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GrowingintoLanguage GrowingintoLanguage DevelopmentalTrajectoriesand NeuralUnderpinnings LILIANATOLCHINSKY AND RUTHA.BERMAN GreatClarendonStreet,Oxford,OX26DP, UnitedKingdom
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©LilianaTolchinskyandRuthA.Berman2023
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Acknowledgments Theauthorsaregratefultothefollowingforhelpwithpreparingthemanuscript forsubmissiontothepublishers:SimonJohnCook,whoservedasourmain copyeditor,SarahWinklerforhelpwithcopyeditingandtrackingdownreferences,VeraRusyanovforherworkonreferences,andIttamarErbwithindexing. WewouldliketothanktheteamatOUPfortheirpatience,theirprofessionalism,andgoodwill,particularlyJuliaSteer,VickiSunter,andSamAugustinDurai Ebenazer,ourprojecteditors.Thanks,too,toPanchoTolchinskyandCatalina Estradaforhelpwiththegraphicdesignofthefigure.Wearegratefultoourrespectivepartners,EduardoLandsmanandYaacovYaar,fortheirsupportandwisdom throughouttheprocessofproducingthiswork.Andtoourmentors,colleagues, andstudents,withoutwhomthisbookwouldnothavematerialized.
Prologue “Languageisthemostmassiveandinclusiveartweknow,amoun- tainousandanonymousworkofunconsciousgenerations.”
EdwardSapir,1921,p.235
“Deathandlifeareinthepowerofthetongue.” Proverbs18:21
Weembarkedonthisendeavortoshowhowlanguagedevelops‘beyondagefive,’ fromchildhoodtoadolescenceandsubsequently.1 Psychologistsandlinguists,like parents,havealwaysbeenfascinatedbytheappearanceofachild’sfirstwords andhowrapidlychildrenturnintotalkers,somuchsothatumpteenbookshave beenwrittenontheirearlylanguage.Oursisabookonolderusersofalanguage. Itdealswithhowschoolchildrenandadolescentsemploylanguageindifferent communicativesettingsandfordifferentpurposes—totellstories,engageinconversations,speculateaboutthefuture,speakmetaphorically,makejokes,reflect onlanguagestructure,andevenwriteacademicessays.
Themiracleofearlylanguageissoamazingthatmanyphilosophersandlinguistsregarditasaninnateendowment,agiftthatmustbeinthegenes.Howcan languagebealearnedbehaviorgivenwhattheycall‘thepovertyofthestimulus’?2 Parentsalmostneverspeakincompletesentences,theyconstantlyrepeatthemselves,theyoftendon’tcorrecttheirchildren’smistakes.Besides,children,like grownups,saythingstheyhaveneverheardbefore.
Wewillargue,instead,thatthereisabundantevidencethatpovertyofinput makeschildrenpoorlanguageusers,whiletheoppositeistrue—arichlinguisticenvironmentmakesforbettertalkersandwriters.Inotherwords,theidea oflanguageasaninborn,geneticendowmentneedstobemodulatedbyexternalfactorsofenvironmentandculture—ambientlanguage(s),homebackground, schooling,socio-economiccircumstances,andsoon.Acrossthebook,weinvoke bothinternalandexternalfactorsasinteractinginlanguagedevelopment:genes, environment,andthenatureofthetask.Theseinvolvewhatspeakersinheritby beinghuman,thesocioculturalhabitatinwhichtheyareraised,andthepurposes forwhichtheyuselanguage,likewritingadiary,chattingatthefamilydinner table,ordecidingiftwowordsmeanthesame.
Theauthorsofthisbookarelinguists,originallytrainedinbothstructuralist (European)andformal(American)linguistics.Forthelastfiftyyears—yes,weare pre-boomerwomen—wehaveattemptedtoexplainhowlanguageoutputschange
withage.Overtheyearsofourscholarlycareers,eachofushasframedanapproach tolanguagedevelopmentinthecontextofgeneralcognitivedevelopment.Rather thantakingeitherdomain—languageorcognition—asprerequisitefortheother, weconceiveofthemasinconstantinteraction,supportingoneanotheralongthe lifespan.However,untilrecently,referencestocognitionandaffectwererather vague,andthebrain—thesiteofcognitionandemotion—waslargelymissing frominquiryintolanguagedevelopment.Currentadvancesinneurobiologyhave enabledustointegratethebrainforprovidingadeeperexplanationof(someof the)developmentalchangesweobserveintheuseoflanguage.Forexample,whyis storytellingsuchanaddictiveactivity?Whydoadolescentsdevelopsuchapeculiar vocabulary?Whyaremetaphoricalmeaningsgraspedbeforeironicones?Howis itthat7-year-oldsareunabletodefinewhatisaword,eventhoughtheyhavebeen usingallkindsofwords(appropriately)sincetheageof2?Howisitthatchildren writebeforetheyread?
Toachieveourgoalofilluminatinglanguageuseanddevelopmenthelpedby neurobiology,ourbookbeginswithanoverviewofthepropertiesofthe working brain,stressingthatthecapacitytolearnandmemorizeaswellastopredictand correcterrorsremainsplasticatleastinto,possiblybeyond,lateadolescence.The factthatcrucialdevelopmentstakeplaceinnearlyeveryaspectoflanguageuse afterearlychildhoodjustifiesthescopeofourinquiry.Thisinitialoverviewon thebehaviorofthebrain,whatitdoesordoesnotenableustoknowanddowith language,providesthesettingfortherestofthebook.Subsequently,(ineachof Chapters2to7),wecommentontheneurobiologicalunderpinningsofparticular facetsoflanguageuse,andtheskillschildrenneedtodeveloptoexpressthemselves adequatelyindifferentrealmsofexperience.
