1. 2 4 6 task You guess the secret rule 2 4 6 < yes, fit the secret rule 7 9 11 < yes, fits the rule Rule is ascending (increasing numbers)

2. Another attempt 2 4 6 < yes, fits the rule -2 4.5 400 < no 7 2 1 < no, do not fit the rule -1 -3 -5 < no 8 10 12 < yes -5 -3 -1 < no 1 3 5 < yes 0 13 20 < no 6 10 18 < no 0 7 10 < no 33 35 37 < yes ANSWER: positive numbers, increasing by 2 Exemplar = set of 3 numbers that you generate

3. Positive/ negative exemplars Your own hypothesis (H) E.g. H: numbers add to 12 Proposed exemplar: 7 2 3 Exemplar fits H  “positive” exemplar E.g., if proposed exemplar: 7 2 1 Exemplar doesn’t fit H  “negative” exemplar

4. expectations E.g. H: numbers add to 12 Proposed exemplar : 7 2 1 Expectation  “no” response, doesn’t fit the rule If the response increases confidence in H, then it’s said to be “confirming”

5. Another expectation E.g. H: numbers add to 12 Proposed positive exemplar: 7 2 3 E.g., he expected a “no” response because he had low confidence in H  then the hypothesis is “disconfirmed”

6. Heuristics for induction and hypothesis testing Rule-of-thumb: Not guaranteed to work, but more likely to get the answer –1) form general hypotheses (not specific ones) E.g. H: numbers increasing by 2 (specific) More general version  numbers increasing –2) form counterfactual hypotheses (i.e., opposing hypotheses)

7. More heuristics –2) form counterfactual hypotheses E.g. H: numbers increasing Counterfactual (opposing) H: numbers decreasing –3) use extreme examples (exemplars) E.g., exemplar : 7 9 1 Extreme exemplar: -7 9,000 1 million –4) use multiple hypotheses Have at least 2 hypotheses in mind always Pick an exemplar that tells which hypothesis is right (discriminating between hypotheses)

8. More heuristics –5) seek disconfirming evidence  find exemplars that show your hypothesis is wrong Peoples’ natural inclination is to seek confirming evidence (confirmation bias)

9. Science as hypothesis testing We had H in 2 4 6 task; in science, it’s called a “theory” We had exemplars in 2 4 6 task; in science, they are “experimental results” In 2 4 6 task, we compared the response (yes or no) with our hypothesis; in science, the scientist compares the results to the theory