Reported are the results of an experiment in which twelve different conservation of length tasks, indicative of passage from Piaget's pre-operational to concrete operations stages of cognitive development, were administered to a sample of individuals from Imbonggu-speaking people, a remote and traditional society in Papua New Guinea. Individuals were systematically selected to represent four varying age levels from 7 to 20 years and four education levels from 0 to 10 years. Results are consistent with neo-Piagetian interpretations of cognitive development which see development proceeding gradually in a continuous rather than stage-like fashion, and as heavily dependent on environmental influences--in this case, English language usage associated with seven or more years of formal schooling. (MNS)