Thinking 2 Flashcards
What is normative reasoning?
-Real decision making scenarios tend to include probable information e.g. likelihood of something occurring
-Probability theories used to give best decision possible in scenarios e.g. Bayes’ Theorem
What is human reasoning?
-Isn’t normative, aren’t applying mathematical theories in day to day life
-Kahneman and Tversky investigated these situations where reasoning is biased
What are the 2 heuristics?
-Biases occurred due to heuristics (cognitive short cuts) to answer complex probabilistic questions
-Representative heuristic
-Availability heuristic
What is the representative heuristic?
-”Likelihood of an event is evaluated by degree to which it is representative of the major characteristics of the process or population from which it originated” - Kahneman and Tversky (1972)
-Assumption that representative or typical members of a category are encountered more frequently
State the 2 studies supporting the representative heuristic
-Kahneman and Tversky (1972)
-Tversky and Kahneman (1981) - The Linda Problem
Describe Kahneman and Tversky (1972) study
-Asked ppts to judge professions from brief descriptions
-Box contained 100 brief descriptions of people
-30 descriptions are of engineers
-70 descriptions are of lawyers
-Subjects draw cards out of the box, read description and have to describe if the person is an engineer or a lawyer
Describe the study Tversky and Kahnemen (1981) study, The Linda Problem
-”Linda is 31 years old, single and 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 anti-nuclear demonstrations”
-Which of the following is most likely?
-Linda is a bank teller
-Linda is a bank teller and is active in the feminist movement
What are the results of the Tversky and Kahnemen (1981) study, The Linda Problem?
-90% of subjects feel as if Linda is more likely to be a feminist bak teller rather than just a bank teller
-HOWEVER, this is wrong!
What are the 2 fallacies?
-Conjunction fallacy
-Gamblers fallacy
Describe the Conjunction fallacy
-Reasoning error where people think that the chance of 2 things happening together is greater than chance of one of the two things happening alone
-Occurs as certain situations appear more likely than general ones
-More representative of what we imagine
Describe the Gambler’s fallacy (Monte Carlo Fallacy)
-Flipping coins, have to guess what comes next (head, tail, head, head, head, head…)
-Both equally likely as coin has no memory
-Mistaken belief that future tosses of a coin are influenced by past events
Summarise the representative heuristic
-Judging the likelihood of an event based on the extent to which it is similar to a prototype in our minds
-Sometimes, it’s helpful to cognitive shortcut
-Sometimes, it can lead to errors in judgement
What is the availability heuristic?
-Getting information wrong due to the availability of the info
-Can be due to media coverage
-Memory effect occurs
-“rule of thumb in which decision makers assess the frequency of a class of the probability of an event by the ease with which instances or occurrences can be brought to mind” - Tversky and Kahneman (1974)
What are the 2 studies supporting the availability heuristic?
-Tversky and Kahneman (1974)
-Lichtenstein et al. (1978)
Describe the study by Tversky and Kahneman (1974)
-Asked ppts which of the following was more frequent:
-’A word in English has K as the 1st letter’
-’A word in English has K as the 3rd letter’
What are the results of this study (Tversky and Kahneman, 1974)?
-69% answered A correctly
-There are twice as many words with K as the 3rd letter as there are with K as the 1st
-Argue that because our lexicon is organised by spelling more words beginning with K are available for retrieval
Describe the study by Lichtenstein et al. (1978)
-Looked at judged frequency of lethal events
-Judging the frequency of an event based on how easily relevant examples or instances come to mind
-If something is readily available in memory, we have a bias to assume it is more likely
-Research has shown that when people apply this heuristic they;
-Underestimate the probabilities of high frequency events
-Overestimate the probabilities of low frequency events
-Shown when judging how many deaths occur from certain things e.g. cancer
What is base rate neglect?
-Ignore general prevalence of tenet happening
-Instead, they favour info related to specific case they are presented with
-This is a problem as base rate is required to make correct judgements
Describe the Taxi Cab Study conducted by Tversky and Kahnerman (1982)
-A cab was involved in a hit and run accident at night. Two cab companies; the Green and the Blue, operate in the city. You are given the following data:
-85% of cabs in city are green and 15% are blue (base rates)
-A witness identified the cab as blue
-Court tested reliability of witness under same circumstances that existed of the night of the accident and concluded that the witness correctly identified each one of the two colours 80% of the time and failed 20% of the time
-What is the probability that the cab involved in the accident was blue (rather than green)?
What are the results of the Taxi Cab Study conducted by Tversky and Kahnerman (1982)?
-The correct answer 0.41 (41%)
Describe the Casscells et al., (1978) Medical Diagnosis study
-Medical students were asked;
-If a test is 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 test results actually has the disease assuming that you know nothing about the persons symptoms or signs
What are the results of the Casscells et al., (1978) Medical Diagnosis study
-45% of ppts responded 95% (response that ignores base rate)
-Only 18% responded 2% (correct Bayesian inference)
-Shows that those in medical profession also experience base rate neglect for diagnostic problems
Describe the study conducted by Cosmides and Tooby (1996)
-Given a piece of text around medical issues
-Asked ‘On average, how many people who test positive for the disease will actually have the disease’
What are the results of the study conducted by Cosmides and Tooby (1996)?
-Probability format - high number of people chose 95% (incorrect)
-Frequency format - high number of people chose 2% (correct)
-Base rate neglect in medical decisions is more likely when presented using probabilities
-Base rate neglect in medical decisions is less likely when presented using frequencies
