topics of research

Modelling language origins and evolutionIJCAI-05

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Topics of ResearchTopics of Research

Evolution of communication

Evolution of signalling systems

Lexicon formation

Grounding

Language diversity

Emergence of grammar


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For each topicFor each topic

What it is. The main research question(s).

Achievements, examples, used techniques.

Open questions.


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Abbreviations of techniquesAbbreviations 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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Lexicon formation

Grounding

Language diversity



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Evolution of communicationEvolution 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)


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ExamplesExamples

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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ExamplesExamples

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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ExamplesExamples

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 issuesOpen issues

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


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Lexicon formation

Grounding

Language diversity



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Evolution of signalling systemsEvolution 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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ExamplesExamples Communication channels:

– Evolving communication without dedicated communication channels ROB & GA (Quinn 2001)2 Robots: Khepera, 2wheels, IR proximity sensorsTask: both robots have to move as far as possible while

remaining at close distance

(i)

(ii)

(iii)

(iv)


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ExamplesExamples

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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Adaptation of (human) vocal tract, auditory

system and their connection.

Evolution of complex utterances and

consonants.


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Lexicon formation

Grounding

Language diversity



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Lexicon formationLexicon 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 approachBasic approach

m1 m2 m3

w1 0.2 0.2 0.3

w2 0.3 0.2 0.4

w3 0.1 0.2 0.3

m1 m2 m3

w1 0.3 0.1 0.3

w2 0.2 0.2 0.1

w3 0.3 0.2 0.2 1.00.10.1w3

0.10.90.1w2

0.00.01.0w1

m3m2m1

1.00.00.1w3

0.41.00.2w2

0.00.11.0w1

m3m2m1


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

Strategy Input from adult population

Learner’s acquired behaviour

Imitator TransmissionReception

TransmissionReception

Transmission’Reception’

Transmission’Reception’

Calculator

Transmission Transmission’

Reception’

Saussurean Transmission Transmission’

Reception’

Saussurean


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ExamplesExamples

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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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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Lexicon formation

Grounding

Language diversity



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GroundingGrounding 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)

From: Pfeifer & Scheier 1999


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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)

Talking Heads Talking Heads (Belpaeme et al. 1998; Steels et al. 2002)(Belpaeme et al. 1998; Steels et al. 2002)


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Talking Heads Talking Heads (Belpaeme et al. 1998; Steels et al. 2002)(Belpaeme et al. 1998; Steels et al. 2002)

Evolution of the word-form “wogglesplat” over 90,000 games.


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ExamplesExamples 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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ExamplesExamples 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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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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Lexicon formation

Grounding

Language diversity



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Language diversity & changeLanguage 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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ExamplesExamplesSocial Impact Theory (Latané 1981) models of language

change (Nettle 1999a; 1999b)

Impact variant p: ip=bp Npa [(si/di

2)/Np]

Impact variant q: iq=bq Nqa [(si/di

2)/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 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.


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ExamplesExamples

Taken from (Nettle 1999b)


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Examples (linguistic diversity)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)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)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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What is the influence of language ecology?

(Livingstone 2002)

Population/language mix

Mixing of social structures


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Lexicon formation

Grounding

Language diversity



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Emergence of syntax/grammarEmergence 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)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

S/love(m,j)->marylovesjohnS/love(h,j)->hannalovesjohn

S/love(x,j)->N/x lovesjohnN/m->maryN/h->hanna

N/m->maryM/m->mary

N/m->mary


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Iterated learning (Kirby 2002)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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ExamplesExamples 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)


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ExamplesExamples 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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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…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 - achievementsSummary - 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 issuesSummary – 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 messageTake home messageThere 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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BREAKBREAK

topics of research

Documents

symbolic communication

individual communication

evolving communication

ga glotin

syllable systems ga

vowel systems lg

competitioncontests

ga maclennan burghardt