Traditional mechanistic accounts of language processing derive almost entirely from the study of monologue. Yet, the most natural and basic form of language use is dialogue. As a result, these accounts may only offer limited theories of the mechanisms that underlie language processing in general. We propose a mechanistic account of dialogue, the interactive alignment account, and use it to derive a number of predictions about basic language processes. The account assumes that, in dialogue, the linguistic representations employed by the interlocutors become aligned at many levels, as a result of a largely automatic process. This process greatly simplifies production and comprehension in dialogue. After considering the evidence for the interactive alignment model, we concentrate on three aspects of processing that follow from it. It makes use of a simple interactive inference mechanism, enables the development of local dialogue routines that greatly simplify language processing, and explains the origins of self-monitoring in production. We consider the need for a grammatical framework that is designed to deal with language in dialogue rather than monologue, and discuss a range of implications of the account.Keywords: common ground; dialogue; dialogue routines; language comprehension; language production; monitoring; perception-behavior link leagues (e.g., Brennan & Clark 1996;Wilkes-Gibbs & Clark 1992; also Brennan & Schober 2001;Horton & Keysar 1996). Well-controlled studies of language production in dialogue may require some ingenuity, but such experimental ingenuity has always been a strength of psychology.The theoretical reason why psycholinguistics has ignored dialogue is that psycholinguistics has derived most of its predictions from generative linguistics, and generative linguistics has developed theories of isolated, decontextualized sentences that are used in texts or speeches, that is, in monologue. In contrast, dialogue is inherently interactive and contextualized: Each interlocutor both speaks and comprehends during the course of the interaction; each interrupts both others and himself; on occasion two or more speakers collaborate in producing the same sentence (Coates 1990). So it is not surprising that generative linguists commonly view dialogue as being of marginal grammaticality, contaminated by theoretically uninteresting complexities. Dialogue sits ill with the competence/performance distinction assumed by most generative linguistics (Chomsky 1965), because it is hard to determine whether a particular utterance is "well-formed" or not (or even whether that notion is relevant to dialogue). Thus, linguistics has tended to concentrate on developing generative grammars and related theories for isolated sentences; and psycholinguistics has tended to develop processing theories that draw upon the rules and representations assumed by generative linguistics. So far as most psycholinguists have thought about dialogue, they have tended to assume that the results of experiments on monologue can be...