COGNITIVE MECHANISMS OF DEDUCTIVE REASONI NG - PROBABILITY, PREVIOUS KNOWLEDGE OR THE FORMAL LOGIC - DISCUSSION

Studies of deductive reasoning have revealed a number of systematic er rors made by reasoners. Some of these systematic errors, belief bias a nd content bias are the focus of this paper. Two hundred and sixty two university students participated in the study. The results indicate t hat when the premises of the most simple forms of syllogisms include s imple mathematical content (e.g., numbers), the acceptance of the conc lusion as logically following from the premises drops from 90-95% when the conclusion is believable, to 25-30% when the conclusion is unbeli evable. However, there is no comparable effects when the premises are concerned with non-math content. Thus the paper provides evidence that belief bias differs across contents of reasoning.