Form‐meaning systemacity and language evoluon · Form‐meaning systemacity and language evoluon...
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Form‐meaning systema/city and language evolu/on Mónica Tamariz [email protected] Tübingen, 1 September 2009
Transcript of Form‐meaning systemacity and language evoluon · Form‐meaning systemacity and language evoluon...
Language as an adaptive system
Language structure is influenced by many pressures
LANGUAGE
Conveyvariedmeanings!
ExpressmyidenFty!
Beeasytolearn!
Beeasytoproduce! Beeasytounderstand!
Language as an adaptive system
LANGUAGE
Expressivity
Learnability
Conveyvariedmeanings!
ExpressmyidenFty!
Beeasytolearn!
Beeasytoproduce! Beeasytounderstand!
Language structure is influenced by many pressures
Overview
1. Form-meaning systematicity
2. Exploring systematicity in Natural Language: A corpus study
3. Systematicity and compositionality in Artificial Languages: An experimental approach
4. Implications for language evolution
1. Systematicity between forms and meanings in language
Systematicity
• TherelaFonshipbetweentwospacesissystemaFcifthestructureofonespacereflectsthestructureoftheother
• Thereforeknowingaboutonestructureprovidesuswithsomeknowledgeabouttheother
Systematicity in language PhonologicalformssystemaFcallyreflectmorphosyntax
DoesitreflectsemanFcs??
present past 3rd person
talk talked talks
play played plays
study studied studies
A systematic lexicon
Wordsthatsoundsimilartendtohavesimilarmeanings
Meaningspace
SystemaFcityreflectsapreferenceforisomorphic/topographic/systemaFcrepresentaFonsinthenervoussystem
Systematic lexicon – Why?
FuncFonsofsystemaFcity:
• Helplearn/understandnewitems
• AllowcreaFvityandgeneralisaFon
Systematic lexicon – What for?
Meaningspace
2. Exploring systematicity in Natural Language: A corpus study
(Tamariz 2005, 2008)
Hypothesis:ThestructureofthementallexiconshowssystemaFcitybetweenformsandmeanings
Method:QuanFtaFvecorpusstudy
Data:Threesubsetsofa1MwordSpanishtranscribedspeechcorpus(MarcosMarin,1992)
252CVCV
146CVCCV
148CVCVCV
Twostudies:
SyntaxandsemanFcs
SemanFcsonly
Looking for systematicity in the lexicon
wordsoffrequency>=20
Measuring systematicity
DistribuFonalsimilarity(Landauer&Dumais,1997;MacDonald,2000)
Phonologicalsimilarity(Tamariz2005,2008)
kasa
lima
nene
kita
kasa
kita lima
nene
Measuring systematicity
DistribuFonalsimilarity(Landauer&Dumais,1997;MacDonald,2000)
Phonologicalsimilarity(Tamariz2005,2008)
k-a-s-a k-i-t-a
v1, v2, v12 c1, c2, c12 stress1, stress2
strv1, strv2 (syntax)
Patterns of coocurrence with:
394 words (Stx+Sem) 320 content words (Sem)
of freq >=200
Measuring systematicity
Phonologicalsimilarity
DistribuFonalsimilarity
FisherdivergenceFD=1.4
(significanceestablishedwithMonteCarloanalysis)kasa
lima
nene
kita
kasa
kita lima
nene
Result
Result
Wordsthatsoundsimilardotendtohavesimilarmeanings
ThereissystemaFcitybetweenformandmeaninginthelexicon
Result
Wordsthatsoundsimilardotendtohavesimilarmeanings
However,toomuchsystemaFcitymayposeaproblemforcomprehension!
ThereissystemaFcitybetweenformandmeaninginthelexicon
Systematicity vs. disambiguation
kiri
kili kini
kisi
• Thelexiconstructureisunderpressure
1. TobesystemaFc(whichhelpsprocessingandlearning)
2. ToavoidambiguiFesderivedfromsystemaFcity
Hypothesis:
Thestructureofthementallexiconisshapedbythesetwoopposedpressures
• SomeaspectsofformssystemaFcallyreflectthestructureofwordmeanings
• Otheraspectsofformsshouldhave“negaFvesystemaFcity”withrespecttowordmeanings
The phonological correlates of systematicity
Method
MeasuresystemaFcitybetween
• DistribuFonalsimilarityand
• Phonologicalsimilarityintermsof
‐ Consonants
‐ Vowels
‐ Stresspagerns
E.g.Dowordsthatsharethefirstconsonanttendtohavesimilarmeanings?
