TO DETERMINE HOW TRAINING WOULD AFFECT CHILDREN FROM DIFFERENT LEVELS OF DEVELOPMENT, FIVE DISADVANTAGED AND FIVE ADVANTAGED PRESCHOOLERS WERE GIVEN SPECIFIC PROBLEM SOLVING TRAINING TO PREPARE TO SOLVE A CRITERION PROBLEM. THIS STUDY WAS AN ATTEMPT TO DISPROVE PIAGET'S THEORY THAT CHILDREN MUST HAVE REACHED A CERTAIN STAGE OF CONCRETE-OPERATIONAL THOUGHT BEFORE THEY CAN SOLVE FORMAL-OPERATIONAL PROBLEMS. A LARGE NUMBER OF CHILDREN WERE NOT NEEDED SINCE PIAGET ASSUMED THAT ALL CHILDREN PROCEED THROUGH FIXED STEPS IN COGNITIVE GROWTH SO THAT ANY VARIANCE WOULD BE SIGNIFICANT. THE INVESTIGATOR TAUGHT THE COMPONENT SKILLS NECESSARY TO SOLVE THE CRITERION PROBLEM BY PRESENTING SIMILAR DIAGRAMMED PROBLEMS ON THE CHALKBOARD WITH PRACTICE IN THE LOGICAL STEPS NECESSARY TO LEAD TO THE CORRECT CONCLUSIONS. THE CULTURALLY ADVANTAGED GROUP QUICKLY GRASPED THE SIMILARITY OF PROBLEM COMPONENTS, WHEREAS THE DISADVANTAGED GROUP NEVER DISCOVERED THE PATTERN AT ALL. WHEN THE CRITERION PROBLEM WAS PRESENTED, SEVEN CHILDREN SOLVED IT. YET, ALL BUT ONE OF THESE CHILDREN HAD NOT REACHED THE STAGE OF CONCRETE OPERATIONS, ACCORDING TO THEIR PERFORMANCE ON THE SMEDSLUND TEST OF LIQUID AMOUNT. THE INVESTIGATOR CONCLUDED THAT THE ABILITY TO HANDLE FORMAL OPERATIONAL PROBLEMS IS A FUNCTION OF SPECIFIC INSTRUCTION RATHER THAN A FUNCTION OF DEVELOPMENT. THIS ARTICLE WAS PUBLISHED IN THE ONTARIO JOURNAL OF EDUCATIONAL RESEARCH, 9, 3, SPRING, 1967. (MS)