Thenextthreechaptersmovealongatimeline:Chapter2trackslanguageusage intheworldof pastexperiences,howpeoplerecounteventsfortellingstoriesin thenarrativegenre;Chapter3looksathowpeoplewieldlanguagein theactual world ofthepresent,forinteractingwithfamilyandpeersordescribingentities andpresentingarguments;Chapter4considersthewayspeoplereflectonpossible worldsandalternative eventualitiesinthefuture.
Wethenmovetotheclustersoflinguisticandcognitiveabilitiesrequiredfordifferentdomainsoflanguageuse.Chapter5takesustotheworldof imagery,where peoplespeakidiomatically,inculturallyfixedways,combiningwordsthatmake nosenseonthesurface,likesayingthatsomeonewhodied kickedthebucket adomainwherepeoplecommunicatebyimplication,indirectspeechacts,and figurativeusages.
Chapter6traceshowpeopleuselanguagetotalk about language,howlanguage isturnedfromameansofcommunicationtoanobjectofreflection.Finally,before movingontoourconcluding‘Afterthoughts,’Chapter7tacklestheworldof literacy,fromdigitaltextingtoacademicessays,wherepeopleusewritingandreading asawayofthinking—andwedistinguishbetweenscript-literacyasmasteringthe
physicalelementsofawritingsystemandtext-literacyasbeingabletohandle differenttypesofwrittendiscourse.Eachofthesixusage-basedchapters(2to7) opensbysurveyingwhatphilosophers,cognitivescientists,and/orhistorianshave hadtosayaboutthetargeteddomains,proceedstooutliningthelinguisticmeans ofexpressionthatcharacterizethemandtheirneurologicalunderpinningsin thebrain,andconcludeswiththedevelopmentaltrajectoriesthatchildrenand adolescentstraverseineachoftheserealmsofexperience.
Runningacrossthebookasawholeareseveralmotifs.
(1)Development:Akeythemeisdevelopment—inthesenseoflanguagechange inthelifeofindividuals.3 Inlinewithmainstreamlinguisticapproaches,weagree thatbeforeage5 everynormalchildisalinguisticgenius. Thebookthatheralded thecomingofageofdevelopmentalpsycholinguisticssomefiftyyearsago(Brown, 1973)endeditsstudywhenthethreechildrenwhosespeechwasrecordedhadnot yetreachedfouryearsofage.Otherstudiesclaimtoshowthatbyage3,“children haveacquiredthebasicphonological,morpho-syntactic,andsemanticregularitiesofthetargetlanguage,irrespectiveofthelanguageorlanguagestobelearned” (Weissenborn&Ho¨hle,2000,p.vii).4 Hereweaimtoshowthat,ateachpoint indevelopment,children(andadults,too)needtocopewithdifferentproblems ofverbalcommunication,forwhichtheyconstantlyneedtodevelopfreshstrategiesofadaptationanddiverseformsofexpression.Forexample,textingpeers requires(linguistic)survivalstrategiesthatdifferfromthoseforconversingata familydinnertableoransweringaquestioninclass—andeachofthesehasits owncharacteristicsamonggrade-schoolerscomparedwithteenagers.
Optimaldevelopmentofanorganismdependsonitsadaptationtovariedsurroundingsratherthansolelyonafull-blownfinalenvironment(Lehrman,1953), sothatallspeciesoforganismshaveevolvedtoadapttotheiruniquenichesateach pointindevelopment.Hereweattempttoconveytoourreadershowchildrenand adolescentsadapttoparticularnichesatdifferentpointsintheirdevelopment,by relyingonrecentadvancesinneurobiologythatdemonstratebrainplasticityand thelengthydevelopmentof executivefunctions. 5
Fourmaintimespanscanbeidentifiedinlanguagedevelopmentingeneral. Startingwith movingintolanguage frombirthto3years,childrencrosstoa psycholinguisticfrontier atlatepreschoolage(around4to5years).Subsequently,at aroundage6to12years,they‘goconventional,’adaptingtothenormsofthe ambientsocietyintheiruseoflanguageasinotherdomains.Laterstill,around ages13to19years,youngpeopleshifttoincreasingautonomyandindividuality ofexpression,withadolescenceawatershedinthetransitionfromchildhoodto adulthoodinlinguisticproficiencyasinsexualmaturationandsocialbehavior.6 Ingoing‘beyondage5,’ourbookfocusesonthelattertwostages.
(2) Neurobiologicalperspectives:Weadopta neoconstructivist approach (Karmiloff-Smith,1992)asadistinctiveframeworkinneurobiologythatshapes ourviewoftherelationshipbetweengeneticendowment,brainstructuring,and
experience,andisrelevanttolearningculturalobjectssuchaswritingormathematics.Thishighlightsseveralpropertiesofthedevelopmentofbrainstructures towardincreasingspecialization,agrowingcapacityforattendingtodifferent aspectsofataskinparallel,andgreaterskillinanticipatingoutcomesbasedon previousexperience.Otherimportantneurobiologicalfactorsinlanguagelearning andusearethehierarchicalorganizationofthebrainthatenablescognitivecontrolanditslong-lastingpowerforlearning,asanenduringcapacitythatmotivates ourinterestinlanguagedevelopmentbeyondearlychildhood.
