Hypothesis sampling systems among preoperational and concrete operational kindergarten children

Groups of 60 preoperational and 60 concrete operational kindergarten children received stimulus differentiation training either with feedback (experimental groups) or without (control groups), prior to a series of discrimination-learning problems in which a blank-trial probe, used to detect the child's hypothesis, followed each feedback trial. The concrete operational children manifested significantly better performances than the preoperational on seven of eight dependent measures examined. There were also significant differences in favor of the experimental groups on three dependent measures. While the results were generally consistent with predictions derived from Piagetian stage theory, it was suggested that this theory must be elaborated to include a perspective derived from conventional developmental learning theory in order to adequately account for these and other data.