Brains Simpler Than Brain Cells?

Consider two possible routes to generating human level artificial intelligence (AI): brain emulation (ems) versus ordinary AI (wherein I lump together all the other usual approaches to making smart code). Both approaches require that we understand something well enough to create a functional replacement for it. Ordinary AI requires this for entire brains, while ems require this only for brain cells.

That is, to make ordinary AI we need to find algorithms that can substitute for most everything useful that a human brain does. But to make brain emulations, we need only find models that can substitute for what brain cells do for brains: take input signals, change internal states, and then send output signals. (Such brain cell models need not model most of the vast complexity of cells, complexity that lets cells reproduce, defend against predators, etc.)

To make an em, we will also require brain scans at a sufficient spatial and chemical resolution, and enough cheap fast parallel computers. But the difficulty of achieving these other requirements scales with the difficulty of modeling brain cells. The simpler brain cells are, the less detail we’ll need to scan, and the smaller computers we’ll need to emulate them. So the relative difficulty of ems vs ordinary AI mainly comes down to the relative model complexity of brain cells versus brains.

Today we are seeing a burst of excitement about rapid progress in ordinary AI. While we’ve seen such bursts every decade or two for a long time, many people say “this time is different.” Just as they’ve done before; for a long time the median published forecast has said human level AI will appear in thirty years, and the median AI researcher surveyed has said forty years. (Even though such people estimate 5-10x slower progress in their subfield in the past twenty years.)

In contrast, we see far less excitement now about about rapid progress in brain cell modeling. Few neuroscientists publicly estimate brain emulations soon, and no one has even bothered to survey them. Many take these different levels of hype and excitement as showing that in fact brains are simpler than brain cells – we will more quickly find models and algorithms that substitute for brains than we will those that can substitute for brain cells.

Now while it just isn’t possible for brains to be simpler than brain cells, it is possible for our best models that substitute for brains to be simpler than our best models that substitute for brain cells. This requires only that brains be far more complex than our best models that substitute for them, and that our best models that substitute for brain cells are not far less complex than such cells. That is, humans will soon discover a solution to the basic problem of how to construct a human-level intelligence that is far simpler than the solution evolution found, but evolution’s solution is strongly tied to its choice of very complex brain cells, cells whose complexity cannot be substantially reduced via clever modeling. While evolution searched hard for simpler cheaper variations on the first design it found that could do the job, all of its attempts to simplify brains and brain cells destroyed the overall intelligence that it sought to maintain.

So maybe what the median AI researcher and his or her fans have in mind is that the intelligence of the human brain is essentially simple, while brain cells are essentially complex. This essential simplicity of intelligence view is what I’ve attributed to my ex-co-blogger Eliezer Yudkowsky in our foom debates. And it seems consistent with a view common among fast AI fans that once AI displaces humans, AIs would drop most of the distinctive features of human minds and behavior, such as language, laughter, love, art, etc., and also most features of human societies, such as families, friendship, teams, law, markets, firms, nations, conversation, etc. Such people tend to see such human things as useless wastes.

In contrast, I see the term “intelligence” as mostly used to mean “mental betterness.” And I don’t see a good reason to think that intelligence is intrinsically much simpler than betterness. Human brains sure look complex, and even if big chucks of them by volume may be modeled simply, the other chunks can contain vast complexity. Humans really do a very wide range of tasks, and successful artificial systems have only done a small range of those tasks. So even if each task can be done by a relatively simple system, it may take a complex system to do them all. And most of the distinctive features of human minds and societies seem to me functional – something like them seems useful in most large advanced societies.

In contrast, for the parts of the brain that we’ve been able to emulate, such as parts that process the first inputs of sight and sound, what brain cells there do for the brain really does seem pretty simple. And in most brain organs what most cells do for the body is pretty simple. So the chances look pretty good that what most brain cells do for the brain is pretty simple.

So my bet is that brain cells can be modeled more simply than can entire brains. But some seem to disagree.

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