Description

Tendency for people to ignore base rates in favor of individuating information.

Kahneman, D., & Tversky, A. (1973). On the psychology of prediction. Psychological Review, 80(4), 237–251.

Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131.

Task

The task is adapted from De Neys and Glumicic (2008). On each item, participants are presented with two kinds of information: base-rates (e.g., "1,000 people participated in a study, including 4 men and 996 women") and information concerning a specific case (e.g., "Dominique is a randomly chosen participant of this study. Dominique is 23 years old and is finishing a degree in engineering. On Friday nights, Dominique likes to go out cruising with friends while listening to loud music and drinking beer"). Participants are required to decide to which one of the groups the imaginary person more likely belongs to. The task includes four no-conflict (congruent) items in which the description of the specific case fits common stereotypes of the smaller population group, and four conflict (incongruent) items in which the base-rates favour the group contrary to the stereotypical characteristic.

Items (4)

1. Among the 1000 people that participated in the study, there were 995 nurses and 5 doctors. John is randomly chosen participant in this research. He is 34 years old. He lives in a nice house in a fancy neighborhood. He expresses himself nicely and is very interested in politics. He invests a lot of time in his career.

Which is more likely?

a) John is a nurse. (correct)
b) John is a doctor.

2. Among the 1000 people that participated in the study, there were 100 engineers and 900 lawyers. George is randomly chosen participant in this research. George is 36 years old. He is not married and is somewhat introverted. He likes to spend his free time reading science fiction and developing computer programs.

Which is more likely?

a) George is an engineer.
b) George is a lawyer. (correct)

3. Among the 1000 people that participated in the study, there were 50 16-year-olds and 950 50-year-olds. Helen is randomly chosen participant in this research. Helen listens to hip hop and rap music. She likes to wear tight T-shirts and jeans. She loves to dance and has a small nose piercing.

Which is more likely?

a) Helen is 16 years old.
b) Helen is 50 years old. (correct)

4. Among the 1000 people that participated in the study, there were 70 people whose favorite movie was "Star Wars" and 930 people whose favorite movie was "Love actually". Nikola is randomly chosen participants in this research. Nikola is 26 years old and is studying physics. He stays at home most of the time and loves to play video games.

Which is more likely?

a) Nikola's favorite movie is "Star Wars"
b) Nikola's favorite movie is "Love actually" (correct)

Scoring

Correct responses are scored as 1 and the total score is the average of the scores.

Sources

Erceg, N., Galić, Z., & Bubić, A. (2022). Normative responding on cognitive bias tasks: Some evidence for a weak rationality factor that is mostly explained by numeracy and actively open-minded thinking. Intelligence, 90, 101619.

De Neys, W., & Glumicic, T. (2008). Conflict monitoring in dual process theories of thinking. Cognition, 106(3), 1248–1299.