integrated information theory

{{Expand section|date=September 2024}}File:Axioms and postulates of integrated information theory.jpg and Christof Koch.{{r|IIT2014}}]]

David Chalmers has argued that any attempt to explain consciousness in purely physical terms (i.e., to start with the laws of physics as they are currently formulated and derive the necessary and inevitable existence of consciousness) eventually runs into the so-called "hard problem". Rather than try to start from physical principles and arrive at consciousness, IIT "starts with consciousness" (accepts the existence of our own consciousness as certain) and reasons about the properties that a postulated physical substrate would need to have in order to account for it. The ability to perform this jump from phenomenology to mechanism rests on IIT's assumption that if the formal properties of a conscious experience can be fully accounted for by an underlying physical system, then the properties of the physical system must be constrained by the properties of the experience. The limitations on the physical system for consciousness to exist are unknown and consciousness may exist on a spectrum, as implied by studies involving split-brain patients{{Cite journal|doi = 10.1007/s11065-020-09439-3|title = Split-Brain: What We Know Now and Why This is Important for Understanding Consciousness|year = 2020|last1 = De Haan|first1 = Edward H. F.|last2 = Corballis|first2 = Paul M.|last3 = Hillyard|first3 = Steven A.|last4 = Marzi|first4 = Carlo A.|last5 = Seth|first5 = Anil|last6 = Lamme|first6 = Victor A. F.|last7 = Volz|first7 = Lukas|last8 = Fabri|first8 = Mara|last9 = Schechter|first9 = Elizabeth|last10 = Bayne|first10 = Tim|last11 = Corballis|first11 = Michael|last12 = Pinto|first12 = Yair|journal = Neuropsychology Review|volume = 30|issue = 2|pages = 224–233| pmid=32399946 | pmc=7305066 |s2cid = 216440326}} and conscious patients with large amounts of brain matter missing.{{Cite journal|url=https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(07)61127-1/fulltext|doi = 10.1016/S0140-6736(07)61127-1|title = Brain of a white-collar worker|year = 2007|last1 = Feuillet|first1 = Lionel|last2 = Dufour|first2 = Henry|last3 = Pelletier|first3 = Jean|journal = The Lancet|volume = 370|issue = 9583|page = 262|pmid = 17658396|s2cid = 7382008}}

IIT aims to explain which physical systems are conscious, to what degree, and in what way. The theory begins from the phenomenological certainty that experience exists, and infers necessary physical postulates that any conscious substrate must satisfy. Specifically, IIT moves from phenomenology to mechanism by attempting to identify the essential properties of conscious experience (dubbed "axioms") and, from there, the essential properties of conscious physical systems (dubbed "postulates").

IIT is grounded in:

Realism – the world exists independently of experience

Operational physicalism – physical existence means the ability to take and make a difference (i.e., to have cause–effect power)

Atomism – causal power can, in principle, be reduced to interactions between minimal units

Starting from the zeroth axiom (experience exists), IIT identifies five essential properties of experience:

Intrinsicality – experience exists for itself

Information – experience is specific

Integration – experience is unitary

Exclusion – experience is definite

Composition – experience is structured

Each axiom is mapped onto a physical postulate about a system’s causal structure:

The system must exert intrinsic cause–effect power

It must specify a specific cause and effect state (via intrinsic information)

It must do so as a whole—irreducibly (measured by small phi, φ)

Only the maximally irreducible substrate (the complex) is conscious

Its subsets must specify structured distinctions and relations, forming a Φ-structure (big Phi)

A system is described by its transition probability matrix (TPM), denoted $T\_U\; =\; p(\backslash mathbf\{u\}\text{'}\; \backslash mid\; \backslash mathbf\{u\})$, over all its possible states. From this, IIT defines:

Intrinsic information (ii) for a state s over a possible cause/effect state $\backslash tilde\{s\}$:

$\backslash text\{ii\}(s,\; \backslash tilde\{s\})\; =\; p(\backslash tilde\{s\}\; \backslash mid\; s)\; \backslash log\_2\; \backslash left(\; \backslash frac\{p(\backslash tilde\{s\}\; \backslash mid\; s)\}\{p(\backslash tilde\{s\})\}\; \backslash right)$

Integrated information (φ) as the irreducibility of that cause–effect structure across the minimum information partition (MIP):

$\backslash phi\; =\; \backslash min\_\{\backslash theta\}\; \backslash left[\; \backslash text\{ii\}(s,\; \backslash tilde\{s\})\; -\; \backslash text\{ii\}\_\{\backslash theta\}(s,\; \backslash tilde\{s\})\; \backslash right]$

Complexes are defined as the systems (subsets of units) that locally maximize φ. Their internal distinctions and relations form the Φ-structure of the system:

$\backslash Phi\; =\; \backslash sum\_\{\backslash text\{distinctions,\; relations\}\}\; \backslash phi$

$\backslash Phi$ corresponds to the quantity of consciousness, while the particular structure of distinctions and relations defines its quality.

IIT proposes an explanatory identity: an experience is identical to the cause–effect structure (Φ-structure) unfolded from a complex in its current state. This identity is not a correlation but a proposed explanation for how subjective experience arises from physical mechanisms.

