Abstract
Two incompatible views of the reasoning schemas of the disjunction “p or q” in relation to Piaget’s theory are (a) that even 5- to 6-year-old children can achieve high performance on disjunctive syllogisms (Braine & Rumain, 1981), and (b) that only children older than 11-12 years old can do so (Nakagaki, 1981, in Japanese). A difference in the conceptual connection between p and q in “p or q” has been assumed to be responsible for the discrepancy. The purpose of the present study was to attempt to resolve this issue and to explore children’s cognitive development on disjunctive syllogisms. Many of the children participating in the present study were able to reason the exclusive class task better than the overlapping class task. The ratio of interpreting disjunction as compatible increased with increasing age. Furthermore, the present data suggest that the age at which children can master the reasoning schemas of disjunction is later, rather than at the early time suggested by Braine & Rumain’s (1981) report.
