Inhelder and Piaget found that somewhere between 12 and 15 years of age, children's thinking shifted from concrete to formal operations. To determine if this shift occurs at approximately the same age for learning disabled children (N=27) compared to normal learning children (N=27) was the task of the study reported. (JN)

Discussed are some situations students face that result in cognitive conflict, possible sources of these conflicts, and strategies which students use to resolve, remove, or circumvent them. A global account for observed systematic errors is offered based on a general problem-solving rule called the "Matching Rule." (KR)