The calculation of even a modestly-sized system's $\backslash Phi^\{\backslash textrm\{Max\}\}$ is often computationally intractable,{{Cite journal |last1=Mayner |first1=William G. P. |last2=Marshall |first2=William |last3=Albantakis |first3=Larissa |last4=Findlay |first4=Graham |last5=Marchman |first5=Robert |last6=Tononi |first6=Giulio |date=2018-07-26 |title=PyPhi: A toolbox for integrated information theory |journal=PLOS Computational Biology |volume=14 |issue=7 |pages=e1006343 |arxiv=1712.09644 |bibcode=2018PLSCB..14E6343M |doi=10.1371/journal.pcbi.1006343 |issn=1553-7358 |pmc=6080800 |pmid=30048445 |doi-access=free}} so efforts have been made to develop heuristic or proxy measures of integrated information. For example, Masafumi Oizumi and colleagues have developed both $\backslash Phi^*${{Cite journal|title = Measuring integrated information from the decoding perspective|arxiv = 1505.04368|date = 2015-05-17|first1 = Masafumi|last1 = Oizumi|first2 = Shun-ichi|last2 = Amari|first3 = Toru|last3 = Yanagawa|first4 = Naotaka|last4 = Fujii|first5 = Naotsugu|last5 = Tsuchiya|doi=10.1371/journal.pcbi.1004654|pmid = 26796119|volume=12|issue=1|journal=PLOS Computational Biology|page=e1004654|bibcode=2016PLSCB..12E4654O|pmc=4721632 | doi-access=free}} and geometric integrated information or $\backslash Phi^G$,{{cite journal |last1=Oizumi |first1=Masafumi |last2=Tsuchiya |first2=Naotsugu |last3=Amari |first3=Shun-ichi |title=Unified framework for information integration based on information geometry |journal=Proceedings of the National Academy of Sciences |date=20 December 2016 |volume=113 |issue=51 |pages=14817–14822 |doi=10.1073/pnas.1603583113 |pmid=27930289 |pmc=5187746 |arxiv=1510.04455 |bibcode=2016PNAS..11314817O |doi-access=free}} which are practical approximations for integrated information. These are related to proxy measures developed earlier by Anil Seth and Adam Barrett.{{cite journal | last1 = Barrett | first1 = A.B. | last2 = Seth | first2 = A.K. | year = 2011 | title = Practical measures of integrated information for time-series data | journal = PLOS Comput. Biol. | volume = 7 | issue = 1| page = e1001052 | doi=10.1371/journal.pcbi.1001052| pmid = 21283779 | bibcode = 2011PLSCB...7E1052B | pmc = 3024259 | doi-access = free}} However, none of these proxy measures have a mathematically proven relationship to the actual $\backslash Phi^\{\backslash textrm\{Max\}\}$ value, which complicates the interpretation of analyses that use them. They can give qualitatively different results even for very small systems.{{Cite journal|last1=Mediano|first1=Pedro|last2=Seth|first2=Anil|last3=Barrett|first3=Adam|date=2018-12-25|title=Measuring Integrated Information: Comparison of Candidate Measures in Theory and Simulation|journal=Entropy|volume=21|issue=1|page=17|doi=10.3390/e21010017|pmid=33266733|pmc=7514120|arxiv=1806.09373|bibcode=2018Entrp..21...17M|issn=1099-4300|doi-access=free}}

In 2021, Angus Leung and colleagues published a direct application of IIT's mathematical formalism to neural data.{{Cite journal |last1=Leung |first1=Angus |last2=Cohen |first2=Dror |last3=van Swinderen |first3=Bruno |last4=Tsuchiya |first4=Naotsugu |date=2021 |title=Integrated information structure collapses with anesthetic loss of conscious arousal in Drosophila melanogaster |journal=PLOS Computational Biology |volume=17 |issue=2 |pages=e1008722 |doi=10.1371/journal.pcbi.1008722 |issn=1553-7358 |pmc=7946294 |pmid=33635858|bibcode=2021PLSCB..17E8722L |doi-access=free}} To circumvent the computational challenges associated with larger datasets, the authors focused on neuronal population activity in the fly. The study showed that $\backslash Phi^\{\backslash textrm\{Max\}\}$ can readily be computed for smaller sets of neural data. Moreover, matching IIT's predictions, $\backslash Phi^\{\backslash textrm\{Max\}\}$ was significantly decreased when the animals underwent general anesthesia.

