Piaget suggested there are four stages of development, rigid in sequence (since questioned), and hierarchical, moving from sensory through to abstract processes. Piaget suggested that what can be learned and applied is restricted…that is until the child is at the right level, certain tasks cannot be learned or  performed, cognitively.

Piagetians never looked beyond the approximate age of 18, although a few neopiagetians and newer cogntive variations have done a bit more work on adults. In my view the most relevant applications of Piaget to adults came much later.

Research found that aproximately 50% of adult population never reached the abstract reasoning stage of development, meaning that they remained limited in their abilities to deal with and understand abstractions, including moral reasoning.

The other development has to do with the underlying mechanisms associated with these stages which Piaget suggested are biologically determined (that’s essentially what developmental psych is about).

The suggestion has been that what restricts or defines the stages is different M-space, where M-space is defined as the number of slots in “working memory” (kinda like ram on a computer). Research indicates
there is a correlation between m-space and movement through Piagetian stages.

One of the primary researchers on m-space is/was Robbie Case, who I studied with and hung out with for a few years.

I read Mr. Howe’s explanation, and find little linkage in the way he stated things. What IS relevant is that if only 50% of adults reach Formal Operations (abstract levels), then they will have trouble making
certain kinds of abstract judgments (hence the link to moral reasoning — Kohlberg, I think).

As an aside (this applies to children), more recent work has indicated that while children at the “wrong” level appear not to be able to learn certain things (e.g. conservation of liquids), that in fact, they can, given
the right instructional techniques and some more time (some of my colleagues were working on that research to develop instructional strategies).

Finally, there’s been suggestion that cognitive deficits stem from events that biologically damage m-space development and size.

The instructional implications are that while m-space may be biologically determined, that a trick of instructional design is to design it so the learning process minimizes m-space requirements and b) that
you teach meta-strategies for a high m-space requirement task that minimize m-space requirements.