“Face It,” says psychologist Gary Marcus in The New York Times, “Your Brain is a Computer”. The op-ed argues for understanding the brain in terms of computation which opens up to the interesting question – what does it mean for a brain to compute?

Marcus makes a clear distinction between thinking that the brain is built along the same lines as modern computer hardware, which is clearly false, while arguing that its purpose is to calculate and compute. “The sooner we can figure out what kind of computer the brain is,” he says, “the better.”

In this line of thinking, the mind is considered to be the brain’s computations at work and should be able to be described in terms of formal mathematics.

The idea that the mind and brain can be described in terms of information processing is the main contention of cognitive science but this raises a key but little asked question – is the brain a computer or is computation just a convenient way of describing its function?

Here’s an example if the distinction isn’t clear. If you throw a stone you can describe its trajectory using calculus. Here we could ask a similar question: is the stone ‘computing’ the answer to a calculus equation that describes its flight, or is calculus just a convenient way of describing its trajectory?

In one sense the stone is ‘computing’. The physical properties of the stone and its interaction with gravity produce the same outcome as the equation. But in another sense, it isn’t, because we don’t really see the stone as inherently ‘computing’ anything.

This may seem like a trivial example but there are in fact a whole series of analog computers that use the physical properties of one system to give the answer to an entirely different problem. If analog computers are ‘really’ computing, why not our stone?

If this is the case, what makes brains any more or less of a computer than flying rocks, chemical reactions, or the path of radio waves? Here the question just dissolves into dust. Brains may be computers but then so is everything, so asking the question doesn’t tell us anything specific about the nature of brains.

One counter-point to this is to say that brains need to algorithmically adjust to a changing environment to aid survival which is why neurons encode properties (such as patterns of light stimulation) in another form (such as neuronal firing) which perhaps makes them a computer in a way that flying stones aren’t.

But this definition would also include plants that also encode physical properties through chemical signalling to allow them to adapt to their environment.

It is worth noting that there are other philosophical objections to the idea that brains are computers, largely based on the the hard problem of consciousness (in brief – could maths ever feel?).

And then there are arguments based on the boundaries of computation. If the brain is a computer based on its physical properties and the blood is part of that system, does the blood also compute? Does the body compute? Does the ecosystem?

Psychologists drawing on the tradition of ecological psychology and JJ Gibson suggest that much of what is thought of as ‘information processing’ is actually done through the evolutionary adaptation of the body to the environment.

So are brains computers? They can be if you want them to be. The concept of computation is a tool. Probably the most useful one we have, but if you say the brain is a computer and nothing else, you may be limiting the way you can understand it.



Link to ‘Face It, Your Brain Is a Computer’ in The NYT.