A significant computational challenge in calculating integrated information is finding the minimum information partition of a neural system, which requires iterating through all possible network partitions. To solve this problem, Daniel Toker and Friedrich T. Sommer have shown that the spectral decomposition of the correlation matrix of a system's dynamics is a quick and robust proxy for the minimum information partition.{{cite journal |last1=Toker |first1=Daniel |last2=Sommer |first2=Friedrich T. |last3=Marinazzo |first3=Daniele |title=Information integration in large brain networks |journal=PLOS Computational Biology |date=7 February 2019 |volume=15 |issue=2 |pages=e1006807 |doi=10.1371/journal.pcbi.1006807 |pmid=30730907 |pmc=6382174 |bibcode=2019PLSCB..15E6807T |doi-access=free}}

While the algorithm{{Cite web |title=CSC-UW/iit-pseudocode |url=https://github.com/CSC-UW/iit-pseudocode |access-date=2016-01-29 |website=GitHub}} for assessing a system's $\backslash Phi^\{\backslash textrm\{Max\}\}$ and conceptual structure is relatively straightforward, its high time complexity makes it computationally intractable for many systems of interest. Heuristics and approximations can sometimes be used to provide ballpark estimates of a complex system's integrated information, but precise calculations are often impossible. These computational challenges, combined with the already difficult task of reliably and accurately assessing consciousness under experimental conditions, make testing many of the theory's predictions difficult.

Despite these challenges, researchers have attempted to use measures of information integration and differentiation to assess levels of consciousness in a variety of subjects.{{Cite journal|title = Cortical reactivity and effective connectivity during REM sleep in humans|journal = Cognitive Neuroscience|date = 2010-09-01|issn = 1758-8936|pmc = 2930263|pmid = 20823938|pages = 176–183|volume = 1|issue = 3|doi = 10.1080/17588921003731578|first1 = M.|last1 = Massimini|first2 = F.|last2 = Ferrarelli|first3 = Mj|last3 = Murphy|first4 = R.|last4 = Huber|first5 = Ba|last5 = Riedner|first6 = S.|last6 = Casarotto|first7 = G.|last7 = Tononi}}{{Cite journal|title = Breakdown in cortical effective connectivity during midazolam-induced loss of consciousness|journal = Proceedings of the National Academy of Sciences of the United States of America|date = 2010-02-09|issn = 1091-6490|pmc = 2823915|pmid = 20133802|pages = 2681–2686|volume = 107|issue = 6|doi = 10.1073/pnas.0913008107|first1 = Fabio|last1 = Ferrarelli|first2 = Marcello|last2 = Massimini|first3 = Simone|last3 = Sarasso|first4 = Adenauer|last4 = Casali|first5 = Brady A.|last5 = Riedner|first6 = Giuditta|last6 = Angelini|first7 = Giulio|last7 = Tononi|first8 = Robert A.|last8 = Pearce|bibcode = 2010PNAS..107.2681F|doi-access = free}} For instance, a recent study using a less computationally-intensive proxy for $\backslash Phi^\{\backslash textrm\{Max\}\}$ was able to reliably discriminate between varying levels of consciousness in wakeful, sleeping (dreaming vs. non-dreaming), anesthetized, and comatose (vegetative vs. minimally-conscious vs. locked-in) individuals.{{Cite journal|title = A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior|journal = Science Translational Medicine|date = 2013-08-14|issn = 1946-6234|pmid = 23946194|pages = 198ra105|volume = 5|issue = 198|doi = 10.1126/scitranslmed.3006294|language = en|first1 = Adenauer G.|last1 = Casali|first2 = Olivia|last2 = Gosseries|first3 = Mario|last3 = Rosanova|first4 = Mélanie|last4 = Boly|first5 = Simone|last5 = Sarasso|first6 = Karina R.|last6 = Casali|first7 = Silvia|last7 = Casarotto|first8 = Marie-Aurélie|last8 = Bruno|first9 = Steven|last9 = Laureys|first10 = Marcello|last10 = Massimini|hdl = 2268/171542|s2cid = 8686961|url = https://orbi.uliege.be/handle/2268/171542}}

IIT also makes several predictions which fit well with existing experimental evidence, and can be used to explain some counterintuitive findings in consciousness research.{{Cite journal |last1=Tononi |first1=Giulio |year=2015 |title=Integrated information theory |journal=Scholarpedia |volume=10 |issue=1 |page=4164 |bibcode=2015SchpJ..10.4164T |doi=10.4249/scholarpedia.4164 |doi-access=free}} For example, IIT can be used to explain why some brain regions, such as the cerebellum do not appear to contribute to consciousness, despite their size and/or functional importance.

Integrated information theory has received both broad criticism and support.

Neuroscientist Christof Koch, who has helped to develop later versions of the theory, has called IIT "the only really promising fundamental theory of consciousness".{{Cite news|title = Sizing Up Consciousness by Its Bits|url = https://www.nytimes.com/2010/09/21/science/21consciousness.html|newspaper = The New York Times|date = 2010-09-20|access-date = 2015-11-23|issn = 0362-4331|first = Carl|last = Zimmer}}

Neuroscientist and consciousness researcher Anil Seth is supportive of the theory, with some caveats, claiming that "conscious experiences are highly informative and always integrated."; and that "One thing that immediately follows from [IIT] is that you have a nice post hoc explanation for certain things we know about consciousness.". But he also claims "the parts of IIT that I find less promising are where it claims that integrated information actually is consciousness — that there's an identity between the two.",{{Cite web|last=Falk|first=Dan|date=2021-09-30|title=Anil Seth Finds Consciousness in Life's Push Against Entropy|url=https://www.quantamagazine.org/anil-seth-finds-consciousness-in-lifes-push-against-entropy-20210930/|access-date=2021-12-16|website=Quanta Magazine|language=en}} and has criticized the panpsychist extrapolations of the theory.{{Cite web|last=Seth|first = Anil K|date=2018-02-01|title=Conscious spoons, really? Pushing back against panpsychism|url=https://neurobanter.com/2018/02/01/conscious-spoons-really-pushing-back-against-panpsychism/|access-date=|website=NeuroBanter|language=en}}

