Functions /= Tautologies

Bryan:

Calling the mind a computer is just a metaphor – and using metaphors to infer literal truths about the world is a fallacy.

Me:

I’m saying that your mind is literally a signal processing system. … While minds have a great many features, a powerful theory, in fact our standard theory, to explain the mix of features we see associated with minds, is that minds fundamentally function to process signals, and that brains are the physical devices that achieve that function.

Bryan:

The “standard theories of minds as signal processors” that Robin refers to aren’t theories at all. They’re just eccentric tautologies. As Robin has frankly admittedly to me several times, he uses the term “signal processors” so broadly that everything whatsoever is a signal processor. On Robin’s terms, a rock is a signal processor. What “signals” do rocks “process”? By moving or not moving, rocks process signals about the mass and distance of other objects in the universe.

Consider an analogy. Our theory of table legs is that they function mainly for structural support; table legs hold up tables. Yes, anything can be analyzed for the structural support it provides, and most objects can be arranged to as to provide some degree of structural support to something else. But that doesn’t make our theories of structural support tautologies. Our theories can tell us how efficient and effective any given arrangement of objects is at achieving this function. It we believe that something was designed to be a table leg, our theories of structural support make predictions about what sort of object arrangement it will be. And if our table is missing a leg, such theories recommend object arrangements to use as a substitute table leg.

Similarly, while any object arrangement can be analyzed in terms of the signals it sends out and the ways that it transforms incoming signals into outgoing signals, all of these do not function equally well as signal processors. If we know that something was designed as a signal processor, and know something about the kinds of signals it was designed to process for what purposes, then our theories of signal processing make predictions about how this thing will be designed. And if we find ourselves missing a part of a signal processor, such theories tell us what sort of replacement part(s) can efficiently restore the signaling function.

Animal brains evolved to direct animal actions. Fish, for example, swim toward prey and away from predators. So fish brains need to take in external signals about the locations of other fish, and process those signals into useful directions to give muscles about how to change the direction and intensity of swimming. This makes all sorts of predictions about how fish brains will be designed by evolution.

Human brains evolved to achieve many more functions than to merely to direct our speed and direction of motion. But we understand many of those functions in quite some detail, and that understanding implies many predictions about how human brains are efficiently designed to simultaneously achieve these functions.

This same combination of general signal processing theory and specific understandings about the functions evolution designed human brains to perform also implies predictions on how to substitute wholesale for human brain functions. For example, knowing that brain cells function mainly to take signals coming from other cells, transform them, and pass them on to other cells, implies predictions on what cell details one needs to emulate to replicate the signaling function of a human brain cell. It also makes predictions like:

In order manage its intended input-output relation, a single processor simply must be designed to minimize the coupling between its designed input, output, and internal channels, and all of its other “extra” physical degrees of freedom. (more)

All of which goes to show that signal processing theory is far from a tautology, even if every object can be seen as in some way processing signals.

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  • Daniel


    This same combination of general signal processing theory and specific understandings about the functions evolution designed human brains to perform also implies predictions on how to substitute wholesale for human brain functions.”

    This strikes me as correct, but also unlikely to convince someone like Brian, given his dualist views about minds/brains/consciousness. If you think that in addition to directing observable bodily behavior (something that, if we understood the signal processing functions of brains well enough, we could probably replicate with artificial brains), brains also generate consciousness, but you also think that consciousness has no straightforward connection to behavior (i.e., a behavioral duplicate of you might still be a zombie), and therefore has no straightforward evolutionary explanation, then the idea that understanding the signal processing functions of brains should be enough to understand how to replicate all of their functions (including the mysterious consciousness-generating ones) will seem a lot less plausible. 

    • http://entitledtoanopinion.wordpress.com TGGP

      Bryan has said that genes plus shared environment do not entirely explain outcomes, and he thinks part of that is “free will”. So his goofy dualist beliefs do impact the behavior he expects to observe.

      • http://profiles.google.com/williambswift William Swift

        Belief in “Free will” is basically of “God-of-the-Gaps”-style argument applied to determinism and human behavior.  There is no evidence that there is anything in human behavior that is not explainable by genetics and environment, but as long as both of them and their interactions are too complex to be completely explained in detail, there will be people trying to claim there is something else in there.

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

         How do libertarian believers in “free will” justify their reverence for the capitalist market–which requires predictable responses to incentives–with that belief?

