David Tinker Nov1192 07:50AM Emergent Properties. I. Introduction FollowupTo: talk.origins

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David Tinker Nov-11-92 07:50AM Emergent Properties. I. Introduction Organization: University of Toronto, Biochemistry From: dtinker@gpu.utcs.utoronto.ca (David Tinker) Message-ID: BxK6o0.Dr9@gpu.utcs.utoronto.ca Reply-To: dtinker@blunile.guild.org Followup-To: talk.origins Newsgroups: talk.origins The recent spate of articles in talk.origins on "emergent properties" generated some heat, but not much light! My colleague, Larry Moran, objects to the term because he suspects (wrongly) that it is based on non-mechanistic or vitalistic superstition, and (rightly) that the term implies there is an obstacle to the reductionist agenda in biology. Other postings imply that the term "emergent properties" is tautologous, and not unique to biology; it has been claimed that everything has emergent properties, so the adjective "emergent" is meaningless. I think the topic is worth further exploration, and submit this article to stimulate discussion. I hope that we have not seen the last word on this topic. First, I do not think there is a satisfactory closed definition of the term "emergent", nor is it universally used by the research school most concerned with such properties, the 'Artificial Life' community. Nevertheless I believe the concept is so well accepted in this community that the term can be used casually with the assurance that it is understood. I turned to my well-thumbed copy of "Artifical Life I" and searched in the annotated bibliography and in the index for terms like "emergent" - see below for the results. Nowhere did I find a definition that would satisfy Larry Moran, but in re-reading the articles I found many clues to a definition. So, being willing to be called a fool, I will essay a definition: ============================================================================= A system may be said to possess "emergent properties" when (a) it is composed of a collection of entities, (b) it has global properties, obeying well- characterised rules that may be used for predictive purposes, that arise from non-linear combinations of local interactions among the entities, and (c) the rules do not depend specifically on the chemical nature of the entities." ============================================================================= Glosses: By "entities" I mean systems which may exist independently, and which make up the system by simple addition to it. Thus the protein molecules in a crystal are entities in this sense, but the atoms in a molecule are not "entities" composing the molecule. By "non-linear" I simply mean the mathematical connotation, as in "non-linear function". I wished to use this term in the definition rather than the less general adjective "non-additive". =========================================================================== Now some questions and tentative answers. 1. Do such systems exist? Yes they do. Three systems with emergent properties that have been well examined are (a) artificial neural networks, (b) organisms that exhibit schooling or flocking behaviour, and (c) cellular automata. 2. You say that the properties are independent of chemical nature of the entities. Does this mean you espouse a non-mechanistic view? Not at all. Let's take flocking behaviour as an example. It appears to arise when entities have a mechanism for detecting spatial proximity of identical entities and a feedback mechanism for maintaining a range of postions relative to their neighbours. Essentially identical behaviour can arise in organism as diverse as fish, insects and birds. It could also arise in collections of robots made out of Lego (tm) - all that is required is there be physical mechanisms for _instantiating_ the local interactions. If I were studying sandpipers, say, I would certainly hope to elucidate the physiological and biochemical mechanisms of recognition and feedback, and to learn how the relevant genes have evolved to optimise these interactions for efficient flocking behaviour. The _instantiation_ of the behaviour does depend on mechanisms which obey the laws of physics and chemistry, but the behaviour itself trans- cends these laws. 3. Aren't these rules merely empirical inventions that will be unnecessary when we understand the mechanisms fully? I don't think so. The work in this area indicates many of the "rules" governing such properties are universal, and have a formal logical structure and grammar. In the sense that thermodynamics is a formal system independent of any specific physical system, so are the laws governing emergent properties. However, it is true that like thermodynamics, "emergo-dynamics" will be ultimately related to lower-level physical theories. 