Clark (1996) said that people normally negotiate humanÐhuman interruptions. Unlike the immediate-interruption method of coordinating interruption, people usually have choices of whether to allow interruptions and how and when to handle them. Clark said that in normal humanÐhuman language usage people have four possible responses to interruption: (a) take-up with full compliance, (b) take-up with alteration, (c) decline, or (d) withdraw (Clark, 1996, pp. 203-205, 331-334). It is useful to design UIs in ways that take advantage of people's innate ability to negotiate interruptions. An external entity that initiates an external interruption may do so in a way that gives the user control. The interface could afford the user four options of when or whether to handle the interruption: (a) handle it immediately (take-up with full compliance), (b) acknowledge it and agree to handle it later (take-up with alteration), (c) explicitly refuse to handle it (decline), or (d) implicitly refuse to handle it by ignoring it (withdraw).