Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!usc!ucsd!sdcc6!sdbio2!rabani From: rabani@sdbio2.ucsd.edu (Ely Rabani/D Smith) Newsgroups: comp.ai.neural-nets Subject: Re: Observations on the State of NN theory Message-ID: <12407@sdcc6.ucsd.edu> Date: 25 Aug 90 04:58:46 GMT References: <3430010@hpwrce.HP.COM> <1990Aug23.143902.758@nlm.nih.gov> Sender: news@sdcc6.ucsd.edu Reply-To: rabani@sdbio2.ucsd.edu (Ely Rabani) Organization: University of California, San Diego Lines: 58 Nntp-Posting-Host: sdbio2.ucsd.edu While I am somewhat ignorant about the area of NN and GA models (for the present,) biology happens to be my field. Now, (1) while it is true that MOST somatic cells, including neurons, do not undergo chromosomal recombination of the meiotic sort there is the exception of lymphoid recombination by which high degree of variability in the immune response is generated; (2) there is the phenomenon of somatic cell crossing over, but it is a rarity so far as it is observed; (3) somatic cells are capable of certain kinds of DNA repair that involve mechanisms similar to those of chromosomal recombination. A difficulty occurs to me at the level of molecular biology. Unless there is some kind of relatively high level descriptor language, the symbols of which are themselsves strung together on the chromosomes derrived from each parent, and it is some sort of recombination between these two (linearly orderred) sets, i.e. positionally contexted cis-acting elements, that is being imputed, I don't quite understand what this supposed recombination accomplishes (if we are strictly concerned with learning by an organism, by this mechanism.) The impression that I have of this model flies in the face of the one gene one protein model of inheritence, where (in general) on which of a pair of homologous chromosomes a gene (allele) resides does not influence the nature (though not necessarily quantitative expression) of its product. On the other hand this kind of recombination (in particular the specifics of the mechanism and what we have to recombine to begin with) is entirely significant evolutionarily at the level of a population. It may be purely prejudicial, but I suspect that this kind of model would be most applicable to specific and narrow behaviours (and perhaps the KINDS of learning they entail) than to more generally applicable and abstract kinds of learning. This is not to say that the latter may not employ the former over domains or sets of domains of learning (in particular, the kinds of assertions made by Chomskians in contrast to empiricist models of language acquisition.) Nonetheless, I find the recombination model, insofar as it implies the recombination of genetic material, most pertinent to things like prey selectivity among crawley things (by some kind of quantitative heritability. ----- Now, if I haven't bored of scared you all away yet, I would like to attend to the second reason for my post: Presently a problem that concerns me is that of character recognition, both printed and handwritten. So far as I have been able to determine, the problem has not been entirely cracked, but there is evidence of progress over both domains. Can anyone supply me with references on the topic, information on the current state of the art, or related general apprehensions? Please e-mail response to: rabani@sdbio2.ucsd.edu Thank you, Ely