11. Reasoning and decision making

Question 1

what do people (compared to computers) do when faced with logical problems?

Answer 1

Faced with logical problems, people often come to conclusions that are judged as incorrect from the perspective of formal logic and mathematics
• On the other hand, computer systems that are based on formal logic make so many silly mistakes that humans never make

Question 2

what are the four areas where human irrationality is often found?

Answer 2

– Reasoning about conditionals
– Reasoning about quantifiers
– Reasoning about probabilities
– Decision making

Question 3

What is an example deductive reasoning?

Answer 3

Broad to specific. Reasoning in situations where the conclusions can be determined to follow with certainty from the premises
E.g.

– Fred is the brother of Mary.
– Mary is the mother of Lisa.
THEREFORE
– Fred is the uncle of Lisa.

Question 4

What is inductive reasoning

Answer 4

specific to broad. Reasoning in situations in which the conclusions follow only probabilistically from the premises

E.g.
– Fred is the brother of Mary.
– Mary is the mother of Lisa.
THEREFORE
– Fred is older than Lisa.

Question 5

what is a conditional statement?

Answer 5

– If A, then B

– An assertion that if an antecedent (A) is true, then a consequent (B) must be true

Question 6

what was involved in wason’s selection task?

Answer 6

• If a card has a vowel on one side, then it has an even number on the other side.
• If a card has a vowel on the one side, then it has an even number on the other side.
• In other words, neither a vowel nor a consonant on the other side of 4 will falsify the rule.

Question 7

what were the results of Wason’s selection task?

Answer 7

Only 10% of participants made the right combination of choices (i.e., E and 7)

Question 8

What do people have difficulty with according to Wason’s selection task?

Answer 8

When presented with neutral material, people have particular difficulty in recognizing the importance of exploring the negation of the consequent

Question 9

what is permission schema?

Answer 9

Performance on the selection task can be enhanced when the material has meaningful content

e.g.
• Griggs and Cox (1982)
– If a person is drinking a beer, then the person must be over 19.

Question 10

What were the results of Griggs and Cox (1982) study?

Answer 10

74% of the participants in Griggs and Cox (1982) selected the logically correct combination

Question 11

What is the relation between Permission schema and Wason’s selection task?

Answer 11

When the conditional statement is interpreted as a rule about what should be the case, performance on the Wason’s selection task tends to be enhanced

Question 12

Why do we perform so poorly on the original Wason’s selection task?

Answer 12

People tend to select cards that will be informative under a probabilistic model, not a strict logical model
– If A, then B
–> B will probably occur when A occurs

Question 13

What was Oaksford and Cater (1994)’s study in Probablistic interpretation?

Answer 13

If a car has a broken headlight, it will have a broken taillight.

• Which cars in the parking lot would you check?
– If a car has a broken headlight, it will have a broken taillight.
– Four choices:
• Cars with broken headlights
• Cars without broken headlights
• Cars with broken taillights
• Cars without broken taillights

first and last are the logically correct choices

• Finding cars that have broken headlights would be reasonable
– There wouldn’t be many of them anyway
– If you find one, it is necessary to check its taillight
• However, do you really want to check all cars that have intact taillights?
• Cars with broken headlights/taillights are very rare
– Thus, if you find a car with a broken taillight, checking it to see whether it also has a broken headlight helps you make reasonable inference
• It is not logical, but informative choice

Question 14

What do we tend to do according to probablistic interpretation?

Answer 14

We tend to interpret conditional statements on the basis of a
probabilistic model, not a strict logical model
– because doing so actually makes sense in many situations in real life

Question 15

what might probalistic interpretation provide an explanation for?

Answer 15

This might be one reason why making the correct (=logical) choice in the original Wason’s selection task is sodifficult

Question 16

what is prior probability?

Answer 16

The probability that a hypothesis is true before consideration of the evidence

Question 17

what is posterior probability?

Answer 17

The probability that a hypothesis is true after consideration of the evidence

Question 18

what needs to be taken into account when calculating posterior probability?

Answer 18

– Prior probability (base rate)
– Evidence
– How reliable the evidence is

Question 19

what does Bayes’s theorem calculate?

Answer 19

computes the posterior probability

Question 20

what is base-rate neglect?

Answer 20

People often fail to take base rates into account in making probability judgments

Question 21

what was Hammerton (1973)’s study on reasoning about probabilities?

Answer 21

– Suppose you take a diagnostic test for a rare form of cancer
– Only 1 in 10,000 people have this cancer
– This cancer results in a positive test 95% of the time
– If a person does not have the cancer, the probability of a positive result is 5%
– If you get a positive result, how do you feel
about it?

• Many people feel that the positive result means their chance of actually having the cancer is 95%
• However, the fact that this type of cancer is very rare (0.01%) is not taken
into account
• The actual probability of having this cancer (given the positive result) is only
0.19%

Question 22

what is the judgement of probability?

Answer 22

We can be biased in our estimates of probabilities when we must rely on factors such as memory and similarity judgments

Question 23

What was Tversky and Khneman (1974)’s study on judgement of probability?

Answer 23

Participants estimated the proportion of English words:
• that begin with k (e.g., kettle)
• with k in the third position

Question 24

what is subjective utility in decision making?

Answer 24

– The subjective value someone places on something
– It usually forms a non-linear function
– The subjective value decreases more steeply in negative direction

Question 25

how do people made decisions under uncertainty?

Answer 25

People make decisions under uncertainty in terms of subjective utilities and subjective probabilities

Question 26

what is the framing effect?

Answer 26

The tendency to make different choices among the same alternatives, depending on the statement of the alternatives
• e.g., getting $5 discount off a $15 item seems larger than getting the same amount of discount off a $125 item

Question 27

what was Kahneman & Tversky, 1984 ‘s study on the framing effect?

Answer 27

Imagine that the U.S. is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600
people. Two alternative programs to combat the disease have been proposed

• If Program A is adopted, 200 people will be saved.

72%

• If Program B is adopted, there is a 1/3 probability that 600 people will be saved and a 2/3 probability that no one will be saved.

28%

• If Program C is adopted, 400 people will die.
22%

• If Program D is adopted, there is a 1/3 probability that nobody will die and a 2/3 probability that 600 people will die.

78%

Question 28

when do framing effects occur?

Answer 28

Framing effects occur when there is no clear basis for choice
• In such situations, we tend to make a decision not on the basis of which decision is actually the best but on the basis of which will be easiest to justify