Full house or Pandora's box? The treatment of variability in post-Piagetian research

This commentary focuses on the conceptual implications of analyses of indiv idual differences in francophone post-Piagetian research. These analyses ar e viewed as preoccupied by the "American question" of measurement and metho d, instead of attempting a theoretical account of the issues raised by intr aindividual and interindividual variability in development.