Abstract: The paper presented briefly discribed a new trend of Piagetian cognitive developmental theory:The transition from the epistemology of the intellectual development to the psychology of the intellectual development. The recent findings of the differential psychology in which provided methods and means for those transition were also introduced. Finally the author speculated upon that focusing on the psychological differentiation in the post-Piagetian theory was significant in pedagogy and clinical psychology.

Key words: Piagetian theory, Differential psychology, Subject(s)