Notes on Sources of Knowledge in Psychology and the Scientific Process

Folk Wisdom, Common Sense, and the Science of Psychology

• Central question: How does psychology, a formal science, handle knowledge about human behavior differently from everyday sources?

• Two broad sources of everyday knowledge:

  • Folk wisdom: Knowledge passed down through generations informally (e.g., advice from elders). Limited for new experiences (e.g., cybersex).

  • Personal observations: Direct experiences, confirming or contradicting folk wisdom, or providing new insights.

• Common sense knowledge is often seen as: $ext{Folk wisdom} + ext{Personal observations}$

• Problems with common sense knowledge:

  • Not guaranteed to be rational or logical; often contains contradictions.

  • Relies on ex post facto reasoning: Explaining events after they happen by selectively choosing supporting beliefs, ignoring contradictions.

  • The "grab bag" analogy: People pull beliefs that fit a situation post-hoc, without checking for overall consistency (like a purse dump).

  • Example: Long-distance relationships can be explained by "absence makes the heart grow fonder" if they succeed, or "out of sight is out of mind" if they fail. These contradictory beliefs impede reliable prediction.

What Science Asks of Knowledge

• Science moves beyond post-hoc explanations, requiring explicit, publicly stated knowledge claims.

• Explicit, public nature: Scientific claims are openly presented for peer scrutiny, critique, and testing.

• Predictions in science: Must be made publicly and tested.

• Predictive validity (PV) measures how well a knowledge system makes accurate predictions:

  • Formula: $PV = \frac{\text{Number of correct predictions}}{\text{Total number of predictions}}$

  • Everyday judgments often have low PV because they are rarely tested rigorously, performing no better than chance (like a coin flip).

The Scientific Method as a Stricter Standard

• Requirements:

  • State knowledge claims explicitly and publicly.

  • Make explicit, testable predictions with specified methods.

  • Present observable evidence supporting or refuting predictions.

  • The testing process is public and subject to peer evaluation.

• Practical and ethical implications:

  • Reduces bias and overconfidence.

  • Public predictions promote transparency and accountability.

  • Favors cumulative progress in knowledge.

Summary Contrast

• Common sense knowledge (folk wisdom + personal observations): Often contradictory, relies on post-hoc explanations.

• Science: Demands explicit claims, public testing, predictive accuracy, and critique to establish robust, reliable knowledge.

• Psychology's value as a science lies in its rigorous, evidence-based approach to understanding human behavior, providing more dependable conclusions than casual reasoning.