4. Aren't all properties of matter "emergent" - e.g. the properties of water? Not in the sense I have defined. The properties of water depend absolutely on the specific interactions of water molecules, whereas the properties I have called "emergent" would arise no matter what entities are involved. 5. Simple things like flocks and cellular automata don't convince me - these are just computer games. Is there any evidence that *real* biological behaviour can be 'explained' by such notions? I'm glad you asked. See the amazing chapter by P. Hogeweg (cited below) in which he models such high-level behaviours as bumblebee sociology. The fact that successful models of living systems can be constructed out of computer instructions or Lego indicates that the properties being modelled are 'real' ones. 6. Wait a minute! I'm beginning to think you are a Moravecian (see Hans Moravec, "Mind Children"). Do you really think biological properties including (choke) consciousness could arise in machines? Is Data (in Star Trek) really human after all? Do you think human beings are machines? Yes. In fact, my conviction that my humanity has "emerged" from the properties of molecules contributes mightily to that emergent property of me, that I call a "religious world-view". 7. How can I learn more about such area so that I can critically discuss this topic on talk.origins? Start with the "Artificial Life" volumes from the Santa Fe insitute, published by Addison Wesley. In my next posting, I'll re-post a *long* annotated bibliography that was prepared by G. Miller and P. Todd, and posted in sci.bio a year ago. ----- Bibliography and Footnotes: ========================== From the annotated bibliography, in C.G. Langton, editor, "Artificial Life I", pp 527-625, Addison Wesley, 1989. (a) Titles containing the word "_emergent_" or "_emergence_". ============================================================= J.H. Holland. "Studies of the Spontaneous Emergence of Self-Replicating Systems using Cellular Automata and Formal Grammars." In A. Lindenmayer and G. Rozenberg, editors, "Automata, Languages, Development", pp 385-404, North Holland, 1976. J.J. Hopfield. "Neural Networks and Physical Systems with Emergent Collective Computational Abilities." Proc. Nat. Acad. Sci. 79:2554-2558, 1982. S.A. Kauffman. "Emergent Properties in Random Complex Automata." Physica D, 10, 1984. (b) Titles that are germane to this posting. ============================================ C.W. Reynolds. "Flocks, Herds and Schools: A Distributed Behavioural Model". Computer Graphics: Proceedings of SIGGRAPH '87, 21(4):25-34, July 1987. S. Wolfram, editor. "Theory and Applications of Cellular Automata." World Scientific, Singapore, 1986. P. Hogeweg. "MIRROR beyond MIRROR, Puddles of LIFE". In C.G. Langton, editor, "Artificial Life I", pp 297-316, Addison Wesley, 1979. Towards a legitimisation of emergent behaviour? =============================================== From C.G. Langton, in "Artificial Life I" page 3: " The "key" concept in AL is _emergent behaviour_. Natural life emerges out of the organized interactions of a great number of nonliving molecules, with no global controller responsible for the behaviour of every part. Rather, every part is a behav_or_ itself, and life is the behav_ior_ that emerges out of all the local interactions among individual behav_ors_. It is this bottom-up, distributed, local determination of behaviour that AL employs in its primary methodological approach to the generation of lifelike behaviors. " From R. Dawkins, _ibib._ page 209 (discussing the biomorphs produced by his 'Blind Watchmaker' program): " ... Our watchword is that as much as possible must emerge rather than being designed. But having seen the range of phenotypes that emerge from the basic program, can we think of any modifications to the basic program that seem likely to unleash opulent flowerings of new emergent properties? ... " -- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: : Prof. David O. Tinker INTERNET: dtinker@blunile.guild.org : : Dept. of Biochemistry uunet.ca!beltrix!blunile!dtinker : : University of Toronto FAX: (416)978-8548 : : Toronto, Ont. M5S 1A8 VOICE: (416)978-3636 : ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: : Blue Nile Software INTERNET: postmaster@blunile.guild.org : : 16 Victoria St. : : Markham, Ont. L6C 1A7 VOICE: (416) 887-5631 : ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- ! David O. Tinker / Department of Biochemistry / University of Toronto / ! ! TORONTO, Ontario, Canada M5S 1A8 / Voice: (416) 978-3636 / ! ! UUCP: dtinker@gpu.utcs.utoronto.ca / BITNET: dtinker@vm.utcs.utoronto.ca !


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