The interactivist model of cognition has been developed by Mark Bickhard over the last 40 years or so. It is related to the viewpoints of Gibson and O’Regan, among others. The model is described in a book (Bickhard and Tervenn, 1996) and a more recent review (Bickhard 2008).

It starts with a criticism of what Bickhard calls “encodingism”, the idea that mental representations are constituted by encodings, correspondences between things in the world and symbols (this is very similar to my criticism of the neural coding metaphor, except Bickhard’s angle is cognitive science while mine was neuroscience). The basic argument is that the encoding “crosses the boundary of the epistemic agent”: the perceptual system stands on only one side of the correspondence, so there is no way it can interpret symbols in terms of things in the world since it never has access to things in the world at any point. The interpretation of the symbols in terms of things in the world would require an interpreter, some entity that makes sense of a priori arbitrary symbols. But this was precisely the epistemic problem to be solved, so the interpreter is a homunculus and this is an incoherent view. This is related to the skeptic argument about knowledge: there cannot be valid knowledge since we acquire knowledge by our senses and we cannot step outside of ourselves to check that it is valid. Encodingism fails the skeptic objection. Note that Bickhard refutes neither the possibility of representations nor even the possibility of encodings, but rather the fact that encodings can be foundational of representations. There can be derivative encodings, based on existing representations (for example Morse is a derivative encoding, which presupposes that we know about both letters and dots and dashes).

A key feature that a representational system must have is what Bickhard calls “system-detectable errors”. A representational system must be able to test whether its representations are correct or not. This is not possible in encodingism because the system does not have access to what is being represented (knowledge that cannot be checked is what I called “metaphysical knowledge” in my Subjective physics paper). No learning is possible if there are no system-detectable errors. This is the problem of normativity.

The interactivist model proposes the following solution: representations are anticipations of potential interactions and their expected impact on future states of the systems, or on the future course of processes of the system (this is close to Gibson’s “affordances”). I give an example taken from Subjective physics. Consider a sound source located somewhere in space. What does it mean to know where the sound came from? In the encoding view, we would say that the system has a mapping between the angle of the source and properties of the sounds, and so it infers the source’s angle from the captured sounds. But what can this mean? Is the inferred angle in radians or degrees? Surely radians and degrees cannot make sense for the perceiver and cannot have been learned (this is what I called “metaphysical knowledge”), so in fact the representation cannot actually be in the form of the physical angle of the source. Rather, what it means that the source is at a given position is that (for example) you would expect that moving your eyes in a particular way would make the source appear in your fovea (see more detail about the Euclidean structure of space and related topics in Subjective physics). Thus, the notion of space is a representation of the expected consequences of certain types of actions.

The interactivist model of representations has the desirable property that it has system-detectable errors: a representation can be correct or not, depending on whether the anticipation turns out to be correct or not. Importantly, what is anticipated is internal states, and therefore the representation does not cross the boundary of the epistemic agent. Contrary to standard models of representation, the interactivist model successfully addresses the skeptic argument.

The interactivist model is described at a rather abstract level, often referring to abstract machine theory (states of automata). Thus, it leaves aside the problem of its naturalization: how is it instantiated by the brain? Important questions to address are: what is a ‘state’ of the brain? (in particular given that the brain is a continuously active dynamical system where no “end state” can be identified); how do we cope with its distributed nature, that is, that the epistemic agent is itself constituted of a web of interacting elementary epistemic agents? how are representations built and instantiated?