Representative Heuristic
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Introduction
The representative heuristic is a cognitive shortcut made when individuals assess the frequency of a particular event based solely on the generalization of a previous similar event. Representativeness is “an assessment of the degree of the correspondence between a sample and a population[…]or between an outcome and a model.” (Gilovich, 2002). In general, common instances are more representative than infrequent events. Although use of the representative heuristic is often the quickest and easiest way of making a decision, similarity does not ensure membership, indicating that a resemblance may instead reflect casual and correlation beliefs. (Gilovich, 2002). There are many different examples of the representative heuristic.
Base rate Fallacy
The base rate fallacy occurs when one fails to correctly take base rate information into account. For example, in an experiment done by Casscells, Schoenberger, and Grayboys (1978), the experiments presented the following question to 60 students and staff at Harvard Medical School: If a test to detect a disease whose prevalence is 1/1000 has a false positive rate of 5%, what is the chance that a person found to have a positive result actually has the disease, assuming you know nothing about the person’s symptoms or signs? The most common answer was 95%, as even the Harvard educated students did not appreciate the effect of the base rate on their answers (Kahneman, 1974).
Regression to the Mean
Regression to the mean refers to the “statistical tendency for extreme scores or extreme behavior return toward the average” (Baumeister, 2008). Some common examples that exemplify the failure to understand regression to the mean are the “sophomore slump” and the Sports Illustrated Jinx. The sophomore slump refers to decrease in performance many exceptional athletes experience after their rookie year. This supposed slump is not really a decrease in performance, but rather a leveling to the average performance of the player. In reality, athletes go through peaks and lows in their performances throughout their career, not just in their second year of playing. (Schwarz, 2005) Another example of regression to the mean is the Sports Illustrated Jinx, which is a myth that suggests that because a team graces the cover of Sports Illustrated, they are cursed to perform worse in subsequent games. This, however, can also be explained by regression to the mean. When a team is put on the cover on Sports Illustrated, more often than not they are having an exceptional year. It only stands to time that as the team progresses, they will return to their average level of play (Wolff, 2002).
Gambler’s fallacy
The gambler’s fallacy is the misperception of chance that occurs when a person believes that an orderly sequence of numbers is less common than a random sequence of numbers and that it is affected by previous events. In other words, a person’s “conception of randomness departs systematically from the laws of chance” (Gilovich, 2002). In an experiment examining this fallacy, Budescu (1987) asked his participants to randomly choose hypothetical heads or tails by pressing one of two keys on a computer. By analyzing the data he got from his subjects, he found that his subjects generated too many alternations, as “they perceive sequences with too many alternation by more random than truly random sequences” (Ward, 2001).
Conjunction Fallacy
The conjunction fallacy dictates that the probability of a co-occurrence of two outcomes can’t be greater than the probability of each outcome alone.(Baumeister, 2008) Kahneman and Tversky asked a number of students the following question: “Linda is 31, 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 antinuclear demonstrations. Is she more likely to be (a) a bank teller, or (b) a bank teller and active in the feminist movement. 86% answered (b)”( Gilovich, 2002). Because representativeness depends on common and distinctive features, it logically “should be enhanced by the addition of shared features” (Gilovich, 2002). However, in the total population, there are more bank tellers than bank tellers who are active feminists, so statistically it is much more probable that Linda is a bank teller.
References
Baumeister, Roy f. and Brad J. Bushman. Social Psychology and Human Nature. Belmont, CA; Thomson Learning, 2008.
Gilovich,Thomas, Dale Griffin, and Daniel Kahneman. Heuristics and Biases -The Psychology of Intuitive Judgment . New York; Cambridge University Press, 2002.
Kahneman, Daniel, Paul Slovic, and Amos Tversky. Judgment under Uncertainty: Heuristics and Biases. New York; JSTOR, 1974.
Schwarz, Alan. “Real Year 2 Curse: Being Good in First Place.” The New York Times. 13 February 2005.
Ward, Lawrence M. “Can People Behave Randomly?” Dynamical Cognitive Science. The MIT Press. 2001. 10 April 2008. http://cognet.mit.edu/library/books/mitpress/0262232170/cache/chap29.pdf
Wolff, Alexander. “Unraveling the Jinx.” SportsIllustrated.com. 15 January 2002. 10 April 2008, http://sportsillustrated.cnn.com/inside_game/alexander_ wolff/news/2002/01/15/wolff_viewpoint/. Insert non-formatted text here
