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  1. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  2. For each topic • What it is. The main research question(s). • Achievements, examples, used techniques. • Open questions. Modelling language origins and evolution IJCAI-05

  3. BE Baldwin Effect CM Competition Models DS Dynamical Systems GA Genetic Algorithms GT Game Theory HC Hill Climbing ILM Iterated Learning Model LA Language Acquisition LG Language games MBL Memory-Based Learning MM Mathematical Modelling NN Neural Networks RNN Recurrent Neural Networks ROB Robotics Abbreviations of techniques Modelling language origins and evolution IJCAI-05

  4. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  5. Evolution of communication • How can communication as such arise as an evolutionary advantageous strategy? • What ecological pressures could have caused communication to have emerged? Based on biological theories, e.g., (Seyfart et al. 1980, Grafen 1990, Krebs & Dawkins 1984, Zahavi 1975, 1977) Marilyn Monroes (Key West, Florida, 1995) by Peter Krogh (Nat. Geographic) Modelling language origins and evolution IJCAI-05

  6. Examples • Evolution of alarm calls (de Jong 1999). • 5 agents, 3 types of predators. • Input: own location, type of predator (if any) • Actions: move 1 horizontal step & and go to a hiding place (vertical locations) • 90% predators visible, 10% not detected to an individual  communication may help eagle Modelling language origins and evolution IJCAI-05

  7. Examples • Evolution of alarm calls (de Jong 1999). • 5 agents, 3 types of predators. • Input: own location, type of predator (if any) • Actions: move 1 horizontal step & and go to a hiding place (vertical locations) • 90% predators visible, 10% not detected to an individual  communication may help Modelling language origins and evolution IJCAI-05

  8. Examples • Evolving communication to • enhance cooperation. • Mate finding, GA (Werner & Dyer 1991), • Predator-prey simulation, GA (MacLennan & Burghardt 1993) • Altruistic behaviour, GA & GT (Di Paolo 2000) • Alarm calls LG (De Jong 2000) • Handicap principle GA (Bullock 1998) • enhance competition • Contests GA (Noble 2000) Modelling language origins and evolution IJCAI-05

  9. Open issues • What ecological pressures or cognitive factors could have facilitated the transition from using iconic to symbolic communication systems? Modelling language origins and evolution IJCAI-05

  10. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  11. Evolution of signalling systems • How can communication channels and sound systems evolve? • How can sensory-motor systems evolve that are used in communication? • How can particular sound systems evolve? Based on phonetic theories & findings such as (Lindblom et al. 1984, Lindblom & Madieson 1988, Madieson 1984) Modelling language origins and evolution IJCAI-05

  12. (iii) (i) (ii) (iv) Examples • Communication channels: • Evolving communication without dedicated communication channels ROB & GA (Quinn 2001) 2 Robots: Khepera, 2wheels, IR proximity sensors Task: both robots have to move as far as possible while remaining at close distance Modelling language origins and evolution IJCAI-05

  13. Examples • Sound systems: • Vowel systems LG (De Boer 1997; 2000), GA (Glotin 1995; Berrah et al. 1996) • Syllable systems GA (Redford et al. 2001), LG (Oudeyer 2001) • Phonemic coding LG (De Boer & Zuidema 2003; Oudeyer 2002) Modelling language origins and evolution IJCAI-05

  14. Open issues • Adaptation of (human) vocal tract, auditory system and their connection. • Evolution of complex utterances and consonants. Modelling language origins and evolution IJCAI-05

  15. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  16. Lexicon formation • How can a shared vocabulary emerge in a population? • Invention • Language acquisition Based on language acquisition literature, such as, e.g., (Clark 1993, Markman…, Tomasello & Barton 1994). Modelling language origins and evolution IJCAI-05

  17. m1 m2 m3 w1 1.0 0.1 0.0 w2 0.2 1.0 0.4 w3 0.1 0.0 1.0 m1 m2 m3 w1 1.0 0.0 0.0 w2 0.1 0.9 0.1 w3 0.1 0.1 1.0 Basic approach Modelling language origins and evolution IJCAI-05

  18. Strategy Input from adult population Learner’s acquired behaviour Imitator Transmission Reception Transmission’ Reception’ Calculator Transmission Reception Transmission’ Reception’ Saussurean Saussurean Transmission Transmission Transmission’ Reception’ Transmission’ Reception’ Examples • Evolution of the Saussurean sign (Hurford 1989) • Searching for evolutionary good learning strategies • 3 strategies: Modelling language origins and evolution IJCAI-05

  19. Examples • Learning strategies • Saussurean sign GA (Hurford 1989) • Obverter learning LG (Batali & Oliphant 1996; Oliphant 1998) • Learning biases ILM, NN, GA (K. Smith 2004) • Joint attention vs. corrective feedback vs. cross-situational learning LG (Vogt & Coumans 2003) • Interaction strategies • Language games LG (Steels 1996) Modelling language origins and evolution IJCAI-05

