Reasoning and Decision-Making Flashcards
Probability judgments often deviate from the dictates of probability theory
What are the 2 theories?
1) Heuristics and the biases
2) Ecological rationality
Apparent biases may be rational responses given the ecology of the human decision-maker
This is known as…?
Ecological rationality
Simplifying strategies that reduce effort but are prone to bias/error
This is known as…?
Heuristics and the biases
Are people generally good or bad at working with probability?
Bad
Define Heuristics and Biases
When people base their intuitive probability and frequency judgments on simple, experience-based strategies (“heuristics”) which are right (or good enough) most of the time
But which will sometimes lead to biased or illogical responses
When people base their intuitive probability and frequency judgments on simple, experience-based strategies (“heuristics”) which are right (or good enough) most of the time
But which will sometimes lead to biased or illogical responses
This is known as…?
Heuristics and Biases
What are the 3 types of Heuristics and Biases?
1) Availability
2) Representativeness
3) Anchoring
1) Availability
2) Representativeness
3) Anchoring
Are these part of Ecological rationality or Heuristics and Biases?
Heuristics and Biases
What view falls within a broader view of cognition that posits two systems:
1) A fast, associative, automatic, “System 1”
2) A slower, deliberative “System 2” that uses sequential processing and rule-based operations.
Heuristics and Biases
Heuristics and biases falls within a broader view of cognition that posits two systems
What are they?
1) A fast, associative, automatic, “System 1”
2) A slower, deliberative “System 2” that uses sequential processing and rule-based operations.
Describe the Availability Heuristic
Judgments are based on the ease with which relevant instances come to mind
Simply = If an event happens a lot then it will be easy to think of many past instances, so basing judgments on availability is sensible.
Judgments are based on the ease with which relevant instances come to mind
Simply = If an event happens a lot then it will be easy to think of many past instances, so basing judgments on availability is sensible.
This is known as…?
a. Availability
b. Representativeness
c. Anchoring
a. Availability
Overestimating the chances that a shark will attack you when you swim in the ocean is an example of…?
a. Availability
b. Representativeness
c. Anchoring
a. Availability
When it is easier to bring to mind things that happen frequently
This is known as…?
a. Availability
b. Representativeness
c. Anchoring
a. Availability
What are the 2 ways availability heuristic can entail bias?
- Our experience of past events does not reflect their true frequencies
- Events are easy to recall for some reason other than their frequency of occurrence
- Our experience of past events does not reflect their true frequencies
- Events are easy to recall for some reason other than their frequency of occurrence
These are implications of…?
a. Availability
b. Representativeness
c. Anchoring
a. Availability
Describe the study by Lichtenstein et al. (1978) in estimating causes of death
List 2 points
1) Ps estimate the number of US deaths per year due to 40 causes
2) The causes ranged from very rare (e.g., botulism, with one death per 100 million people) to very common (e.g., stroke: 102 000 deaths per 100 million people)
Describe the results of the study by Lichtenstein et al. (1978) in estimating causes of death
Ps over-estimated rare causes and underestimated common causes
Ps over-estimated rare causes and underestimated common causes of death
Why does this occur?
Because rare events/causes of death gets a lot of attention in media
But common events/causes of death happen too frequently that often, the media does not cover them because it would be too repetitive
Describe the study by Tversky & Kahneman (1973) on the effect of memory
List 3 points
1) Ps listened to list of 39 names including:
19 famous women and 20 less famous men
OR
19 famous men
20 less famous women
2) Some Ps had to write down as many names as they could recall
3) Others were asked whether the list contained more names of men or of women
Describe the results of the study by Tversky & Kahneman (1973) on the effect of memory
List 2 points
1) In the recall task, Ps retrieved more of the famous names (12.3 out of 19) than the non-famous names (8.4 out of 20). That is, famous names were more available.
2) 80 out of 99 (81%) Ps judged the gender category that contained more famous
names to be more frequent.
(e.g., the people given a list of 19 famous men and 20 less famous women reported that there were more men than women in the list)
1) In the recall task, Ps retrieved more of the famous names (12.3 out of 19) than the non-famous names (8.4 out of 20). That is, famous names were more available.
2) 80 out of 99 (81%) Ps judged the gender category that contained more famous
names to be more frequent.
(e.g., the people given a list of 19 famous men and 20 less famous women reported that there were more men than women in the list)
What do these results suggest?
List 2 points
1) It seems that people made their proportion estimates by assessing the ease with which examples of each come to mind
2) When one category was easier to retrieve (via the fame manipulation) it was judged more frequent, even when it was actually experienced less often
When one category was easier to retrieve (via the fame manipulation) it was judged more frequent, even when it was actually experienced less often
This is an example of…?
a. Availability
b. Representativeness
c. Anchoring
a. Availability
When people mistakenly believe that two events happening together is more likely than one of the events happening alone
This is known as…?
Conjunction fallacy
When subjective probability estimates sometimes violate this principle: The probability of event “A” cannot be less than
the probability of the conjunction “A and B”.
This is known as…?
Conjunction fallacy
Describe Tversky and Kahneman’s (1983) study on conjunction fallacy
List 2 points
1) Ps were asked; In four pages of a novel (about 2,000 words), how many words would you expect to find that have the form:
a. seven letter words that end with ING
b. seven letter words with ‘n’ as the penultimate letter
2) All ING words have N as the penultimate letter, so the number of N words must be at least as large as the number of ING words.
Describe the results of Tversky and Kahneman’s (1983) study on conjunction fallacy
List 2 points
1) Ps estimated, on average, 13.4 ending in ING words
2) But Ps only estimated 4.7 words with N as the penultimate letter
1) Ps estimated, on average, 13.4 ending in ING words
2) But Ps only estimated 4.7 words with N as the penultimate letter
What do these results suggest?