Philosopher David Chalmers, famous for the idea of the hard problem of consciousness, has expressed some enthusiasm about IIT. According to Chalmers, IIT is a development in the right direction, whether or not it is correct.{{Citation|last=Chalmers|first=David|title=How do you explain consciousness?|date=2014-07-14|url=https://www.ted.com/talks/david_chalmers_how_do_you_explain_consciousness|language=en|access-date=2021-12-16}}

Max Tegmark has tried to address the problem of the computational complexity behind the calculations. According to Max Tegmark "the integration measure proposed by IIT is computationally infeasible to evaluate for large systems, growing super-exponentially with the system's information content."{{cite journal |last1=Tegmark |first1=Max |title=Improved Measures of Integrated Information |journal=PLOS Computational Biology |date=2016 |volume=12 |issue=11 |page=e1005123 |doi=10.1371/journal.pcbi.1005123|pmid=27870846 |pmc=5117999 |arxiv=1601.02626 |bibcode=2016PLSCB..12E5123T |doi-access=free}} As a result, Φ can only be approximated in general. However, different ways of approximating Φ provide radically different results.{{cite journal |last1=Mediano |first1=Pedro |last2=Seth |first2=Anil |last3=Barrett |first3=Adam |title=Measuring Integrated Information: Comparison of Candidate Measures in Theory and Simulation |journal=Entropy |date=2019 |volume=21 |issue=1 |page=17 |doi=10.3390/e21010017|pmid=33266733 |pmc=7514120 |arxiv=1806.09373 |bibcode=2018Entrp..21...17M |doi-access=free}} Other works have shown that Φ can be computed in some large mean-field neural network models, although some assumptions of the theory have to be revised to capture phase transitions in these large systems.{{cite journal |last1=Aguilera |first1=Miguel |last2=Di Paolo |first2=Ezequiel |title=Integrated information in the thermodynamic limit |journal=Neural Networks |date=2019 |volume=114 |pages=136–146 |doi=10.1016/j.neunet.2019.03.001|pmid=30903946 |doi-access=free |hdl=10810/32812 |hdl-access=free}}{{cite journal |last1=Aguilera |first1=Miguel |title=Scaling Behaviour and Critical Phase Transitions in Integrated Information Theory |journal=Entropy |date=2019 |volume=21 |issue=12|page=1198 |doi=10.3390/e21121198 |pmc=7514544|bibcode=2019Entrp..21.1198A |doi-access=free}}

In 2019, the Templeton Foundation announced funding in excess of $6,000,000 to test opposing empirical predictions of IIT and a rival theory (Global Neuronal Workspace Theory, GNWT).{{Cite web |title=Accelerating Research on Consciousness: An Adversarial Collaboration to Test Contradictory Predictions of Global Neuronal Workspace and Integrated Information Theory |url=https://www.templetonworldcharity.org/projects-database/0389 |access-date=2023-07-16 |website=www.templetonworldcharity.org |language=en}}{{Cite journal |last1=Melloni |first1=Lucia |last2=Mudrik |first2=Liad |last3=Pitts |first3=Michael |last4=Koch |first4=Christof |date=2021-05-28 |title=Making the hard problem of consciousness easier |url=https://www.science.org/doi/10.1126/science.abj3259 |journal=Science |language=en |volume=372 |issue=6545 |pages=911–912 |doi=10.1126/science.abj3259 |issn=0036-8075 |pmid=34045342 |s2cid=235218711}} The originators of both theories signed off on experimental protocols and data analyses as well as the exact conditions that satisfy if their championed theory correctly predicted the outcome or not.{{Cite journal |last1=Melloni |first1=Lucia |last2=Mudrik |first2=Liad |last3=Pitts |first3=Michael |last4=Blumenfeld |first4=Hal |last5=Lange |first5=Floris de |last6=Jensen |first6=Ole |last7=Kreiman |first7=Gabriel |last8=Luo |first8=Huan |last9=Chalmers |first9=David |last10=Dehaene |first10=Stanislas |date=2019-01-16 |title=Adversarial Collaboration to test GNW and IIT. |url=https://osf.io/mbcfy/ |language=en |doi=10.17605/OSF.IO/MBCFY |website=Center for Open Science}}{{Cite journal |last1=Melloni |first1=Lucia |last2=Mudrik |first2=Liad |last3=Pitts |first3=Michael |last4=Bendtz |first4=Katarina |last5=Ferrante |first5=Oscar |last6=Gorska |first6=Urszula |last7=Hirschhorn |first7=Rony |last8=Khalaf |first8=Aya |last9=Kozma |first9=Csaba |last10=Lepauvre |first10=Alex |last11=Liu |first11=Ling |last12=Mazumder |first12=David |last13=Richter |first13=David |last14=Zhou |first14=Hao |last15=Blumenfeld |first15=Hal |date=2023-02-10 |title=An adversarial collaboration protocol for testing contrasting predictions of global neuronal workspace and integrated information theory |journal=PLOS ONE |language=en |volume=18 |issue=2 |pages=e0268577 |bibcode=2023PLoSO..1868577M |doi=10.1371/journal.pone.0268577 |issn=1932-6203 |pmc=9916582 |pmid=36763595 |doi-access=free}} Initial results were revealed in June 2023.{{Cite journal |last=Finkel |first=Elizabeth |date=2023-06-30 |title=Consciousness hunt yields results but not clarity |url=https://www.science.org/doi/10.1126/science.adj4498 |journal=Science |language=en |volume=380 |issue=6652 |pages=1309–1310 |bibcode=2023Sci...380.1309F |doi=10.1126/science.adj4498 |issn=0036-8075 |pmid=37384689 |s2cid=259287604}} None of GNWT's predictions passed what was agreed upon pre-registration while two out of three of IIT's predictions passed that threshold.{{Cite bioRxiv |biorxiv=10.1101/2023.06.23.546249 |author=Ferrante, O. |title=An adversarial collaboration to critically evaluate theories of consciousness |collaboration=Cogitate Consortium |date=2023-06-26}} The final, peer-reviewed results were published in the 30 April 2025 issue of Nature.{{Cite journal |last1=Cogitate Consortium. |last2=Ferrante |first2=O. |last3=Gorska-Klimowska |first3=U. |display-authors=2 |date=2025-04-30 |title=Adversarial testing of global neuronal workspace and integrated information theories of consciousness |url=https://www.nature.com/articles/s41586-025-08888-1 |journal=Nature |doi=10.1038/s41586-025-08888-1|doi-access=free }}

