Memes & Changing language

Transcription

1 Memes & Changing language Richard K. Belew Evolution?! Computational models of evolution, learning Computational analyses of cultural artifacts

2 What do you think? A B C

3 Believing evolution? Gallup, 1997 n=1,000 sampling error +/- 3.2% Intelligent design? Randomness? Science vs. religion?

4 Preview Example of a symbol s evolution A computationally precise characterization of evolution Memes An experiment! Applications in corpus analysis General modeling issues for CogSci

5 Summary Evolution is a powerful adaptive process Cultures certainly change Do selectionist models offer the best accounts? Vast amounts of new evidence becoming available The interactions between culture and biological evolution will only increase in the future

6 Summary (cont) Key terms Replication rate Fitness Mutation Intention Temporal/spatial distribution Neutral drift

7 Evolution of symbols A Brief History Ancient history which evolved to exploit a coincidental mneumonic... which becomes a modern bumper sticker! Perhaps an entire species of bumper stickers! Survey data {T. Lessl]

8 A Brief History The fish symbol has been used throughout history by pagan and earth-based religions. Ancient Goddesses in China, Egypt and India were represented by the fish symbol. In ancient Greece the fish symbol represented the Goddess of Love. Venus, the ancient Roman empire's Goddess of Love was also represented by a fish symbol. She was so revered that Christian authorities insisted on taking over the symbol. The Christians revised the symbol's associated mythology to fit their own purposes. Today, the fish symbol has "evolved" yet again to represent Evolution, Science and Political Freedom; as well as all of the topics on our emblems page. According to EvolveFish.com!

9 Ancient history... Jesus Christ God s Son Savior Fish In the beginning there was Christian grafftti

10 ... which evolved to exploit a coincidental mneumonic

11 ... which becomes a modern bumper sticker!

12 Perhaps an entire species of bumper stickers! DARW IN Jesus lives! DARW IN Jesus!

13 Survey data {T. Lessl] Survey [Lessl] Lessl s interpreation

14 Lessl s interpreation "By inserting Darwin's name in to the place on the fish icon usually reserved for Christ, the Icthus symbol is ritually profaned," said Lessl, "which is to say, emptied of its religious meaning. By putting Darwin's name where Christ's would traditionally go, the Darwin fish does not assert, as one might think, that science is salvation and that Darwin is its prophet. For the majority of those who display this emblem, Darwin's role seems to be that of anti-messiah. This is more like the inversion rituals of carnival, where some drunken peasant is dressed up as the king. Its purpose is not to elevate the peasant but to make fun of the king."

15 Evolution Charles Darwin ( ) Definitions Basic algorithm GA at a glance Structured populations

16 Charles Darwin ( ) Replication Mutation Selection

17 Definitions Individual x i = (0,1) L ; string of L bits Population X = {x i } population Generation X t in time ; X = P, size of ; population at a point

18 Basic algorithm Create X 0, randomly do ; Generation forall x i in X Evaluate fitness f(x i ) in R Determine num. offspring g(x i ) in J ; g(x i ) = P Form X t+1 = g(x i ) copies of x i Apply genetic operators Ω to X t+1 until X t+1 has converged ; (X X t+1 )

19 GA at a glance X t f(x) g(x) X t <f(x)>= Mutation Crossover

20 Structured populations Island models Minimal gene flow 2d version

21 Memes: Cultural analog of gene Replicator in the soup of human culture,... unit of cultural transmission, of imitation Dawkins 76, Chap11 (revised 1989) D. Campbell (1974): Evolutionary Epistemology Other biologically inspired models of culture Cavalli-Sforza & Feldman (1981) Boyd & Richerson (1985)

22 Experimental Memetics Experiment (22 jan 03) Algorithm

23 Algorithm 1. Divide your piece in half 2. Optional: Add graffiti If you do, add the SAME graffiti to all instances on half You can add different notes to the two halves 3. Pass your two halves to two neighbors Odd: Front/Back Even: Left/Right 4. SELECT: your favorite ONE from the TWO sheets passed you (Wad up the other; we ll collect) Go to #1

24 Dan Dennett What kind of biological analogy? Virus? Symbiotic host/guest Parasite: negative effect on host Commensal: neutral Mutual: positive Genes hold culture on a leash [E. O. Wilson]

25 Dan Dennett (cont) Intentional stance (on cultural analysis) analyzing the flux of events in terms of agents and their (rational) actions and reactions a meme is an information packet with an attitude Intention + biology = genetic engineering! [P. Kitcher, Lives to Come]

26 Dawkins data! If the meme is a scientific idea... a rough measure of its survival value could be obtained by [its citation count] notes, citations to [Hamilton 64] used as evidence of EXPONENTIAL growth In distinction to simply CUMULATIVE citation rates, ala influential other influential texts

27 Evolution, Development, Learning, Culture Adaptation as sine qua non of cognitive system Adaptation to invariants of environment at varying time-scales Cultural change Evolution as primary adaptive system Interaction among adaptive mechanisms

28 Adaptation as sine qua non of cognitive system What is invariant in adaptive systems will depend on the time intervals during which we observe them. There are at least three time scales of relevance to such systems, corresponding to three different forms of adaptation. - On the shortest time scale intelligent --- hence adaptive --- systems continually change their behavior in the course of solving each problem situation they encounter... - On a somewhat longer time scale, intelligent systems make adaptations that are preserved and remain available for meeting new situations successfully... - On the longest time scale, intelligent systems evolve. Cognitive Science: The newest science of the artificial H. Simon, 1980

29 Adaptation to invariants of environment at varying time-scales Environmental variation

30 Cultural change Environmental variation Slower than individuals can change But faster than evolution can adapt

31 Evolution as primary adaptive system Chronologically (The?) defining characteristic of living systems Emergence of subsequent adaptive mechanisms Ontogenesis Learning Culture

32 Interaction among adaptive mechanisms Only models subsuming multiple adaptive mechanisms can speak to interactions among them But the constituent models (eg, of evolution, learning, etc.) will necessarily be simplified Confusions abound Inheritance of acquired characteristics [Lamarck] Ontogeny recapitulates phylogeny [Haeckel] Nature XOR nurture? Nativist XOR empiricist? Race predicts IQ

33 Inheritance of acquired characteristics [Lamarck] G(t0) Evolution G(t3) Development Lamarck was wrong! No reverse transcription Ph(t1) Learning Ph(t2) Time Adaptive Indivuals in Evolving Populations NBU Summer School - 19 Jul 04 Richard K Belew 2004

34 Mediating environment G(t0) Critical Development Gamete Soma Development Periods Baldwin Effect Evolution Environment Behavior G(t3) Lamarck was wrong! No reverse transcription Ph(t1) Learning Learning Ph(t2) Time Adaptive Indivuals in Evolving Populations NBU Summer School - 19 Jul 04 Richard K Belew 2004

35 Baldwin effect Even if we accept [that individuals' learning cannot alter information in the gene], it is still possible for individual learning to facilitate evolution. If individuals vary genetically in their capacity to learn, or to adapt developmentally, then those most able to adapt will leave most descendants, and the genes responsible will increase in fitness. In a fixed environment, when the best thing to learn remains constant, this can lead to the genetic determination of a character that, in earlier generations, had to be acquired afresh each generation. [John Maynard Smith]

36 Summary Evolution is a powerful adaptive process Cultures certainly change Do selectionist models offer the best accounts? Vast amounts of new evidence becoming available The interactions between culture and biological evolution will only increase in the future

37 Summary (cont) Key terms Replication rate Fitness Mutation Intention Temporal/spatial distribution Neutral drift