Individual differences in syllogistic reasoning: deduction rules or mental models?

Two studies examined the correlates of reasoning ability on a syllogistic reasoning task in subjects who lacked formal background in logic. The main issue addressed was the extent to which reasoning proficiency arises from the consideration of multiple possible set relations (mental models) as opposed to explicit or implicit reliance on deduction rules. Evidence for the use of both models and rules was obtained. Although "good" and "poor" reasoners differed even when time constraints were imposed (consistent with the supposition of a better set of rules among good reasoners), good reasoners showed more improvement and chose to take longer amounts of time when time constraints were removed, suggesting that they considered more alternatives than did the poor reasoners. A comparison between these two groups and a third group of subjects, graduate students who had studied logic, reveals striking differences in both accuracy and speed.