CATEGORIZATION AND INTENSIONAL LOGIC IN C HILDREN

The purpose of this study was to show that criteria for assessing logi calness based solely on extensional quantification and its various << traps >> are not sufficient for accurately delimiting developing ratio nality. This theoretical and methodological limitation is clearly illu strated here for the case of categorization. We compared the extension al logic performance (success or failure in Piaget'S quantification of inclusion task) and the intensional logic performance of 72 children between the ages of 5 and 8. Three intensional logic tasks were used t o test for meaningful implication : Forced-Choice-Transitivity, Entail ment, and Partition. The results indicated that already at the extensi onal logic failure level (preoperational, non-including level), childr en are << intensional logicians >>. The discussion deals with the rela tionship between rationality and the inhibition of extensional reasoni ng biases.