(3) Formandfunction:FollowingpsycholinguistslikeKarmiloff-Smith(1979, 1992)andSlobin(1973,2001),ourconcerniswiththeinterrelationsbetweenlinguisticformsandtheirdiscoursefunctionsratherthanwitheitheroneortheother. By linguisticforms,werefertothestructuralelementsoflanguage—morphemes, words,clauses,sentences.Andforusaslinguists,ratherthanpedagoguesor purists, grammar referstotheprinciplesthatgovernhowpeopleactuallyuse languagewhentheyspeakandwriteratherthanrulesof correct usage. 7 Across languages,grammaticalformsfallintodifferentinteractingstructuraldomains: Phonology—howthesoundsofalanguage,itsconsonantsandvowels,itsintonationpatternsandtones,arepronouncedandhowtheyarecombinedtoform wordsandgroupsofwords; Morphology—howwordsarebuiltupinalanguage fromelementslikeroots,stems,prefixes,andsuffixes;andSyntax—howwordsare combinedtogethertoformphrases,clauses,andsentences.8
Weapproachthegrammaticalstructuresoflanguageanditslexicon(people’s mentalword-stock,theirvocabulary)infunctional terms:wequeryhowlinguistic formsareemployedindifferentcommunicativecontextsandforvariedpurposes. Thatis,ourconcerniswith authenticuse oflanguage.
(4) Languageknowledgeandlanguageuse:Awell-knowndistinctionpopularizedbyChomsky-inspiredlinguisticsisthedichotomybetweenso-called competence and performance.Performance,thewaypeoplenaturallytalkindifferentcircumstances,isconsideredastheexternalrealizationofanunderlying competence.Theperformancefacetoflanguagemaycontainhesitations,mistakes, orspeechfragments,whereascompetenceisviewedasintact,reflectingthesystemofformalprinciplesknownby“anidealspeaker-listener,inahomogenous speech-community”thus“unaffectedby[performancelimitations]”(Chomsky, 1965,p.3).Werejectthisdichotomysinceforus,whatpeopleknowabouttheir languageisnotonlymanifestedinitsuse,itisalso shaped byhowtheyuseitfor differentpurposes.9 Peoplecannotknow,andchildrencannotlearn,alanguage withoutusingit,andthemoreandbettertheyuseit,thericheranddeepertheir knowledgeofit.Besides, how weuselanguageisaffectedbythesocialsituation ofcommunication(athomeorschool,withfriendsorcolleagues,inintimatepersonalcontactorformalsettings).10 Languageusealsodependsontheparticular genreofdiscourse—conversations,jokes,stories,lectures,essays,scientificarticles, etc.Genrehasapowerfulimpactonhowpeoplespeakorwrite.Fromayoungage,
childrenemploylanguagedifferentlyinconversingwithfriends(thegenreof peer talk),whentellingastory(the narrative genre),orwhenexpoundingonatopic (an expository genre).
Comprehension(interpretingwhatapersonhearsorreads)andproduction (formulatingwhatapersonsaysorwrites)arebothfacetsoflanguageuse—though somemistakenlyidentifycomprehensionwithcompetence.Fromearlychildhood throughoutthelifespan,comprehensiontypicallyprecedesandexceedsproduction(Campbelletal.,1982;Keenan&MacWhinney,1987).Peopleunderstand morewordsthantheyproduceintheirownspeechorwriting(theirreceptiveversusproductivevocabulary),andweallunderstandcomplexsyntactic constructionsthatwemightneverourselvesproduce.
Thisbookdealsmainlywithproduction,sincecomprehensionstudiesaretypicallyexperimentallystructuredanddealwithisolatedlinguisticformsratherthan text-embeddedusageinauthenticcontexts.Weareinterestedintheunconsciously internalizedknowledgethatspeaker-writersrecruitwhentheyuselanguageto chat(orallyorbytexting),toargue,ortoanalyzeatopic.Butwealsoconsiderthe factthatpeoplecanbringthisunconsciousknowledgetothesurfacebyexplicit mentionofanalyticalfeaturesoftheirlanguagebymeansof meta-linguistic commentary(Chapter6).Thismighttaketheformofachildsaying“Iknowwhy elephant issuchalongword,becauseanelephantisbigandamouseissmall”; andahigh-schoolstudentwillrecognizethatawordthatsoundsthesamemay havedifferentspellings(Chapter7),differentmeanings,anddifferentsyntactic functions(e.g.,theverbs RODE, ROWED,andthenoun ROAD).11
(5)Literacy:Becomingliterateisanintegralpartoflaterlanguagedevelopment, bothtobeafullyfunctioningmemberofone’scommunityandasafactorthat changespeople’sknowledgeandperceptionoftheirlanguage.Wechallengethe typicaloppositionbetweenlanguageacquisitionasa natural processandliteracy asaninstructionaloutcome:languageisneitherstrictlynaturalnorislearningto readandwritestrictlyinstructional,suggestingthatwemayneedtoreassessthe notionof natural processes.
Individualsraisedinliteratesocietiesoftodayneedtoadapttoconstantly changingcommunicationtechnologiessoastoparticipateactivelyintheirsocioculturalenvironment.Atthesametime,literatepeopleneedtoadapttothe socio-culturalandrhetoricalconventions oftheirculture.12 Inmanytraditional cultures,agoodstorymustcarryamoral;infood-gatheringsocieties,narratorstellingastoryaboutaquestwillprovidedetailsoftheroutetakenbythe participant(s),highlightingthescriptofpathsinexpeditionsaimedatfinding food.Incontrast,narratorsraisedingoal-orientedWesterncultureswilldescribe thesame situationintermsoftheendpointgoaloftheprotagonist(s),showing culture-bounddifferencesinwhatpeopleconsiderrelevantorimportanttoconveytoothers.Thisvariationisalsodevelopmentallymodified,sincethe content oftextsproducedbyyoungerchildreninagivensocietydiffersfromthatoftheir
elders,affectedbothbytheirsharedsocio-culturalbackgroundandbythecognitiveboundariesoftheirworldknowledge.Weshowthat,withage,narratorsshift tomoreabstractandesoterictopics,forexamplebydescribingconflictinterms ofphysicalfightingtodisagreementsinprinciple,bytalkingabouttheftofconcretepossessionstoplagiarizingofideas.Andwealsoqueryhowsuchvariation isaffectedbydifferentrhetoricaltraditions(ContinentalversusAnglo-American, say)thatshapelanguageuseforacademicpurposesinthecontextofglobalization andthehomogenizingimpactoftheinternet.13
(6) Filteringbylanguage:Languagedevelopmentis filtered bythesetoflexicalandgrammaticaloptionsprovidedbytheparticularlanguagethatisbeing acquired(Berman&Slobin,1994,pp.517–533).LearnersofEnglishfaceadifferenttaskfromlearnersofthesameageandbackgroundacquiringHebrewor Spanishasafirstlanguage.Thisdoesnotmeanthatitismoredifficulttobecome anativespeaker inonelanguagethananother;onthecontrary,thepathtobecominga proficientspeaker inone’sfirstlanguagefollowsasimilartimelineinZuluor Portuguese,inGermanorTurkish.Butthewayspeakersformulatetheirideasin thedomainsofourconcernhere(tellingastoryorajoke,arguingaboutthecurrentstateofaffairs,orrelatingtofuturepossibilities)willdependontheparticular lexicalelementsandgrammaticalstructuresoftheirnativelanguage.
