Deductive reasoning in right-brain damaged.

Deduction is a high level cognitive ability which has not been much analyzed in neuropsychology. Cognitive psychologists and cognitive scientists strongly debate the nature of the mental processes involved in deductive reasoning. A theory particularly pertinent to the neuropsychology of thinking is Mental Model Theory, which postulates the use of analogical representations in reasoning. Studies on unilateral neglect in neuropsychology show that the right hemisphere is involved in analogical representations. On these theoretical bases we make a critical prediction about the role of the right hemisphere in reasoning. This paper investigates the ability of right-brain damaged patients to deal with two main sorts of deduction: syllogistic and relational reasoning. Our results suggest a significant involvement of the right hemisphere in reasoning. Also, as far as syllogistic reasoning is concerned, the results allow for the existence of a verbal component, beside the analogical one.