Fallacies are a particular type of informal argument that are psychologicallycompelling and often used for rhetorical purposes. Fallacies are unreasonablebecause the reasons they provide for their claims are irrelevant orinsufficient. Ability to recognize the weakness of fallacies is part of what wecall argument literacy and imporatant in rational thinking. Here we examineclassic fallacies of types found in textbooks. In an experiment, participantsevaluated the quality of fallacies and reasonable arguments. We instructedparticipants to think either intuitively, using their first impressions, oranalytically, using rational deliberation. We analyzed responses, responsetimes, and cursor trajectories (captured using mouse tracking). The resultsindicate that instructions to think analytically made people spend more time onthe task but did not make them change their minds more often. When participantsmade errors, they were drawn towards the correct response, while respondingcorrectly was more straightforward. The results are compatible with“smart intuition” accounts of dual-process theories of reasoning,rather than with corrective default-interventionist accounts. The findings arediscussed in relation to whether theories developed to account for formalreasoning can help to explain the processing of everyday arguments.