Investigates the relationship between class inclusion and reasoning in 56 Dutch Children between 6 and 14 years of age. Concludes that when the children failed to respond correctly to questions about the validity of syllogisms, they did so because they lacked sufficient understanding of the premises. (HOD)

Examined the relationship between 7-, 9-, and 11-year old children's performance on a battery of selected Piagetian measures and on a proportional reasoning task. Found a strong relationship between stage level and (1) the complexity of hypotheses used, (2) the use of the proportional hypothesis, and (3) the overall use of logical hypotheses. (HOD)