# Chapter 13 - Judgement, Decisions and Reasoning Flashcards

-judgement:

about appearance etc

-Decisions:

the process of making choices between alternatives, based on judgements that we make

-Reasoning:

the process of drawing conclusions

Inductive Reasoning

- the process of drawing general conclusions based on specific observations and evidence, the conclusions we reach are probably but not definitely true
- reasoning that is based on observation
- reaching conclusions from evidence

inductive reasoning

-Observation

-all the crows I’ve seen in Pittsburg are black. When I visited my brother in Washington, DC, the crows I saw there were back too

Conclusion

-I think it is a pretty good bet that all crows are black

Strength of Argument

- representativeness of observations – how well do the observations about a particular category represent all the members of that category?
- number of observations
- quality of observations

Used to make scientific discoveries

inductive reasoning

hypothesis and general conclusions

Used in everyday life

inductive reasoning

-make a prediction about what will happen based on observation about what has happened in the past

Heuristics

- ”rules of thumb” that are likely to provide the correct answer to a problem, but are not foolproof
- provide us with shortcuts to help us generalize form specific experiences to broader judgements and conclusions
- two more commonly used heuristics include the availability heuristic and the representativeness heuristic

-Availability heuristic:

events more easily remembered are judged as being more probable than those less easily remembered (Tversky and Kahneman, 1973)

- Which is more prevalent, words that begin with letter r, or words in which r is the third letter?
- Most people stated that there are more words that start with r. Actually, there are three times more words that have r in the third position

Illusory Correlations:

correlation appears to exist, but either does not exist or is much weaker than assumed. Wearing a “lucky shirt” for a certain outcome to occur, no real relationship exists

stereotypes:

oversimplified generalizations about a group or class of people that often focuses on the negative -selective attention to the stereotypical behaviours makes these behaviours more available, based on the availability heuristic (Chapman and Chapman, 1969)

-Representativeness heuristic:

the probability that A is a member of class B can be determined by how well the properties of A resembles properties normally associated with class B

- based on how much an event resembles other events
- the probability that A come from B can be determined by how well A resembles properties of B
- use base rate information if it is all that is available
- base rate: the relative proportion of different classes in the population
- use descriptive information if available and disregard base rate information
- we randomly pick on male from the population of the US. The male, Robert, wears glasses, speaks quietly, and reads a lot. Is it more likely that Robert is a librarian for a farmer?

-Use base rate information if it all that available

- In a group of 100 people, there are 30 farmers and 1 librarian. We pick one male, Robert. Is it more likely that Robert is a librarian or a farmer?
- Use descriptive information and disregard base rate information
- in a group of 100 people, there are 30 farmers and 1 librarian, and we pick Robert
- The male, Robert, wears glasses, speaks quietly, and reads a lot. Is it more likely that Robert is a librarian for a farmer?

Conjunction rule:

probability of two events cannot be higher than the probability of the single constituents

- but 81% of participants picked two - bank teller, feminist example

Heuristics cont’d (ignore law of large number)

-law of larger numbers:

the larger the number of individuals randomly drawn from a population, the more representative the resulting group will be of the entire population

- from a group of 10,000 people (5000 males and 5000 females), we choose two groups. First group with 1000 people and the second group with 10 people
- for which group, the percent of males will be closer to 50% - larger

confirmation bias:

tendency to conform rather than falsify hypothesis, people look for information that confirms their hypothesis and ignore information that refutes it

-the myside bias:

tendency for people to generate and evaluate evidence and test their hypothesis in a way that is based towards their own opinions and attitudes

- Lord and coworkers (1979) had those in favor of capital punishment and those against it read the same article - those in favor found the article convincing - those against found the article unconvincing

the backfire effect:

a person’s viewpoint could actually become stronger when faced with corrective facts opposing their viewpoints

Deductive Reasoning

-determining whether a conclusion logically follows from statements (premises)

syllogism:

- basic from of deductive reasoning
- two statements called premises
- third statement called conclusion

-categorical syllogism

- describe relation between two categories, using all, no, or some
- syllogism is valid if conclusion follows logically from its two premises
- validity in this context indicates that the conclusion follows logically from its two premises

- Aristotle’s “perfect” syllogism
- Premise 1: All A are B
- Premise 2: All B are C
- Conclusions: therefore, all A are C

- If two premises of a valid syllogism are true, the syllogism’s conclusion must be true
- do not confuse “validity” with “truth”

- Premise 1: all birds are animals

- premise 2: all animals have 4 legs

- premise 3: all birds have 4 legs- valid but premise 2 and the conclusion are not true