Results TheimpactofdifferentphonologicalparametersonsystemaFcity
consonantsvowelsstress
Allvaluesp<0.01exceptwherestated
CVCVwords
Results TheimpactofdifferentphonologicalparametersonsystemaFcity
consonantsvowelsstress
Allvaluesp<0.01exceptwherestated
CVCVwords
• ConsonantshaveposiFveimpact
• Vowels,negaFveimpact
• StressedvowelinthepenulFmatesyllable,negaFveimpact
• Otherstress,posiFveimpact
Results TheimpactofdifferentphonologicalparametersonsystemaFcity
consonantsvowelsstress
Allvaluesp<0.01exceptwherestated
CVCVCVwords
• ConsonantshaveposiFveimpact
• Vowels,mostlynegaFveimpact
• StressedvowelinthepenulFmatesyllable,negaFveimpact
• Otherstress,posiFveimpact
Results TheimpactofdifferentphonologicalparametersonsystemaFcity
consonantsvowelsstress
Allvaluesp<0.01exceptwherestated
CVCCVwords
• Consonantshavemixedimpact
• Vowels,mostlynegaFveimpact
• StressedvowelinthepenulFmatesyllable,negaFveimpact
• Otherstress,posiFveimpact
Discussion IntheSpanishlexicon…
• Thestructureofconsonants,stresspagernandthestressedfinalvowelhasadaptedtothepressureforsystemaFcity
• Thestructureofvowels,especiallythestressedvowelinthepenulFmatesyllablehasadaptedtothepressureforeasydisambiguaFon
• TheseresultssupportthehypothesisthatthelexiconisanadapFvesystem,evolvingundermulFplepressures
(OtherlanguagesmayhavefounddifferentsoluUonstothisconflict)
3. Systematicity and compositionality in Artificial Languages:
An experimental approach
Systematicity and compositionality
HolisFc
lop=
mer=
sus=
pina=
e=
koF=
• ComposiFonalityisaspecialtypeofsystemaFcitybetweenformsandmeanings
“InacomposiFonalsystem,themeaningofanexpressionisafuncFonofthemeaningofitscomponentparts,plusthewaythepartsarecombinedtogether”
+
+
+
lopi loto
napi nato
mepi meto
+
+
+
lop mer
sus pina
e koF
ComposiFonal
lo‐=
na‐=
me‐=
‐pi=
‐to=+
+
+
+
Compositionality and Expressivity
ComposiFonalityfacilitatesemergentcategoriesandgeneralisaUon
(Ifthemeaningspaceisstructured)
+
+
+
lopi loto
napi nato
mepi meto
+
+
+
lop mer
sus pina
e koF
ComposiFonal
lo‐=
na‐=
me‐=
‐pi=
‐to=+
• Extrameanings:
1=outsideshape
2=insert
• GeneralisaFonpossible
HolisFc
lop=
mer=
sus=
pina=
e=
koF=
• Noextrameanings
• GeneralisaFonnotpossible
+
+
+
Why is language compositional?
• ThestructureoflanguageevolvedoverthousandsofhumangeneraFonswholearnitandthenuseit
• WeassumethatiniFallylanguagewasnotcomposiFonal(e.g.Wray,2002)
• Howdiditcometohavethisstructure?
– Theroleofindividuallearning
– Theroleofculturaltransmission
The role of individual learning (Tamariz & Smith 2008)
• Hypothesis– ThereisalearningbiasfavouringcomposiFonalmappings
betweensignalsandmeanings
• PredicFon– MorecomposiFonallanguagesareeasiertolearn
• Test– ArFficialLanguageLearningexperiment– ConstructarFficiallanguageswithdifferentlevelsof
composiFonalityandseewhicharebegerlearned
Artificial languages
MEANINGS
27differentmeanings
+
FORMS
3‐syllablepseudowords
27differentforms
Procedure
Training
hune
lene
letupi
miko
lekono
TesFng
1.Signals
Task:Typename
2.Meanings
Task:Selectpicture
lekono
_
27screensx3Fmes
Variables
• Independentvariable
4levelsofinputlanguagecomposiFonality
LANG1 LANG2 LANG3 LANG4
RegMap0.154 0.456 0.754 1.00
• Dependentvariable
Learnability– MeasuringhowwellthecomposiFonallanguagestructurewas
learned
Measuring Compositionality (RegMap)
RegMap measures the confidence that a signal and a meaning are unambiguously and consistently associated
lene
letu
hune
leko
Co-occur Freq
le - 3 2 2
- ne 2 - ko 2
miko
√
√
€
RegMap(X | Y ) = 1− H (X | Y )log(nx )
Results
Learnability of the compositional language structure
Similarity of compositional language structure of input and output languages
Results and discussion
MorecomposiFonallanguagestructuresarelearntbeger
ParFcipantsseemstohavealearningbiasforcomposiFonality
IndividuallearningmayhaveplayedaroleinlanguagebecomingcomposiFonal
Learnability of the compositional language structure
Results and discussion
MorecomposiFonallanguagestructuresarelearntbeger
ParFcipantsseemstohavealearningbiasforcomposiFonality
IndividuallearningmayhaveplayedaroleinlanguagebecomingcomposiFonal
Learnability of the compositional language structure
Butwheredoesthisbiascomefrom?
