Inference and Mental Models
The defendant left town before the restaurant closed. The arsonist put a match to the cooking oil in the kitchen after the restaurant closed.
What conclusion would you draw? Probably, you would infer that the defendant could not have started the fire because, barring some remote scenario, the culprit must have been there to start the fire. The question for psychologists is: what mental process enabled you to reach your conclusion? In principle, it could be syntactic or semantic. Most psychologists who have studied the topic favour syntactic theories, but over the past decade a growing number have entertained the possibility of a semantic theory. My plan in this chapter is to describe one particular semantic theory-the theory ofmental models-and to illustrate its power by applying it to three areas of reasoning: first, a hitherto uninvestigated area (temporal reasoning), secondly an established area (reasoning with sentential connectives), and thirdly the most studied area of all (Peter Wason's selection task).