All writers produce text content and ideally connect it together according to discourse conventions. Weinvestigate whether a particularly strong discourse convention, the need for causal coherence in narratives, can predict the kind of text writers will produce. Causality has been found to be a significant discourse factor in reading comprehension and hence can be expected to determine also what writers produce during composition. In Experiment 1, writers composed short continuations at various points throughout a simple narrative, whereas in Experiment 2, writers composed continuations to complete several narratives. The results indicate that causality indeed plays a major role in composition. Writers tend to produce new text in such a way that it is causally connected to the prior text. Furthermore, writers favored causal relations of necessity or of necessity and sufficiency while largely avoiding relations of sufficiency alone, which suggests a general discourse constraint to be maximally informative (e.g., Grice, 1975).All writers must produce ideas (Collins & Gentner, 1980;Torrance, Thomas, & Robinson, 1996) and ideally, writers also provide coherence by connecting those ideas in some genre-appropriate way (McCutchen & Perfetti, 1982). Scardama1ia (1985, 1987) captured these observations by describing two sets of knowledge on which writers draw during writing: (1) Writers use topic knowledge (including the evolving text) to produce relevant ideas, and (2) writers use discourse knowledge to structure how the ideas are arranged and to determine which topic ideas are relevant (McCutchen, 1986; MeCutchen & Perfetti, 1982).Topic and discourse knowledge play important, but different, roles in determining which ideas are produced and how they are ultimately connected. For example, if a writer knows more about baseball and less about soccer (varying topic knowledge), the writer has different limits in what he/she is able to say when composing a description of each game. Regardless of topic knowledge, however, the writer's discourse knowledge should cue him/her to attempt to say something in each of several categories for the genre of "game description," such as mentioning "the object of the game," "the rules," "the number of players," and so on (e.g., Bereiter & Scardamalia, 1982 1986). Coe (1987) has referred to conventions for the form of the discourse as heuristics that help writers search for particular kinds of information to produce for text. A very explicit example ofdiscourse conventions exists in the Publication Manual ofthe American Psychological Association (1994), which helps writers by specifying what kinds of ideas are considered relevant for a research report and how they are to be arranged. Thus, available topic information limits specific content, whereas discourse knowledge influences what kinds of topic information are produced and how they are connected. If this view is correct, it should be possible, given a genre with well-known discourse conventions, to make predictions about the kinds of ...