what computes?

Here is a press release from Queens university:

Queen’s University professor Selim Akl has provided additional proof to the theory that nature computes. Dr. Akl (School of Computing) placed rolled oats on a map of Canada, covering the major urban areas. One urban area held the slime mold. The slime mold reached out for the food, creating thin tubes that eventually formed a network mirroring the Canadian highway system.
“By showing species as low as slime mold can compute a network as complex as the Canadian highway system, we were able to provide some evidence that nature computes,” says Dr. Akl.

Humans and human made machines compute (perhaps so do parrots and chimps) but highways and slime molds do not compute. Computing is done with symbols, usually numbers, and with operations on those symbols, usually mathematical or logical operations. There are other ways to arrive at the same solution as a computation, but they are computations just because the end point is the same. Road systems are the way they are because builders were interested in saving time, effort, money. Slime molds are going to save energy while gaining resources. These processes can be modeled mathematically but they are not done in symbolic way.

This attitude has bothered me for years. The mathematics is not more real than the physical thing. Reality is real and mathematics is just a system used to model it. We invented mathematics and it does not exist outside our brains. Nature does not compute except through human thoughts and actions.

It is very interesting that slime molds can reproduce the Canadian highway system with rewards based on the Canadian population distribution – but they did not calculate it – no computation. It was done with biological processes not arithmetic.

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