The decades-long bet on consciousness is over—and it’s philosopher 1, neuroscientist 0

A 25-year scientific bet is over. In 1998, neuroscientist Christoph Koch made a bet with philosopher David Chalmers that the mechanism by which brain neurons produce consciousness would be discovered by 2023. Both scientists agreed publicly on June 23, at the annual meeting of the Association for the Scientific Study of consciousness (ASSC) in New York that this is still in progress – and declared Chalmers the winner.

What ultimately helped settle the bet was a key study testing two leading hypotheses about the neural basis of consciousness, the findings of which were revealed at the conference.

“It was always a relatively good bet for me and a bold bet for Kristoff,” says Chalmers, who is now co-director of the Center for Mind, Brain, and Consciousness at NYU. But he also says that’s not the end of the story and that the answer will come eventually: “There’s a lot of progress in the field.”

The big bet

Consciousness is everything one experiences – what one tastes, hears, feels and much more. It is what gives meaning and value to our lives, says Chalmers.

Despite enormous efforts—and a 25-year stake—researchers still don’t understand how our brains produce it. “It started as a very big philosophical mystery,” adds Chalmers. “But over the years it has gradually become, if not a ‘scientific’ mystery, at least one that we can partially understand scientifically.”

Koch, a Distinguished Research Fellow at the Allen Institute for Brain Sciences in Seattle, Washington, began his search for the neural imprints of consciousness in the 1980s. Since then, he has invested in identifying “the bits of the brain that are really important—really necessary to ultimately generate a sense of seeing or hearing or wanting,” as he puts it.

At the time Koch proposed the bet, some technological advances made him optimistic about solving the mystery sooner rather than later. Functional magnetic resonance imaging (fMRI), which measures tiny changes in blood flow that occur with brain activity, is taking laboratories by storm. And optogenetics—which allowed scientists to stimulate specific sets of neurons in the brains of animals like nonhuman primates—entered the scene. At the time, Koch was a young assistant professor at the California Institute of Technology in Pasadena. “I was very taken by all these techniques,” he says. “I thought: 25 years from now? No problem.”

Opposite cooperation

For many years the bet was almost forgotten. That is until a few years ago, when it was recovered by Per Snapprud, a Stockholm-based science journalist who interviewed Chalmers in 1998. His recording of the chat reminded the couple of the terms they had placed on the bet and the wine case that was at stake.

At the time, both Koch and Chalmers were involved in a major project supported by the Templeton World Charitable Foundation, based in Nassau, Bahamas, aimed at accelerating the study of consciousness.

The goal was to create a series of “adversarial” experiments to test different hypotheses about consciousness by having competing researchers collaborate on research design. “If their predictions don’t come true, it would be a serious challenge to their theories,” says Chalmers.

Findings from one of the experiments — which involved several researchers, including Koch and Chalmers — were revealed Friday at the ASSC meeting. It tests two of the leading hypotheses: integrated information theory (IIT) and global network workspace theory (GNWT). IIT suggests that consciousness is a “structure” in the brain formed by a specific type of neural connectivity that is active as long as a particular experience is occurring, such as viewing an image. This structure is thought to be located in the posterior cortex, at the back of the brain. On the other hand, GNWT suggests that consciousness arises when information is broadcast to areas of the brain through an interconnected network. Transmission, according to the theory, occurs at the beginning and end of the experience and involves the prefrontal cortex, at the front of the brain.

Six independent laboratories conducted the competition experiment following a pre-registered protocol and using a variety of complementary methods to measure brain activity. The results – which have not yet been peer-reviewed – do not fully match either theory.

“This tells us that both theories need to be reconsidered,” says Lucia Meloni, a neuroscientist at the Max Planck Institute for Empirical Aesthetics in Frankfurt, Germany, and one of the researchers involved. But “the degree of this revision is somewhat different for each theory.”

Unfulfilled predictions

“In terms of IIT, what we observed is that indeed areas in the posterior cortex contain information in a sustained way,” Meloni says, adding that the finding seems to suggest that the “structure” postulated by the theory is being observed. But the researchers found no evidence of sustained synchronization between different brain regions, as predicted.

Regarding the GNWT, the researchers found that some aspects of consciousness, but not all, could be identified in the prefrontal cortex. Furthermore, the experiments found evidence for the emission postulated by the theory’s proponents, but only at the beginning of the experience—not at the end, as predicted.

So GNWT performed slightly worse than IIT during the experiment. “But that doesn’t mean IIT is true and GNWT isn’t,” Meloni says. This means that proponents must rethink their proposed mechanisms in light of new evidence.

Other experiments are underway. As part of the Templeton Foundation initiative, Koch participated in the study testing IIT and GNWT in the brains of animal models. And Chalmers is working on another project evaluating two other hypotheses about consciousness.

It’s rare for proponents of competing theories to get around the table and be open to having their predictions tested by independent researchers, Meloni says. “It took a lot of courage and confidence from them.” She believes that projects like these are essential to the advancement of science.

As for the bet, Koch was reluctant to admit defeat, but the day before the ASSC session he bought a case of fine Portuguese wine to fulfill his commitment. Would you consider another bet? “I would double,” he says. “Twenty-five years from now is realistic because the techniques are getting better and, you know, I can’t wait more than 25 years, given my age.”