Some scientists suspect our brains are just fancy computers.

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Some scientists suspect our brains are just fancy computers.

Something very cool happened recently in Minnesota. At the Seven Pines Symposium, where well-regarded theorists come together to discuss core philosophical questions in science, two famous thinkers on computation and the brain held a debate. On one side was Roger Penrose, an 84-year-old Oxford mathematical physicist responsible for some of the fundamental building blocks of modern physics. On the other was Scott Aaronson, a 35-year-old theoretical computer scientist at MIT who’s considered as one of the most important researchers in his field.

The question up for debate: Is your brain nothing more than a fancy computer?


Penrose has made enormous contributions to the study of general relativity and the large-scale structure of the universe. But he’s probably best known in popular culture for his somewhat idiosyncratic ideas about the human brain: Namely, that thought and consciousness exist outside the limits of conventional, computational logic and physics. Penrose, to summarize several books’ worth of ideas in a single sentence, argues that the human brain transcends algorithmic computation through an exotic, undiscovered physics that empowers it to interact with the quantum world. In that way, he says, it is fundamentally unlike a computer.

Aaronson disagrees, though he takes pains to explain how much he respects the older scientist’s perspective.

(“It was hard to decide which prospect I dreaded more,” he writes, “me ‘scoring a debate victory’ over Roger Penrose, or him scoring a debate victory over me.”)

There are a number of points and subtleties to understand in his critique of the idea that brains are somehow different from computers. But the most important parts come down to the limits of our brains and sheer possible power of computers.

Fundamentally, Aaronson said, he doesn’t see any reason to accept that human brains are capable of processes and answering problems that conventional computers – if supplied with enough power and the right software – could not.

Humans as a group might seem to converge toward some truths you can’t achieve through formal logic, Aaronson argues. But there’s no reason to believe that that’s a result of anything other than trial and error and the scientific method, both skills computers could conceivably learn.

Further, he doesn’t see any reason a complete human brain couldn’t be simulated in a computer, even if right now we lack the power:

A biologist asked how I could possibly have any confidence that the brain is simulable by a computer, given how little we know about neuroscience. I replied that, for me, the relevant issues here are “well below neuroscience” in the reductionist hierarchy. Do you agree, I asked, that the physical laws relevant to the brain are encompassed by the Standard Model of elementary particles, plus Newtonian gravity? If so, then just as Archimedes declared: “give me a long enough lever and a place to stand, and I’ll move the earth,” so too I can declare, “give me a big enough computer and the relevant initial conditions, and I’ll simulate the brain atom-by-atom.” The Church-Turing Thesis, I said, is so versatile that the only genuine escape from it is to propose entirely new laws of physics, exactly as Penrose does-and it’s to Penrose’s enormous credit that he understands that.

In other words: If you agree that your brain exists in the physical universe, and we know that computers can model the physical universe, it’s reasonable to assume that given enough power and information, computers can model your brain.


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