1. Deduction • biases and content effects • bias = whenever there is a systematic deviation in performance from the normative approach

2. Belief Bias • make conclusions based on personal beliefs about the world (you are supposed to use logical rules to draw conclusions) • Selma Hayek looks best sporting the “uni-brow” that she had in “Frida” • Ben Affleck and Jennifer Lopez will have a longlasting marriage

3. Validity of the silly statement • sometimes being logical, means providing reasons for your conclusions • Women look their best when sporting a “unibrow” • The actress that played “Frida” sported a unibrow • Selma Hayek is the actress that played “Frida” • Selma Hayek looked best sporting the “unibrow” that she had in “Frida”

4. Laboratory evidence • Believable conclusions = are consistent with your personal beliefs • Unbelievable conclusions = are inconsistent with your personal beliefs (e.g., unibrow statement) • also, valid and invalid conclusions • believable/valid, believable/invalid, unbelievable/valid, unbelievable/invalid

5. Results • Evans, Newstead, & Byrne (1993) • % of conclusions accepted as valid • Valid Invalid • Believable 86% 66% • Unbelievable 62% 13% • conclusion: the believability of a statement has a strong influence on people’s critical thinking (i.e., belief-bias effect)

6. content effects • def.: whenever the “content” (i.e., the specific words) influences your critical thinking performance • normative approach  content is irrelevant and should not influence your performance

7. Wason selection task • Manchester Leeds Train Car • (imagine that these are four cards, each having a city on one side and a mode of transportation on the other) • “Every time I go to Manchester I travel by train” • answer: turn over Manchester and Car

8. results in laboratory • Wason & Shapiro (1971) • showed that students did a good job with this version of the task compared to an abstract version • conclusion  adding realistic words (content) to an abstract problem improved performance (thus, it’s a content effect)

9. guaranteed solution to the selection task (algorithm) • D B 3 5 7 • If a card has a D on one side, then it has a 3 on the other side. • answer: D, 5, 7 • p not p q not q not q • If p, then q • answer: p, not q

10. Test 1 Study Guide • normative approach, descriptive approach • logic, def. of rational • logic vs. real-life • syllogisms, deduction, parts of the syllogism, validity of conclusion, algorithm, Euler’s circles • conditional reasoning problems, conditional, content of a problem vs. logical structure

11. Test 1 (cont.) • logical rules related to conditional reasoning, affirming the antecedent, etc. (including modus ponens, modus tollens) • Wason selection task, abstract vs. realistic content of a problem • logical operators, if…then, and, or, not; two types of “or” (exclusive, inclusive) • disjunctive reasoning; deontic content or deontic reasoning

12. Test 1 (cont.) • bias, belief-bias, personal beliefs vs. logic, content effects