Uncontrolled logic: intuitive sensitivity to logical structure in random responding

It is well established that beliefs provide powerful cues that influence reasoning. Over the last decade research has revealed that judgments based upon logical structure may also pre-empt deliberative reasoning. Evidence for ‘intuitive logic’ has been claimed using a range of measures (i.e. confidence ratings or latency of response on conflict problems). However, it is unclear how well such measures genuinely reflect logical intuition. In this paper we introduce a new method designed to test for evidence of intuitive logic. In two experiments participants were asked to make random judgments about the logical validity of a series of simple and complex syllogistic arguments. For simple arguments there was an effect of logical validity on random responding, which was absent for complex arguments. These findings provide a novel demonstration that people are intuitively sensitive to logical structure.