Head to head
Integrated Information Theory vs Higher-Order Thought Theory
Integrated Information Theory (IIT) and Rosenthal’s Higher-Order Thought, compared field by field from their entries in the Atlas.
At a glance
- Integrated Information Theory belongs to the Information family in Kuhn's Landscape of Consciousness, Higher-Order Thought Theory to Materialism.
- On AI consciousness, Integrated Information Theory says “No” and Higher-Order Thought Theory says “Possible”.
- On life after death, Integrated Information Theory says “Uncertain” and Higher-Order Thought Theory says “No”.
- On mind uploading, Integrated Information Theory says “No” and Higher-Order Thought Theory says “Possible”.
- On meaning and purpose, Integrated Information Theory says “Uncertain” and Higher-Order Thought Theory says “Humanistic only”.
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The claim
In brief
Integrated Information TheoryIIT is an original, radical model that proposes a definition for conscious experience and specifies which physical systems can possess it, starting from the phenomenology of consciousness (axioms). It translates these axioms into physical postulates based on intrinsic cause-effect power, featuring a mathematical measure Φ(Phi) to quantify a system's capacity for informational integration, which correlates with the degree of consciousness.
Higher-Order Thought TheoryDavid Rosenthal holds that a mental state is conscious when its subject has a higher-order thought that he or she is in that state, a thought that need not itself be conscious and does not seem to rest on inference. Mental qualities such as the redness of a sensation exist whether or not they are conscious; Rosenthal explains them separately, by how they map the perceptible properties we can discriminate.
What consciousness is
Integrated Information TheoryConsciousness is identified as a Φ-structure, a maximally reduced conceptual structure existing in 'qualia space'. An experience is identical to this conceptual structure, meaning its phenomenal properties correspond precisely to the physical properties of the cause-effect structure unfolded from the physical substrate of consciousness (PSC).
Higher-Order Thought TheoryA state’s being conscious consists in the subject being aware of it by way of a suitable higher-order thought that one is in that state.
Big questions
Can AI be conscious?Differ
Integrated Information TheoryNoKoch, a proponent, argues that consciousness is not computable. Digital computers have negligible integrated information (Φ(Phi)) due to hardware structure, meaning they can never be sentient, regardless of intelligence.
Higher-Order Thought TheoryPossibleSince consciousness depends on having suitable higher-order thoughts about one’s own states, a system able to form such thoughts would meet the condition in principle.
Integrated Information TheoryUncertainIf phenomenal consciousness requires a radically new structure (like IIT's postulates), the potential permanence of these 'inscrutable things' cannot be rejected, leaving the possibility of survival open, even though IIT does not explicitly espouse life after death.
Higher-Order Thought TheoryNoConscious states are natural states of an organism, so nothing remains conscious once those states stop occurring.
Integrated Information TheoryNoIf consciousness is a fundamental property tied to real cause-effect power, a digital simulation (uploading) would only create a 'perfect zombie'—an entity that acts like the original but lacks subjective consciousness—because the simulation is virtual, lacking the required real cause-effect power.
Higher-Order Thought TheoryPossibleIf the relevant first-order states and higher-order thoughts were reproduced, the view gives no principled reason the copy would lack consciousness.
Integrated Information TheoryUncertainWhile the measurement and analysis of consciousness do not convey ultimate meaning, the speculative nature and novelty of the innumerable nth dimensional conceptual structures (conscious percepts) warrants suspending judgment on ultimate meaning/purpose/value.
Higher-Order Thought TheoryHumanistic onlyThe theory is a naturalistic account of mental states and carries no cosmic purpose.
Nature of mind
Ontology
Integrated Information TheoryIIT's fundamental ontology is the ontological primacy of phenomenal existence, based on an intrinsic powers view where what truly exists in physical terms are intrinsic entities capable of cause and effect. Koch notes that the theory insists consciousness must be incorporated into the basic description of reality at the rock-bottom level.
