive state and a reflection of negotiation strategies to mutually guide a dialogue, with pitch and amplitude values signaling the degree of concordance with the current topics. These prosodic forms are potentially usable in spoken dialogue system to porvide intelligent responding systems that are responsive to human motivations in dialogues.