Why we are so good at catching cheaters.

Data that appear to exhibit a 'cheater detection' effect on performance in the Wason Selection task are widely interpreted as implying that deontic reasoning is effected by a domain specific, cognitive module. The 'cheater detection module' is said to offer a clear example of an effect of evolutionary selection on human cognitive architecture. This interpretation depends critically on assuming that deontic conditionals and their indicative controls are identical in structure; hence that the asymmetries in S's performance must be effects of content variables. I argue that this assumption is untrue and that structural features of deontic conditionals predict the 'cheater detection' data without assumptions about either the architecture or the history of cognition. According to this analysis, the putative cheater detection effect on the Wason task is actually a materials artifact.