The role of enculturation (Brown & Tamariz, 2008)
• Hypothesis– ThelearningpreferenceforcomposiFonalstructureisgivenby
culturalknowledgesuchasliteracy
• PredicFon– LiteratesarebegeratlearningcomposiFonallanguagesthan
illiterates
• Test– MusicalArFficialLanguageLearningexperiment
– ConstructarFficialmusicallanguageswithdifferent levelsofcomposiFonalityandseewhicharebeger learned
Procedure
Training
hune
miko
TesFng
Signals
Task:Singtune
27screensx3Fmes
lene
lekono
27signalspresented
letupi
Variables
• Independentvariables– 3levelsofinputlanguagecomposiFonality
LANG1 LANG2 LANG3
RegMap 0.004 0.66 1.00
– 2levelsofmusicalliteracy(literate/illiterate)
• Dependentvariable– LearnabilityofthecomposiFonalstructureoflanguages
Results
ItseemsthatliteracyenhancesthepreferenceforlearningcomposiFonalsystems
Learnability of the compositional language structure
Discussion: The role of individual learning
• TheseresultsindicatethatindividuallearningmayincreaselanguagecomposiFonality
• Thiseffectmaybeenhancedbyculturalknowledgesuchasliteracy
• ButlanguageevolvedasitwastransmigedovermanygeneraFons…
The role of cultural transmission (Kirby, Cornish & Smith, 2008)
• Hypothesis– Culturaltransmissioncontributestotheemergenceof
systemaFcstructureinlanguage
• PredicFon– Theeffectsofindividuallearningareenhancediniterated
learning
• Test– IteratedArFficialLanguageLearningexperiment
– MeasuresystemaFcityandlearnability
kimako
koni
kanige
kuni
winige
komako
Genera/on0:randomsignals
MEANINGS
27differentmeanings
Languages and procedure
Genera/on1
• OneoftheiniFalrandomlanguages
Results
huhunigu kemuniwa
kihupo
wakiki pokiheku waguhuki
nihu niguki koni
muwapo powa
hukinimu
wako hukeko pohumu
muko kokeguke
kimu
kekewa konihuke
kopo
huwa hukike
ponikiko
kowagu kokihuko kiwanike
• ThesamelanguagesomegeneraFonslater
Results
• LanguagesareincreasinglysystemaFcandlearnable
Results
Learning error Systematicity
• LanguagesareincreasinglysystemaFcandlearnable• Composi/onalityisapparent,butitisnotquan/fied
Results
Learning error Systematicity
• ForeachgeneraFon,calculateRegMapofallpairsofmeaningandformdimensions
E.g.forGeneraFon2:
Quantifying compositionality (Cornish, Tamariz & Kirby, in press)
Segment 1
Results
Emergence of compositionality over cultural transmission
Segment 2
Emergence of compositionality over cultural transmission
Results
Segment 3
Emergence of compositionality over cultural transmission
Results
Discussion
• WehaveobservedapreferenceforindividualstolearnsystemaFclanguages
• ThatpreferencemaybeenhancedbyculturalinsFtuFonssuchasliteracyandteaching
• CulturaltransmissioncanmediatetheaccumulaFonoflanguagesystemaFcityoverFme
Conclusion
• Manypressures,someFmesconflicFng,havelestheirmarkonlanguagestructureoveritslongevoluFonaryhistory.
• Thebalanceofsystema/cityinlanguageisanadaptaFontomanyfactors
– Neuralconstraints(preferenceforisomorphic,systemaFcmappings)
– Learnedbiases(livinginastructured,culturalworld,welearntoexpectstructure)
– LanguagefuncFon(theneedtoproduceandunderstandflexibly)
– CulturaltransmissionovergeneraFons
References • Tamariz(2005).ExploringtheadapFvestructureofthementallexicon(unpublished
PhDthesis).
• Tamariz(2008).ExploringsystemaFcitybetweenphonologicalandcontext‐cooccurrencerepresentaFonsofthementallexicon.TheMentalLexicon,3(2):259‐278.
• Kirby,Cornish&Smith(2008).CumulaFveCulturalEvoluFonintheLaboratory:anexperimentalapproachtotheoriginsofstructureinhumanlanguage.PNAS,105(31):10681‐10686.
• Tamariz&Smith(2008).QuanFfyingtheregularityofthemappingsbetweensignalsandmeanings.In:A.D.M.Smith,K.Smith,R.FerreriCancho,Eds.,TheevoluUonoflanguage,pp.315‐322.
• Tamariz(inpress).CouldarbitraryimitaFonandpagerncompleFonhavebootstrappedhumanlinguisFccommunicaFon?InteracUonStudies.
• Cornish,Tamariz&Kirby(2010).ComplexadapFvesystemsandtheoriginsofadapFvestructure:whatexperimentscantellus.SpecialissueonLanguageasacomplexAdapFveSystem.LanguageLearning:59:4S1.
• Brown,J.E.andTamariz,M.(2010).TheroleofliteracyandpracFceintheevoluFonoflinguisFcstructure.In:A.D.M.Smith,B.deBoer,M.Schouwstra,Eds.,TheevoluUonoflanguage.
