" In the field of research on human learning and growth, one-time snapshots of learning effects are not enough. They do not test each of the several theories involved. They may be too artificial and contrived actually to allow the key constructs to exert their effects. Design experiments over repeated cycles in live settings offer a powerful alternative solution to these problems." Bunderson 2003, p. 14 pdf
A conceptual framework of learning on which domain-specific, individualized, theories of learning can be constructed.