      • http://profiles.google.com/williambswift William Swift

        Philosophical libertarian (believers in free will) DOES NOT equal political/economic libertarian.  I am a strict determinist and an economic libertarian, the market is the only really effective means available of coordinating the complex desires of a functional society (at least one larger than a village or hunter-gatherer band).  No “free will” needed, luckily since, like God, there is no evidence it exists.

      • http://entitledtoanopinion.wordpress.com TGGP

        Caplan once argued that libertarian politics mesh with rejecting Hobbes’ belief in materialism/determinism, ethical subjectivism and “depravity”. Oddly enough I sided with Hobbes on all those issues while identifying as a libertarian. I don’t identify as a libertarian any more, not because I’ve changed my position on much over the years, but just to “keep my identity small”.

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

        Caplan once argued that libertarian politics mesh with rejecting Hobbes’ belief in materialism/determinism, ethical subjectivism and “depravity”.

        Then Robin’s argument, which depends on materialist thinking, begs the question for Caplan. (And while Caplan accuses Robin of having strange beliefs, Caplan’s beliefs take the cake.)

        I’m with Caplan against Hobbes only as regards “depravity.” I’d say Robin is with Caplan only as regards believing in ethical objectivism (and occasionally Robin sounds agnostic on that). Most importantly, Robin is with Hobbes on depravity; at least I think homo hypocritus is depraved.

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

         Free will doesn’t exist (http://tinyurl.com/3yluywf), and neither do qualia (http://tinyurl.com/c3zq8ht) (which dualists–and even others–accept). But it shouldn’t be thought that all em atheists believe in idealist hocus pocus.

        Perhaps Robin is convinced because the readily available objections to his theory that the brain has a pure signal-processor component or functionality are such fantasies like free will.

        I don’t want to rest the far-mode case against ems (surely a far-mode construct) on a near-mode analysis (partly because I don’t know enough neurophysiology). But it may help if I suggest a near-mode candidate for the role of polluting the purity of neural signal processing.

        Probably many guessed: Affect.. Until the late 1980s, almost all neuroscientists thought emotion was a mere intrusion on cognition. This allowed them to maintain the unlikely image of the brain as a pure signal processor. Today, we know otherwise. Affect does carry information, of course, but affect isn’t, I don’t think, “signal processing.” Instead, the affect system dumps combinations of chemicals into our circulation. The chemicals don’t provide information about causes or correlates because the same chemical will be reused to a broad array of particular global effects.Affect has causal effects on cognition not reducible to the information it contains. But the important carry away is that affect is integral to the functioning of cognition: accurate cognition must be supported by appropriate affect.

      • Silent Cal

        My neuroanatomy knowledge is also limited, but my understanding is that affect functions through neurons, just like cognition; the chemicals it ‘dumps’ are, ultimately, released into synapses by axons, the same mechanism used by cognition. Model all the neurons, and you’ve modeled both affect and cognition.

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

        affect functions through neurons, just like cognition; the chemicals it ‘dumps’ are, ultimately, released into synapses by axons, the same mechanism used by cognition. Model all the neurons, and you’ve modeled both affect and cognition.

        Actually, that seems right.

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

        the chemicals it ‘dumps’ are, ultimately, released into synapses by axons

        If we grant that only what’s transmitted at the synapses is relevant, what would distinguish a signal processor from something else? It seems important to have a near-mode model of what would fail to function as a signal processor.

        What about if the synapses work stochastically? Then (assuming determinism) the action at a synapse in a particular instance would be caused in part by conditions outside the synapse–that is, by causes that aren’t also information.

  • Silas Barta

    If you think about evolution as designing things *to* do something, rather than clumsily finding a local optimum, you’re gonna have a bad time.

    • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

       Silas Barta, here, succinctly states the key point.

    • Tim Tyler

      Objections to functional talk in biology quickly become tiresome.  If you can’t stomach people saying that legs are for walking and eyes are for seeing, you need to get with the program.

      • Silas Barta

         I can stomach that there is a non-trivial sense in which that is true [1], but design talk generally (and Robin_Hanson’s post specifically) will lead you to think that the features are accomplishing their role in some optimal sense, rather than simply the best out of a local neighborhood.