Theideaoffilteringcanalsorefertoanindividual’sperspectiveinusinglanguage indifferentcircumstances.Thesituationswetalkorwriteaboutdonotpresent themselvestousaspre-encodedverbally.The same experiences,events,andideas arefilteredbyspeakers’worldknowledgeandtheperspectivetheyselectfortalking aboutagivenstateofaffairs.Twopeoplemightrespondcompletelydifferentlyto beinginisolationduringtheCOVID-19pandemic:SpeakerA:“Itwasawelcome time-outfromthehassleandbustleofmyordinarylife”;SpeakerB:“Itsentme intoastateoftotalclaustrophobia.”Besides,howweencodetheworldverbally dependsonthe linguisticchoices wechoosetomake.Thisisbecause“different lexico-grammaticalchoicescanbemobilizedtorealizethesamerhetoricalgoals equallyconvincingly”(Chang&Schleppegrell,2011,p.148).Peoplecananddo usedifferentwordsandgrammaticalconstructionstoexpressthesameidea.14
Apuzzlehereishow,ifatall,languagedevelopmentisaffectedbywhethera languagehasdedicatedgrammaticalmeansformarkingagivenconceptualdistinction.Forexample,Englishhastwodifferentformsfortalkingaboutsituations thatareinprocessatthetimeofspeakingasagainsthabitualstatesofaffairs:compare‘she istalking Russian/she talks Russian’(Chapter3).ButnotallEuropean letaloneSouth-EastAsianlanguagesmakeanovertdistinctionbetweenthetwo. Thesameistrueofthedifferencebetweenhypotheticalandcounterfactualconditionalsentences: Ifyoutriedharder,youwouldsucceed/Ifyouhadtriedharder, youwouldhavesucceeded (Chapter4).Doesthismeanthatspeakersofsomelanguagesdonotunderstandthedifferencebetweenwhatisgoingonrightnowor whatisgenerallytrue?Orbetweenapossibilitythatcanstillberealized(youcould
stillsucceed)andonethatisnolongerpossible(youdidn’ttryhardenoughsoyou didn’tsucceed)?Wedoubtthatthisisso.Ontheotherhand,“ifalinguisticformis highlyaccessible,itsfunctionaldevelopmentmaybeaccelerated”(Slobin,2001,p. 624),sothathavinganovertlyavailableformmaymakeagivendistinctionconceptuallymoresalientforspeakersingeneral.Hereweareleftwithwhatwefind tobestillalargelyunresolvedpuzzle.
Slobin’spath-breakingstudyonuniversalandparticularinlanguageacquisition (1982),comparingthelinguisticperformanceofchildrenaged2to4years,native speakersoffourdifferentlanguages(English,Italian,Serbo-Croatian,Turkish), showedthatthe2-year-oldswereallalikeintheirverbalabilities,andclearlyless proficientthantheolderchildren.YetallthespeakersofEnglishwerelinguisticallymorelikeoneanother,andmorelikeadultEnglishspeakers,thanwerethe Italian,Turkish,or(then)Serbo-Croatians.Thisinsighthasledustoavoidan Anglo-centricbiastoarguethatthefactorsofage(development)andtargetlanguage(typology)interactacrossthelifespaninmovingfrominitialtoadvanced statesoflinguisticknowledgeandlanguageuse.
Thechildrenandyoungpeoplethatpopulateourbookaregenerallyso-called mainstream studentsraisedinIsrael,theU.S.,andSpain,althoughthroughoutwe alsogiveexamplesfromotherlanguages.Theyaretypically-developingchildren andadolescents,whodonotsufferfrominternaldisordersorlanguage-related physicaldisabilities.Werecognizethecriticalimportanceofatypicaldevelopmentforsheddinglightonlanguageknowledge,development,anduse(Thomas &KarmiloffSmith,2003).Butthepresentvolumewouldhavedoubledinsizehad wegiventhisdomainitsdue.
Finally,thebookisdedicatedtothelateAnnetteKarmiloff-Smith—colleague, teacher,andfriend.Ourapproachislargelyinspiredbyherideasondevelopment, hercontributionstoneuro-constructivistthinking,andherneithernativistnor empiricistconceptualizationofhumancognition.Sheissorelymissedbyusboth andwouldhavebeenaninvaluableconsultantatallphasesofourworkonthis book.
Notes 1. TakenfromthetitleofKarmiloff-Smith’s(1986a)chapter‘Somefundamentalaspects oflanguagedevelopmentafterage5.’
