The metaphor is delicious.
Theory is substantial, even beautiful.
Facts blow about freely, depending upon imperfect instruments and constantly threatened by unexamined assumptions about what those instruments can validly reveal. But we were never treated to full-length, detailed reports of the empirical work that must have underlain Russia's clinical and research developments of ZPD since Vygotsky's time. Lacking access to the background studies, we adapted our familiar instruments and simply imagined what a ZPD experiment might look like when using clinical groupings of children as we define them. This led to empirical tests of the ZPD as it relates to static psychometric intelligence. They were compared with 18 gifted children who were much younger, about 8 yr old, with mean static IQ 138 and mental ages individually matched with those of the MR children.