In a March 2025 Nature Neuroscience commentary titled “Consciousness or pseudo-consciousness? A clash of two paradigms,” proponents of IIT listed 16 peer-reviewed studies as empirical tests of the theory’s core claims.{{Cite journal |last1=Tononi |first1=Giulio |last2=Albantakis |first2=Larissa |display-authors=1 |title=Consciousness or pseudo-consciousness? A clash of two paradigms |url=https://www.nature.com/articles/s41593-025-01880-y |journal=Nature Neuroscience |publication-date=2025-03-10 |volume=28 |issue=4 |pages=694–702 |doi=10.1038/s41593-025-01880-y}} A commentary in the same issue by Alex Gomez-Marin and Anil Seth, titled “A science of consciousness beyond pseudo-science and pseudo-consciousness,” argued that, despite current empirical limitations, IIT remains scientifically legitimate.{{Cite journal |last1=Gomez-Marin |first1=Alex |last2=Seth |first2=Anil K. |title=A science of consciousness beyond pseudo-science and pseudo-consciousness |url=https://www.nature.com/articles/s41593-025-01913-6 |journal=Nature Neuroscience |publication-date=2025-03-10 |volume=28 |issue=4 |pages=703–706 |doi=10.1038/s41593-025-01913-6|pmid=40065186 }}

Influential philosopher John Searle has given a critique of the theory saying "The theory implies panpsychism" and "The problem with panpsychism is not that it is false; it does not get up to the level of being false. It is strictly speaking meaningless because no clear notion has been given to the claim."{{cite magazine |last1=Searle |first1=John |author-link1=John Searle |title=Can Information Theory Explain Consciousness? |url=https://www.nybooks.com/articles/2013/01/10/can-information-theory-explain-consciousness/ |website=The New York Review of Books}} Searle's take has itself been criticized by other philosophers for misunderstanding and misrepresenting a theory that may actually be resonant with his own ideas.{{Cite journal |last=Fallon |first=Francis |date=2020-09-01 |title=Integrated Information Theory, Searle, and the Arbitrariness Question |journal=Review of Philosophy and Psychology |language=en |volume=11 |issue=3 |pages=629–645 |doi=10.1007/s13164-018-0409-0 |issn=1878-5166 |s2cid=149881007}}