2. ThetermwascoinedbyNoamChomskyinhis1980“replytoPiaget.”
3. Thenaturalsciencesdistinguishbetween ontogeny—theoriginanddevelopmentof anorganismusuallyfromthetimeoffertilizationoftheeggtoadulthoodacrossthe lifespan—asagainst phylogeny—thestudyoftheevolutionarydevelopmentofgroups oforganismsbasedonsharedgeneticandanatomicalcharacteristics.Thisperspectiveisbeyondthescopeofourundertaking,nordowetakeintoaccount diachronic linguistics,concerningchangesinagivenlanguageacrosstime.
4. Thisledto(re)namingthefield‘languageacquisition,’intheviewthatlanguageis acquirednaturally,withoutspecialinstruction,ratherthan‘languagelearning,’which impliessomeinstructionorconsciouslearningratherthanspontaneousprogression ofknowledge.
5. Executivefunctions arethecognitiveprocessesnecessaryforselectingandsuccessfullymonitoringbehaviorsthatfacilitatetheattainmentofchosengoals,intheform ofmentalabilitieslikeworkingmemory,flexiblethinking,andself-control.
6. Acrossthebook,wherechronologicalagesarementioned—e.g.,12months,age3;6,15 to16years—thesearegrossapproximationssomewherearoundtheaverageormedian agerangeforagivenphenomenonasdocumentedinresearchonlanguagedevelopmentaroundtheworld.Whenmeanageincludesyearandmonths,thetwovaluesare separatedbyasemi-colon(e.g.,6;8 = sixyears,eightmonths).
7. ThetermenteredEnglishfromOldFrench grammaire viaLatinfromGreek grammatikē(tekhnē) ‘(art)ofletters,’from gramma, grammat- ‘letterofthealphabet, thingwritten,’withgrammaroneofthethreepillarsofMedievalscholarship,together withrhetoricandlogic.Tothisday,manyidentifyitwith‘correctusage’(whateverthat means),takingtheclassicallanguagesasmodels,andconsideringthevernacularsof everydayspeechbeneaththedignityofformalstudy.Inmodernlinguistics,incontrast, grammar referstothe structural aspectsoflanguage,howlinguisticelementsarebuilt upintolargerunits,frommorphemestowordsandontophrases,clauses,andupto fullsentences(again,whateverismeantbycommontermslike‘word’or‘sentence’). Infact,thenotionof sentence islargelyanartifactofformalgrammarsorlinguistic scholarshipratherthanaviableconstructforactualusageinspeech(Halliday,1989) oreveninwriting(Chafe,1994).
8. Forexample,theEnglishword elephant cantakethegrammaticalinflection-s toform itsplural,andthederivationalsuffix -ine changingitfromanountoanadjective elephantine.
9. Thisdichotomyhasbeenqueriedonseveralgrounds.ThesociolinguisticWilliam Labov(1972a)remarks:“Itisnowevidenttomanylinguiststhattheprimarypurpose ofthe[performance/competence]distinctionhasbeentohelpthelinguistexcludedata whichhefindsinconvenienttohandle….Ifperformanceinvolveslimitationsofmemory,attention,andarticulation,thenwemustconsidertheentireEnglishgrammarto beamatterofperformance”(pp.109–110).
10. Someresearchers(e.g.,DeBusser&LaPolla,2015)gosofarastoarguethattheextralinguisticenvironmenthasaneffectnotonlyonhowlanguageisusedindifferent circumstances,butalsoonthegrammaticalstructureoflanguages.
11. Wordsthatsoundthesamebutarespelleddifferently,like road, rode, rowed,or write, rite,and right,arecalled homophones;wordsthatarespelledthesamebuthavemore thanonemeaning,like watch, adder, battery,arecalled homonyms.
12. Unlikeinancienttimes,weusetheterm‘rhetoric’initscontemporarysense,toapply tothelinguisticandstylisticresourcesutilizedbyaspeaker/writerfororganizingand deliveringapieceofdiscourse.
13. Aleitmotifofourworkisthedistinctionbetween grammaticalforms asrequiredby thestructuralconstraintsofagivenlanguage(itsphonology,morphology,andsyntax)
andrhetoricaloptionsthatpeopleselectoutofthisrepertoireofformswhenexpressing themselvesinspeechorwriting.
14. PerhapsLewisCarrollputthisbestin ThroughtheLookingGlass (1871,pp.364–365).
“‘WhenIuseaword,’HumptyDumptysaidinratherascornfultone,‘itmeansjust whatIchooseittomean—neithermorenorless.’
‘Thequestionis,’saidAlice,‘whetheryoucanmakewordsmeansomanydifferent things.’
‘Thequestionis,’saidHumptyDumpty,‘whichistobemaster—that’sall.’”
Brainsforlanguage(andeverythingelse) Thelittleboyisnearly14monthsold.Hisparentsareecstatic:Juantalks!Heproducedafewsoundssqueezedtogether,somethinglike‘awhe’thatsoundedlike agua,theSpanishwordforwater.Yethisparentsaresoconvincedoftheinevitabilityoflanguagedevelopmentthatifsomemonthspasswithoutnewoutputsfrom theirchild,theywillbegintoworry.Infact,Juanwasabletocommunicatewith othersevenearlier:hecouldshowhewantedtoreachanobjectbypointing,he couldbabbleusingmeaninglessbutlanguage-likesyllables,andwouldshowanger orpleasurebyfacialexpressionsandbodylanguage.But,asparentsknowintuitively,linguisticdiscourseissomethingelse.Indevelopingalanguage,children appropriateasystemofelementscalledspeechsoundsthatcombineinendlesswaystoconveymeaninginincreasinglydiversecontexts.Communication enabledbylanguageisatoncehighlyregulated(noteverycombinationofelementsismeaningful)yetopen-ended:peoplecantalkandwriteaboutanything conceivable.
