Cognitive Neuroscience and Neuropsychology

Reasoning in the activity of evaluating arguments. All arguments involve the claim that one or more propositions (the premise) provide some grounds for accepting another proposition (the conclusion). Philosophers have sorted arguments into two broad categories – induction and deduction – based on the nature of the relationship between premise and conclusion. Valid deductive arguments involve the claim that their premises provide absolute grounds for accepting the conclusion. For example: (A) All men are mortal; Socrates is a man; therefore, Socrates is mortal. Validity is a function of the logical structure as opposed to sentence content. Arguments where the premises provide only limited grounds for accepting the conclusion are broadly called inductive arguments. For example: (B) Socrates is a cat; Socrates has 32 teeth; therefore, all cats have 32 teeth. (C) Socrates is a cat; Socrates has a broken tooth; therefore, all cats have a broken tooth. Neither is a valid argument. However, most of us would be prepared to accept the conclusion in (B) as plausible or reasonable but we would not accept the conclusion of (C) as plausible or reasonable. Interestingly, both arguments have an identical logical structure; they differ only in content. So, unlike deduction (e.g. A), induction (e.g. B, C) is a function of the content of the sentence and our knowledge of the world. It is usually a matter of knowing which properties generalize in the required manner and which do not. While philosophers are interested primarily in the epistemic relationship between premises and conclusion, psychologists are concerned with the cognitive processes/mechanisms involved in drawing the inference. Cognitive theories of reasoning can be divided into two broad categories. There is a class of theories that differentiate between inductive and deductive reasoning and postulate different mechanisms to explain each1,2 and another class of theories that do not differentiate between induction and deduction and postulate a unitary account of human reasoning.3,4 The class of cognitive theories that differentiate between deduction and induction accept the philosophers’ formulation of deduction as a formal rule governed process. They claim that the human organism in endowed with a competence knowledge of deduction in the form of internalized rules similar to those of formal logic.1,2 When subjects successfully draw valid inferences, they are displaying their underlying competence. When they make errors, these errors are explained in terms of performance factors such as memory limitations, attentional factors, failure to engage the task, etc. Cognitive Neuroscience and Neuropsychology