We are interested in studying turn-taking in dialogue, in particular human-computer discourse. Humans and computers can communicate in any number of ways, such as through an operating system command line, a direct manipulation interface, or even natural language. Turn-taking is a basic fact of life that interacting agents must deal with: who should say what, and when? In some situations, turn-taking is a simple matter of following a predefined script, such as reciting wedding vows, or following the World Wide Web HTTP protocol. However, in much human-human dialogue, a more flexible and dynamic form of turn-taking is needed since it is impossible to always predict how a conversation will progress.