Lecture Outline #11--Errors and Biases in Reasoning

I. General Comments on Epistemology

A. The distinction between descriptive and prescriptive (normative) theories
1. Example of a normative theory: Expected Utility Theory (EUT)
a) People are generally risk-averse

b) But framing effects: risk-averse when problem is framed in terms of gains, but risk-seeking when problem is framed in terms of losses

A. Our belief in the validity of our reasoning ability makes us vulnerable to making errors
1. Fong and Klein (1995)--People think that they are really terrific at making social judgments.

A. Traditional/philosophical explanations--Aristotle, Plato...to Freud

B. Cognitive explanations--people are limited capacity information processors

C. Kahneman and Tversky's research on judgmental heuristics (availability heuristic; representativeness heuristic)

A. Nisbett and Wilson (1977): People lack introspective access to the true causes of their behavior

A. Vividness effects--Volvo-Saab thought experiment; Reyes, Thompson, and Bower (1981)

B. Media effects

A. Kahneman and Tversky's lawyer-engineer problem--people ignore base-rate information

B. Failure to recognize the importance of sample size--fail to employ the law of large numbers

A. People tend to seek information that confirms their hypothesis
1. Snyder and Swann (1978); Fong and Markus (1982)

B. People tend to pay more attention to information that confirms their hypothesis
1. Snyder and Cantor (1979)--confirmatory search processes

C. Theories are very resistant to change, even when the theory is completely discounted
1. Ross, Lepper, and Hubbard (1975)--social sensitivity experiment: perseverence effects

2. Freud's psychoanalytic biography of Leonardo DaVinci

D. Mixed evidence enhances belief in the theory--Lord et al. (1979)-- death penalty study

IX. What Can We Do to Improve Judgments and Decisions?

A. Recognize that we are often wrong.

B. Understand the nature of errors and biases in judgment, particularly the role of theories

1. Rosenhan's (1973) pseudopatient study

2. Rosenthal & Jacobson (1966) classroom study

C. Understand the importance of statistical principles in making judgments (Fong, Krantz, & Nisbett, 1986)