Theoretical computer scientist Scott Aaronson has criticized IIT by demonstrating through its own formulation that an inactive series of logic gates, arranged in the correct way, would not only be conscious but be "unboundedly more conscious than humans are."{{cite web |last1=Aaronson |first1=Scott |date=21 May 2014 |title=Why I Am Not An Integrated Information Theorist (or, The Unconscious Expander) |url=https://www.scottaaronson.com/blog/?p=1799 |website=Shetl-Optimized: The Blog of Scott Aaronson}} Tononi himself agrees with the assessment and argues that according to IIT, an even simpler arrangement of inactive logic gates, if large enough, would also be conscious. However he further argues that this is a strength of IIT rather than a weakness, because that's exactly the sort of cytoarchitecture followed by large portions of the cerebral cortex,{{cite web |last1=Aaronson |first1=Scott |date=30 May 2014 |title=Giulio Tononi and Me: A Phi-nal Exchange |url=https://www.scottaaronson.com/blog/?p=1823 |website=Shetl-Optimized: The Blog of Scott Aaronson}}{{cite web |last1=Tononi |first1=Giulio |title=Why Scott should stare at a blank wall and reconsider (or, the conscious grid) |url=http://www.scottaaronson.com/tononi.docx |website=Shetl-Optimized: The Blog of Scott Aaronson}} specially at the back of the brain, which is the most likely neuroanatomical correlate of consciousness according to some reviews.{{Cite journal |last1=Boly |first1=Melanie |last2=Massimini |first2=Marcello |last3=Tsuchiya |first3=Naotsugu |last4=Postle |first4=Bradley R. |last5=Koch |first5=Christof |last6=Tononi |first6=Giulio |date=2017-10-04 |title=Are the Neural Correlates of Consciousness in the Front or in the Back of the Cerebral Cortex? Clinical and Neuroimaging Evidence |url=https://www.jneurosci.org/content/37/40/9603 |journal=Journal of Neuroscience |language=en |volume=37 |issue=40 |pages=9603–9613 |doi=10.1523/JNEUROSCI.3218-16.2017 |issn=0270-6474 |pmc=5628406 |pmid=28978697 |s2cid=41370141}}

Philosopher Tim Bayne has criticized the axiomatic foundations of the theory.{{cite journal |last1=Bayne |first1=Tim |date=2018 |title=On the axiomatic foundations of the integrated information theory of consciousness |url= |journal=Neuroscience of Consciousness |volume=2018 |issue=1 |pages=niy007 |doi=10.1093/nc/niy007 |pmc=6030813 |pmid=30042860 |doi-access=free}} He concludes that "the so-called 'axioms' that Tononi et al. appeal to fail to qualify as genuine axioms".

IIT as a scientific theory of consciousness has been criticized in the scientific literature as only able to be "either false or unscientific" by its own definitions.{{cite journal |last1=Doerig |first1=Adrian |last2=Schruger |first2=Aaron |last3=Hess |first3=Kathryn |last4=Herzog |first4=Michael |date=2019 |title=The unfolding argument: Why IIT and other causal structure theories cannot explain consciousness |journal=Consciousness and Cognition |volume=72 |pages=49–59 |doi=10.1016/j.concog.2019.04.002 |pmid=31078047 |doi-access=free}} IIT has also been denounced by other members of the consciousness field as requiring "an unscientific leap of faith".{{cite journal |last1=Lau |first1=Hakwan |last2=Michel |first2=Matthias |date=2019 |title=On the dangers of conflating strong and weak versions of a theory of consciousness |url=http://psyarxiv.com/hjp3s/ |journal=PsyArXiv |doi=10.31234/osf.io/hjp3s |s2cid=203047817}} The theory has also been derided for failing to answer the basic questions required of a theory of consciousness. Philosopher Adam Pautz says "As long as proponents of IIT do not address these questions, they have not put a clear theory on the table that can be evaluated as true or false."{{cite journal |last1=Pautz |first1=Adam |date=2019 |title=What is Integrated Information Theory?: A Catalogue of Questions |journal=Journal of Consciousness Studies |volume=26` |issue=1 |pages=188–215}} Neuroscientist Michael Graziano, proponent of the competing attention schema theory, rejects IIT as pseudoscience. He claims IIT is a "magicalist theory" that has "no chance of scientific success or understanding".{{cite journal |last1=Jarrett |first1=Christian |date=5 April 2020 |title=Consciousness: how can we solve the greatest mystery in science? |url=https://www.sciencefocus.com/the-human-body/consciousness-how-can-we-solve-the-greatest-mystery-in-science/ |journal=BBC Science Focus Magazine |access-date=2 February 2021}} Similarly, IIT was criticized that its claims are "not scientifically established or testable at the moment".{{cite web |last1=Lau |first1=Hakwan |title=Open letter to NIH on Neuroethics Roadmap (BRAIN initiative) 2019 |url=https://inconsciousnesswetrust.blogspot.com/2020/05/open-letter-to-nih-on-neuroethics.html |website=In Consciousness We Trust|date=28 May 2020}}.

Neuroscientists Björn Merker, David Rudrauf and Philosopher Kenneth Williford co-authored a paper criticizing IIT on several grounds. Firstly, by not demonstrating that all members of systems which do in fact combine integration and differentiation in the formal IIT sense are conscious, systems which demonstrate high levels of integration and differentiation of information might provide the necessary conditions for consciousness but those combinations of attributes do not amount to the conditions for consciousness. Secondly that the measure, Φ, reflects efficiency of global information transfer rather than level of consciousness, and that the correlation of Φ with level of consciousness through different states of wakefulness (e.g. awake, dreaming and dreamless sleep, anesthesia, seizures and coma) actually reflect the level of efficient network interactions performed for cortical engagement. Hence Φ reflects network efficiency rather than consciousness, which would be one of the functions served by cortical network efficiency.{{cite journal |last1=Merker |first1=Björn |date=19 May 2021 |title=The Integrated Information Theory of consciousness: A case of mistaken identity |journal=Behavioral and Brain Sciences |volume=45 |pages=e41 |doi=10.1017/S0140525X21000881 |pmid=34006338 |doi-access=}}

