Basically, the theory says that whenever and wherever possible, an organism will off-load memory in ways that lower the energy costs of storing and retrieving.
Spreading the Load. The body and brain, thanks to evolution and learning, are adept at spreading the load. Bodily morphology, development, action and biomechanics, as well as environmental structure and interventions, can reconfigure a wide variety of control and learning problems in ways that promote fluid and efficient problem solving and adaptive response.
Self-Structuring of Information. The presence of an active, self-controlled, sensing body allows an agent to create or elicit appropriate inputs, generating good data (for herself and for others) by actively conjuring flows of multimodal, correlated, time-locked stimulation.
Supporting Extended Cognition. The presence of an active, self-controlled, sensing body (a) provides a resource that can itself act as part of the problem-solving economy and (b) allows for the co-opting of bioexternal resources into extended but deeply integrated cognitive and computational routines.
Our problem-solving performances take shape according to some cost function or functions that, in the typical course of events, accord no special status or privilege to specific types of operation (motoric, perceptual, introspective) or modes of encoding (in the head or in the world).
Online problem solving will tend to defer to perceptuomotor modes of information access. That is, we will often rely on information retrieved from the world even when relevant information is also neurally represented.