List 2 points
1) People may be basing their judgments on the mental availability of relevant instances
2) It is easy to think of “ing” words (e.g., by thinking of words that rhyme) but we are less accustomed to retrieving words based on their penultimate letter, so N words are harder to retrieve and thus seem rarer.
Under what circumstance will the conjunction fallacy problem disappear?
If/when participants apply a more systematic mental search strategy
Define the representativeness heuristic
Judgments are based on the extent to which an outcome (or item) is representative of the process or category in question
Simply = Judgments of probability are based on assessments of
similarity
Judgments are based on the extent to which an outcome (or item) is representative of the process or category in question
Simply = Judgments of probability are based on assessments of
similarity
This is known as…?
The representativeness heuristic
According to the representativeness heuristic, when estimating a probability – for example, how likely it is that a person belongs to a particular category or the probability that an observed sample was drawn from a particular population
What do people assess?
The similarity between the outcome and the category (or between the sample and the population)
When estimating a probability – for example, how likely it is that a person belongs to a particular category or the probability that an observed sample was drawn from a particular population – people assess the similarity between the outcome and the category (or between the sample and the population)
This is known as…?
a. Availability
b. Representativeness
c. Anchoring
b. Representativeness
Judgments of probability are based on assessments of similarity
This is known as…?
a. Availability
b. Representativeness
c. Anchoring
b. Representativeness
“an assessment of the degree of correspondence between a sample and a population, an instance and a category, an act and an actor or, more generally, between an outcome and a model.” (Tversky & Kahneman, 1983, p. 295).
This applies to…?
a. Availability
b. Representativeness
c. Anchoring
b. Representativeness
Suppose that you meet a new person at a party and try to estimate the probability that they have tried internet dating.
The idea is that you base your judgment on the similarity between the person and your stereotype of internet-daters – that is, on the extent to which the person is representative
of the category “people who have tried internet dating”
This is an example of…?
a. Availability
b. Representativeness
c. Anchoring
b. Representativeness
Describe Kahneman and Tversky’s (1973) study on base rate neglect
List 5 points
1) Ps were told that a panel of psychologists had interviewed a number of engineers and lawyers and produced character sketches of each person.
2) They were told that 5 such descriptions had been randomly selected and that they should rate, from 0-100, the likelihood that each sketch described one of the engineers
3) Ps assess the extent to which the description of Jack is similar to each of the two categories – lawyers and engineers
(To the extent that Jack is more similar to the stereotypical engineer, he is more likely to be judged an engineer)
4) Because this assessment of similarity is independent of the prevalence of lawyers and engineers in the population, the resulting probability judgment is independent of the base rates for these two professions
5) Some participants were told that the population from which the descriptions were drawn consisted of 30 engineers and 70 lawyers. Others were told that the population comprised 70 engineers and 30 lawyers. That is, Kahneman and Tversky manipulated the base rates for the two possible outcomes.
Describe the results of Kahneman and Tversky’s (1973) study on base rate neglect
1) 55% of Ps judged the probability that Jack is an engineer when they were told that the population from which the descriptions were drawn consisted of 70 engineers and 30 lawyers
2) 50% of Ps judged the probability that Jack is an engineer when they were told that the population from which the descriptions were drawn consisted of 30 engineers and 70 lawyers
Define base rate neglect
People’s tendency to ignore relevant statistical information in favor of case-specific information
1) 55% of Ps judged the probability that Jack is an engineer when they were told that the population from which the descriptions were drawn consisted of 70 engineers and 30 lawyers
2) 50% of Ps judged the probability that Jack is an engineer when they were told that the population from which the descriptions were drawn consisted of 30 engineers and 70 lawyers
What do these results suggest?
The personality description might provide some information about Jack’s likely occupation, but this should be combined with information about the number of engineers and lawyers in the population from which his description was randomly drawn.
However, people ignored these base probabilities and simply judged based on the description of Jack only
People’s tendency to ignore relevant statistical information in favor of case-specific information
This is known as…?
Base rate neglect
Describe Kahneman and Tversky’s (1973) study on base rate neglect part 2
List 4 points
1) Ps were given a list of 9 academic subject areas (e.g., computer science, medicine, law, humanities).
2) The prediction group was told that the sketch of Tom was prepared by a psychologist during
Tom’s final year in high school, and that Tom is now a graduate student. They were asked to rank the 9 academic subjects by the probability that Tom is specialising in that topic, based on his description
Simply = Rank each subject by likelihood Tom is specialising in it
3) The base-rate group was not shown the Tom W. sketch but “consider[ed] all first year graduate students in the US today” and indicated the percentage of students in each of the 9
subject areas – that is, the estimated the base rates for each subject area.
Simply = Estimate what percentage of all students study this topic
4) The representativeness group ranked the 9 subject areas by the degree to which Tom W. “resembles a typical graduate student” in that subject area
Simply = Rank each subject by how representative Tom is of a typical student
Describe the results of Kahneman and Tversky’s (1973) study on base rate neglect part 2
List 2 points
1) Across the 9 subjects, probability judgments (mean likelihood rank) were very positively correlated with representativeness judgments or mean similarity rank (r = .97) but negatively correlated with mean estimated base-rate (r= -.65)
2) Predictions were based on how representative people perceive Tom W. to be of the various fields, and ignored the prior probability that a randomly-selected student would belong to those fields (base rate neglect).
Judgments based on representativeness will be largely independent of …?
Base rates
Judgments based on representativeness will be largely dependent of base rates
True or False?
False
So, judgments based on representativeness will be largely independent of base rates
Define the Anchor-and-Adjust heuristic
Judgments are produced by adjusting from a (potentially irrelevant) starting value (anchor), and these adjustments are often insufficient