Integrated Information Theory, also called IIT, is a theory posited by psychiatrist and neuroscientist Giulio Tononi in 2004. With the idea, Tononi hoped to explain what consciousness is and why it might be associated with certain physical systems like those found in the brain. Since its initial publishing, IIT has been developed for over a decade, with the most recent version of the theory (called ITT 3.0) being published in 2014.
Incidents both uplifting and tragic, from the Paris Attack to SpaceX’s successful rocket landing, demonstrate how diverse and endlessly relevant consciousness is among human beings.
Fundamental to IIT is its decision to approach the problem of explaining consciousness by “starting with consciousness” or accepting the existence of consciousness as certain from the get-go. The theory then attempts to reason about the properties that a postulated physical substrate would have to have in order to account for that consciousness. In order to jump from the phenomenology of consciousness to the mechanism that underlies it, IIT assumes that if a conscious experience can be fully accounted for by an underlying physical system, the properties of that physical system must be constrained by the properties of the experience. IIT then attempts to identify the essential properties of conscious experience, called axioms, and then to find the corresponding properties of conscious physical systems, called postulates.
The aforementioned axioms are lined up in an attempt to isolate the essential aspects of all conscious experience, meaning that every existing axiom should apply in every possible occurrence of consciousness. The most versions of the axioms can be summed up as follows:
Intrinsic experience- consciousness exists and each experience here and now actually exists. A person’s experience comes from a person’s intrinsic perspective, which is independent of external observers.
Composition- consciousness has an intrinsic structure in which each experience is composed of multiple phenomenological distinctions which can be sorted by their elementary or higher-order natures.
Information- Consciousness is specific in that each experience is the particular way it is; it is composed of a specific set of phenomenal distinctions what differ it from other possible experiences. An experience may include everything from phenomenal distinctions that specify spatial locations, several concepts, higher-order “bindings” of first-order distinctions, and even negative concepts like the absence of a bird or a bicycle.
Integration- Consciousness is unified in that each experience is irreducible to non-interdependent, disjoint subsets of phenomenal distinctions, meaning when you see you see everything in your field of vision in all the colors you can see, as opposed to just the left or just red, white and black. Seeing a blue book cannot be reducible to seeing a book without the color blue plus the color blue without the book; it all happens together.
Exclusion- consciousness is definite; each experience has the set of phenomenal distinctions it has and it flows as fast as it flows, and there are limits to each experience in terms of what must and cannot be perceived.
Perhaps my next entry will discuss the postulates of the IIT, but for now a teaser: they’re separated into the same categories, but deal more directly with cause-effect systems and the constitution of elements. Until then, thanks for reading.