Childrenlearnearlyonwhatcombinationsaremeaningfulintheambientlanguageand,overtime,cometouselanguagefordifferentpurposesandindifferent scenarios.Thistransformsthewaypeoplethinkanduselanguageinavirtual cycle,an‘iterativebi-directionalinteractivity’betweenthinkingandusinglanguage.1 Learningalanguagemeansenteringthiscycle.Beforetheystartschool, normallydevelopingchildrenhavemasteredmuchofwhatthereistoknowabout theirlanguage.2 However—andthisisthe leitmotif ofthisbook—theywillcontinuebuildingandcruciallychangingthisknowledgeuntiltheirteenageyearsand beyond,inconstantinteractionwithothers.
Whatdoparentsconsidertheirchild’s firstword?Anysequenceofsounds s/heproducesthatresemblesaknownword,liketheEnglish doi for‘doggie,’ theSpanish wawa for agua ‘water,’ortheHebrew aba for‘Daddy,man.’These expressions—thoughfarfromconventionaladulttermsinpronunciationorthe entitiestheyapplyto—reflecttheuniquelyhumanabilityofmatchingstrings ofsoundstomeanings.Thishugecognitiveandcommunicativeleapoccursat aroundage1year,from8–9monthstoaround18months,among typicallydeveloping children.(Forouruseoftheterm‘age,’seenote4inthePrologue.) Thismarksthebeginningofalongandfascinatingjourneyconnecting words toworlds,firstreferringtoobjectsineverydaysurroundings,like kabo ‘pig’in theKalulilanguageofPapuaNewGuinea.Astheygrowolder,thewaychildren
talkchangessimilarlyindifferentcultures:theirpressed-togethersoundsbecome increasinglylikewordsintheambientlanguage(s);andbyage2years,children willcombinetheseitemsintoutterancesthatexpressdesires(gimmeball, more milk),complaints(soretummy),anddescriptionsofstatesofaffairs(allgonebaby milk, thassabigball).3
Bylatepreschool,childrenwillbeabletostringutterancestogethertotellstories (Ronnyhitme,soItoldtheteacher,andshesaidhe’sanaughtyboy),subsequentlyto discussabstractpossibilitiesinthefuture(Idon’tknowwhenDaddywillcome,but hetoldmehe’dbringmeapresentfromhistrip),touselanguageformetaphor,for writingandreading,andthemanyotheractivitiesperformedbyliteratemembers oftheirspeechcommunity.
Thesethreefacts—(i)emergenceofspeechatsimilaragesindifferentlanguages andpartsoftheworld,(ii)unstoppable(non-pathological)developmentinapredictabledirection—fromwordsviaword-combinationstoextendeddiscourse, and(iii)useofspeechthatisattunedtoaspecificlanguageenvironmentandto particularcommunicativeintentions—indicatethatlanguagedevelopmentispart ofourmaturationashumanbeings,thatithasageneticunderpinning.Yet,wewill argue,languagedevelopmentisatthesametimestronglydependentontheenvironment.Anditalsodependsonthe task facingalanguageuser—quarrelingwith aclassmate,takingpartinfamilyget-togethers,tellingastory,orwritinganessay.
Elizabeth Bates(1979) putitclearly:“Theformofthesolution[totheproblemofbehavioraluniversals]isdeterminedbytheinteractionof three sources ofstructure:genes,environment,andthenatureofthetask”(p.17).Genesand environmentprovidethematerialandrelevantinputstosolvingthetask,while socio-cognitivegrowthandexperiencewithlanguageuseprovidetherestofits solution.
Ourview,then,encompassesbothinternalandexternalfactorsimpingingon thedevelopingorganism.Thegoalofthisbookistoshedlightonwhenand howtheenvironmentinfluenceslanguagedevelopmentandhowgenetic,environmental,andtask-relatedfactorsinteractbeyondtheearlystagesoflanguage acquisition.
Afterreadingthischapteryouwillbeacquaintedwith:
• ourmotivesfortakinganeurologicalperspectiveonlanguage,tounderstand thegeneticandneurologicalcapacitiesunderlyinglanguageuseanddevelopment,bymeansofashortjourneythroughthepartsofthebrainthatlearn language;
• howresearchershavearguedforthebiologicalcomponentoflanguage acquisition—suchasbyprovingtheexistenceofa criticalperiod,anagelimit forthecapacitytoacquirelanguagenatively;
• thefactthatmuchofthebrain’sfunctioningisnotaccessibletoconscious control,byconsideringtheprocessesof priming and relearning;
• theneuro-constructivistapproach,asadistinctiveframeworkinneurobiologythatsupportsourviewoftherelationshipbetweengeneticendowment,brainstructuring,andexperience;
• themainpropertiesofthedevelopingbrain:(i)itsincreasingspecialization; (ii)itsgrowingcapacityforparallelprocessing;(iii)itsfunctioningasan anticipatorymachinebasedonsensory-motorexperience;(iv)itshierarchicalorganizationenablingcognitivecontrol;and(v)itslong-lastingcapacity forlearning,acharacteristicthatmotivatesourinterestinlaterlanguage developmentswellbeyondearlychildhood;
• thecrucialchangesthattakeplaceinlearninganduseoflanguageinfour distinctperiodsoflife:frombirthto3years,whenchildrenmoveintolanguage;age4to5years,asapsycholinguisticfrontierbetweenearlyandlater languageacquisition;age6to12,whenchildren‘goconventional’;andage 13to19,whenyoungpeoplebecomeautonomousand(sometimes)creative individuals.
