Keynote series Dr. Melanie Boly - The Nature of Consciousness: A Clash of Paradigms in Integrated Information Theory

By Alejandra Lopez-Castro

The Quest to Define Phenomenal Existence

Consciousness remains one of the most enigmatic phenomena in science. How does subjective experience arise from physical processes in the brain? One of the most ambitious attempts to answer this question is Integrated Information Theory (IIT), which has evolved through several iterations, with IIT 4.0 being its latest formulation. The theory seeks to mathematically describe the properties of conscious experience, what it calls phenomenal existence, in precise physical terms. At the same time, critics argue that IIT may conflate genuine consciousness with pseudo-consciousness, leading to a fundamental clash between competing paradigms in neuroscience.

IIT 4.0: Quantifying Consciousness

IIT posits that consciousness corresponds to the capacity of a system to integrate information in a way that cannot be reduced to its parts. The theory introduces a key metric, Φ (phi), which quantifies the degree of integration and differentiation within a network. A system with high Φ is presumed to have a rich conscious experience, whereas a system with Φ near zero is unconscious.

The latest version, IIT 4.0, refines earlier formulations by more rigorously defining the axioms of experience—intrinsic existence, composition, information, integration, and exclusion. These axioms are translated into postulates about physical systems, allowing researchers to assess whether a given system (biological or artificial) possesses consciousness. For example, the human brain’s complex, highly interconnected structure yields a high Φ value, whereas a digital computer, despite processing vast amounts of information, may lack true integration and thus remain unconscious.

The Challenge of Pseudo-Consciousness

Despite its mathematical elegance, IIT has faced significant criticism. Dr. Melanie Boly, a prominent neuroscientist, has raised concerns that the theory may mistakenly attribute consciousness to systems that merely simulate it. In her work, she highlights the distinction between genuine consciousness, rooted in biological processes, and pseudo-consciousness, which might emerge in artificial systems that replicate informational integration without true subjective experience.

Boly argues that IIT’s reliance on purely structural and informational criteria could lead to false positives. For instance, a highly interconnected artificial neural network might exhibit a high Φ value without actually being conscious. This raises a critical question: Is consciousness merely a matter of information integration, or does it require specific biological mechanisms that remain poorly understood

Two Competing Paradigms

The debate reflects a deeper divide in consciousness research. On one side, proponents of IIT advocate for a formalist approach, where consciousness is a measurable property of any sufficiently complex system, biological or not. On the other side, skeptics like Boly favor a biological paradigm, which holds that consciousness is inextricably linked to living organisms with specific evolutionary and physiological traits.

This clash has profound implications. If IIT is correct, we may one day engineer conscious machines or detect consciousness in unexpected places (e.g., advanced AI or even certain large-scale networks). Conversely, if Boly’s critique holds, then consciousness may remain a uniquely biological phenomenon, resisting reduction to pure information theory.

The Future of Consciousness Science

As research progresses, empirical evidence will be crucial in resolving this debate. Advances in neuroimaging, artificial intelligence, and theoretical modeling may help determine whether Φ truly correlates with conscious experience or if additional biological constraints are necessary.

For now, IIT 4.0 stands as one of the most rigorous attempts to formalize consciousness in physical terms. Yet, as Boly’s work emphasizes, the line between real and illusory consciousness remains blurred. The challenge for scientists is not just to measure consciousness but to define it in a way that distinguishes true subjective experience from mere complexity.

Ultimately, understanding consciousness may require more than mathematics—it may demand a fundamental rethinking of what it means to exist as a conscious being.

Don't miss the interview with Dr. Boly that you'll find in the blog post. And don't miss the keynote talk this June at the OHBM Annual Meeting 2025

Source:

Tononi, G., Albantakis, L., Barbosa, L., Boly, M., Cirelli, C., Comolatti, R., Ellia, F., Findlay, G., Casali, A. G., Grasso, M., Haun, A. M., Hendren, J., Hoel, E., Koch, C., Maier, A., Marshall, W., Massimini, M., Mayner, W. G., Oizumi, M., Szczotka, J., … Zaeemzadeh, A. (2025). Consciousness or pseudo-consciousness? A clash of two paradigms. Nature neuroscience, 28(4), 694–702. https://doi.org/10.1038/s41593-025-01880-y

Albantakis, L., Barbosa, L., Findlay, G., Grasso, M., Haun, A. M., Marshall, W., Mayner, W. G. P., Zaeemzadeh, A., Boly, M., Juel, B. E., Sasai, S., Fujii, K., David, I., Hendren, J., Lang, J. P., & Tononi, G. (2023). Integrated information theory (IIT) 4.0: Formulating the properties of phenomenal existence in physical terms. PLoS computational biology, 19(10), e1011465. https://doi.org/10.1371/journal.pcbi.1011465