A Neuroscientist’s Theory of Everything
Karl Friston takes us on a safari of his free-energy principle.
Karl Friston wanted me to know he had plenty of time. That wasn’t quite true. He just didn’t want our conversation—about his passion, the physics of mental life—to end. Once it did, he would have to step outside, have a cigarette, and get straight back to modeling COVID-19. I caught the University College London neuroscientist at 6 p.m., his time, just after he had sat on a panel at a COVID-related press conference. He apologized for still having on a tie and seemed grateful to me for supplying some “light relief and a distraction.”
A decade ago, Friston published a paper called “The Free-Energy Principle: A Unified Brain Theory?” It spells out the idea that the brain works as an editor, constantly minimizing, “squashing” input from the outside world, and in the process balancing internal models of the world with sensations and perceptions. Life, in Friston’s view, is about minimizing free energy. But it’s not just a view of the brain. It’s more like a theory of everything. Friston’s free-energy theory practically sets your brain on fire when you read it, and it has become one of the most-cited papers in the world of neuroscience. This May, Friston published a new paper, “Sentience and the Origins of Consciousness,” that takes his ideas into new intellectual territory.
Friston, currently a Wellcome Trust Principal Fellow and Scientific Director of the Wellcome Trust Centre for Neuroimaging, invented statistical parametric mapping, a brain scanning technique that has allowed neuroscientists to assess, as never before, the activity in specific brain regions and their roles in behavior. The discoveries he’s helping to make about the nature of the brain come out of a psychiatrist’s concern for the well-being of his patients, suffering from chronic schizophrenia. “Most of our practical work on causal modeling, data analysis, and imaging sciences was motivated and actually funded by schizophrenia research,” Friston said. “It has been a central part of my life and career for decades.”
The applications of Friston’s research are tangible and have made major contributions to mental disease, brain imaging, and now the COVID-19 pandemic. Venturing into the theory behind them, however, is a safari through a jungle of fascinating and at times beguiling concepts. Friston’s ideas have been on my radar for some time, so I was excited to jump right in. He was a passionate tour guide, taking us through a landscape of some of the most stimulating topics in science today, from consciousness to quantum physics to psychedelics.....MUCH MORE
In “The Free-Energy Principle,” you write the world is uncertain and full of surprises. Action and human perception, you argue, are all about minimizing surprise. Why is it important that things—including us—minimize surprise?
If we minimize surprise now, then on average over time, we’re minimizing the average surprise, which is entropy. If a thermostat could have beliefs about its world—it might say, “My world is about living at 22 degrees centigrade”—so any sensory information from its thermal receptors that departs from that is surprising. It will then act on the world to try and minimize that surprise and bring that prediction error back to zero. Your body’s homeostasis is doing exactly the same thing.
Does the brain minimize surprise in order to conserve energy?
You could certainly say that. But I wouldn’t quite put it like that. It’s not that the brain has a goal to exist. It just exists. It looks as if it has a goal to exist. What does existing mean? It’s always found in that configuration. The brain has to sample the world in a way that it knows what’s going to happen next. If it didn’t, you’d be full of surprises and you’d die....
