Lecture+5 - 305:03 Cognition Fall 2009 Dr.JulienMusolino...

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Fall 2009 305:03 – Cognition Dr. Julien Musolino “The mind is what the brain does” – Steven Pinker
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Outline _____________________________ We sometimes misperceive the world around us We tend to oversimplify our thinking We underestimate the role of chance and coincidence in shaping events Discussion of your assignment
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How we simplify _______________________________________________________ Our decisions can be quite complex In fact, if we wanted to maximize the accuracy of our judgments, we would have to gather an enormous amount of information
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Heuristics _______________________________________________________ Heuristics: general rules of thumb that we use to simplify complicated judgments Advantages: reduce the time and effort required to make a decision, and often result in reasonably good decisions Disadvantages: heuristics can lead to systematic biases that result in grossly inaccurate judgments
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Heuristics _______________________________________________________ The representativeness Heuristic The availability Heuristic Medical decisions Racial profiling Causes of death Drugs: scaring the population
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The representativeness Heuristic _______________________________________________________ Base rates and medical decisions
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Base rates _______________________________________________________ The test is 100% accurate in indicating a person has the virus when they actually have it The test indicates a person has the virus when they don’t actually have it 5% of the time (false positive rate) The virus is present in 1 out of 500 people
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Ignoring base rates _______________________________________________________ You were screened for the virus and the test came back positive. What is the probability that you actually have the virus? A lot of people, including medical professionals say 95%
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Ignoring base rates _______________________________________________________ 500 1 499 The test is 100% accurate in indicating a person has the virus when they actually have it The test indicates a person has the virus when they don’t actually have it 5% of the time (false positive rate) 1 1 499 25 (0.05 x 499 = 25)
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Ignoring base rates _______________________________________________________ The test will say that 26 people have the virus (25 + 1) Whereas in fact, only 1 person in those 26 have the virus 1 in 26 is only 3.8%!
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This note was uploaded on 11/28/2011 for the course PSYCHOLOGY 830:301 taught by Professor Staff during the Fall '10 term at Rutgers.

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Lecture+5 - 305:03 Cognition Fall 2009 Dr.JulienMusolino...

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