        If you think of the brain as designed *to* process signals, you will miss out on just how kludgey it is, and how much it diverges from what a (human-like) intelligence would do in making an optimal information processor, *and* how much it is influenced by having performed other roles and constrained to be compatible with previous iterations.

        [1] the sense that those things *accomplish* that role, and that, among all their effects on the body, if it were fail in that role, it would have the most negative effect on the body’s continued survival — e.g. the heard is for pumping blood in that, if it stopped pumping blood, this would be more fatal than if it failed to dissipate heat to the body, which is another effect it has

      • http://juridicalcoherence.blogspot.com/ Stephen R. Diamond

        Objections to functional talk in biology quickly become tiresome.  If you can’t stomach people saying that legs are for walking and eyes are for seeing, you need to get with the program.

        All science outside physics is necessarily vague, and accordingly, function talk has proved indispensable in biology. But functions have been invoked to answer distinct questions, and for some, they aren’t sound.

        If you ask, why did the heart evolve? the response, “to circulate the blood,” is illuminating despite being incomplete. But if you ask about some unknown characteristic of the heart (if any today remain), it’s unsound to try to infer this characteristic from its optimality for circulating the blood.

        It’s illuminating to say the brain’s function is signal processing, just as it is to say circulation is the heart’s function, but the inference from optimal function to structure is unsound.

    • DonaldWCameron

      That may the definitive flaw in the theory of evolution.
      There is more than one flaw in the theory, Another flaw in evolutionary theory is DNA. Trying to equate the elegance of DNA to brute aimless chance is clumsy and muddled.
      How can one accept the absolute speed of light and reject design?

    • http://www.facebook.com/daniel.carrier.54 Daniel Carrier

      Evolution is not intelligent in the way humans are, but it is an optimization process. While the causal process may differ, evolution, like humans, makes things in a certain way because it fulfills a certain function. This is what we say when we mean that evolution designs things to do something.

      In other words, evolution clumsily finds a local optimum for doing something.

  • ladderff

    In other words Bryan is being smug. Stop the presses.

  • Robert Koslover

    Would you consider a human brain to be more like an analog or a digital computer?  The initial impulse is to say analog, but are you sure?  And in any case, almost all modern computers are digital.  If we want to emulate biological brains, should we be applying purely-digital means?

    • http://www.facebook.com/daniel.carrier.54 Daniel Carrier

      A human brain is a universal Turing machine. It can be emulated on any other universal Turing machine. It doesn’t matter whether either is analog or digital, or even if it’s classical or quantum, except for how large the emulator has to be and how long it will take.

      • Robert Koslover

         Hmm.  I’ve found a number of interesting discussions of your point (some pro, some con) on the web.  Thanks for the suggestion to think in these terms.

  • EliWilliam2020

    Congratulations, you may be the only person who has ever proved Bryan Caplan wrong.

  • DonaldWCameron

    “All of which goes to show that signal processing theory is far from a
    tautology, even if every object can be seen as in some way processing
    signals.”

    The medium is the message?

  • http://www.alexandergieg.org/ Alexander Gieg

    Two problems, one related to the blog post, another in some of the discussions:

    a) The argument that the mind is like our current most advanced artifact is a “confusion of genres”. From the fact that a mind can produce a device of category ‘x’ doesn’t follow that a mind is a device of category ‘x’. At best, it can be argued that it is at least as complex as devices of category ‘x’. Whether they are more or not, though, is an open and unanswerable question, given that a future device category might be more complex than those in ‘x’, at which point said new device category becomes the lowest complexity estimation for a mind.

    So: in the XVI century, clocks. Nowadays, computers. In future, something else.

    b) Arguing against free will because hard sciences all show determinism isn’t valid, for hard sciences are heavily dependent on math and formal logic, both of which are, inherently and by design, fully deterministic. This means that determinism is a precondition and formal premise of said sciences, and hence that determinism cannot be *concluded* from them, as doing so would be a clear cut case of begging the question.

    It should be noted that a related incorrect reasoning is that of trying to reduce mind to some kind of logical language. Logic is a feature of minds, so the error, depending on how it’s constructed, can be either a case of taking the part for the whole, or a fallacy of composition.

  • Eddy P. Williams

    Yeahh… I think it is so difficult to do this.

  • http://twitter.com/grobstein Dave Gottlieb

    Isn’t it time to retire the idea that a “tautology” is necessarily a trivial observation?