Topics of Research

1
Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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For each topic

• What it is. The main research question(s).
• Achievements, examples, used techniques.
• Open questions.

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Abbreviations of techniques

• 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

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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Evolution of communication
Marilyn Monroes (Key West, Florida, 1995)
by Peter Krogh (Nat. Geographic)

• 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)

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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
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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

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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)

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Open issues

• What ecological pressures or cognitive factors
  could have facilitated the transition from using
  iconic to symbolic communication systems?

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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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)

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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

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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)

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Open issues

• Adaptation of (human) vocal tract, auditory
  system and their connection.
  
• Evolution of complex utterances and consonants.

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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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).
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Basic approach
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Examples

• Evolution of the Saussurean sign (Hurford 1989)
• Searching for evolutionary good learning
  strategies
  
• 3 strategies

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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)

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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

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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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)

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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)

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Talking Heads (Belpaeme et al. 1998 Steels et
al. 2002)
Evolution of the word-form wogglesplat over
90,000 games.
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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)

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Examples

• Grounding grammar
• Construction grammars LG (Steels 2004)
• Compositionality LG, ILM (Vogt 2005)
• Verbs and nouns GA, ROB (Cangelosi Parisi 2001
  Marocco et al. 2003)

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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).

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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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)
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Examples

• Social Impact Theory (Latané 1981) models of
  language change (Nettle 1999a 1999b)
  
• Impact variant p ipbp Npa ?(si/di2)/Np
• Impact variant q iqbq Nqa ?(si/di2)/Nq
• bp/q is a constant,
• Np/q is 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 ipiq and q if iqip
• Mutation rate probability that the above rule
  is properly used. (social distance factor)
  
• Initial population has variant p.

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Examples
Taken from (Nettle 1999b)
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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)

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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 flux LG, 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)

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Examples (observations)

• Evolution of signalling abilities GA (Werner
  Dyer 1991)
  
• Emergence of conventionalised signals NN
  (Hutchins Hazelhurst 1995) LG (Livingstone
  Fyfe 2000)

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Open issues

• What is the influence of language ecology?
  (Livingstone 2002)
  
• Population/language mix
• Mixing of social structures

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Topics of Research

• Evolution of communication
• Evolution of signalling systems
• Lexicon formation
• Grounding
• Language diversity
• Emergence of grammar

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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)
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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

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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.
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Examples

• Nativist accounts
• Co-evolution of UG/LAD GA (Kirby Hurford 1997
  Briscoe 2000)
  
• Evolution of LAD GA (Turkel 2002) GABE (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)

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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)

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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, )

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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)
  

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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

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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

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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.

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