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    Recursion And The Human Mind
    By Samuel Kenyon | December 5th 2011 07:56 PM | 16 comments | Print | E-mail | Track Comments
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    Lead software engineer at iRobot Corp., user experience (UX) designer, agile manager, actor, writer, atheist transhumanist. My blog will attempt...

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    It's certainly not new to propose recursion as a key element of the human mind--for instance Douglas Hofstadter has been writing about that since the 1970s.



    Michael C. Corballis, a former professor of psychology, came out with a new book this year called The Recursive Mind. It explains his specific theory that I will attempt to outline here.



    As I understand it, his theory is composed of these parts:
    1. The ability of the human mind to generate concepts recursively is what causes the main differences between homo sapiens and other animals.
    2. A Chomskian internal language is the basis for all external languages and other recursive abilities. (See this blog post by Corballis for a summary of an internal language as a universal grammar).
    3. External languages evolved on top of the recursive abilities primarily for storytelling and social cohesion.
    4. External languages started with gestures, and most likely were followed by mouth clicking languages before vocal languages emerged.

    You'll notice that toolmaking and other modern human capabilities are not mentioned in my list there. That is because those are considered to be evolved/developed after the recursive mind appeared and after rudimentary language based on recursion appeared. The author talks about how the ability to build multi-part tools and using tools to make tools probably depends on recursion, but he thinks that came after a certain amount of language development.



    A host of abilities might be dependent on recursive thinking, even things we take for granted like story telling. Planning, talking about the future, and making fictional stories all might be dependent on recursive processing.



    Corballis has been doing research on gestures for a long time. By gestures we mean both bodily and facial. It certainly sounds plausible based on the evidence we have that gestures might have been the first real external language. Corballis claims that the discovery of mirror neurons added support for this theory. A primate watching another one perform an action has mental processing similar to actually doing the same action itself. Corballis proposes here and in previous works that sign language with grammar and syntax appeared long before it was mainly replaced with the cultural development of vocal speech.

    (As a related aside, see this TED video about the power of communication via dance.)

    Conclusion Part 1 (updated)


    So why exactly would recursion be of interest to single out? Isn’t it just one of many run-of-the-mill features of information processing which the mind might make use of? Basically, Corballis proposes this (see also this paper):

    Generative functions require recursiveness. Episodic memory requires generative functions. Episodic memory may be unique to humans. Planning future events and making fictional stories requires episodic memory. Communication of future events and storytelling–which in turn requires ways to communicate the time component–may have co-evolved with human external language abilities.


    Conclusion Part 2 and a Warning



    It's certainly an interesting theory, and I can buy that recursion is part of, if not the single key element, of a general protocol in the mind. Even if we forget the linguistic aspect, the power of recursion seems to be a fundamental ability of the mind at some level.

    Fortunately, as a computer programmer (amongst my many roles), I don't have to limit myself as academics love to do when talking about the sole "language of mind" or the single important algorithm or type of algorithm needed to turn an pre-human mind into a human mind. I can easily imagine lots of protocols (I think that is a better word than "language" for system communications) at all kinds of arbitrary levels, in many relationships to each other. I think it's kind of silly to assume there's only one universal protocol and that it underlies all the others. Even in a digital computer (of which most computers are), the only "general" protocol that underlies all others is the fact that information is represented with binary. You have to go to another level above that to describe anything else, and it won't be completely general. And a digital computer is much simpler than the brain.

    But what about the fundamental difference between humans and other animals? Well, again, recursion seems to be a good candidate, but it wouldn't surprise me if it's only one of several intertwined informational abilities that make human minds different than others.

    References

    [1] Corballis, M.C. The Recursive Mind. Princeton University Press, 2011.

    Image Credits

    Inception Chair by Vivian Chiu
    book cover, Princeton University Press
    Derek O' Reilly
    Rhys Davenport (found via Sean Williams)
    Sierpinski Triangle, public domain

    Comments

    vongehr
    What surprises me about recursion is that it does not get the same treatment as quantum proposals: One thing mysterious, the other mysterious, so must be connected. While this is often based on a mere incapacity to understand quantum theory, this kind of argument really makes sense in case of the recursion proposals. I have never seen any argument that goes beyond what is basically gasping at pictures of fractals and being awestruck. The whole Goedel Escher Bach was already like that.
    I am sure you disagree (?), but can you make this recursion blah blah any more concrete?
    SynapticNulship
    One thing mysterious, the other mysterious, so must be connected.

    That's a good point--and also why I added the "and a Warning" section in my conclusion. I am not now, nor have I ever been, convinced by physics envy claims of the one true expression, algorithm or structure in the mind. Or the one concrete explicit thing that makes humans "special"...even though were aren't really that special.

    I have never seen any argument that goes beyond what is basically gasping at pictures of fractals and being awestruck.
    I put some images here in the hope that a short article punctuated by images would have a slight chance at actually being read and possibly comprehended by a general audience that is not necessarily familiar with recursion (in either linguistics or computer science).

    The whole Goedel Escher Bach was already like that.
    Perhaps that's why Corballis did not mention GEB or Hofstadter at all in his book.
    SynapticNulship
    I am sure you disagree (?), but can you make this recursion blah blah any more concrete?

