Overview
This lecture explains how to evaluate the trustworthiness of information by distinguishing scientific thinking from everyday reasoning, focusing on the nature of scientific methods, reasoning, and theories in psychology.
Scientific vs. Everyday Reasoning
- Everyday and scientific statements are both hypotheses—best guesses about the world.
- Scientific reasoning uses induction: drawing general conclusions from specific, systematically collected observations.
- Everyday reasoning often relies on anecdotal evidence or personal experiences, which are less reliable.
- Good scientific theories are testable, consistent, generalizable, simple, and fruitful (lead to new discoveries).
- Falsifiability (the capacity to be disproven) is a key feature separating science from pseudoscience.
Interpreting Research Results
- Scientific hypotheses are tested with experiments, but results only offer support, not definitive proof.
- Inductive reasoning leads to conclusions based on probabilities, not certainties.
- Deductive reasoning applies general principles to specific cases and can provide proof if premises are true.
- Small or biased samples can produce unreliable results; scientific studies aim for representative samples.
- Anecdotal evidence is limited due to memory issues and lack of systematic observation.
Trust in Science & Null-Hypothesis Significance Testing
- Science is trusted because it uses systematic observation, representative samples, and probabilistic reasoning.
- Null-hypothesis significance testing (NHST) evaluates whether observed data differ from what would be expected by chance.
- Type I error: rejecting a true null hypothesis (false positive).
- Type II error: failing to reject a false null hypothesis (false negative).
- Probability values (p-values) set thresholds for determining the likelihood of errors.
Scientific Theories and Revision
- Scientific theories are comprehensive frameworks supported by substantial evidence.
- Theories must be empirically testable and open to falsification and revision.
- Science updates theories when new data provide better explanations.
Objectivity and Values in Science
- Science is a human, social activity and involves facts (objective information) and values (beliefs about what should be).
- No science is completely objective; personal and cultural values influence research questions and interpretations.
- Multiple levels of analysis (biological, cognitive, behavioral, social/cultural) offer different perspectives on phenomena.
Science in Context
- Science is one way of knowing, alongside common sense, personal experience, and faith—each has value and limitations.
- Scientific thinking is systematic and allows for establishing causality and generalizing findings.
Key Terms & Definitions
- Anecdotal evidence — biased evidence from personal experience.
- Causality — one variable causes an effect.
- Correlation — measure of relation between variables.
- Deductive reasoning — applying general rules to specific cases.
- Empirical — based on observation or evidence.
- Falsify — ability for a claim to be tested and refuted.
- Hypothesis — tentative explanation subject to testing.
- Inductive reasoning — drawing general conclusions from specific observations.
- Null-hypothesis significance testing (NHST) — tests probability of observed results under the null hypothesis.
- Type I error — false positive in research.
- Type II error — false negative in research.
- Scientific theory — empirically supported, testable, and predictive explanation.
Action Items / Next Steps
- Review the differences between scientific and everyday reasoning.
- Practice evaluating claims for falsifiability.
- Reflect on the influence of values in scientific research.
- Complete assigned discussion questions or related readings as directed.