Conjunction Fallacy (Representative Conjunctions)
The cited studies ask whether conjunction errors persist outside social stereotypes, when uncertainty comes from chance, when experts judge, or when financial incentives are offered.
THE IDEA
MORE REPRESENTATIVE CONJUNCTIONS
Earlier studies in the source revealed massive violations of the conjunction rule in the domain of person perception and social stereotypes. Does the conjunction rule fare better in other areas of judgment? Does it hold when the uncertainty regarding the target events is attributed to chance rather than to partial ignorance? Does expertise in the relevant subject matter protect against the conjunction fallacy? Do financial incentives help respondents see the light? The subsequent studies were designed to answer these questions, but their results are not included in this excerpt.
When to use it
Evaluating risk in investments where a specific scenario might seem more likely than a general one.
Judging the probability of multiple symptoms in medical diagnosis, where a specific combination may appear more representative.
Assessing the likelihood of a sequence of events in project planning, where a detailed narrative seems more plausible than a simple statement.
FROM THEORY TO EVERYDAY LIFE
In practice
The Linda Problem
A classic example of the conjunction fallacy: Participants are told that Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy and was deeply concerned with issues of discrimination and social justice. When asked to rank probabilities, many people say that 'Linda is a bank teller and active in the feminist movement' is more likely than 'Linda is a bank teller,' violating the conjunction rule because the conjunction cannot be more probable than one of its components.
A MOMENT TO REFLECT
Put it to work.
Why does the conjunction fallacy often occur in social stereotypes?
Can expertise in a domain reduce the likelihood of committing the conjunction fallacy?
How do financial incentives affect people's judgment of conjunctions?
Often confused with
CONTINUE THE CONVERSATION
Source texts
- Heuristics and Biases The Psychology of Intuitive Judgment (Thomas Gilovich, Dale Griffin, Daniel Kahneman)