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