Deductive Reasoning

What is deductive reasoning?

reasoning to a conclusion from a set of premises or statements where that conclusion follows necessarily from the assumption that the premises are true

How can a conclusion be drawn from deductive reasoning?

with certainty and based on formal logic

What is conditional reasoning?

a form of logical reasoning that follows an if-then structure

What does a major premise/conditional statement do?

establishes a cause-and-effect relationship

e.g. if i attend all of my lectures, then i will do well on my exam - attending lectures leads to success on the exam

What does a minor premise confirm?

confirms that the condition set in the major premise has been met

e.g. i attend all of my lectures

What is denial of the antecdent?

a logical fallacy where no definitive conclusion can be made - you dont meet the first condition but doesnt mean the conclusion wont be met

What is affirmation of the consequent?

logical fallacy where minor premise outcome is confirmed but no specification about how it was achieved

What is modus tollens?

a form of deductive reasoning which follows the pattern: major premise (conditional statement) - minor premise (negation of Q) - conclusion (negation of P)

What statement follows conditional reasoning?

if p then q

p = antecendent/modus ponens not q = consequent/modus tollens (logically valid inferences)

not p - denial of antecedent q = affirmation of consequent (logically invalid inferences)

How do you distinguish 4 inferences in conditional reasoning?

depending on which part appears in minor premise

How is a conditional statement often interpreted as in everyday language?

as a biconditional (you will get £10 if and only if you mow my lawn)

but in formal logic, conditional statement does not necessarily imply the reverse

When does logical reasoning become harder?

when applied to abstract content

What do people generally find easy to apply?

modus ponens - if P then Q - P is true so Q must be true.

What do most struggle with?

modus tollens - if P then Q - Q is false so P must also be false

What do many mistakenly commit?

denial of the antecedent (if P then Q - P is false so Q must be false) and affirmation of consequent (if P then Q - Q is true so P must be true)

What does Evans study highlight?

reasoning tendencies when dealing with conditional logic

What does Johnson-Laird’s mental model theory represent?

possibilities given premise info

only true possiblies are represented (principle of truth)

Why are alternative mental models created?

to identify counterexamples but if no counterexamples are found then conclusion is valid

What does limited WM capacity mean?

that sometimes not all possible mental models are created

What do valid inferences require?

1 model

What do invalid inferences require?

2 models

What are the strengths of mental models?

predictions have been confirmed experimentally

predict pps responses to 95% accuracy

What are weaknesses of mental models?

assume more deductive reasoning occurs than it actually does

underspecification of process inv in mental model formation

do not account for ambiguous reasoning problems

How can reasoning be influenced?

by different types of premises (Ruth Byrne) showing how reasoning is not just logical but influenced by context and how premises are framed

How can a simple conditional premise be modified?

by introducing alternative/additional premises which change how ppl infer conclusions

What did Byrnes’ 1989 experiment investigate?

investigate how diff types of contextual info influences ppls reasoning with conditionals

What did Byrne’s experiment show?

that while ppl can apply valid logical rules in some cases, they can still make systematic reasoning errors

shows how context can shape how ppl interpret logical conditionals, sometimes leading to errors

What is Wason’s selection task?

to select only those cards that wouldnt need to be turned over to decide if rule is correct

What can prior knowledge do?

improve and hinder reasoning performance

What do people do when evaluating logical statement?

generate counterexamples

What is De Ney’s research similar to?

Byrne’s idea of alternative and additional premises in reasoning bc both studies examine how ppl naturally think of alt explanations when reasoning about conditionals

What did DeNeys et al find?

inferences acceptance is affected by a no. counterexamples

high Wm capacity is better at reasoning

What happens in Wason’s Selection task?

logically correct choice inv checking both confirmation (modus ponens) and falsification (modus tollens) conditions but ppl often fails to pick the logically correct cards, revealing cognitive biases

What is matching bias?

where ppl tend to select the cards that directly match the terms in the rule rather than thinking abt what would falsify the rule

What did Oaksford argue?

that real world reasoning is often probabilistic rather than strictly logical

What did Oaksford and Chater suggest?

that humans use prpbability based heuristics rather than strict logic when solving Wason’s task - we focus on what is most likely to be informative in a given situation

What often conflicts?

logical reasoning and real life decision making bc people rely on biases and probabilistic thinking rather than strict logic