The article reports the results of a study in which twelve different conservation of length tasks, indicative of passage from Piaget's preoperational to concrete operational stages of cognitive development, were administered to a sample of individuals from a remote and traditional society in Papua New Guinea. Individuals were systematically selected to represent varying age and education levels. Results are consistent with earlier research which has shown that conservation of length, and, by implication, concrete operations, is fully achieved only after 7 or more years of formal schooling.