1. Reasoning and Decision Making or The Shortcuts of the Human Mind (a. k
Reasoning and Decision Making or The Shortcuts of the Human Mind (a.k.a Heuristics) by Elan Dubrofsky and Dina Tsirlin

2. Reasoning
Cognitive processes by which people start with information and come to conclusions that go beyond that information

4. Deductive Reasoning
Syllogism
Two statements called premises
Third statement called conclusion
Categorical Syllogism
Describe relation between two categories using all, no, or some
Premise 1: All computer scientists are nerds.
Premise 2: All nerds can name all six Star Wars movies.
Conclusion: All computer scientists can name all six Star War movies.

5. Deductive Reasoning
Syllogism is valid if conclusion follows logically from its two premises
Aristotle’s “perfect” syllogism
Premise 1: All A are B
Premise 2: All B are C
Conclusion: Therefore, All A are C

6. Deductive Reasoning
If two premises of a valid syllogism are true, the syllogism’s conclusion must be true.
Do not confuse “validity” with “truth”
The following syllogism is valid but not true
All birds are animals
All animals have four legs
All birds have four legs

7. How Well Can People Judge Validity?
Errors in evaluation
Atmosphere effect: use of words “all”, “some” or “no” in premises increase the probability of a conclusion with those words

8. Belief bias: if syllogism is true or agrees with a person’s beliefs, more likely to be judged valid

9. How do people go about determining whether a syllogism is valid/invalid?

10. Mental Models of Deductive Reasoning
Specific situation that is represented in a person’s mind that can be used to help determine the validity of syllogisms
Iterative process
Look for exceptions
if no exception accept model and establish validity
if exception modify the model until can be satisfied

11. Deductive Reasoning
Conditional syllogisms
“If p, then q.”
If I lend Emt $20, Then I won’t get it back.
I lent Emt $20. Therefore, I won’t get my $20 back
Four types of conditional syllogisms
Affirming the antecedent
Denying the consequent
Affirming the consequent
Denying the antecedent

13. The Wason Four-Card Problem
Effect of using real-world items in a conditional-reasoning problem
Determine minimum number of cards to turn over to test: If there is a vowel on one side, then there is an even number on the other side.

14. Caption: The Wason four-card problem (Wason, 1966).

15. The Wason Four-Card Problem
Falsification principle: to test a rule, you must look for situations that falsify the rule (exception)
Most participants fail to do this
When problem is stated in concrete everyday terms, correct responses greatly increase

16. The Wason Four-Card Problem
Pragmatic reasoning schema: thinking about cause and effect in the world as part of experiencing everyday life
Permission schema: if A is satisfied, B can be carried out
Used in the concrete versions
People are familiar with rules

17. Evolutionary Perspective on Cognition
Evolutionary principles of natural selection
Wason task governed by built-in cognitive program for detecting cheating

18. Evolutionary Perspective on Cognition
Cosmides and Tooby (1992)
Created unfamiliar situations where cheating could occur
Participants did well
Evidence against permission schema

19. Inductive Reasoning
Premises are based on observation and we generalize from these cases to more general conclusions with varying degrees of certainty

20. Inductive Reasoning
Strength of argument
Representativeness of observations
Number of observations
Quality of observations

21. ACTIVITY: Which argument is stronger? Why?
Observation: All sushi places I’ve seen in Vancouver charge a lot for sashimi. When I visited my family in Ottawa, the sashimi was expensive too Conclusion: All sushi places charge a lot for sashimi.
Observation: Here in Ottawa, the sun has risen every morning Conclusion: The sun is going to rise in Ottawa tomorrow.

22. Inductive Reasoning
Used to make scientific discoveries
Hypotheses and general conclusions
Used in everyday life
Make a prediction about what will happen based on observation about what has happened in the past

23. Heuristics
Availability heuristic: events more easily remembered are judged as being more probable than those less easily remembered
Is it easier to die for car accident of plane crash?

24. Caption: Likely-causes-of-death experiment results
Caption: Likely-causes-of-death experiment results. Pairs of “causes of death” are listed below the graph, with the least likely cause on the left. The number in parentheses on the right indicates how many more times more people were actually killed by the cause on the right. The bars in the graph indicate the number of people who judged the least likely alternative in each pair as causing the most deaths. (Adapted from Lichtenstein et al., 1978).

25. Heuristics
Illusory correlations: correlation appears to exist, but either does not exist or is much weaker than assumed
Stereotypes

26. A little experiment...
Rate info: Among 100 people, 70 are lawyers, 30 are engineers

27. A little experiment...
Description: Jack, 45 yrs old, 4 kids, conservative, careful. Not interested in politics, many hobbies: math puzzles & carpentry – Lawyer or engineer?

28. Heuristics
Representativeness Heuristic: the probability that A comes from B can be determined by how well A resembles properties of B
Use base rate information if it is all that is available
Use descriptive information if available and disregard base rate information

29. Heuristics
Violation of Conjunction rule
Conjunction rule: probability of two events cannot be higher than the probability of the single constituents

30. Caption: Because feminist bank tellers are a subset of bank tellers, it is always more likely that someone is a bank teller than a feminist bank teller.

31. Heuristics
The Confirmation Bias: tendency to selectively look for information that conforms to our hypothesis and overlook information that argues against it

32. Heuristics
The Confirmation Bias
Lord and coworkers (1979)
Had those in favor of capital punishment and those against capital punishment read the same article
Those in favor found the article in favor
Those against found the article against

33. Decision Making
Economic utility theory
People are rational and if they have all relevant information they will make a decision which results in the maximum expected utility

34. Decision Making
Utility: outcomes that are desirable because they are in the person’s best interest
Maximum monetary payoff

35. Decision Making
Problems for Utility Approach
Not necessarily money, people find value in other things
Many decisions involve payoffs that cannot be calculated
“Good enough” philosophy (Herb Simon, Psychologist Nobel Prize!!!)

36. Caption: Behavioral results of Sanfey and coworkers’ (2003) experiment, showing responders’ acceptance rates in response to different offers made by human partners and computer partners.

37. Decision Making
Focusing illusion: focus on just one aspect of situation and ignore other aspects that may be important
Dating and happiness
California versus Midwest living

38. Decision Making
Decisions depend on how choices are presented
Opt-in procedure
active step to be organ donor
Opt-out procedure
Organ donor unless request not to be
Subject’s consent to research participation
Active Consent
Passive consent

39. Decision Making
Risky decisions
Risk-aversion strategy used when problem is stated in terms of gains
Risk-taking strategy when problem is stated in terms of losses

41. Decision Making
Framing effect: decisions are influenced by how a decisions is stated
Can highlight one aspect of situation

42. Decision Making
Decision-making process includes looking for justification so a rationale presented with decision

43. Decision Making
Tversky and Shafir (1992)
“pass” - go on trip
“fail” - do not
“I don’t know yet” – wait to find out results before making decision to go on trip or not

44. In Conclusion...
We're only human... therefore our thinking is very flawed.
Be careful to make sure that when you use a heuristic, it's not leading you down a dangerous path.