Chapter 12 Deductive Reasoning Flashcards
Deductive reasoning
Given some specific premises, judge whether those premises allow you to draw a particular conclusion based on the principles of logic
Conditional/propositional reasoning task
Describes the relantionship between conditions;
If… then…; judged as valid or invalid
Syllogism
Two statements that we must assume to be true, plus a conclusion
Propositional calculus
A system from categorizing the four kinds of reasoning used in analyzing propositions/statements
Antecedent
The first proposition or statement; the antecedent is contained in the “if…” part of the sentence
Consequent
The proposition contained in the “then…” part of the sentence
Affirming the antecedent
Means that you say the if part of the sentence is true the kind of reasoning leads to a valid or correct conclusion
The fallacy of affirming the consequent
You say the then part of the sentence is true. This kind of reasoning leads to an invalid conclusion
The fallacy of denying the antecedent
You say the if part of the sentence is false. Denying the antecedent also leads to an invalid conclusion
Denying the consequent
You say the then part of the sentence is false. This kind of reasoning leads to a current conclusion
Dual-process theory
Type 1 processing- fast and automatic
Type 2 processing- slow and controlled
Applies to both deductive reasoning and decision making
Difficulties with Linguistically Negative Information
People take longer to evaluate problems that contain linguistically negative information.
People are more likely to make errors on these problems.
causes working memory strain, especially when denying the antecedent or denying the consequent
leads to frequent errors when translating the statement into more accessible, linguistically positive forms
Difficulties with Abstract Reasoning Problems
People are more accurate when they solve reasoning problems that use concrete examples rather than abstract, theoretical examples.
diagrams can be helpful
Everyday knowledge may override the principles of logic.
Belief-Bias Effect
When people make judgments based on prior beliefs and general knowledge, rather then on the rules of logic
Confirmation bias
People tend to try to confirm or support a hypothesis rather than try to disprove it
people are eager to affirm the antecedent, but reluctant to deny the consequent by searching for counterexamples.
The Confirmation Bias
Concrete Versions of the Wason Selection Task
replace numbers and letters with concrete situations from everyday life
People perform much better when the task is concrete, familiar, and realistic.
Griggs and Cox (1982)—drinking age example
Performance improved when task implies a social contract.
The Confirmation Bias
Applications in Medicine
People seek confirming evidence when self- diagnosing disorders (e.g., insomnia).
Both medical students and psychiatrists tend to select information consistent with their original diagnosis rather than investigate information that might be consistent with another diagnosis.
Decision making
assessing and choosing among
several alternatives
no clear-cut rules
no “correct” decision
we often rely on heuristics
Kahneman and Tversky
proposed that a small number of heuristics guide human decision making
The same strategies that normally guide us toward the correct decision may sometimes lead us astray.
small-sample fallacy
We assume a small small will be representative of the population from which it was selected
Representative heuristic
We judge that a sample is likely if it is similar to the population form which this sample was selected for
Base rate
How often an item occurs in the population
Base for fallacy
Emphasizing the representativeness and understanding of-emphasizing important information about base rates
Base Rate and Representativeness
Kahneman and Tversky (1973)
Demonstrated that people rely on representativeness when asked to judge category membership.
even when provided with base-rate information, people tend to ignore it
stereotypes
Conjunction rule
The probability of the conjunction of two events cannot be larger than the probability of either of its constituents
Conjunction fallacy
When people judge the probability of the conjunction of the two events to be greater than the probability of a constituent event
The Conjunction Fallacy and Representativeness
People tend to judge using representativeness instead of statistical probability.
Students with high SAT scores are actually more likely than other students to demonstrate the conjunction fallacy
Summary of Representativeness Heuristic
We use the representativeness heuristic when we make decisions based on whether a sample looks similar in important characteristics to the population from which it is selected.
The representativeness heuristic is so appealing that we tend to ignore other important characteristics that we should consider, such as sample size and base rate.
We also fail to realize that the probability of two events occurring together (e.g., bank teller and feminist) needs to be smaller than the probability of just one of those events (e.g., bank teller).
Availability Heuristic
We tend to estimate frequency or probably in terms of how easy it is to think of relevant examples
Availability Heuristic only…
Availability Heuristic can…
Only accurate when availability is correlated with true, objective frequency
Can be distorted by recency and familiarity
Recency and Availability
Macleod and Campbell
-When people were encouraged to recall pleasant events from their past, they later judge pleasant events to be more likely in their future.
-When people were encouraged to recall unpleasant events, they later judged unpleasant events to be more likely.
-implications for psychotherapy
Familiarity and Availability
Brown et al
-Population estimates for various countries
-points of view shown by the media
-people need to use critical thinking and shift to type 2 processing
The Recognition Heuristic
When comparing the relative frequency of two categories, if people recognize one category and not the other, they conclude that the recognized category has the higher frequency
This strategy generally leads to an accurate decision
Illusory correlation
People believe that two variables are statistically related, even though there is no real evidence for this relationship
Social cognition approach
Says that stereotypes can be traced to normal cognitive processes
Illusory correlation and availability
Chapman and Chapman
used randomly assigned sexual orientation
to supposed inkblot responses
● showed that student participants formed an
illusory correlation between people’s
reported sexual orientation and their
responses on an inkblot test
Summary of availability heuristic
Slides 873-875
The Anchoring and Adjustment Heuristic
When making an estimate, people begin with a
first approximation (anchor) and then make
adjustments to that number on the basis of
additional information.
People rely too heavily on the anchor, and their
adjustments are too small; over influence of
current hypotheses or beliefs, top-down processing
Research on the anchoring and adjustment heuristic
Multiplication example
If the first munger was large, the estimates were higher than if the first number was small
Single-digit numbers anchored the estimates far too low
Confidence interval
A range within which we expect a number to fall a certain percentage of the time
Estimating Confidence Intervals
Studies find that, in general:
-estimated confidence intervals tend to be too narrow
-anchor may be erroneous and adjustments too small
-people don’t really understand confidence intervals
Summary of Anchoring and Adjustment
-When we use the anchoring and adjustment heuristic, we begin by guessing a first approximation or anchor. Then we make adjustments to that anchor.
-This heuristic is generally useful, but we typically fail to make large enough adjustments
-The anchoring and adjustment heuristic also explains our errors when we estimate confidence intervals; we usually supply ranges that are too narrow, given our uncertainty about the anchor
Ecological rationality
People create a wide clarity of heuristics to help them make useful adaptive decisions in the real world
Default heuristic
If there is a default option, then people will generally be more likely to choose it
Framing effect definition
The outcome of a decision can be influenced by:
-the background context of the choice
-the way in which a question is worded
The wording of a question and the framing effect
People are distracted by surface structure of
the questions.
The exact wording of a question can have a
major effect on the answers
Tversky and Kahneman
Prospect theory
When dealing with possible gains, people tend to avoid risks
When dealing with possible losses, people tend to seek risks
Overconfidence
Confidence judgemnts are higher then they should be based on actual performance
Illusory correlation — anchoring and adjustment
General studies on overconfidence
occurs in a variety of situations
• own decisions vs. statistically observable
measurements
• variety of personal skills
• individual differences
• cross-cultural differences
Crystal-ball technique
Has a decision maker imagine a complete accurate crystal ball indicates that your hypothesis is incorrect
My-side bias
Overconfidence that one’s own view is correct
in a confrontational situation; often results in
conflict; cannot even consider the possibility
that their opponent’s position may be at least
partially correct
Planning fallacy
People tend to underestimate the amount of time (or money) required to complete a project
Estimate the task will be relatively easy to complete
