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Elements of a decision
judgment: to judge or form an opinion
reasoning: the process of drawing conclusions
decision: the process of choosing between alternative
inductive reasoning
the process of drawing a general conclusion based on specific observations
ex: summers reach 100 degrees , it will be 100 degrees this summer
specific cases = broad principles
deductive reasoning
the process of determining whether a specific conclusion logically follows from general statements
ex: all men are mortal. Socrates is a man. Therefore Socrate is mortal.
broad principles = specific cases
Bottom-up process for inductive reasoning
facts or observations > hypothesis > theory
ex: Dr. House
Top-down process for deductive reasoning
hypothesis > facts > conclusion
ex: Sherlock
if the premise is true, the conclusion is probably true
inductive reasoning
ex:
The temperature in
Riverside reaches 100°
every summer. > Therefore, it
will reach 100° in Riverside
this summer.
if the premise is true,
the conclusion is
definitely true
deductive reasoning
ex:
All men are mortal. Socrates is a man = therefore, socrates is mortal
Representativeness of observations
How well observations about a particular category represent al members of that category
- stronger inductive arguments
Number of observations
How many observations are made
- stronger inductive arguments
Quality of evidence
Observations can be supported by scientific evidence
- stronger inductive arguments
Confirmation bias
We look for info that supports our opinions and ignore info that refutes it
- inductive arguments are weakened by a bias to confirm (or support) our opinions
Myside bias
We evaluate evidence in a way that's biased toward our own opinions and attitudes
ex: a group FOR capital punishment "evidence of the deterring effect of capital punishment was convincing"
vs a group AGAINST capital punishment "evidence of the deterring effect of capital punishment was NOT convincing"
Backfire effect
Our support for a given opinion can be stronger when faced with facts that oppose it
Heuristics
Educated guesses, intuitive judgments, or common sense used to solve a problem quickly
Availability heuristic
- Events that come to mind more easily are judged as being more probable
ex: what is more likely to kill you? Taking a shower or a tornado? We would choose tornado because the risks associated with it come to mind more easily in in reality more people die from shower accidents
- Undue weight is given to anecdotal evidence that comes to mind more easily
ex: ur mom saying her Volvo sucks vs commercial saying it's great)
- Our conclusions are biased by evidence that is more available
ex: that noise outside must be... a little critter (watching something peaceful)... a serial killer! (Watching a horror movie)
Illusory correlations
When a relationship between two events appears to exist, but, in reality, there is little or no relationship
ex: it always rains after I wash my car
- stereotypes are a common form of illusory correlation
Representativeness heuristic
Events that are more similar to a given category are more likely to be judged as being part of that category
- base rate
- conjunction rule
- law of large numbers
we rely on representativeness to the occupation categories and ignore the base rate
ex: If Joe is weird and eccentric you are more likely to assume he is a comedian rather than a doctor despite the fact 2.5 ppl every 1000 ppl are drs and Joe really is a dr
Base rate
The relative proportion of different classes in the population
ex: 1,000,000 doctors; 800,000 lawyers; 2,500 comedians
Conjunction rule
the probability of a conjunction of two events cannot be higher than the probability of the events alone
law of large numbers
the more individuals that are randomly drawn from a population, the more representative the group will be of the entire population
syllogism
consist of two broad statements (premises) and a conclusion
categorical syllogism
statements being with "all", "no", or "some
ex: All teachers are inspiring, Prf. DZ is a teacher, Prf. DZ is inspiring
conditional syllogism
the first premise has ann "if...then" format
ex: If I study, then I will get a good grade. I studied. I will get a good grade. (If P, then Q, P, Q)
If P, then Q, P, Q
If P, then Q, not Q, not P
If P, then Q, Q, P
- it's easier to see the logic is invalid when using statements that also make it inaccurate
If P, then Q, not P, not Q
- it's easier to see that the logic is invalid when using statements that also make it inaccurate
valid syllogism
the conclusion follows logically from the premises
ex: All dogs are animals. All animals eat food. All dogs eat food. (true
not all valid syllogism are true
ex: All dogs are animals, all animals have wings, all dogs have wings (not true)
invalid syllogism
the conclusion does not follow logically from the premises
ex: all dogs are animals, some animals are small, some of the dogs are small (possibly true)
Not all invalid syllogisms are not true
ex: All dogs are animals, some animals are in space, some of the dogs are in (not true)
belief bias
the tendency to think a syllogism is valid if its conclusions are believable
falsification principle
to test a rule, it's necessary to llok for a situation that would falsify it
ex: You are given four cards. Each card has a number on one side and a letter on the other. If a card has a vowel on one side, then it has an even number on the other side.
- which cards do you need to turn over to test the rule?
cards corresponding to invalid syllogisms will not help you to test the rule
Abstract vs concrete
real life problems are easier to solve than abstract problems
Expected utility theory
assumes if people have all relevant information, they will make a decision that results in outcomes that help to achieve their goals
Framing effect
decisions are influenced by how the choices are stated
ex: beef 75% lean 25% fat, condom 95% success rate 5% failure rate
Status quo bias
the tendency to do nothing when faced with making a decision
ex: countries using OPT-IN organ donation procedure (smaller numbers) vs countries using OPT-OUT organ donation procedure (larger numbers)
Risk aversion
the tendency to avoid taking risks
Dual systems approach
idea that we may have different systems for decision making
Our decisions can be biased by other, seemingly unrelated factors
