# Oregon State Legislature

Psychology of Addictive Behaviors.

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Representative Teresa Alonso Leon Party: Representative Jeff Barker Party: Representative Phil Barnhart Party: Representative Deborah Boone Party: Representative Janelle Bynum Party: Representative Brian Clem Party: Representative Margaret Doherty Party: Representative Paul Evans Party: Representative Julie Fahey Party: Representative David Gomberg Party: Representative Chris Gorsek Party: Representative Mitch Greenlick Party: Representative Ken Helm Party: Representative Diego Hernandez Party: Representative Paul Holvey Party: Representative Alissa Keny-Guyer Party: Representative Tina Kotek Party: Representative John Lively Party: Representative Pam Marsh Party: Representative Caddy McKeown Party: The findings supported the authors' predictions that people make predictions based on how representative something is similar , rather than based on relative base rate information.

In another study done by Tversky and Kahneman, subjects were given the following problem: A cab was involved in a hit and run accident at night. Two cab companies, the Green and the Blue, operate in the city. A witness identified the cab as Blue. What is the probability that the cab involved in the accident was Blue rather than Green knowing that this witness identified it as Blue?

The correct answer, found using Bayes' theorem , is lower than these estimates:. Representativeness is cited in the similar effect of the gambler's fallacy , the regression fallacy and the conjunction fallacy. The use of the representativeness heuristic will likely lead to violations of Bayes' Theorem.

However, judgments by representativeness only look at the resemblance between the hypothesis and the data, thus inverse probabilities are equated:. As can be seen, the base rate P H is ignored in this equation, leading to the base rate fallacy. The base rate fallacy describes how people do not take the base rate of an event into account when solving probability problems. For example, participants were asked how many people out of answered true to the question "I am a conscientious person" and also, given that a person answered true to this question, how many would answer true to a different personality question.

They found that participants equated inverse probabilities e. A medical example is described by Axelsson. This statistic often surprises people, due to the base rate fallacy, as many people do not take the basic incidence into account when judging probability.

Research by Bar-Hillel suggests that perceived relevancy of information is vital to base-rate neglect: Some research has explored base rate neglect in children, as there was a lack of understanding about how these judgment heuristics develop. The authors found that the use of the representativeness heuristic as a strategy begins early on and is consistent. The authors also found that children use idiosyncratic strategies to make social judgments initially, and use base rates more as they get older, but the use of the representativeness heuristic in the social arena also increase as they get older.

The authors found that, among the children surveyed, base rates were more readily used in judgments about objects than in social judgments. There was also evidence that children commit the conjunction fallacy. Finally, as students get older, they used the representativeness heuristic on stereotyped problems, and so made judgments consistent with stereotypes. Research suggests that use or neglect of base rates can be influenced by how the problem is presented, which reminds us that the representativeness heuristic is not a "general, all purpose heuristic", but may have many contributing factors.

A group of undergraduates were provided with a description of Linda, modeled to be representative of an active feminist. Then participants were then asked to evaluate the probability of her being a feminist, the probability of her being a bank teller, or the probability of being both a bank teller and feminist. Probability theory dictates that the probability of being both a bank teller and feminist the conjunction of two sets must be less than or equal to the probability of being either a feminist or a bank teller.

A conjunction cannot be more probable than one of its constituents. However, participants judged the conjunction bank teller and feminist as being more probable than being a bank teller alone. From probability theory the disjunction of two events is at least as likely as either of the events individually. For example, the probability of being either a physics or biology major is at least as likely as being a physics major, if not more likely.

However, when a personality description data seems to be very representative of a physics major e. Evidence that the representativeness heuristic may cause the disjunction fallacy comes from Bar-Hillel and Neter Thus, only when the person seems highly representative of a category is that category judged as more probable than its superordinate category. These incorrect appraisals remained even in the face of losing real money in bets on probabilities.

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