While consciousness remains elusive, neuroscientists do offer various insights into it. The exploration is far from lacking.
“We already have a multitude of theories in the realm of consciousness; we don’t necessarily need more,” stated Oscar Ferrante, a neuroscientist at the University of Birmingham.
For those interested in theories explaining how our minds generate subjective experiences, consider Adaptive Resonance Theory, Dynamic Core Theory, or First Order Representational Theory, alongside the semantic pointer competition theory. In fact, a 2021 survey discovered 29 distinct theories of consciousness.
Dr. Ferrante is part of a group aiming to condense that number to potentially just one. However, they face significant obstacles due to the conventional methods used to study consciousness: formulating a theory, conducting experiments to gather evidence, and advocating for their theory over others.
“There’s little incentive for us to abandon our own ideas,” remarked Lucia Melloni, a neuroscientist at the Max Planck Institute for Empirical Aesthetics in Frankfurt, Germany.
Seven years ago, Dr. Melloni, along with 41 fellow scientists, initiated a comprehensive study on consciousness with the hope of breaking this cycle. Their objective was to unite two opposing groups to collaboratively design an experiment to assess how well each theory predicted brain activity during conscious experiences.
The team, known as the Cogitate Consortium, presented their findings on Wednesday in the journal Nature. However, they encountered the very conflicts they aimed to circumvent.
Dr. Melloni and her collaborators began drafting their study plans in 2018. Their approach involved adversarial collaboration, where scientists with conflicting theories partnered with neutral researchers. They selected two theories for investigation.
One theory, the Global Neuronal Workspace Theory, was proposed in the early 2000s by Stanislas Dehaene, a cognitive neuroscientist associated with the Collège de France in Paris. This theory asserts that we consciously perceive the world when key frontal brain regions transmit sensory information throughout the entire brain.
The second theory, put forth by Giulio Tononi from the University of Wisconsin and his colleagues, is called Integrated Information Theory. This theory posits that rather than attributing consciousness to specific brain regions, we should consider how conscious experiences are characterized by a sense of self and rich, detailed perceptions that coalesce into a cohesive whole — akin to Proust’s recollections triggered by consuming a madeleine.
The researchers then examined what type of physical network, whether a brain or something else, could produce such experiences. Their conclusion was that it necessitates processing vast amounts of information across diverse compartments that then share this information, creating a unified experience.
The Cogitate Consortium designed an experiment to rigorously evaluate both theories. Advocates for the theories supported the experiment.
“It was particularly gratifying since it marked a rare attempt to resolve conflicts instead of merely engaging in parallel research,” Dr. Melloni noted.
However, both she and her colleagues recognized the considerable scope of adversarial collaboration. They enlisted several young researchers, including Dr. Ferrante, spending two years formulating the experiment and putting their lab setups to the test. They began scanning the brains of 267 volunteers in late 2020, operating across eight laboratories in the U.S., Europe, and China.
The researchers had participants engage in video games designed to evaluate their conscious awareness of visual stimuli. In one such game, they attempted to catch colored disks as they passed by. Occasionally, a blurred face would also appear on the screen, prompting participants to press a button if they recognized it.
To enhance understanding, the researchers employed three distinct tools to monitor the participants’ brain activity.
Some participants, undergoing epilepsy surgery, consented to have electrodes temporarily inserted into their brains. A second group underwent fMRI scans to measure blood flow in their brains. The third group was examined using magnetoencephalography, which captures the brain’s magnetic fields.
By 2022, the researchers commenced data analysis. The results from all three techniques were consistent. Both theories made some accurate predictions regarding brain activity during conscious visual experiences, yet they also made incorrect predictions.
“Both theories are incomplete,” remarked Dr. Ferrante.
In June 2023, Dr. Melloni presented the findings at a conference in New York. The Cogitate Consortium uploaded the results online and submitted them to Nature, seeking publication in the journal.
Hakwan Lau, a neuroscientist at Sungkyunkwan University, was one of the reviewers who provided a critical assessment. He argued that the Cogitate Consortium had failed to clearly delineate where in the brain each theory’s predictions would be tested.
“It’s challenging to convincingly argue that the project genuinely tests the theories in a meaningful manner,” Dr. Lau commented in his July review.
Dr. Lau, who has developed his own theory of consciousness, shared his evaluation online in August and contributed to an open letter condemning both the Cogitate experiment and Integrated Information Theory. This letter garnered 124 signatures from experts.
This group, referring to themselves as “IIT-Concerned,” directed considerable criticism at Integrated Information Theory, labeling it pseudoscience and referencing harsh critiques from scientists in recent years.
They highlighted that Integrated Information Theory extends beyond merely explaining brain function; if any system capable of integrating information possesses consciousness, then one could argue that even plants might have a degree of consciousness.
Critics contended that the Cogitate Consortium’s experiment did not fulfill its claims, as it failed to adequately address the foundational aspects of the theory. “As researchers, we have a responsibility to shield the public from scientific misinformation,” Dr. Lau and his colleagues asserted.
Their letter, published online in September 2023, ignited a debate on social media. The authors additionally released a commentary detailing their objections, which was featured in the journal Nature Neuroscience last month.
In response, Dr. Tononi and his colleagues challenged the IIT-Concerned letter in the journal, stating that it “displayed enthusiasm but lacked factual basis,” and described the new commentary as an “attempt at damage control, wrapped in a philosophy-of-science guise.”
Meanwhile, the Cogitate Consortium paper was still undergoing peer review, and when it was finally published on Wednesday, it continued to elicit mixed reactions.
Anil Seth, a neuroscientist at the University of Sussex, praised the study’s scale and the identification of limitations within each theory. “I’m thrilled to see it; it’s an outstanding piece of work,” he remarked.
Nonetheless, the IIT-Concerned skeptics maintained their stance. Joel Snyder, a psychologist at the University of Nevada, Las Vegas, asserted that the predictions made by each team could have also stemmed from alternative theories, suggesting the experiment lacked precision in testing either theory.
“This is likely to create confusion,” Dr. Snyder commented.
Dr. Lau reflected that the new study had seemingly not narrowed down the extensive list of consciousness theories. “From recent discussions, I don’t sense that these challenges have influenced any of the theories,” he noted.
However, Dr. Seth emphasized the benefit of challenging theories against one another, even if it doesn’t result in researchers discarding their own views. “From a successful adversarial collaboration, the hope is that others may reconsider their positions,” he explained.