Deductive and Inductive Reasoning
People Bad at Conditional Reasoning Tasks
"If p then q" is not the same as "If q then p" -Difficulties reasoning with abstract information
Snyder & Swann (1978): Findings
1/2 framed for extroversion and 1/2 for introversion
Chapman & Chapman (1959)
81% of participants believed this conclusion was valid -All A's are B's, -A;; C's are B's -Therefore, all A's are C's
Inductive Strength
A strong argument is one in which the truth of the premises increases confidence in the conclusion -Premises provided stronger or weaker support for conclusion
Syllogism
A type of logical argument that contains two or more premises, completed with a conclusion that may or may not follow from the premises -People are remarkably bad at reasoning about syllogisms
Modus Ponens
Affirming the antecedent: VALID
Evolutionary Adaptation Threory
Basic characteristics of the mind have come about through process of natural selection -Adapted for survival needs
Modus Tollens
Denying the consequent: VALID
Deductive Reasoning
Drawing conclusions from a set of premises using principles of logic -Reasoning from the general to the specific
The Wason Selection Task
If a card has a circle on one side, then it must have an even number on the other -Turn over cards: circle and 7
Belief Bias
If a syllogism's conclusion happens to be something we believe to be true, we're likely to judge that conclusion to be valid
Deductive Validity (Conclusions)
If premises are true and reasoning proceeds according to logical rules, the conclusion cannot be false
Concrete Conditional Reasoning
If someone is drinking beer, then they must be 21 or over -74% people got right two cards: 19, and beer
Conditional Reasoning
If...then statements that end with a conclusion -"If P then Q"
Affirming the consequent
Invalid
Denying the Antecedent
Invalid
Why Real-world Content Easier
Knowledge about rules that govern thoughts and actions -If a person satisfies a particular condition, that person can carry out a particular action
Inductive Reasoning Conclusion
Not necessarily true given the premises
Snyder & Swann (1978)
Participants asked to conduct interviews to determine interviewee's personality traits -Led to expect either an extrovert or introvert
Confirmation Bias in Inductive Reasoning: Wason (1966, 1968)
Participants given a number series that conforms to a rule and must discover the rule by offering their own number series -Experimenter answers "yes" or "no"
Confirmation Bias in Inductive Reasoning: Wason (1966, 1968): Findings
Participants had difficulty discovering the relatively simple rule (number that increase) because they tended only to try to confirm their hypothesis rather than disconfirm it
Snyder & Swann (1978): Conclusion
Participants tended to choose questions from the list that served to confirm their beliefs about the interviewee
The Wason Selection Task: Less than 10% Get Right
People assume the conditional is bidirectional
Abstract vs. Concrete Information
People reason much more effectively with concrete rather than abstract information
Inductive Reasoning
Reasoning about conclusions that are likely given some set of premises; deals with probably truth -Reasoning from the specific to the general
Cosmides & Tooby (1992)
Rules activate permission schema, which is something that we come about through our evolutionary/adaptive history -Lets us detect when people are cheating
Confirmation Bias
Tendency to seek out information that confirms hypothesis rather than disconfirming it
Diversity (Inductive Reasoning)
The more premise categories differ from each other, the stronger the inference
Typicality (Inductive Reasoning)
The more typical the premise category, the stronger the inference to an inclusive category
Reasoning
The process of drawing conclusions from given information -Evaluating conclusions based on given information
Consequent
The proposition following then -The result
Antecedent
The proposition that comes 1st, following if -The condition
Built-in Program to Detect Cheaters
When people cheat it doesn't bode well for the survival of others -Allows for detection of rule violation in even unfamiliar contexts
