PSY 341 Lecture Notes - Lecture 25: Modus Ponens, Expected Utility Hypothesis, List Of Fallacies

• School: University at Buffalo
• Department: Psychology
• Course: PSY 341
• Professor: Mauner Gail

Document Summary

Modus ponens and modus tolens are the normative models for conditional reasoning. If john understands all the lectures in his calculus class (a), then he will ace the final exam (c). John did not ace the final exam; therefore, john did not understand all the lectures in his calculus class. Valid logical deduction/conclusion -> modus tolens: but, this conclusion strikes us as odd. We (cid:272)a(cid:374) i(cid:373)agi(cid:374)e other reaso(cid:374)s for joh(cid:374)"s poor perfor(cid:373)a(cid:374)(cid:272)e. Perhaps people are doing something other than deductive logic for deductive reasoning. What causes these reasoning errors: possible explanation. Modus ponens involves confirmation: this is easy for us. Modus tolens requires disconfirmation: explains higher errors on modus tolens. When it is (too) hard to do logical deductions (or we are too lazy), we seek conclusions that match the 2nd premise. Difficulties with modus tolens: wason task. Demonstrates failure of modus tolens and confirmatory response biases.