A letter published on 15 September 2023 in the preprint repository PsyArXiv and signed by 124 scholars asserted that until IIT is empirically testable, it should be labeled pseudoscience.{{Cite journal |author=Fleming, S. M. |author2=Frith, C. |author3=Goodale, M. |author4=Lau, H. |author5=LeDoux, J. E. |author6=Lee, A. L. F. |display-authors=etal |date=2023 |title=The Integrated Information Theory of Consciousness as Pseudoscience |url=https://psyarxiv.com/zsr78/ |doi=10.31234/osf.io/zsr78 |doi-access=free |type=Preprint |access-date=2023-09-18 |website=PsyArXiv}} A number of researchers defended the theory in response. Computer scientist Hector Zenil based his criticism of IIT and what he considers a similarly unscientific theory, Assembly theory (AT), on the lack of correspondence of the methods and theory in some IIT research papers and the media frenzy.{{Cite web |last=Zenil |first=Hector |title=How Some Scientific Journalism is Failing Us, to both Readers & (less self-promotional) Scientists – Medium |url= https://hectorzenil.medium.com/how-scientific-journalism-is-failing-us-to-both-readers-and-non-self-promotional-scientists-5899dde19d7e |access-date=2023-09-27 |language=en-US}} He criticized the shallowness and misleading nature of the media coverage, including that which appeared in journals such as Nature and Science. He also criticized the testing methods and evidence used by IIT proponents, noting that one test amounted to simply applying LZW compression to measure entropy rather than to indicate consciousness as proponents claimed. An anonymized public survey invited all authors from peer-reviewed papers published between 2013 and 2023 found by a query of Web of Science using "consciousness AND theor*". Of the 60 respondents, 8% "fully" agreed, and 20% did "not at all" agree with the letter, with the remainder falling in between these poles.{{Cite web |date= |title=Do you agree with the open letter titled: "The Integrated Information Theory of Consciousness as Pseudoscience"? |url=https://comcensus.org/public/publicMain.php?q=open_letter_IIT |access-date=20 September 2024 |website=comcensus.org}}

The 10 March 2025 Nature Neuroscience commentary "What Makes a Theory of Consciousness Unscientific?" was signed by many of the same writers as the letter. It asserts that "the core ideas of IIT lack empirical support and are metaphysical, and not scientific" and refers to "the core claims of IIT, which we argue are unscientific".{{cite journal |last1=IIT-Concerned |last2=Arnold |first2=Derek H. |last3=Baxter |first3=Mark G. |last4=Bekinschtein |first4=Tristan A. |last5=Bengio |first5=Yoshua |last6=Bisley |first6=James W. |last7=Browning |first7=Jacob |last8=Buonomano |first8=Dean |last9=Carmel |first9=David |last10=Carrasco |first10=Marisa |last11=Carruthers |first11=Peter |last12=Carter |first12=Olivia |last13=Chang |first13=Dorita H. F. |last14=Charest |first14=Ian |last15=Cherkaoui |first15=Mouslim |date=2025-03-10 |title=What makes a theory of consciousness unscientific? |url=https://www.nature.com/articles/s41593-025-01881-x |journal=Nature Neuroscience |language=en |volume=28 |issue=4 |pages=689–693 |doi=10.1038/s41593-025-01881-x |issn=1097-6256 |pmid=40065187 }}

{{Portal|Philosophy|Psychology}}

{{Div col|colwidth=15em|small=no}}

• Causality
• Consciousness
• Global workspace theory
• Hard problem of consciousness
• Mind–body problem
• Neural correlates of consciousness
• Phenomenology (philosophy)
• Phenomenology (psychology)
• Philosophy of mind
• Qualia
• Sentience

