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Re: [GP] Plane of symmetry

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  • Gordon D. Pusch
    ... Suppose you are communicating over a noisy channel; how do you ensure that aq message has been reliably transmitted ? One way is to use redundancy, by
    Message 1 of 14 , May 21, 2003
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      Varun Aggarwal <varun.aggarwal@...> writes:

      > However I didnt clearly understand one of the responses...
      >
      > "If a potential mate is symmetrical, they have expressed their genes
      > twice and got the same answer each time. If they are unsymmetric,
      > they have either had an accident or have an underlying genetic
      > problem. Either way a symmetric mate is a better bet than an
      > unsymmetric one."
      >
      > How is a symmetric mate a better bet than an assymetric one?

      Suppose you are communicating over a noisy channel; how do you ensure that
      aq message has been reliably transmitted ? One way is to use redundancy,
      by repeating the message so that its recipient can check how well the two
      copies agree with each other.

      Now assume you are using a "comma-free code," i.e., there are no natural
      punctuation delimiters; how do you know when a message has even _ended_ ?
      One way is to transmit a message follwed by its reverse, so that the total
      redundant message forms a palindrome. (For example, DNA regulatory regions
      are very often "reverse palindromes" --- a signal followed by its reversed
      complement.) Since long near-palindromes are unlikely to occur by chance,
      if you receive one, it's good indicator that the signal was a message
      that has been corrupted by only a small amount of noise, with the degree
      of asymmetry being an indicator of how bad the noise is.

      Note, finally, that a neural network to recognize symmetry is fairly easy
      to construct, so it is not surprising nature has exploited symmetry as a
      "checksum" for mate selection.


      -- Gordon D. Pusch

      perl -e '$_ = "gdpusch\@...\n"; s/NO\.//; s/SPAM\.//; print;'
    • Lee Spector
      Meta 2 cents: I personally think this thread has relevance to GP and I m happy to see it here. On symmetry: I think Braitenberg s beautiful book Vehicles
      Message 2 of 14 , May 21, 2003
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        Meta 2 cents: I personally think this thread has relevance to GP and I'm
        happy to see it here.

        On symmetry: I think Braitenberg's beautiful book "Vehicles" (MIT Press)
        provides some simple but important insights about the role of symmetry in
        body design (at least).

        -Lee




        At 8:02 PM +0530 5/21/03, Varun Aggarwal wrote:
        Hello

        Thanks for all the responses. They were an interesting read and have given
        me new directions to think. However I didnt clearly understand one of the
        responses...

        "If a potential mate is symmetrical, they have expressed their genes
        twice and got the same answer each time. If they are unsymmetric,
        they have either had an accident or have an underlying genetic
        problem. Either way a symmetric mate is a better bet than an
        unsymmetric one."

        How is a symmetric mate a better bet than an assymetric one?

        I had no intentions to take the group to something which doesnt concern gp.
        However, if I am right natural selection for algorithms and algorithms to
        understand natural selection complement each other, so can this come in the
        bracket of GP. Please let me know.

        Thanks
        Varun


        ----- Original Message -----
        From: <mailto:M.Sewell@...>Martin Sewell
        To: <mailto:genetic_programming@yahoogroups.com>genetic_programming
        Sent: Tuesday, May 20, 2003 4:36 AM
        Subject: Re: [GP] Plane of symmetry

        At 23:57 18/05/2003 +0530, Varun Aggarwal wrote:
        >I was just wondering that all animals we see have a single plane of
        >symmetry (some might have more) in their external appearance (though
        >plants dont have).
        >
        >Any answers why nature evolved symmetric structure, that too mostly with a
        >single plane of symmetry, and that too only externally.

        At 12:01 19/05/2003 +0100, Norman Paterson wrote:
        >If a potential mate is symmetrical, they have expressed their genes twice
        >and got the same answer each time. If they are unsymmetric, they have
        >either had an accident or have an underlying genetic problem. Either way
        >a symmetric mate is a better bet than an unsymmetric one.

        The above is true and concerns sexual selection which, as a special form of
        natural selection, is not sufficient to answer the question of natural
        selection.

        >Plants don't choose mates by appearance. Appearance is only skin deep, so
        >internal symmetry won't get you a mate.

        Insect-pollinated flowers have large, coloured, scented petals (and nectar)
        in order to attract insects.

        Cheers

        Martin




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        --
        Lee Spector
        Dean, School of Cognitive Science
        Associate Professor of Computer Science lspector@...
        Cognitive Science, Hampshire College http://hampshire.edu/lspector/
        Amherst, MA 01002 413-559-5352, Fax: 413-559-5438
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