Critical Thinking and Scientific Research

1. Critical Thinking and Scientific Research • Hypothesis: A specific, testable proposition, often derived from a theory. • Operational Definition: Description of the exact operations and methods used. • Variable: Some factor or characteristic that is manipulated or measured.

2. The Role of Theories

3. Case Studies: Taking a Closer Look • Features: Intensive examination of the behavior and mental processes associated with a specific person or situation. • Strengths: Provide detailed descriptive analysis of new, complex, or rare phenomena. • Pitfalls: May not provide representative picture of phenomena.

4. Surveys: Looking at the Big Picture • Features: Standard set of questions asked of a large number of participants. • Strengths: Gather large amounts of descriptive data relatively quickly and inexpensively. • Pitfalls: Sampling errors, poorly phrased questions, and response biases can distort results.

5. Naturalistic Observation:Watching Behavior • Features: Observations of humans or animal behavior in the environment in which it typically occurs. • Strengths: Provides descriptive data about behavior presumably uncontaminated by outside influences. • Pitfalls: Observer bias and participant self-consciousness can distort results.

6. Experiments: Exploring Cause and Effect • Features: Manipulation of an independent variable and measurement of its effects on a dependent variable. • Strengths: Can establish a cause-effect relationship between independent and dependent variables. • Pitfalls: Do results generalize to the real world.

7. Establishing Causality • Correlation (Is there a relationship?) • Directionality (Does the cause precede the effect?) • Confounds (Are there alternate cause?)

8. Three Correlations

9. Three Correlations

10. Three Correlations

11. “R” as a measure of linearcorrelation None -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 Stronger Negative Stronger Positive Return

12. “Spurious” Correlation

13. “Third Variable” Correlations Height “True” Causes ● Nutrition ● Genetics Weight

15. Correlation, Directionality, Confound? • “Carrots Kill” • ANSWER: • “Lesser childhood motor coordination is associated with greater obesity” • ANSWER: • “Facebook users have lower GPAs and are more narcissistic” • ANSWER: • “Blacks and Whites are genetically inferior because they have lower IQs than Orientals” • ANSWER: • “Survey finds women who consume more caffeine are later less likely to conceive” • ANSWER: • “Erratic eye movements are associated with poor reading” • ANSWER: • “Brain tumors found in seven Swedes carrying cell phones” • ANSWER:. • “An active sex life contributes to higher grades: More sex, higher grades. • ANSWER: Source: Brehm, Kassin, Fein, Social Psychology, 4/e (1999)

16. Genetics or Environment • Does schizophrenia run in families because of genes or environment?

17. Family Studies • 1st degree relatives (e.g., offspring, siblings) share an average of 50% of their genes • 2nd degree relatives (e.g., half siblings, niece/nephew, grandchild) share approx 25% of their genes • 3nd degree relatives (e.g., great-grandchild) 12.5% of their genes

18. Family studies

19. What’s the confound?

20. Twin Studies • Compare identical and fraternal twins. Both have a “similar” environment but only twins share 100% of their genes. • – higher concordance rate in identical (48%) and concordance than fraternal twins (17%) suggests a contribution for genetics, although one worries that identical twins seek out more similar environments than fraternal twins • Compare identical twins raised together and apart. • – any difference found must be due to whatever environmental differences existed in the adoptive families (not enough studies to date)