Lecture 7: Judging Probabilities and Frequencies

Question 1

What is the availability heuristic?

Answer 1

Judgements are based on the ease with which relevant instances come to mind.
If you can bring to mind something, e.g., an event, it is likely to occur frequently, if you cannot, it is likely not a common occurrence.
People either overestimate rare events or underestimate common events.

Question 2

What is the representativeness heuristic?

Answer 2

Judgements of probability are based on assessments of similarity.

Question 3

What are heuristics?

Answer 3

Simple, experience-based strategies. Reduce effort but are prone to bias/error.

Question 4

What is ecological rationality?

Answer 4

Apparent biases may be rational responses given the ecology of the human decision-maker.

Question 5

When can availability entail bias?

Answer 5

> Our experience of past events does not reflect their true frequencies
Events are easy to recall for some reason other than their frequency or occurrence.

Question 6

Tversky and Kahneman (1973)

Answer 6

> Ppts listened to list of 39 names. 1st condition: comprised of 19 famous men and 20 less famous women. 2nd condition: 19 famous women and 20 less famous men.
Recall: ppts retrieved more of the famous names than the non-famous names - famous names were more available.

Question 7

What is the conjunction fallacy?

Answer 7

A common reasoning error in which we believe that two events are happening in conjunction one is more probably than the other.

Question 8

What is base rate neglect?

Answer 8

Base rate neglect, the tendency to underweight base rate or prior information compared with current, individuating information.

Question 9

What is anchoring?

Answer 9

When asking someone to make an estimate, giving them a number beforehand affects the estimate they produce. (e.g., studies by Tversky & Kahnemann AND Chapman & Johnson)

Question 10

What is the anchor-and-adjust heuristic?

Answer 10

Idea that we use the anchor as an initial estimate of the target value and adjust from that starting point in the right direction; our judgement is biased towards the anchor value.
The assimilation of a numeric estimate towards another, anchor value

Question 11

What are the two formats of ecological rationality?

Answer 11

> Natural Frequencies
Misperception of randomness

Question 12

What did Gigerenzer and colleagues say?

Answer 12

> Probability theory and normalized probabilities are recent.
We are much better at tracking natural frequencies.

Question 13

What are 2 formats of ecological rationality?

Answer 13

• natural frequencies
• misperception of randomness

Question 14

What is the gambler’s fallacy?

Answer 14

The belief that a run of one outcome increases the probability of another (when the events are actually independent).

Question 15

What are 2 explanations for why humans are bad at making probability judgments?

Answer 15

> Heuristics
Ecological rationality

Question 16

What are the 2 systems involved in your decision making?

Answer 16

> Fast, intuitive one [used the most]
Slow, rational one

Question 17

What are 3 examples of heuristics?

Answer 17

> Availability
Representativeness
Anchoring

Question 18

How can availability heuristics bring in error?

Answer 18

May be more likely to remember shocking or frightening events leading you to think they occur often, e.g., shark attacks

Question 19

What did a study find when asking people to estimate causes of death? Which heuristic is this consistent?

Answer 19

People:
- overestimate rare events
- underestimate common events

Consistent with availability heuristics

Question 20

What did a study investigating the effect of memory on availability find?

Answer 20

• it is easier to remember famous names than less famous names
• ppts judged that the gender with famous names was more frequent [as it is easier to bring the famous names to mind]

Question 21

What can the availability heuristic lead to?

Answer 21

The conjunction fallacy

Question 22

What is the conjunction fallacy?

Answer 22

A common reasoning error in which we believe that when two events are happening in conjunction, one is more probable than the other.
This is because people will find one easier to bring to mind than the other so think it can occur more often.

Question 23

Give an example of a conjunction fallacy

Answer 23

“In 4 pages of a novel, how many words would you expect to find that have the form “___ing” and “___n_”

Question 24

What is base rate neglect an example of?

Answer 24

The representativeness heuristic

Question 25

What is a potential issue with the anchoring heuristic?

Answer 25

• Incentive, warnings and cognitive capacity have little effect on accuracy
• Many other mechanisms produce the same effect

Question 26

What is the inverse fallacy?

Answer 26

The mistaken belief that the probability given the null hypothesis, P(D | H0), is equivalent to the probability of the null hypothesis given the data, P(H0 | D).

Question 27

What does Bayes theorem tell us about probabilities?

Answer 27

Bayes’ theorem tells us how we should update our beliefs to give the posterior probability that H is true, given our prior belief and the new data

Question 28

what are natural frequencies?

Answer 28

a joint frequency of two events, such as the number of patients with disease and who have a positive test result, and is an alternative to presenting the same information in conditional probabilities

presenting information with rational numbers rather than percentages is easier to understand

Question 29

are people good at judging when something is random or not?

Answer 29

no

Question 30

what is the gambler’s fallacy consistent with?

Answer 30

misconceptions of randomness

Question 31

what is the gambler’s fallacy?

Answer 31

the belief that a run of one outcome increases the probability of another [when the events are actually independent]

Question 32

give an example of the gambler’s fallacy

Answer 32

the probability of getting “heads” from a fair coin is the same after a run of 3 heads as after a run of 3 tails

Question 33

what is the hot hand fallacy consistent with?

Answer 33

misconceptions of randomness

Question 34

what is the hot hand fallacy?

Answer 34

the expectation of “streaks” in sequences of hits and misses whose probabilities are, in fact, independent

Question 35

what is the hot hand fallacy?

Answer 35

the expectation of “streaks” in sequences of hits and misses whose probabilities are, in fact, independent

Question 36

give an example of the hot hand fallacy?

Answer 36

basketball fans believe that a player’s next shot was more likely to score after a run of successful shots than after a run of misses

Question 37

which heuristic can be used to explain both the gambler’s fallacy and the hot hand fallacy?

Answer 37

the representativeness heuristic

problematic as the same heuristic is being used to explain opposite effects

Question 38

what is an alternative explanation for the hot head fallacy?

Answer 38

past experience:
- many aspects of intentional human performance really do show positive recency
- e.g., if you practice a new game, your shooting success will increase
- HHF = an appropriate generalisation of past experience to situations which also use human performance, but where outcome probabilities are in fact, independent

Question 39

what is an alternative explanation for the gambler’s fallacy?

Answer 39

past experience:
- inappropriate generalisation of past experience
- random mechanical outcomes = sampling without replacement
- intentional human performance = positive recency

e.g., taking a red sweet from a bowl means its less likely to take another red sweet next time.

Question 40

how could memory constraints explain misconceptions of randomness?

Answer 40

that the supposed “fallacies” of human judgement and decision-making are often perfectly rational given the finite and imperfect information afforded by the environment and our limited mental capacities

Question 41

what are 2 realistic conditions to consider about the human condition when looking at the properties of a fair coin toss

Answer 41

• people only ever see finite sequences
• people can only hold a short subsection of a sequence in memory (e.g., the last 4 outcomes)