Integrated Information Theory
Overview
Integrated Information Theory (IIT) is a theory of consciousness proposed by the neuroscientist Giulio Tononi in 2004 and developed since with Christof Koch among others. It starts from what it takes to be the essential properties of experience (that it exists intrinsically, is structured, specific, unified and definite) and argues that a physical system is conscious to the degree that it integrates information: that its state as a whole carries information above and beyond that carried by its parts taken separately. The quantity of integrated information is called phi (Φ), and the theory holds that any system with non-zero phi has some experience, and that the quality of the experience is given by the structure of the system's causal relations.
Notes
- IIT is the only version of panpsychism with a number in it, and it is testable in a way its philosophical cousins are not. It makes some predictions in the right direction: the cerebellum, with four times as many neurons as the cortex, contributes little to consciousness, and on IIT that is because its circuitry is feed-forward and poorly integrated; measures loosely inspired by phi do track the loss of consciousness under anaesthesia and in sleep.
- Its best-known problem is that phi can be made arbitrarily large by a simple, regular network of logic gates (a two-dimensional grid or an expander graph) doing nothing that anyone would call thinking, so that on the theory such a grid would be far more conscious than a human. Tononi has accepted the consequence. Most critics, and I, take it as a reductio.
- In 2023 an open letter signed by over a hundred consciousness researchers described IIT as pseudoscience, after a press release presented an adversarial-collaboration test as a draw between IIT and global workspace theory. The letter was, I think, unfair to the theory, which makes predictions and has had some disconfirmed, and fair to the panpsychist conclusions and the clinical claims being drawn from it ahead of the evidence.
- My position (Panpsychism, Consciousness): integration is probably one of the things a conscious system does, and the theory is useful as a measure. As a definition of consciousness it is refuted by its own consequences. Consciousness is what a particular kind of information processing is like from the inside, and "integrated" does not pick out the kind.