posted 4/12/06
Reading assignment:  Chapter 14

Video #1662 (Available from Media Services)

Heuristics & Biases

• __________ = the phenomenon
•  Systematic deviation from a normative standard
• _________ = the descriptive theory
•  Simple strategy that usually gives the normative answer, but which leads to systematic bias in some circumstances

• 3 biases from Kahneman and Tversky
• Availability bias
• Conjunction Fallacy
• Anchoring

• Assess the frequency of a class or the probability of an event by the ______________________________________.
• Instances of large classes or likely events are usually accessed faster and easier.
• But, availability is also influenced by factors other than frequency/probability.
• sometimes events are _________ but not _______________

• People judge a _____________ to be more likely than a _______________.
• Or air travel to be more dangerous than car travel.

• Which are more common:
• Words with r as the first letter
• Words with r as the third letter
• Much easier to think of example words that start with r, so think that is more frequent.
• But here, greater availability is due to _______________, not greater frequency.
• _____________ = judging more “available” events to be more likely, even when they are not.

• How long is the Mississippi River?  More or less than 3,000 miles?
• Answers are influenced by the ___________________.
• Explanation? “Anchoring and adjustment” — subject starts with anchor and adjusts (____________) to final response

• What is the percentage of African countries in the United Nations, more or less than 10%?  [or 65%]
• (Anchor number determined by spin of wheel of fortune.)
• What is the percentages? ______%
• Median responses were _____% and _____% for the two groups.

• Tversky & Kahneman original description:
• Estimate a quantity by starting from an initial value that is adjusted to yield the final answer.  Adjustment is frequently insufficient.
• Current theories of anchoring
• Don’t talk about __________________
• Instead implicate memory priming processes
• Information consistent with the anchor is more ____________.

• Subjects judge that it is more likely that Linda in a feminist bankteller than that she is a bankteller.
• Violates conjunction rule of _____________ Theory
• p(A) > p(A & B)
• Explanation : __________________ Heurstic
• Judge likelihood that X is a member of category Y by determining how representative X is of Y
• Problematic because other factors (such as category size) are also relevant.

• Descriptive Theory
• Probability judgments based on __________________ or representativeness
• If Linda is similar to a feminist bankteller, than Linda is likely to be a feminist bankteller
• If A is similar to B, then A is likely to be related to B or to be caused by B.

• Conjunction fallacy
• _____________________
• Insensitivity to sample size
• Misconceptions of chance
• Insensitivity to predictability
• Illusion of validity
• Misconceptions of regression

• Linda’s description is more representative of a feminist bank teller than of a bank teller.
• Conjunction rule and probability theory are irrelevant to representativeness

• Which is more likely
• A flood in California that kills more than 1000 people.
• An earthquake that triggers a flood in California that kills more than 1000 people.
• Easier to________________ that produce the latter.
• Similarly, easier to image a scenario in which a man over age 55 has a heart attack, than on in which a man has a heart attack.

• Tests a __________ account of the Conjunction Fallacy
• Maxim of ___________:  speaker should say what is relevant.
• If experimenter gives a description of Linda, it must be relevant to the judgment I am supposed to give.

• Linda is active in the feminist movement.
• Linda is a bank teller.
• Linda is a bank teller and active in the feminist movement.

Typicality Judgments

• How typical are each of the following statements of Linda?
• Linda is active in the feminist movement.
• Linda is a bank teller.
• Linda is a bank teller and active in the feminist movement.
• Then rank order the statements for likelihood.
• Should prevent Ss from thinking that the Linda description needs to be relevant to the likelihood judgments

• When asked to rank order the statements for likelihood, the statements appeared like this:
• Linda is active in the feminist movement.
• Linda is a bank teller whether or not she is active in the feminist movement.
• Linda is a bank teller and active in the feminist movement.
• Should prevent Ss was interpreted “bankteller” as “non-feminist bankteller”

Methods

• Subjects:  120 students in this class
• Procedure: Paper-and-pencil questionnaire completed during class
• Linda description
• Typicality ratings (for some conditions)
• Rank order likelihood (w/ WON vs. regular wording)
• Set problems using Venn Diagrams

• 56% of Ss ranked FBT as less likely than both F and BT
• 27% showed the usual type of conjunction fallacy:  FBT > BT
• 17% showed an unusual conjunction fallacy:  FBT > F
• Why so many unusual CFs?

• It seems that many Ss found it confusing to rank order likelihood.
• Rank of 1  means most likely
• Rank of 3 means least likely
• Many Ss seem to have used 3 to mean most likely and 1 mean least likely.
• We checked how many Ss ranked F ahead of BT (e.g., F = rank 1, BT = rank 2)

Number of Conjunction Fallacies

	Typicality Judgments Yes	Typicality Judgments No
"Whether or not" wording
Regular wording

Score on Venn Diagram Problems (out of 8 possible)

	Typicality Judgments Yes	Typicality Judgments No
"Whether or not" wording
Regular wording