META-PROPOSITIONAL REASONING WITH KNIGHT-KNAVE PROBLEMS - THE IMPORTANCE OF BEING HYPOTHESIZED

We report three experiments, which investigate the role of hypotheses for metalogical puzzles, in which some persons are always telling the truth and other persons are always lying. In Experiment 1, the subject s received an accurate or an inaccurate single hypothesis or no hypoth esis. Accurate hypotheses did lead to an increase of correct conclusio ns, while inaccurate hypotheses did lead to a decrease of correct conc lusions. This is a failure to replicate the results of Byrne and Handl ey (1995): In their experiment with a separate control-group, inaccura te hypotheses did not lead to a decrease of correct conclusions. In Ex periment 2, subjects received reformulated single hypotheses, in order to avoid unconditional acceptance of the given hypotheses by the subj ects. However, the same results were obtained as in Experiment 1. Ther efore, subjects seem to try to verify the given hypotheses. In Experim ent 3, subjects were given double hypotheses, in order to avoid verifi cation. As a consequence, there was no difference between problems wit h an accurate, an inaccurate and no hypothesis. The results are discus sed in terms of strategies in reasoning.