Higher-Order Thought TheoryPhysicalism (naturalistic functionalism)
Mind and body
Integrated Information TheoryIIT asserts an explanatory identity: an experience is identical to a Φ-structure. It contends that the conscious entity is the Φ-structure expressing its causal powers, not the neural substrate itself. This framework leaves no room for emergence or dualism.
Higher-Order Thought TheoryMental states, their qualities, and the higher-order thoughts that make them conscious are all natural states of the organism; Rosenthal expects neural correlates of consciousness to be whatever mechanism produces the higher-order awareness.
Fundamental or emergent
Integrated Information TheoryConsciousness is defined by intrinsic existence and characterized as belonging to the basic description of reality. The theory rejects emergence.
Higher-Order Thought TheoryEmergent
Qualia
Integrated Information TheoryDistinct conscious experiences are conceptual structures in a 'qualia space'. The qualitative feel (phenomenal properties) corresponds one-to-one to the physical properties of the maximally irreducible cause-effect structure, which is also called a quale.
Higher-Order Thought TheoryMental qualities are fixed by their role in perceptual discrimination and occupy a ‘quality space’ that mirrors the similarities among perceptible properties. Because these qualities do not depend on consciousness, a sensation can have qualitative character without being conscious, as in subliminal perception.
How it works
Mechanism
Integrated Information TheoryThe core principle is Integrated Information (Φ(Phi)), which quantifies the system's irreducibility. The Exclusion Postulate ensures that only the maximally irreducible cause-effect structure (the Φ-structure) exists intrinsically, defining the boundaries and grain of consciousness.
Higher-Order Thought TheoryA non-inferential higher-order thought that one is in a given state, which makes that first-order state conscious even when the thought itself is unconscious.
Where it is
Integrated Information TheoryConsciousness is not limited to biological brains. IIT predicts the conscious structure resides in the posterior cortex (occipital, parietal, and temporal cortices). Systems with maximally irreducible intrinsic cause-effect power possess consciousness.
Higher-Order Thought TheoryNot stated
What it does
Integrated Information TheoryConsciousness is identified as unfolded intrinsic causal power, which is the ability to effect change. Only this intrinsic entity (the Φ-structure) can cause, supporting the claim that true free will exists for systems with high Φ(Phi).
Higher-Order Thought TheoryNot stated
Evidence and criticism
Testability
Integrated Information TheoryIIT claims scientific testability, employing quantitative measurement. However, critics argue that the theory is not truly empirically tested, and its core predictions may be idiosyncratic.
Higher-Order Thought TheoryConceptually testable
Tests so far
Integrated Information TheoryCalculating Φ(Phi) for specific neural networks (e.g., visual cortex).,Monitoring brain activity as subjects slip into anesthesia.,Adversarial collaboration experiments testing predictions about sustained activity in the posterior cortex.
Higher-Order Thought TheoryNot stated
Criticisms
Integrated Information TheoryThe theory faces criticism for anti-common sense predictions (imputing consciousness to simple objects). A public letter characterized IIT as 'pseudoscience'. Critics challenge that experiments test only idiosyncratic predictions and not the core metaphysical ideas. Chalmers noted the 'pseudoscience' label was disproportionate and caused vast collateral damage.
Higher-Order Thought TheoryFirst-order theorists argue that higher-order awareness is an unneeded extra ingredient, and deflationists say being aware of a conscious state is like ‘smiling a smile’. Rosenthal replies that a deflated awareness cannot explain the contrast between conscious and unconscious states.
Sources
Key sources
Integrated Information Theory
- From the phenomenology to the mechanisms of consciousness: integrated information theory 3.0, Oizumi, Albantakis, Tononi (2014)
- Consciousness: here, there and everywhere?, Tononi and Koch (2015)
- Only what exists can cause: an intrinsic powers view of free will, Tononi et al. (2022)
Higher-Order Thought Theory
- Rosenthal’s Higher-Order Thought, Landscape of Consciousness, David Rosenthal (2005)
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