  20. Open issues • How can we scale up to realistic lexicon sizes and population sizes? • What learning biases have evolved and how? • How have interaction strategies evolved? • strategies for producing utterances, listening and turn taking Modelling language origins and evolution IJCAI-05

  21. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  22. From: Pfeifer & Scheier 1999 Grounding • How can individual agents use, construct, interpret and share symbolic communication meaningfully? • Intentionality (Brentano 1874) or Symbol grounding problem (Harnad 1990) Take inspiration from, e.g., (Deacon 1997, Searle 1980, Peirce 1931 , Wittgenstein 1967, Lakoff 1987, Langacker 1987, Clark 1993, Tomasello 1999) Modelling language origins and evolution IJCAI-05

  23. Talking Heads (Belpaeme et al. 1998; Steels et al. 2002) • Setup with two cameras on a tripod. • Each camera resembles a Talking Head. • PowerMac for processing • Environment: geometrical figures on white-board. • Experiment: Language evolution on the Internet (largely uncontrolled, because interaction with human users) Modelling language origins and evolution IJCAI-05

  24. Talking Heads (Belpaeme et al. 1998; Steels et al. 2002) Evolution of the word-form “wogglesplat” over 90,000 games. Modelling language origins and evolution IJCAI-05

  25. Examples • Lexicon grounding • Mushroom world NN, GA (Cangelosi et al. 2000) • Naming • Mobile robots LG, ROB (Steels & Vogt 1997; Vogt 2000) LG, ROB, NN (Billard & Dautenhahn 1999) • Talking Heads LG, ROB (Belpaeme et al. 1998; Steels et al. 2002) • Cross-situational learning LG (A.D.M. Smith 2003; Vogt 2003) • Survival task LG, ROB (Vogt 2002) • Emergence of colour categories LG, GA (Belpaeme & Steels, BBS In press) Modelling language origins and evolution IJCAI-05

  26. Examples • Grounding grammar • Construction grammars LG (Steels 2004) • Compositionality LG, ILM (Vogt 2005) • Verbs and nounsGA, ROB (Cangelosi & Parisi 2001; Marocco et al. 2003) Modelling language origins and evolution IJCAI-05

  27. Open issues • How can ‘real meaningful’ communication emerge in a realistic task environment? • Emergence of theory of mind or other intention reading skills. • Emergence of most linguistic aspects, such as verbs, case-systems, abstract concepts, function words, time, etc., largely unexplored (let alone understood). Modelling language origins and evolution IJCAI-05

  28. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  29. Language diversity & change • What are the conditions that make languages so diverse? • Dialects • Languages • Language contact • Language change Based on findings and theories from, e.g., (Dunbar 1996, Crystal 1987, Labov 1972, Chambers 1995) Modelling language origins and evolution IJCAI-05

  30. Examples Social Impact Theory (Latané 1981) models of language change (Nettle 1999a; 1999b) • Impact variant p: ip=bp Npa [(si/di2)/Np] • Impact variant q: iq=bq Nqa [(si/di2)/Nq] • bp/qis a constant, • Np/qis nr. of agents speaking p or q, • a non-linear adoption factor (if linear, all agents will end up speaking the dominant variant). • [(si/di2)/Np/q]average impact of variant p or q. • Learner adopts p if ip>iq and q if iq>ip • Mutation rate – probability that the above rule is properly used. (social distance factor) • Initial population has variant p. Modelling language origins and evolution IJCAI-05

  31. Examples Taken from (Nettle 1999b) Modelling language origins and evolution IJCAI-05

  32. Examples (linguistic diversity) • Social structures • Social impact theory CM (Nettle 1999a; 1999b) • Spatially distributed populations • Dialect diversity LG, NN (Livingstone 2002) • Lexicons LG (Steels & McIntyre 1999) • Ecological influences • Survival behaviours GA (Arita & Koyama 1996) • Stochastic dynamical processes • Macro models of language change MM, DS (Niyogi & Berwick 1995; Niyogi 2000) • Micro models of language change DS, LA, GA (Briscoe 2000a; 2000b) Modelling language origins and evolution IJCAI-05

  33. Examples (language change) • Individual level • Aging structure in language acquisition LG (de Boer & Vogt 1999) • Critical periods for language acquisition GA (Hurford 1991; Hurford & Kirby 1998) • Population level • Flux of agents, stochasticity in sensorimotor experiences LG (Steels & Kaplan 1998) • Language level • Self-organisation LG, DS(de Jong 1999) LG (de Boer 2000) • Lexical change without population fluxLG, NN(Stoness & Dircks 1999) • Rate and pattern of change MM (Pagel 2000) • Lexical change over populations ILM, LG (A.D.M. Smith, in press) • Iterated learning models ILM, LG (Brighton, Kirby, Smith, Vogt, Zuidema) Modelling language origins and evolution IJCAI-05

