Performance on reasoning tasks like the Wason selection task (Wason, 1968) have demonstrated that people are generally prone to confirmation bias unless the rules evoke a social contract that may or may not be broken (Gigerenzer & Hug, 1992). Social Contract Theory (Cosmides, 1989) posits that enhanced performance on rules invoking a social contract is due to an evolved mechanism that protects us from being cheated. A similar mechanism may exist as a result of other evolutionary pressures, such as contagion or physical threats. The present study was designed using a two-alternative forced-choice version of the Wason selection task to determine how people reason about rules invoking the threat of illness. We created rules expressed in a cause-symptom manner as well as an symptom-as-caused-by manner. The results demonstrate that the order of symptom and cause has some effect on accuracy. However, our results primarily demonstrate an increase in rejecting aspects of the rule and a reduction in confirmation bias when a threat of illness is implied as compared to control rules that contain no such threat.