As a preparatory step to the design of a preschool curriculum, this study examines three of the complex cognitive behaviors exemplified by the concrete operations period and its developmental prerequisites. Middle-class children in a university laboratory nursery setting were pretested, matched for age and randomly assigned to an instruction or a comparison control group. The instruction group was trained in two clusters of four children per teacher on labeling-classification, discrimination-memory, and seriation tasks. Each cluster consisted of a younger boy, a younger girl, an older boy and an older girl. Each session consisted of 20-30 minutes of organized activity and there were 12 sessions over a 3-week period for each training condition. The control group children had an equivalent amount of separate small group activity with a preschool teacher. The results of posttesting and transfer tasks support the contention that the developmental status of the curriculum target population will determine to a great extent the success or failure of an educational intervention effort. Age-related maturational components are important considerations in any curriculum attempt to modify the course of cognitive development. One half the document presents bibliography and appendixes detailing the training programs. (WY)