Thinking: Reasoning
Reasoning: manipulating internal
representations to arrive at new knowledge or
to draw new conclusions.
Syllogistic reasoning: based on ‘accepted’
premises upon which conclusions are drawn.
Task it to decide if conclusions are valid or not
Valid conclusion: must be only conclusion
possible based on relationships described in
premises. Must be necessitated by premises,
not just possible based on premises
Syllogistic reasoning
• Premise: statement assumed to be true for
sake of argument, not necessarily empirically
true
• Premise: All boys are athletes
• Premise also usually expresses a relationship
between certain concepts, so boys are related
to athletes in that all boys are a member of
the category athletes.
Syllogistic reasoning
• Conclusion: to be valid must be necessitated
by the premises. Must be only possible
conclusion drawn base on relationships
expressed in premises.
• Conclusion: a valid conclusion cannot just be
reasonable or plausible based on premises, it
must be necessary.
Venn or Euler diagrams for solving syllogisms
Valid conclusion: all doctors are greedy
Syllogistic reasoning
• P1: All boys are athletes
• P2: All athletes are muscular
• C: All boys are muscular
• Valid: Use Venn Diagrams to determine.
Syllogistic reasoning
• P1: All boys are athletes
• P2: All muscular people are athletes
• C: All boys are muscular people
• Valid?
• See website for more reasoning problems
Conditional reasoning
• If: antecedent condition
• Then: consequent
• When the antecedent condition is met, the
consequent will occur (no question about it!)
• Observation – what condition is actually
present
• Conclusion: (valid or not valid)
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
Conditional reasoning
•
•
•
•
If she has red hair
Then she buys new shoes
Observation: she has red hair (affirming antecedent)
Conclusion: she buys new shoes (valid?)
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
• If she has red hair
• Then she buys new shoes
• Observation: she has not red
hair (denying the
antecedent)
• Conclusion: she buys not
new shoes (valid?)
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
• If she has red hair
• Then she buys new shoes
• Observation: she buys new shoes (affirming
the consequent)
• Conclusion: she has red hair (valid?)
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
• If she has red hair
• Then she buys new shoes
• Observation: she buys not
new shoes (denying the
consequent)
• Conclusion: she has not red
hair (valid)
• More problems on my
website
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
Conditional Reasoning: Summary
Wason Selection Task
• Rule: if there is vowel on one side then there is an even
number on the other side of the card
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
Abstract reasoning vs. Social contracts reasoning
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
Decision Making
Physical differences vs. Symbolic differences
Physical differences: JND or difference threshold – minimum physical difference
necessary for detection
Distance effect: the farther the comparison departs from the JND the faster or easier
the discrimination
Symbolic distance effect:
decisions are faster, easier as
symbols depart farther from
each other. Rts for judging
greater value decrease as
difference between numbers
increases for all age subjects
Decision Making
Semantic congruity effect: faster decisions when decisions “make sense” with
relevant semantics dimensions involved
Faster response time for congruent on left and slowed
response times for both conditions above.
Decision Making
• Plausible reasoning and distortions of geographic knowledge
(ex: which is farther west San Diego, CA or Reno, NV?)
Algorithms and Heuristics
Algorithm: step by step procedure guaranteed
to provide a solution. Usually only applicable to
very narrow, well-defined problems
Ex: mathematical formulas, recipes
Heuristics: less certain, but more generally
applicable problem-solving methods
Ex: football: control line of scrimmage, avoid
turnovers; chess: control center of board; life:
get an education, stay out of jail.
Types of Heuristics
Anchoring bias
Base rate bias
•
Prof Smith has dark hair, black-rimmed glasses and reads poetry. 100% of Philosophers look
this way, only 1% of Engineers do. Is it more likely that Smith is an philosopher or engineer?
Naïve Physics
Misunderstanding of motion
Mental models drawn from
experience sometimes
don’t correspond to the
reality of the physical
world.