Middle and upper class 3- and 4-year-old children were exposed to three consecutive 5-week treatment conditions in the naturalistic setting of a half-day laboratory nursery school program. During the first treatment condition, the teacher emphasized low level cognitive questions; during the second, high level cognitive questions; and during the third, low level cognitive questions. The level of teacher's cognitive demands for all treatment conditions was classified according to the observational instrument, the Individual Cognitive Demand Schedule (ICDS). Subjects significantly increased their scores on two verbal problem solving tasks following exposure to high level cognitive questioning and significantly decreased their scores on the same tasks following exposure to low level cognitive questioning. (Author/CS)