COG 100 Lecture Notes - Lecture 6: Conjunction Fallacy, Heuristics In Judgment And Decision-Making, Representativeness Heuristic
5 May 2018
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The conjunction fallacy is a fallacy that occurs when you rank the whole (a+b) to be more
probable than A alone. For A+B to happen either A or B is needed so they are more
probable to occur rather than the whole. Most people rank the occurrence of A+B higher
than the specific condition (a or b). It happens because prior knowledge and the more details
(a+b has more details than A) seems more likely. Example is the linda. She's an activist
concerned in justice and race. Patients asked which is more likely. Linda is a bank teller or
linda is a bank teller who is an activist. People chose the second option (a+B) because it
seemed more probably even though probability shows that A is more probably. That is the
violation of probability in the conjunction fallacy. It is a representativeness heuristic because
the belief that A+B is more probably is based on prior knowledge which affects our belief.
● The conjunction fallacy is a formal fallacy that occurs when it is assumed that specific
conditions are more probable than a single general one. when given a list, people will rank A+B
more likely than just A, it violates because to get A+B, A needs to exist
● ex.) Nuclear war in asia (A). Radicals take over the pakistan government and there is a nuclear
war in Asia (A+B). Conjunction cannot be more likely than each of its conjuncts, so A+B
● it seems more likely because of our prior knowledge and the more details specified. A does not
have the contact points that A+B has
Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student,
she was deeply concerned with issues of discrimination and social justice, and also participated in
anti-nuclear demonstrations.
Which is more probable?
1. Linda is a bank teller.
2. Linda is a bank teller and is active in the feminist movement.
The majority of those asked chose option 2. However, the probability of two events occurring
together (in "conjunction") is always less than or equal to the probability of either one occurring
alone—formally, for two events A and B
11. Explain the heuristic of anchoring and adjustment. How does it produce mistaken results,
give an example or two to illustrate. How might it be similar to precedence effect?
The heuristic of anchoring and adjustment is psychological based on probabilities and how
humans assess them. Everyone has an average or mean set in mind and that is the anchor
part. They make adjustments as experience go on. It relates to precedence heuristic because
people tend to stick with their initial thoughts so what ever probability is their initial thought is
anchor and adjustments follows. It can produce mistaken results because people's probabilities
aren't always correct and reliable.
● Lecture 11/28
○ Anchoring and Adjustment:
■ Precedence effect:
■ First piece of information holds more weight than following
● People will tend to stick to their initial thought because it came first
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The conjunction fallacy is a fallacy that occurs when you rank the whole (a+b) to be more probable than a alone. For a+b to happen either a or b is needed so they are more probable to occur rather than the whole. Most people rank the occurrence of a+b higher than the specific condition (a or b). It happens because prior knowledge and the more details (a+b has more details than a) seems more likely. She"s an activist concerned in justice and race. Linda is a bank teller or linda is a bank teller who is an activist. People chose the second option (a+b) because it seemed more probably even though probability shows that a is more probably. That is the violation of probability in the conjunction fallacy. It is a representativeness heuristic because the belief that a+b is more probably is based on prior knowledge which affects our belief.
