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Flashcards in Reasoning Deck (28)
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1

What is deductive reasoning?

-Starting with some sort of premises, then you deduce a conclusion
-Determining the conclusions that must follow given that certain statements are true
-Premise 1: All planets are made of cheese
-Premise 2: Earth is a planet
-Conclusion: Earth is made of cheese

2

-If it is raining, then Fred’s hair gets wet.
-It is raining.
-Fred’s hair gets wet.
HOW MANY PEOPLE (%) AGREED THIS WAS A VALID INFERENCE?

-98% agreed this was a valid inference (Marcus & Rips, 1979)

3

-If it is raining, then Fred’s hair gets wet.
-Fred’s hair does not get wet.
-It is not raining.
HOW MANY PEOPLE (%) AGREED THIS WAS A VALID INFERENCE?

-52% agreed this was a valid inference (Marcus & Rips, 1979)
-Need to go off what the first premise says

4

-If it is raining, then Fred’s hair gets wet.
-Fred’s hair gets wet.
-It is raining.
HOW MANY PEOPLE (%) AGREED THIS WAS A VALID INFERENCE?

-33% agreed this was a valid inference (Marcus & Rips, 1979)

5

-If it is raining, then Fred’s hair gets wet.
-It is not raining.
-Fred’s hair does not get wet.
HOW MANY PEOPLE (%) AGREED THIS WAS A VALID INFEFENCE?

-21% agreed this was a valid inference (Marcus & Rips, 1979)

6

Why do people make mistakes?

-People can reason logically, but often fail to understand formal, logical tasks (e.g. Braine, 1978). E.g. not tasks they’re used to
-People do not reason logically (e.g. Woodworth & Sells, 1935)
-We should not expect people to reason in line with formal logic (e.g. Oaksford & Chater, 1994). Argued that it is not the right type of test, not evolved to think this way

7

What are the Theories of deductive reasoning?

-Abstract-rule theories
-Mental models
-Dual systems approach
-Probabilistic approach

8

What is the Abstract rule theory?

-Braine (1978)
-People reason logically but make mistakes:
– if they misunderstand the task
– if the required reasoning places too many demands on working memory
-Limited capacity to make sense of the task, can’t store and process

9

What can improve reasoning performance? (Abstract rule theory)

-Performance can be improved by presenting additional clarifying sentences (to reduce comprehension errors, e.g. Braine et al., 1984)
-However, such additional information can also impair performance on some tasks (e.g. Byrne, 1989)

10

What is the Mental model theory?

-Johnson-Laird (e.g. 1999)
-Everyday comprehension processes (mental models) are used on reasoning problems
-People create mental models to represent premises
-Reasoning involves examination of mental model and/or attempts to create alternative models

11

What is principle of truth?

-Conclusions are drawn based on the initial model. People then try to falsify that conclusion by constructing alternative models
-The creation of alternative models is very demanding on working memory.
-THEREFORE “individuals … tend to construct mental models to represent explicitly only what is true…” (principle of truth) Johnson-Laird (1999)

12

What did Newstead et al (1999) look into?

-Mental models theory predicts that people will consider more conclusions in problems where they must create more mental models
-Gave tasks permitting one or several mental models
-No difference in number of conclusions considered

13

What is the Dual systems approach?

-Reviewed by Evans (2003)
-Reasoning involves two systems
-Fast, automatic, based on prior knowledge, belief and heuristics (rules of fun, e.g. shortcuts)
– Slow, deliberate, abstract, based on logic

14

What did -Oaksford and Chater (e.g. 2001) find about probabilistic reasoning?

-People use ‘probabilistic reasoning’ rather than logic to solve deductive reasoning tasks

15

What are Thematic materials?

-Perhaps people are better at reasoning when the material is meaningful?
-BUT correct answer does not necessarily imply correct reasoning
-Memory cuing hypothesis (Griggs & Cox, 1982)
-Good memory, not meaning you are good at reasoning

16

What is Social contract theory?

-We have strategies for detecting cheats who receive benefits without incurring the appropriate costs.
-We should be particularly good at versions of the Wason task that involve social contracts.
-Cosmides & Tooby (1989)

17

What did Gigerennzer and Hug (1992) find about pensions?

-‘If an employee gets a pension (P) then s/he has worked for 10 years (Q)’
-Who is violating the rule?
-Pension P
-No Pension not-P
-Worked 10 years Q
-Worked 8 years not-Q
-Imagine you are the employer OR imagine you are the employee

18

Problems for social contract theory

-Some facilitatory contexts do not involve costs and benefits that are socially exchanged – BUT these have not always replicated
-Only applies to ‘deontic versions of the Wason task (‘if you do X you must do Y’) and not to ‘indicative’ versions (‘if there is a P then there is a Q’)

19

What did Oaksford and Chater (1994) find about selection tasks?

-Selection task is not deductive, but a matter of ‘optimal data selection’
-Confirming instances may be useful, as well as counterexamples
-What matters is the expected reduction in uncertainty concerning whether rule is true or false. According to this measure: P > Q > not-Q > not-P
-Meta analysis of over 30 experiments using different versions of the selection task
-89% choose A P
-62% choose 4 Q
-25% choose 7 NOT Q
-16% choose D NOT P

20

Deductive reasoning: summary

-People make characteristic errors in deductive reasoning
-These are attributed to:
– Failure to understand the task
– Lack of logical approach
– Tendency towards probabilistic approach in line with real-life reasoning

21

What is Inductive reasoning?

-Going beyond the information provided to draw generalised conclusions – Hypothesis testing
-Note that conclusions may not always be true

22

What were the results of the Wason 2-4-6 task?

-Only 21% correct with first statement of rule (but over 70% correct in the end)
-Tendency to attempt to confirm (rather than disconfirm) original hypothesis
-1960

23

What did Tweney et al (1980) find when looking at performance?

-Performance does not improve when specifically instructed to use a disconfirmatory approach

24

What did Mynatt et al (1977) look at when Firing particles?

-Select direction in which to fire particle across the screen
-Then choose one of a pair of possible screens on which to test hypothesis (by firing additional particles)
-Confirmation, disconfirmation & control groups

25

What did Mynatt et al (1977) find?

-Percentages of people choosing ‘confirm’ screen:
-Confirm group: 71%
-Disconfirm group: 70%
-Control: 71%
-People consistently chose screens that would allow them to confirm their hypotheses
-But 91% of participants changed to a correct hypothesis when given disconfirmatory evidence

26

What did Mitroff (1974) find when looking at NASA scientists?

-Majority of NASA scientists (N = 40) interviewed were highly committed to confirming their own theoretical positions
-They argued that without it, many good, new, but undeveloped ideas would die as a result of premature falsification
-The scientists who held such views were rated as especially prominent and successful by their peers

27

Are we rational?

-What’s the norm?
-Do we expect people to reason in line with formal logic?
-Or might we decide that reasoning is ‘rational’ if it is optimally adapted to the environment (e.g. ‘adaptive rationality’ proposed by Anderson, 1990)

28

Summary

-People often make ‘errors’ in deductive and inductive reasoning
-This may be because laboratory tasks are often highly contrived and hard to relate to real-life situations
-Often the way people behave makes sense for real-life reasoning