{{Div col end}}

{{Reflist}}

{{Library resources box}}{{Commons category}}

• {{cite journal |last1=Albantakis |first1=L |last2=Barbosa |first2=L |last3=Findlay |first3=G |last4=Grasso |first4=M |last5=Haun |first5=AM |last6=Marshall |first6=W |last7=Mayner |first7=WGP |last8=Zaeemzadeh |first8=A |last9=Boly |first9=M |last10=Juel |first10=BE |last11=Sasai |first11=S |last12=Fujii |first12=K |last13=David |first13=I |last14=Hendren |first14=J |last15=Lang |first15=JP |last16=Tononi |first16=G |title=Integrated information theory (IIT) 4.0: Formulating the properties of phenomenal existence in physical terms. |journal=PLOS Computational Biology |date=October 2023 |volume=19 |issue=10 |pages=e1011465 |doi=10.1371/journal.pcbi.1011465 |doi-access=free |pmid=37847724|pmc=10581496 |arxiv=2212.14787 |bibcode=2023PLSCB..19E1465A }}
• {{cite journal |doi=10.1038/nrn.2016.44|title=Integrated information theory: From consciousness to its physical substrate|year=2016|last1=Tononi|first1=Giulio|last2=Boly|first2=Melanie|last3=Massimini|first3=Marcello|last4=Koch|first4=Christof|s2cid=21347087|journal=Nature Reviews Neuroscience|volume=17|issue=7|pages=450–461|pmid=27225071}}
• {{cite journal |doi=10.4249/scholarpedia.4164 |doi-access=free |title=Integrated information theory|year=2015|last1=Tononi|first1=Giulio|journal=Scholarpedia|volume=10|issue=1|page=4164|bibcode=2015SchpJ..10.4164T}}
• {{cite journal |doi=10.1371/journal.pcbi.1003588|title=From the Phenomenology to the Mechanisms of Consciousness: Integrated Information Theory 3.0|year=2014|last1=Oizumi|first1=Masafumi|last2=Albantakis|first2=Larissa|last3=Tononi|first3=Giulio|s2cid=2578087|journal=PLOS Computational Biology|volume=10|issue=5|pages=e1003588|pmid=24811198|pmc=4014402|bibcode=2014PLSCB..10E3588O |doi-access=free}}
• [http://www.architalbiol.org/aib/article/viewFile/15056/23165867 Integrated Information Theory: An Updated Account (2012) (First presentation of IIT 3.0)] {{Webarchive|url=https://web.archive.org/web/20141216073839/http://www.architalbiol.org/aib/article/viewFile/15056/23165867 |date=16 December 2014 }}
• {{cite journal |doi=10.2307/25470707|doi-access=|jstor=25470707|title=Consciousness as Integrated Information: A Provisional Manifesto|year=2008|last1=Tononi|first1=Giulio|journal=The Biological Bulletin|volume=215|issue=3|pages=216–242|pmid=19098144}}
• {{Cite journal |doi=10.1186/1471-2202-5-42|year=2004|last1=Tononi|first1=Giulio|title=An information integration theory of consciousness|journal=BMC Neuroscience|volume=5|page=42|pmid=15522121|pmc=543470 |doi-access=free}}

• [https://www.iit.wiki/ IIT-wiki]: An online learning resource aimed at teaching the foundations of IIT; includes texts, slideshows, interactive coding exercises, and sections for discussion and asking questions.
• [http://integratedinformationtheory.org/ integratedinformationtheory.org]: a (somewhat out-of-date) hub for sources about IIT; features a [http://integratedinformationtheory.org/calculate.html graphical user interface to an old version of PyPhi.]
• {{IEP|int-info|Integrated Information Theory of Consciousness}}

• [https://github.com/wmayner/pyphi PyPhi]: an open-source Python package for calculating integrated information.
• [http://integratedinformationtheory.org/calculate.html Graphical user interface]
• [https://pyphi.readthedocs.io/en/stable/ Documentation]

• [https://mitpress.mit.edu/books/feeling-life-itself The Feeling of Life Itself: Why Consciousness is Widespread but Can't Be Computed] by Christof Koch (2019)
• [https://www.amazon.com/Phi-Voyage-Brain-Giulio-Tononi/dp/030790721X Phi: A Voyage from the Brain to the Soul] by Giulio Tononi (2012)

• New Scientist (2019): [https://www.newscientist.com/article/mg24432540-200-how-does-consciousness-work-a-radical-theory-has-mind-blowing-answers/ How does consciousness work? A radical theory has mind-blowing answers]
• Nautilus (2017): [http://nautil.us/issue/47/consciousness/is-matter-conscious Is Matter Conscious?]
• Aeon (2016): [https://aeon.co/essays/could-machines-have-become-self-aware-without-our-knowing-it Consciousness creep]
• MIT Technology Review (2014): [http://www.technologyreview.com/news/531146/what-it-will-take-for-computers-to-be-conscious/ What It Will Take for Computers to Be Conscious] {{Webarchive|url=https://web.archive.org/web/20151127145512/http://www.technologyreview.com/news/531146/what-it-will-take-for-computers-to-be-conscious/ |date=27 November 2015 }}
• Wired (2013): [https://www.wired.com/2013/11/christof-koch-panpsychism-consciousness/ A Neuroscientist's Radical Theory of How Networks Become Conscious]
• The New Yorker (2013): [http://www.newyorker.com/tech/elements/how-much-consciousness-does-an-iphone-have How Much Consciousness Does an iPhone Have?]
• New York Times (2010): [https://www.nytimes.com/2010/09/21/science/21consciousness.html?pagewanted=2&_r=1&sq=integrated%20information%20theory&st=nyt&scp=1 Sizing Up Consciousness by Its Bits]
• Scientific American (2009): [http://www.scientificamerican.com/article.cfm?id=a-theory-of-consciousness A "Complex" Theory of Consciousness]
• IEEE Spectrum (2008): [https://spectrum.ieee.org/a-bit-of-theory-consciousness-as-integrated-information A Bit of Theory: Consciousness as Integrated Information Theory]

• Christof Koch (2014): [https://www.youtube.com/watch?v=LGd8p-GSLgY The Integrated Information Theory of Consciousness]
• David Chalmers (2014): [https://www.ted.com/talks/david_chalmers_how_do_you_explain_consciousness How do you explain consciousness?]

{{Consciousness}}

Category:Computational neuroscience

Category:Consciousness

Category:Information theory

Category:Panpsychism