# experimental typical reasoning

DaisyLocs
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## TypicalReasoning.doc

Typical Reasoning Minimum time to complete this experiment: 20 minutes

Background:

Tversky and Kahneman (1983) are well known for their research showing that people's estimates of probability are often very different from the objective probabilities. The reason, they argue, is that people often use heuristics to help them estimate the answer. Heuristics can be seen as sacrificing some accuracy for an increase in speed. By using heuristics, people can very quickly come up with an answer that is usually good enough for day-to-day purposes. These heuristics, however, can lead to incorrect judgments.

One of the most striking errors is known as the conjunction fallacy. In its most simple form, it says that people think that having both A and B occur is more likely than having just A occur or just B occur. According to objective probabilities, the probability of two events occurring has to be less than the probabilities of either of the events happening by itself. In some circumstances, however, people are more likely to say the conjunction (having both events occur) is more likely.

In particular, the conjunction fallacy is more likely when the items are typical than when they are atypical. For example, read the following: Julie is 26 years old, has a degree in physical education, has been physically fit since childhood, and loves the outdoors. People think it is more likely that Julie is a ski instructor who also teaches aerobics (a conjunction involving an activity thought to be more typical of ski instructors) than that Julie is a librarian who also teaches aerobics (a conjunction involving an activity thought to be less typical of librarians). When the activity is particularly typical, the conjunction can be thought more likely than the single events (e.g., that Julie is a ski instructor). This demonstration is based on an experiment by Shafir, Smith, and Osherson (1990). You will read short descriptions about several people and you will be asked to rate the probability that these people have certain professions and/or engage in certain activities.

a. Describe one advantage and one disadvantage of using heuristics, such as typical reasoning

b. Did your data confirm the prediction that you would be more certain of the answers to the questions (give higher ratings) if the behaviors outlined in the questions seemed typical of the persons described? If your data did not confirm this prediction, how do you explain your results?

c. Describe how you went about judging the certainty of your answers to the questions asked. Use your answer to 1 of the 12 questions as an example of how you came to rate the question in the way that you did.

d. What is a stereotype? How do stereotypes relate to the findings of this experiment?

e. How might the methods and results of this experiment be related to experiences in your everyday life?

Basic Questions

1. What is an advantage of using heuristics? What is a disadvantage of using heuristics?]

2. . Describe the conjunction fallacy.

3. For this demonstration, on average did participants give higher ratings for single events or conjunctions of events? Based on the demonstration results, are participants making their judgments by using objective probabilities? Why or why not?