Six mildly and moderately retarded children (ages 6-8) were instructed in the Piagetian constructs of unidimensional classification and/or seriation using the "Piacelleration" learning set technique. After one semester, subjects made significant gains on: classification and seriation tasks, the Peabody Picture Vocabulary Test, and the…

Describes longitudinal study of the development of understanding of two logical properties of number by 36 children during the first three years of primary school in Glasgow. Piagetian tests and number skills tests were administered to explore the acquisition of number as class and number as order concepts. (Author/LRW)