PSY246 Lecture Notes - Lecture 11: Pragmatics, Wason Selection Task, Solomon Asch
2 Jun 2018
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Thinking and Reasoning Week 11:
• Andrew Wakefield – vaccines have caused increase in autism diagnosis
o Vaccines only cause autism in a small number of ‘vulnerable’ infants
o These numbers are too small to be detected by epidemiological studies
• Intervention study aimed at increasing vaccination
• Correcting misinformation led to reduced negativity towards vaccines but
decreased intention to vaccinate
• Other interventions had no effect either way (Nyhan et al. 2014)
• ‘Deficit’ model of science communication assumes that people just need more
and better info
• Attempts at science communication often have no effect and sometimes make
things worse
Reasoning skills –
• Logical reasoning, how we take information and make inferences about the
state of world based on info
• ‘The science of deduction’
• Inductive reasoning
o Reasoning from specific observations to general conclusions
o Conclusions are probabilistic rather than definitive
o E.g. John majored in accountancy, now works in an accountancy firm,
thus John is an accountant
o Bertrand Russell: a turkey is fed at 9am everyday, on Christmas Eve at
9am he assumes he will be fed
• Deductive reasoning
o Reasoning from accepted premises to specific conclusions
o Inference is valid if conclusion follows necessarily from the premises
given
o Inference is valid even if counterfactual
o E.g. all dogs can fly, a poodle is a breed of dog, poodles can fly
Modus ponens (valid inferences) –
• If p then q, p therefore q
• All bananas are yellow, this is a banana, therefore it is yellow
• THIS IS A VALID INFERENCE
Modus tollens (valid inferences) –
• All bananas are yellow, this is not yellow, therefore it is not a banana
• If p then q, not q, therefore not p
• 73% made Modus tollens inference
Error: Affirming the consequent (invalid inference) –
• If p then q, q therefore p – 62% made this error
• All bananas are yellow, this is yellow, therefore it is a banana (invalid
inference)
Error: denying the antecedent (invalid) –
• All bananas are yellow, this is not a banana, therefore it is not yellow (invalid)
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• If p then q, not p therefore not q
• 55% made this error
Why are reasoning tasks so difficult?
• Real life reasoning is probabilistic rather than absolute
• Need to disregard the problem content and prior beliefs
• Disregard everyday meaning of same terms
• Ignore reasonable inferences
• If you mow the lawn then I will give you $5, inductive inference is that if you
don’t mow the lawn, you wont get $5 – this is not a valid deductive inference
Wason’s selection task –
• Wason and Shapiro 1971
o Most participants turn over ‘E’ – correctly apply modus ponens rule
o Fewer than 10% turn over ‘7’ – failure to apply modus tollens rule
Pragmatics rules –
• Permission rule: driving, drinking, voting
o If an action is to be taken, then a precondition must be satisfied
• Pragmatic rules are activated by content of reasoning problem
o In the Wason selection task, permission rule was not activated by
description (vowels and numbers)
Evidence for pragmatic rules –
• Envelope problem
o If the letter is sealed, then it has a 5-d stamp on it
o Hong Kong subjects are familiar with the ‘sealed envelope’ scenario
• Cholera problem
o If the form says ‘entering’ then the other side lists cholera among the
list of diseases
Karl Popper – “A scientific idea can never be proven true because no matter how
many observations seem to agree with it, it may still be wrong”
• Conclusions = scientists should focus on falsification
Mitroff 1974 – Lunar geologists spent most of their time trying to confirm their own
hypotheses
• They weren’t averse to falsifying other people’s hypotheses
Fugelsang et al. 2004 – molecular biologists responded to findings inconsistent with
their hypothesis by blaming problem with method
• More likely to modify their theories if findings replicated
• Falsification impractical if evidence isn’t decisive
Judgements and Heuristics (Rules of Thumb):
• System 1 thinking – operates automatically and quickly with little or no effort,
and no sense of voluntary control
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Thinking and reasoning week 11: andrew wakefield vaccines have caused increase in autism diagnosis, vaccines only cause autism in a small number of vulnerable" infants, these numbers are too small to be detected by epidemiological studies. Intervention study aimed at increasing vaccination: correcting misinformation led to reduced negativity towards vaccines but decreased intention to vaccinate, other interventions had no effect either way (nyhan et al. Deficit" model of science communication assumes that people just need more and better info: attempts at science communication often have no effect and sometimes make things worse. Reasoning skills : logical reasoning, how we take information and make inferences about the state of world based on info. Inductive reasoning: reasoning from specific observations to general conclusions, conclusions are probabilistic rather than definitive, e. g. John majored in accountancy, now works in an accountancy firm, thus john is an accountant: bertrand russell: a turkey is fed at 9am everyday, on christmas eve at.