1.1 Aneurobiologicalperspectiveonlanguage In1969thepsychologistEricLennebergproposedthat“thedevelopmentof languageinchildrencanbestbeunderstoodinthecontextofdevelopmentalbiology”(p.635).Headvancedthehypothesisofalimitedtime-spanin whichbrainsareuniquelyattunedtoacquiringlanguage(orlanguagesinthe caseofearlybi-ormulti-lingualism).Hedefinedthisasa criticalperiod fornative-likeacquisitionoflanguage,occurringduringthefirstfewyearsof life.Subsequentresearchhasextendedtheideaofbiologicaldeterminismin relationtoacriticalperiodfornativelanguageacquisitioninvariousways (Knudsen,2004).
ThediscoveryofGenie,theferalchildwhohobbledintoaLosAngelescounty welfareofficein1970,providedunhappyevidenceforLenneberg’s criticalperiod hypothesis.Atage13,havingbeendeprivedoflanguageinput,Geniedidnottalk, andeffortstoteachhertodosoprovedlargelyfutile(Curtiss,1977).Othersources ofevidencealsopointtoacriticalperiodafterwhichnativelanguageacquisition isinhibited(J.L. Locke,1997).ThepsycholinguistElissa Newport(1990) applied twosuchmethodstotestbiologicaldeterminism.Sheexaminedwhathappens tothelanguageofdeaforhearing-impairedchildrenwholackearlyexposureto spokenorsignedlanguage;4 andsheobserveddevelopmentofasecondlanguage (L2)inchildrenwholackedearlyexposuretotheL2.Heranalysesofhowlanguage develops—inchildrenexposedtoAmericanSignLanguage(ASL)frombirthcomparedwiththosewholearnitonlylater,andinchildrenwhoacquireEnglishasa nativelanguagecomparedwiththosewhostartlearningitlaterinlife—revealed whatmostofushaverealizedatsomepointinourlives:ifonestartslearninga
newlanguageafterschool-age,itwillbeverydifficulttobetakenasanative,even afteryearsofstudy.
Adifferentpictureemergesfromathirdwayoftestingclaimsforacritical period:byexaminingtheconsequencesof braindamage.Theso-called‘lesion method’isatraditionalresearchstrategyinneurologyandneuropsychology.5 Analyzinghowmentaloperationsbreakdownafterbraininjuryallowsresearchers toidentifytheoperationsthatunderliecognitiveprocesses.Whenappliedto brain-damagedadults,thisilluminateshowbrainstructuresrelatetofunctions withintheneurocognitivesystem(Stilesetal.,2012).Forexample,autobiographicalmemoriesfromanindividual’spersonalhistory,whicharesupportedbybrain structuresthatunderliestorytelling(asdiscussedinChapter 2),arelimitedin brain-damagedpatientstomemoriesacquireduptoorshortlybeforetheonset oftheirinjury(Young&Saver,2001).
Whenappliedto children,thelesionmethodmayshedlightonquestionsof neurocognitiveplasticityanddevelopmentaladaptation(Stilesetal.,2012).If researcherscandemonstratethatotherareasofaninjuredbraincanmakeupfor thedamageincurred only whentheinjurytakesplaceatanearlyage,theywill haveprovedthatthereisacriticalperiodlimiting compensation,asasignofbrain plasticity.
Whenlesionsoccurinspecificareasinthelefthemisphere(LH)beforeor justafterbirth,atimeofspecialreadinessforacquiringlanguage,childrenshow markeddeficitsinacquiringtheirinitialvocabulary(Stilesetal.,2005).Theseearly impairmentsarenolongernoticeablebyaroundage5years,suggestingthatthe immaturebraincancompensateforsuchdeficits.Incontrast,adultswithdamage insimilarlanguageareasshowconsiderablelanguageimpairmentwithvariable, oftenatbestonlymoderate,recovery(Damasio,1992; Lazar&Antoniello,2008).
RajaBeharelle(RajaBeharelleetal.,2010)comparedright-handedadolescents whohadsustainedpre-orperinatalleft-hemispherestrokeswiththeirintactsiblings.Theyusedfunctionalmagneticresonanceimaging,fMRI,toexaminethe brainactivityofparticipantsperformingacategoryfluencytask,i.e.,namingitems inacertaincategory(likeanimalsorfoods).Healthyadolescentsshowedstrong activityinleftandlessinrighthemisphere(RH)structures.Incontrast,onthe sametask,patientswithearlyinjurymobilizedactivityeitherintherightorin bothhemispheres,withmarkedindividualdifferences.Itseemsthatourbrain findsdifferentwaystocompensatefordamage.
Theseandrelatedfindingsunderminetheconstrainingroleofthecriticalperiod ofbrainplasticity.Itturnsoutthatlanguagelearningisenabledbyabiological readinessatseveralanatomicalsites,andthatthislearningcapacityisimprovedby therequiredexperienceattherighttime.Wherethisisnotthecase,asinlateexposuretosignlanguagefordeafchildren,oranewtargetlanguageforL2learners, thebrainaltersitscapacitytolearnfromexperience.Butthiscapacitydoesnotdisappear:it changes.L2learnersmaynotattainanative-likelevelofcommand,but
theyarestillcapableoflearninganotherlanguage,althoughwithmarkedindividualdifferences.Besides,whentheanatomicalsiteinchargeofenablinglanguage learningsuffersdamageduringthecriticalperiod,otherbrainsitesarerecruited toaccomplishthelanguage-learningtask.Thatis,thereareotherpotentialbrain organizationsforimplementinglanguageafterearlyLHbraininjury,afactthat reflectssubstantialplasticity.
Theseandrelatedevidenceforearlyplasticityofthebraininthefaceofchangingenvironmentalinputhasledresearcherstotalkabouta sensitive ratherthan acriticalperiodinemergingneuralorganizationandassociatedbehaviorduring thelifespan.InSection 1.4.1,weshowhowlearning-associatedinputshapespatternsofconnectivityandrefinestheneuralsystemsinthebrain,makingthem morespecializedforprocessingparticularinputs.Aslearningproceeds,patterns ofconnectivityintensify,andfunctionswithinaregionbecomemorespecifically defined.Theendofthesensitiveperiodmaythussignaltheendofthelearning processitself,thestabilizingofaneuralsystemonceexpertiseisacquiredinaskill area(Johnson,2005).
