Kevin Lande has an article up at Aeon which is one of the best discussions of the brain as a computational system that I’ve seen in a while. For an idea of the spirit of the piece:
The claim that the brain is a computer is not merely a metaphor – but it is not quite a concrete hypothesis. It is a theoretical framework that guides fruitful research. The claim offers to us the general formula ‘The brain computes X’ as a key to understanding certain aspects of our astonishing mental capacities. By filling in the X, we get mathematically precise, testable and, in a number of cases, highly supported hypotheses about how certain mental capacities work. So, the defining claim of the theoretical framework, that the brain computes, is almost certainly true.
Though we are in a position to say that it is likely true that the brain is a computer, we do not yet have any settled idea of what it means for the brain to be a computer. Like a metaphor, it really is unclear what the literal message of the claim is. But, unlike a metaphor, the claim is intended to be a true one, and we do seek to uncover its literal message.
Even if you agree to the literal claim that the brain computes since, after all, our best theories hold that it computes X, Y and Z, you might be unsure or disagree about what it is for something to be a computer. In fact, it looks like a lot of people disagree about the meaning of something that they all agree is true. The points of disagreement do not spoil the point of agreement. You can have a compelling reason to say that a claim is true even before you light upon a clear understanding of what that claim means about the world.
The overall article is pretty long, but if you have strong opinions on this, I encourage you to read the whole thing.
I’m pretty firmly convinced that the brain is a computational system. When I read about the operations of neurons and synapses, and the circuits they form, the idea that I’m looking at computation is extremely compelling. It resonates with what I see in computer engineering with the logic gates formed by transistor circuits, or with the vacuum tubes and mechanical switches of earlier designs.
Apparently I’m not the only one, because neuroscientists talk freely and regularly about computation in neural circuits. It’s not really a controversial idea in neuroscience. The computational paradigm is simply too fruitful scientifically, and no one has really found a viable alternative theoretical framework.
Of course, many neuroscientists are careful to stipulate that the brain is not like a commercial digital computer, and I do think this is an important point. Brains aren’t Turing complete, and they certainly don’t have the Von Neumann architecture that most modern commercial computers resemble. But as the article discusses, these systems are a small slice of possible computational systems.
If we restrict the word “computation” to only being about what these devices do, then we need to come up with another word to describe the other complex causal systems that sure appear to be doing something like computation. I’ve used the word “causalation” before to describe these systems. But commercial computers are also causalation machines, so this just brings us right back to the bone of contention. Both commercial computers and brains appear to be causal nexuses, and computation could be described as concentrated causality.
The stumbling block for many, of course, is that the brain doesn’t follow any particular abstract computational design. It’s a system that evolved from the bottom up. So like any biological system, it’s a messy and opportunistic mish-mash. Still, scientists are gradually making sense of this jumble, and computationalism is an important tool for that.
Anyway, one of the things I’ve learned in the last few years is that a lot of people really hate the idea of the brain as an organic computer. It’s yet another challenge to human exceptionalism. So I anticipate a fresh wave of anti-computational responses to this piece.
What do you think? Are there reasons I’m not seeing to doubt the brain is a computational system? And if so, is there another paradigm worth considering?