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BHS 204-01 Methods in Behavioral Sciences I

BHS 204-01 Methods in Behavioral Sciences I. April 9, 2003 Chapter 2 (Stanovich) – Falsifiability: How to Foil Little Green Men in the Head. Logic of Experimentation. Two forms of logic: Deduction – moving from general principles to specific conclusions.

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BHS 204-01 Methods in Behavioral Sciences I

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  1. BHS 204-01Methods in Behavioral Sciences I April 9, 2003 Chapter 2 (Stanovich) – Falsifiability: How to Foil Little Green Men in the Head

  2. Logic of Experimentation • Two forms of logic: • Deduction – moving from general principles to specific conclusions. • Induction – moving from specific observations to general principles. • Induction is used during naturalistic and exploratory research. • Deduction is used during experiments.

  3. Propositional Logic • Modus Ponens (confirmatory) • If p then q • Observe p • Conclude q • Modus Tollens (disconfirmatory) • If p then q • Observe not-q • Conclude not-p

  4. Logical Fallacies • Affirming the consequent • If p then q • Observe q • Conclude p • Denying the antecedent • If p then q • Observe not-p • Conclude not-q

  5. Falsifiability • Seeking support for hypotheses commits the logical fallacy of affirming the consequent. • Instead, we must test hypotheses by seeking disconfirmatory evidence. • A testable theory is one that can be proven wrong – if it is wrong. • It must have the chance to fail. • A theory cannot explain every outcome.

  6. Popper’s Approach • Predictions from theory (hypotheses) must be specific. • They must state what will happen and what will not happen. • General predictions or all-encompassing predictions cannot be tested (are unfalsifiable). • When data accumulates that contradicts theory, then theory must be changed. • Data is not thrown out – explanations are.

  7. Two Hypotheses • Null hypothesis (H0): • There will be no difference between treatment and control groups (no treatment effect). • Alternative hypothesis (H1): • There will be a difference of a particular kind. • Directionality – states how the treatment group will differ from the control group. • We test the null hypothesis and by rejecting it (disconfirming it) can accept the alternative.

  8. The Neyman-Pearson Approach • Two theories can be compared by predicting incompatible outcomes: • If theory A is correct, hypothesis A will be confirmed and B will be disconfirmed. • If theory B is correct, hypothesis B will be confirmed and A will be disconfirmed. • The comparison is not with the control group ( is there a treatment effect or not) but with the predictions made by the two theories.

  9. Errors are Important • We learn something, even when an experiment does not “work” – does not produce the expected result. • Knowledge advances when we find that our ideas are wrong and can abandon incorrect beliefs. • We must be willing to let evidence guide belief – not the other way around. • Scientists criticize each other’s ideas in an ongoing dialectic that produces change.

  10. Working on the Fringes • Interesting questions are those that: • Exist at the fringes of knowledge. • Can be tested using existing methods. • Many questions are important but untestable. • Some questions are interesting to the public but not to scientists because they have already been answered: • ESP and other paranormal claims, astrology.

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