1The fact that the spoken texts of classroom interaction -particularly those involving teacher with whole class -are co-constructed relatively smoothly, despite the number of participants involved, suggests that they are organized in terms of standard strategies, embodied in typical forms of discourse that have evolved for responding to recurring types of rhetorical situation (Miller, 1984;Kamberelis, 1995). That is to say that, like written texts, they can be thought of as being constructed according to one of a set of educational genre specifications. One such rhetorical structure, the ubiquitous 'triadic dialogue' (Lemke, 1990) (also known as the IRE or IRF sequence (Mehan, 1979;Sinclair & Coulthard, 1975), has attracted considerable attention in recent years, and has variously been seen as, on the one hand, essential for the co-construction of cultural knowledge (Heap, 1985;Newman et al., 1989) and, on the other, as antithetical to the educational goal of encouraging students' intellectual-discursive initiative and creativity (Lemke, 1990;Wood, 1992).Drawing on episodes of teacher-whole-class interaction collected during a collaborative action research project, this paper will show, however, that the same basic IRF structure can take a variety of forms and be recruited by teachers for a wide variety of functions, depending on the goal of the activity that the discourse serves to mediate and, in particular, on the use that is made of the followup move.
________________________________________ 2In his seminal writings on the dialogic nature of 'utterance ', Bakhtin (1986) pointed out that all utterances both respond to what has preceded and anticipate a further response. While this is true, it is also the case that, in speech, many utterances tend to be more oriented either to what preceded or to what will follow, as is the case with the relationship that holds between the members of an 'adjacency pair', such as 'question-answer' (Sacks, Schegloff, & Jefferson, 1974). On the other hand, not all conversational 'exchanges' are limited to two 'moves', and many are much longer.There are two main reasons for this.First, as Halliday (1984) has argued, there are two basic exchange-types: a) Demand -Give-inresponse and b) Give (unsolicited) -Accept. However, a third equally basic type is frequently created by the combination of the first two: c) Demand -Give-in-Response -Accept. Where information is the 'commodity' exchanged, this gives rise to the three-move exchange structure:Question -Answer -Acknowledgement (Halliday, 1984 In this structure, however, only one participant typically initiates the exchange -the teacher; and the teacher always has the right to provide the third move, often, as above, by evaluating the student's contribution for its conformity to what he or she considers to be a correct or acceptable response.These differential rights to moves in the exchange have often been discussed in terms of the power differential between teachers and students (e.g. Lemke, 1990), and there is no doubt t...