Piaget, in describing the sequence of classificatory development, describes class inclusion as composed of two processes; hierarchical classification and post-whole comparisons. In the experiment reported here, elementary school children, trained in the concept of sets in first grade mathematics were given a task where they were required to assess…

This longitudinal study investigated the relationship of stress arising from medical problems of newborns to parent-infant interaction through the infant's first year. Significant interactive differences between full term and premature infants were found in feeding situations during the neonatal period and in floor play at eight months. The sample…