  34. Examples (observations) • Evolution of signalling abilities GA (Werner & Dyer 1991) • Emergence of conventionalised signals NN (Hutchins & Hazelhurst 1995) LG (Livingstone & Fyfe 2000) Modelling language origins and evolution IJCAI-05

  35. Open issues • What is the influence of language ecology? (Livingstone 2002) • Population/language mix • Mixing of social structures Modelling language origins and evolution IJCAI-05

  36. Topics of Research • Evolution of communication • Evolution of signalling systems • Lexicon formation • Grounding • Language diversity • Emergence of grammar Modelling language origins and evolution IJCAI-05

  37. Emergence of syntax/grammar • Under what conditions can (aspects of) syntactic or grammatical structures emerge? • Nativist accounts • Cultural accounts • Hybrid accounts • Grounding Investigate theories from, e.g., (Bickerton 1990, Chomsky 1990, Pinker & Bloom 1990, Tomasello 2003, Wray 1998) Modelling language origins and evolution IJCAI-05

  38. S/love(x,j)->N/xlovesjohn N/m->mary N/h->hanna S/love(m,j)->marylovesjohn S/love(h,j)->hannalovesjohn N/m->mary M/m->mary N/m->mary Iterated learning (Kirby 2002) • Population dynamics with overlap (i.e. each generation 1 adult, 1 learner) • Transmission bottleneck • Predicate logic meaning representation • Invention mechanism -> holistic, or exploiting existing rules (words are random strings) • Heuristic induction mechanism: • Chunking • Merging Modelling language origins and evolution IJCAI-05

  39. Iterated learning (Kirby 2002) Phase-space plot of expressivity vs. language size shows the emergence of syntactic language after many generations. Picture courtesy of Simon Kirby. Modelling language origins and evolution IJCAI-05

  40. Examples • Nativist accounts • Co-evolution of UG/LAD GA(Kirby & Hurford 1997; Briscoe 2000) • Evolution of LAD GA (Turkel 2002) GA+BE (Yamauchi 2001) • Evolutionary constraints for UG MM, GT (Nowak et al. 2000; 2001; Komarova et al. 2001) • Cultural accounts (transmission bottlenecks) • Heuristic grammar inducers ILM (Kirby 2000; 2001; 2002; Zuidema 2001) • Minimum description length ILM (Teal & Taylor 1999; Brighton & Kirby 2001) • Hebbian learners ILM, NN (K. Smith 2003; Kirby et al. 2002) • Static populations RNN (Batali 1998) MBL (Batali 2002) • Issues in Optimality Theory ILM (Jäger 2003) Modelling language origins and evolution IJCAI-05

  41. Examples • Hybrid approaches • Constructivist evolution GA, LG (Hashimoto & Ikegami 1996; Zuidema & Hogeweg 2000) • Learnable languages HC,RNN (Tonkes et al. 2000; Tonkes & Wiles 2002) • Sequential learning • Word order constraints SL, RNN (Christiansen & Devlin 1997; Christiansen & Ellefson 2002) • Grounded approaches • Construction grammars LG, ROB (Steels 2004) • Compositional structures LG, ILM, ROB (Vogt 2005) • Verbs and Nouns GA, NN, ROB (Cangelosi & Parisi 2001; 2004;Marroco et al. 2003) Modelling language origins and evolution IJCAI-05

  42. Open issues • Increasing complexity to human level • Is there a biological endowment for the emergence of grammar? How? • How much can cultural evolution explain with respect to the transition towards grammar? • Modelling co-evolution syntax & semantics • Evolution of language acquisition mechanisms (induction mechanism, Theory of Mind, …) Modelling language origins and evolution IJCAI-05

  43. One big open issue… • Did the human brain evolve to facilitate language, was it the other way around or was there a co-evolution between brain and language, cf. (Deacon 1997)? • Few computational models start looking at this problem (see, e.g., Dominey in press) Modelling language origins and evolution IJCAI-05

  44. Summary - achievements • Evolution of • communication • vowel systems • lexicons • compositional languages and other aspects of grammar • Understand aspects of grounding • Models of language change and diversity • Some understanding of neural aspects Modelling language origins and evolution IJCAI-05

  45. Summary – open issues • Ecological pressures/cognitive factors for evolution of symbolic communication • Biological and cultural endowment for emergence of grammar • Scaling towards human level complexity • Population sizes • Population dynamics • Vocalisations • Grammars • Semantics • Etc. • Biological adaptation of • Vocal tract/auditory system • Language acquisition skills • Intention reading skills • Meaningful behaviour • Co-evolution of language and brain Modelling language origins and evolution IJCAI-05

  46. Take home message There are many models, based on hypotheses and scenarios. Although some theories are mutually exclusive, many are not. Try not to focus on one model, hypothesis or explanation when researching language evolution; better combine the best bits of the different models. E.g., different language acquisition strategies can perform better when applied together, rather than when used in isolation. Modelling language origins and evolution IJCAI-05

  47. BREAK Modelling language origins and evolution IJCAI-05