Your claim is true as far as it goes (I don’t think anyone here is asserting that human brains contain halting oracles or do some other sort of hypercomputation, and while we’re not quite sure if the laws of physics are computable, we haven’t seen any reason to think brains take advantage of it if they aren’t, Penrose’s musings aside), but it isn’t very useful for understanding how a brain’s typical operation compares to the typical designs, features, and bugs common in electronic computers we design, build, and program.
Brains are actually not necessary for this comparison. A computer that runs on an x86 architecture is Turing-complete, and a computer that runs Malbolge is Turing-complete, but there are some pretty significant practical limits in using what you know about one to predict the behavior of the other. And in practice, no human ever has built a Turing machine or any Turing-complete computer, because we build machines with finite hardware that run at finite processing speed for finite time and output answers with a finite number of bits. But if you’d like to continue to regard all Turing-complete formal systems as equivalent in practice, I suggest replacing your laptop, desktop, tablet, or smartphone with a carefully constructed Magic: The Gathering deck.
Your point seems to be that if material determinism is correct (not arguing otherwise) and neural processing can be replicated by computational algorithms, then the brain is by definition a computer.
The brain is only replicated by computational algorithms in a purely probalistic sense, though (similar enough outputs for similar enough inputs). It itself is not implementing those algorithms, and I really disagree with the presumption that it is a “morphism of a turing machine”
Oxford: an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program.
Merriam-Webster: one that computes, specifically a programmable usually electronic device that can store, retrieve, and process data.
American Heritage Dictionary: a device that computes, especially a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information.
dictionary.com or wiktionary.org: a programmable electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations. Mainframes, desktop and laptop computers, tablets, and smartphones are some of the different types of computers.
Some of these also mention the old definition of people who perform computations by hand. None mention Turing machines. If that’s the only definition you found and not the electronic things people keep on their desks, it’s because you didn’t look very hard, or rather took a technical abstraction and assumed it’s the only possible use. It’s like disagreeing that running on a treadmill is work because the total displacement is zero.
Almost everything a brain does is something that no existing or theoretical Turing machine can do. It regulates biological functions, it creates and responds to a rich melange of chemical and electrical signals, it is holistic and parallel, it recognizes faces and smells, it experiences a wide range of emotion that directs its behavior, etc. A brain is not just a piece of hardware that you can run software on and get a predictable and consistent result; even the subtlest change in brain chemistry can radically alter the way it behaves.
A brain and a computer (Turing machine or otherwise) only seem especially similar when you compare them based on what they have in common rather than what sets them apart from each other.
The western rationalist tradition has for centuries pedaled the idea of pure reason and that man is in essence a rational entity. This has lead to endless versions of the brain in a bath stories that imagine a disembodied brain that is still somehow unchanged, preserving its rational essence. The messy truth that humans are irrational, biological creatures is apparently very unsettling for many
No, they want you to show a Turing machine controlling limbs. You’re trying to make them the same thing, but that implicitly restricts your attention to calculations they perform; Turing machines don’t have outputs for peripherals generally.
Gotta say, I am enjoying the irony that you started attacking people for magical thinking about souls and all, but then it turns out you’re the one here glossing over that the most important thing a brain does is actually hook up to a body.
Similarly, some have based their pursuit of a human-like AI on the idea that all you really need is to make a perfect simulation of a human brain in a computer. Which of course wouldn’t really work because if you wanted a human-like mind you’d need to feed that simulation a lifetime of sensory input and feedback for the mind to develop just as it would in a human body. Before you know it you’re stuck simulating an entire virtual universe.
Not to mention all the intricacies of the super-important gut-brain connection. How many crazy world events were a result of decisions someone made while hangry?
There’s so much that we’re just barely getting our first tiny inkling of. A little while back I saw autism expert Temple Grandin give a talk about studies showing clear links between autistic behavior and the population of gut flora in your stomach, which tends to be very different for people on the autism spectrum.
My motor axons and muscles propagate electrical action potentials. I can (and have) used electrical current to initiate these action potentials that make my muscle contract. I could wire up a computer to a stimulator with controled output to activate motor neurons/muscles in a coordinated pattern (and have proposed projects doing just that in other species). No computer (even if we define it to include arbitrary peripheral interfaces) can control my body in the same sense that my nervous system does, though
When you say a “Turing machine” you clearly mean any device that has a morphism to the formal definition of a turing machine, surely because we aren’t talking about actual tape erasing here. Nobody thinks that a brain is a machine stamping and erasing dots on a tape. Every turing complete chipset thus falls under that definition of “computer”. So @Scientist seems to be saying that there is no silicon chip calculating machine out there that can control a limb.
If your unfamiliar, you might enjoy this. Its a documentary on the Blue Brain project’s failed attempts to replicate the brain in silico. Its good but I’m not sure how much general audience appeal it has
A: “There is nothing a human heart can do that a rotary lobe pump can’t!”
B: “Can a rotary lobe pump be placed into a human chest cavity to circulate blood through a living body, powered by nothing more than oxygenated blood and signals from the autonomic nervous system?”
Why? I mean, this doesn’t even have to do with actual calculation but why can’t you imagine a machine that has the same electrochemical inputs to the neurons that would process the same thing? I’m having a hard time understanding what you think is special about the brain in this sense.
What is the special thing about a priori physical chemistry that would make it impossible to even conceive of a machine that could control a body that isn’t a brain? Is it magic?
I believe that one of the quirks of the brain is that, when reflecting upon itself, any comparison to a sufficiently complex system evaluates to “Yeah, pretty much, I can see that.”
Yeah I think the internet here is a poor analogy. A network can be made from anything: computers, threads, wire, rivers, etc. But the idea of networks themselves as a mathematical construct don’t apply to these networks either as they have their own unique quirks. We see that fungi nutrient networks: they’re flexible to the point of seeming smart (perhaps smarter) but clearly they don’t think. The brain may be the same kind of thing. We assume we think as in an inner play going on in our heads running parallel to the world we see around us but maybe that model is wrong. And maybe we don’t think at all but rather work off of some other mechanism. I’m not touting behaviorism here as that got smashed decades ago with mice experiments but over all the idea that an inner play (story) we create along with what we perceive/experience doesn’t fit with reality. Just a random idea I guess.
