A working memory model of relations between interpretation and reasoning∗

Interpretation is the process whereby a hearer reasons to an interpretation of a speaker’s discourse. The hearer normally adopts a credulous attitude to the discourse, at least for the purposes of interpreting it. That is to say the hearer tries to accommodate the truth of all the speaker’s utterances in deriving an intended model. We present a non-monotonic logical model of this process which defines unique minimal preferred models and so efficiently simulates a kind of closed-world reasoning of particular interest for human cognition. By analysing Byrne’s (1989) ‘suppression’ data we show that variants on this logic can capture and motivate subtly different interpretative stances which different subjects adopt, thus enriching empirical understanding about what subjects are doing in this task. We then show that this logical competence model can be implemented in spreading activation network models. A one pass process interprets the textual input by constructing a network which then computes minimal preferred models for (3-valued) valuations of the set of propositions of the text. The neural implementation distinguishes easy forward reasoning from more complex backward reasoning in a way that may be useful in explaining directionality in human reasoning. Formal correspondences between the non-monotonic logic and an abstracted form of the ACT-R architecture offer a route to understanding relations between discourse processing and other cognitive tasks studied in that framework. Our most general aim in this paper is to differentiate interpretation tasks from derivation tasks with which they are sometimes confused, and in doing so, to establish a more productive relation between logical and psychological studies of human reasoning and memory. Elsewhere we have argued that Wason’s selection task can be understood as largely invoking interpretative processes in subjects (Stenning and van Lambalgen [24], [25]). Stenning ∗The second author is grateful to the Netherlands Organization for Scientific Research (NWO) for support under grant 360-80-000. This paper was inspired by a visit to Walter Schaeken and Kristien Dieussaert (cf. [8]).