S2W4Judg Flashcards
Judgement
Deciding the likelihood of various events using incomplete information (likelihood rather than choice).
Inductive Reasoning
Making a conclusion that is probably, but not definitely, true:
All of the swans I have seen are white
I expect that all swans are white
Factors contributing to strength of an inductive argument
Representativeness of observations:
o How well do observations of category represent all members of it
Number of observations
Quality of the evidence
Availability Heuristic
Events that are more easily remembered are judged to be more probable than events that are less easily remembered.
Availability Heuristic
Tversky & Kahneman (1973)
Which are more prevalent in English, words that begin with the letter r or words in which r is the third letter?
70% said more words begin with r
In reality 3x more words have r in the third position
Easier to think of words that start with r than words with r as third letter
Availability Heuristic
Lichtenstein et al (1978)
Participants asked to judge prevalence of causes of death
Given pairs of causes of death and asked to say which was more prevalent
Appendicitis twice as fatal as pregnancy but pregnancy receives more media attention so people got a lot of pairs wrong.
Affect Heurist
Basing a judgement on how much dread one feels (if you’re scared you think it’s more likely to happen).
Illusory Correlation
You believe a correlation is present between two events, but this is false or weaker than assumed.
May be a stereotypes:
Oversimplified generalisation about group
(often negative)
Every time you see someone doing something negative it reinforces your stereotype even though it’s the minority.
Representativeness Heuristic
The probability that A is a member of class B.
Determined by how well properties of A resemble properties usually associated with class B.
Representativeness Heuristic
Kahneman and Tversky, (1974)
Randomly pick one male from population.
Robert, wears glasses, speaks quietly, and reads a lot. Is it more likely that Robert is a librarian or a farmer?
Most people guess librarian
Far more farmers than librarians in population
Ten times more male farmers than librarians (base rate information)
When only base rate is available, people will use this information
When descriptive information is available, people disregard base rate information, causing errors.
Conjunction Rule
Probability of two events cannot be higher than the probability of the single constituents.
Which of the following is more probable?
Linda is a bank teller
Linda is a bank teller and a feminist.
85% chose 2
Participants influenced by repetitiveness heuristic
Ignored the conjunction rule
Law of Large Numbers
The larger the number of individuals randomly drawn from a population, the more representative the resulting group will be of the entire population.
The larger the sample the more representative it is of the population.
Law of Large Numbers
Tversky and Kahneman (1974)
In the large hospital 45 babies are born each day.
In the small one 15 babies are born each day.
Although the overall proportion of genders is 50/50
Which hospital will have more days where 60%+ were girls?
- the large
- the small
- the same
22% picked small
22% picked large
56% picked same
Correct answer: the small hospital
Smaller samples of numbers of individuals less likely to be representative of general population.
Myside Bias
Tendency for people to evaluate evidence and test hypotheses in a way that is biased toward own opinions
Errors occur when people let their own opinions and attitudes influence how they evaluate evidence needed to make decisions.
Myside Bias
Lord et al. (1979)
Gave questionnaire to two groups, one in favour of capital punishment and one against.
Presented them with descriptions of research studies into capital punishment.
Participants rated articles – responses reflected attitudes they had at the start of the study.
Confirmation Bias
Tendency to selectively look for information that conforms to our hypothesis and overlook information that argues against it.
Confirmation Bias
Wason (1960)
2, 4 & 6 conform to a rule.
Write down sets of numbers and reasons for your choice to discover my rule.
I shall tell you whether your numbers conform to the rule or not and then you can tell me the rule.
Most common hypothesis was increasing intervals of two
Actual rule was three numbers in increasing order of magnitude.
Secret is to find sequences that don’t satisfy your rule but do satisfy Wason’s.
