 Various studies investigate their test subjects’ tendency to reason according to specific inference principles of NMLs. Most studies support the descriptive adequacy of the rules of system P. There are, however, some open or controversial issues. For instance, while some studies report results suggestive of the adequacy of weakened monotony principles such as Cautious Monotony  (Schurz 2005,  Neves et al. 2002,  Pfeifer and Kleiter 2005)  and Rational Monotony  (Neves et al. 2002),  Benferhat et al. (2005) report mixed results. Specificity considerations play a role in the reasoning process of test subjects in  Schurz (2005),  whereas according to  Ford and Billington (2000)  they do not.  Benferhat et al. (2005)  are specifically interested in the question whether the responses of their test subjects corresponded better to Lexicographic Closure or to Rational Closure. While the results were not fully conclusive they still suggest a preference for the former. 