Questions: Representativeness Heuristic and Similarity Judgment

Question 1

Linda is described as a philosophy graduate, deeply concerned with social justice, and active in feminist causes. Which of the following should be judged MORE probable based on probability theory alone?

• A. 'Linda is a bank teller and a feminist' — because the description matches this profile better
• B. 'Linda is a bank teller' — because any single event is at least as probable as that event combined with another
• C. The two statements are equally probable, since both describe the same person
• D. 'Linda is a feminist' — because nothing in the description contradicts this

Answer: (B)

By the conjunction rule, P(A∩B) ≤ P(A) always holds. 'Linda is a bank teller' must be at least as probable as 'Linda is a bank teller AND a feminist.' The conjunction adds a constraint, which can only keep or reduce the probability. Option A is the conjunction fallacy: participants judge the conjunction more probable because it better resembles Linda's description — representativeness (similarity) overrides the probability axiom. Option D is a distractor; while plausible, it's not what the question tests.

Question 2

A researcher is told that a study sample is drawn from a group containing 90% salespeople and 10% librarians. A participant is described as 'meticulous, reserved, and fond of cataloguing.' Most people judge the participant is probably a librarian. What does this illustrate?

• A. Confirmation bias — people interpret the description to match what they already believe
• B. Base rate neglect — the representativeness of the description crowds out the population ratio that should anchor the judgment
• C. The availability heuristic — librarians are more mentally available because the description is vivid
• D. Anchoring — the description serves as an anchor that the base rate fails to adjust

Answer: (B)

Base rate neglect is a direct consequence of representativeness. The description matches the librarian prototype closely, so the representativeness heuristic produces a strong intuition that the person 'is' a librarian. But the base rate (90:10 in favor of salespeople) is powerful information that should dominate in the absence of a very diagnostic description. When a description is provided, it crowds out base rate information even when the base rate would overwhelmingly favor the alternative. This was demonstrated by Kahneman and Tversky's engineer-lawyer paradigm.

Question 3

People with statistical training are largely immune to the conjunction fallacy because their knowledge of probability rules overrides the representativeness heuristic.

• T. True
• F. False

Answer: False

False. Kahneman and Tversky found that the conjunction fallacy is robust even among participants with statistical training, including doctoral students in decision science. The representativeness heuristic operates intuitively and fast (System 1 in dual-process terms), and statistical knowledge does not automatically override it. Trained individuals can correct their responses if they slow down and deliberately apply the conjunction rule, but spontaneous intuitive judgments remain susceptible to the fallacy. This is precisely what makes the heuristic theoretically important — it is not simply a knowledge gap.

Question 4

When no descriptive information about an individual is available, people are most likely to commit the conjunction fallacy because they have very little to guide their judgment except category membership.

• T. True
• F. False

Answer: False

False — this reverses the conditions for the conjunction fallacy. The fallacy arises specifically when a vivid, detailed description is provided that resembles a prototype. Without descriptive information, people have no representativeness cue to exploit, and they are more likely to rely appropriately on base rates or categorical probabilities. The conjunction fallacy is a consequence of having too much prototypical detail, not too little. When descriptive information is absent, the main failure mode is ignoring variability or making uniform probability estimates, not conjunctions.

Question 5

Why does providing a detailed description of a person cause people to neglect base rate information when estimating the probability of category membership?

Model answer: A detailed description activates the representativeness heuristic: people assess how well the description matches the typical member of a category (a prototype) and use that match as a proxy for probability. This similarity judgment is cognitively easy and intuitively compelling. Base rate information — how common the category is in the population — is abstract and statistical, requiring deliberate reasoning. When a vivid description is available, it dominates attention and crowds out the base rate, even when the base rate is the more informative input.

The core insight is that representativeness substitutes an answerable question (how similar is this to the prototype?) for a harder one (what is the probability given all available information?). The description is highly salient; the base rate feels less relevant because it doesn't match the specific individual described. This substitution is automatic and efficient in most everyday contexts, but systematically misleading when base rates are informative — as they almost always are for probabilistic judgments about individuals.