Emergent Properties

Gessler, Nicholas (gessler@ANTHRO.SSCNET.UCLA.EDU)
Tue, 31 May 1994 10:46:00 PDT

To continue a periodic discussion on Darwin-L and Anthro-L on the notion of
EMERGENCE as it is being used in the Artificial Life community, I am
forwarding the following article that was posted on the "Emergence" bulletin
board at alife.santafe.edu. In our own Artificial Life group at UCLA the
subject of emergence has come up numerous times, and although David Tinker
was not present he has captured much of what was said. What we
arrived at as a definition follows Luc Steels' formalization which
goes something like this: "Given a system with a global behavior
completely determined by the local behaviors of its components, a
global behavior can be said to be EMERGENT if it requires a set of
descriptors which is different from the set required to describe the
local behaviors."

Someone on Darwin-L asked rhetorically whether anyone in evolution still
believed in Teleology. It would be interesting to rephrase that question to
ask whether any phenomena explained as teleological in a non-computational
paradigm could be subsumed under the the computational paradigm of emergence?
I suspect so. I also have a nagging suspicion that emergence is central to
biological evolution and possibly also to cultural evolution, if not the
entire range of natural phenomena. I've breached the subject with Gould,
Rapoport, and Mayer who have all commented that the field of Alife is "rich."

To obviate any misunderstandings, in my view evolution is a change in gene
(or trait) frequency in a population over time (I will not use the word
"progress)." And cultural evolution can come about through both Darwinian
and Lamarckian mechanisms {appeal to authority: Mayer}.

I must admit I'm having difficulty keeping up with this thread on several
bulleting boards, but even though the postings are sporadic, they are

Nick Gessler

FORWARDED FROM: Gessler, Nicholas (G) ANTHRO
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Date: Fri, 27 May 94 15:08:30 MDT
From: gessler@alife.santafe.edu
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To: gessler@anthro.sscnet.ucla.edu (dtinker@alife.santafe.ed)
Subject: Re: Emergent Properties
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In article <2qul6k$e8r@tierra.santafe.ede> you wrote:

: To try and start a little discussion in this fascinating area, I'm
: reposting an article I put in "talk.origins" some time ago. Much
: of what I said then is probably old hat to readers here, but I'd be
: interested in reactions and other ideas. (By the way if anyone is
: interested in the bibliography mentioned in this posting, I still have
: it - let me know if you'd like a copy via E-mail).

: ========================
: Newsgroups: talk.origins
: From: dtinker@gpu.utcs.utoronto.ca (David Tinker)
: Subject: Emergent Properties. I. Introduction
: Organization: University of Toronto, Biochemistry
: Date: Wed, 11 Nov 1992 15:50:22 GMT

: 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,
: 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
: of a collection of entities, (b) it has global properties, obeying well-
: characterised rules that may be used for predictive purposes, that arise
: non-linear combinations of local interactions among the entities, and (c)
: 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
: 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
: 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
: 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? ...

: --

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