Integration rather than age influences the performance of deductive reasoning

Abstract

This work merges from our interest for the evolution of deductive reasoning across the life cycle from youth to older age. With time, reasoning resources seem to be compromised and constrained, even if on the other side they seem more flexible. The literature on deductive reasoning considers that deduction only takes place between integrable premisses, that is, premisses whose elements share any categorematical term. The present research designed, applied and analyzed an instrument to measure deduction. The measure is based on integration as a general rule to deduce a conclusion from two premisses. The internal consistency of the instrument was .775 and its validity was approved by 10 experts. The transversal design had a sample of 37 young and 42 older persons, 12 of which had university degrees. Both young and old groups commit less failures with integrable elements than with non-integrable (p=.000), Importantly, the group of young reasoners show less correct answers differences between integrable and non-integrable inferences. As a conclusion, the high number of deductive errors among older persons in non integrable inferences can be explained because they seem to handle heuristic rules with a low abstraction level, of the kind: “if premisses are not integrable, then the inference is false”. The higher scores obtained by young reasoners with non integrable inferences is eventually explained in terms of the search for subjacent logical reasons in non integrable or even apparently incoherent inferential tasks.