    Yeah. Obviously you could read the book, but maybe I can try to blogify some examples, besides of course old-fashioned sentence generation.
    vongehr
    Yes, I could read the book, if not everybody wrote another book every few years regardless they have done little but promoting their last book meanwhile. I do not read any books anymore if I have not somebody telling me very convincingly indeed that there is something extremely useful in a very specific book. And even with this method, "recursive mind" would be buried under ten other books.
    I have researched the Ackermann function, perhaps the best serious example of recursion. Iterated or recursive addition is multiplication. Iterated or recursive multiplication is exponentiation. Since recursion itself can be recursively applied you end up with addition, multiplication, exponentiation, tetration and on and on. My web site at http://www.tetration.org discusses what lies beyond exponentiation.

    Gerhard Adam
    I'm also not sure what is meant here, beyond what seems intuitively obvious.  After all, what is the alternative to recursive processing?  linear? 
    SynapticNulship
    The benefit I've provided to the world is to attempt to break down a scientist's book into the core fundamental claims. Unfortunately, that may result in the book's message seeming a great deal less sexy or innovative.

    I think Corballis has two things that he is really trying to contribute to science (and I could be wrong here):

    1. He's one of the people that takes a bit of Chomsky, but not all, and tries to combine it with evo-devo.

    2. He's in the minority (or it used to be a minority) that think a gesture-based language was the first real external language, not speech.
    vongehr
    I am interested in whether you, since you are very much into this subject matter, could tell us, perhaps guided by insight from this book, what the importance of recursion is - after all, the title is "Recursive Mind" (not "Bits from Noam plus Gestures"). Maybe just a title chosen by the publisher?
    If "Quantum Mind" is to be poo pooed because it does not explain the red of the rose already, how does recursion fare any better?
    "I can buy that recursion is part of, if not the single key element, of a general protocol in the mind, ... the power of recursion seems to be a fundamental ability of the mind at some level."
    SynapticNulship
    Basically, Corballis proposes this:

    Generative functions require recursiveness. Episodic memory requires generative functions. Episodic memory may be unique to humans. Planning future events and making fictional stories requires episodic memory. Communication of future events and storytelling--which in turn requires ways to communicate the time component--may have co-evolved with human external language abilities.
    Gerhard Adam
    So the distinguishing characteristic hinges on episodic memory ...

    FYI
    http://pascasarjana.mercubuana.ac.id/26/Griffiths_etal_1999_Episodic_TrendsCognSc.pdf
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088528/pdf/TB011453.pdf
    http://news.nationalgeographic.com/news/2003/08/0822_030822_tvanimalmemory.html
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088530/pdf/TB011483.pdf
    http://www.ccs.fau.edu/~bressler/EDU/AdvCogNeuro/pdf/iceman.pdf

    Of course, it seems that humans possess a more robust form of episodic memory, which is to be expected given our cognitive abilities and our ability to abstract.  So, I suspect that the traits Corballis discusses are present in all animals, which strongly suggests that it was the co-evolution with language that probably gave humans the "boost" necessary to move beyond the cognitive realm that most animals exist in.

    Even this link, while largely anecdotal, suggests that episodic memory does play a role in animal survival (not comparing it to the human level).
    http://www.nytimes.com/1998/05/26/science/science-watch-older-and-wiser.html
    SynapticNulship
    Even this link, while largely anecdotal, suggests that episodic memory does play a role in animal survival (not comparing it to the human level).
    http://www.nytimes.com/1998/05/26/science/science-watch-older-and-wiser.html
    In this 2009 article co-authored by Corballis (http://rstb.royalsocietypublishing.org/content/364/1521/1317.full), they consider the studies of various jays and primates that seem to have a kind of episodic memory, and basically discount those abilities as still not being as flexible and general as the mental time travel of humans.

    Gerhard Adam
    I completely agree.  My only point was to establish some boundary conditions on the uniqueness attributed to human cognition.  In my view, this provides us a view into how such a trait could have evolved, if we see more primitive versions in other animals (rather than simply appearing from nowhere).
    SynapticNulship
    BTW, thanks for the links to episodic memory papers.
    Gerhard Adam
    The ability of the human mind to generate concepts recursively is what causes the main differences between homo sapiens and other animals.
    I'm not sure what he means here, but this is clearly wrong when viewing  behaviors of other animals.  The ability for a dog to catch a frisbee in flight or anticipating a stick being thrown, indicates recursive processing (just to mention the most obvious).

    I think the notion of language evolving from gestures is true in a trivial sense, but it is insufficient to account for it.  Many animals have gestures and expressions which appear to be sufficient to convey most of the information necessary for survival.

    In my view, language only makes sense when we cannot express ideas through gestures or expressions because the subject we are trying to convey doesn't exist (i.e. it's an abstraction).  I can easily point to a tree, or an animal, or whatever and convey an idea.  However, if I want to propose meeting at a location some distance away that we have a shared memory of, then I can't simply gesture.  I must have a "coded expression" that we can agree represents this remote location. 

    Language only makes sense as a means to express abstract ideas that have no other way of being articulated because they reside only in our minds.  Anything with an external manifestation can readily be expressed or indicated by a few simple gestures and doesn't require language. 
    SynapticNulship
    I'm not sure what he means here, but this is clearly wrong when viewing  behaviors of other animals.  The ability for a dog to catch a frisbee in flight or anticipating a stick being thrown, indicates recursive processing (just to mention the most obvious).

    It's not clear to me yet whether recursion in the mind really does start with humans or not, and/or if it's merely recursion at a particular level.

    Language only makes sense as a means to express abstract ideas that have no other way of being articulated because they reside only in our minds.  Anything with an external manifestation can readily be expressed or indicated by a few simple gestures and doesn't require language

    To clarify the gestural theory says that early humans had a sign language with grammar and syntax. So a gesture or facial expression, as with any symbol, can represent something abstract and be used to compose sentences in the grammar.

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