CurrentresearchonL2learning,basedonmorethantwomillionlearners ofEnglishasasecondlanguage,proposesextendingthesensitiveperiodtoage 17–18(Hartshorneetal.,2018).ThestudyalsoindicatesthatearlyL2learnersare notsuperiortoadultlearnersoverall,rathertheycopebetterwithdifferentfacets ofthetask:earlylearnersoutdoadultsinpronunciation,butadultsarebetterwith syntacticfeatureslikewordorder.Thisdifferencehastodowithdifferentialattentiontoelementsofthenewlanguage:childrengraspmultiwordstrings,guidedby theirintonation,whereasliterateadultstendtoprocessL2inputwordbyword. Theadvantageofearlylearners,then,isnotsimplyduetothedeclineofasensitive period,butalsotodifferencesinhowtheylearn(Havron,2017).
Then,too,theadventoftechnologiesthatenableresearcherstolookinsidethe livinghumanbrainhasradicallychangedthewaywethinkaboutbraindevelopment.Theydemonstratethatnoteverythingthatiscrucialaboutlanguagereaches maturationduringtheearlyyears,callingintoquestiontheconvictionofthebulk ofresearchonchildlanguagethattothisdayislargelyconfinedtothespeechof infants,toddlers,andpreschoolchildren,oftennolaterthanage3years(Brown, 1973;Weissenborn&Ho¨hle, 2000).Againstthisbackground,wenowproceedto howthefunctioningofourbrainsupportslifelonglearninganduseoflanguage.
1.2 Unconscioussteering Althoughourbrainregulatesthe typeofattention wepaytotheworld,controlof thisattentionusuallyescapesconsciousaccess.Forexample,wedonotattendto soundsthatourbraincannotprocess,althoughtheymaybeaccessibletoourdog orcat.Similarly,adultspeakersofEuropeanlanguagescannotprocesstheclicksof
Bantulanguagessincetheyarenotpartoftheirworld,buttheymaybediscernable toinfantsbornintonon-Bantuspeakingenvironments.6 Theworldsthatweexperiencedependonthetypicallyunconsciousprocessingcapabilitiesofourbrain, whichchangeasaconsequenceofdevelopmentanddifferinginputsfromtheenvironment.Everydomainofexperience—speech,space,time,number—undergoes bothmacroandmicrochangesinprocessingcapabilities;andsodoestheworld asweperceiveandunderstandit.
Imagineyouhavereadastoryaboutrabbitsandarethenaskedtowritetheword hair.Youwouldlikelywrite HARE.Readingaboutrabbits(interactionwithinput fromtheenvironment)haspreparedyourbraintofocusonthe“rabbit”meaning of hare,activatingawordpronouncedthesamebutspelleddifferentlyfromthe oneelicited.Orimagineyouoncelearnedthelyricsofasongbyheart,butnow canonlyrememberabitofit.Inabilitytoretrievesomethingdoesnotmeanthat itiscompletelygonefromyourlong-termmemory.Lateron,relearningitwill bemuchquickerbecauseyourpreviouslearningofthesonghasmodifiedyour currentabilitytolearnit.
Therabbitandthesongexamplesillustratethepsychologicalphenomena of priming and relearning (Bargh&Morsella,2008). Primingistheactivation ofcertainassociationsandmemory,evenwithoutawarenessofwhatevokes them;relearningreferstothefacilitatingeffectofpreviouslylearnedmaterial. Bothdemonstratehowspecificinputfromthesurroundingsmaychangefurther perceptionofandinteractionwiththeenvironment,andhowthesechangesoccur.
Asaninstanceof priming,theactivationof HARE insteadof HAIR forreaders oftherabbitstorycameaboutwithoutawareness.7 Similarly,for relearning in thesongexample,althoughthelearningprocessingwasexplicit(throughsuccessiverehearsals),whatremainedofit(retainedinlong-termmemory)wasstored implicitly.Partofwhatwedo,think,andfeelcanbebroughtintoconsciousnessand,insomecases,canbenamedandverballyexplained.Yetmostofwhat weknowaboutourlanguagehasnotbeenexplicitlytaught,anditsuseisnot consciouslycontrolled.
Ourbrainprocessesdifferentkindsofinput—music,pictures,writtenand spokenlanguage—throughoursenses.Andwedependonthisprocessingfor understandingtheworldandourselves.Butthebrain“runsitsownshow,”soto speak.Decision-making,planning,predicting,learning,andalsoforgettingrun deepinourneuralinnercosmos,accountingforthewaywemoveinspace,grasp objects,solveproblems,approachpeople,and—ourmainconcern—uselanguage totalk,read,andwrite.Weprocessfeaturesofourlanguagethatareimplicitly depositedandstoredinourbrainafternon-consciousrehearsal.Eagleman(2011) putitwell:“Yourconsciousnessislikeatinystowawayonatransatlanticsteamship, takingcreditforthejourneywithoutacknowledgingthemassiveengineering underfoot”(p.4).
Consider,forexample,acommonbehaviorduringlanguageuse.Whenpeoplechat,tellastory,orgivedirections,theyoftenmakechangesintheirspeech, whetheraword(1)orpartofasentence(2).
(1) Turnrightatthe first thethirdcorner
(2) Turnrightthen don’tturnright betternot
These self-repairs usuallyimprovethemessagethatspeakersareattemptingto conveyandtheresultingexpressioniscomprehensible,eventhoughtheadjacentstringsofwordsmaynotstrictlyfollowtherulesofgrammar—asin(1) and(2).
Peopleareusuallysurprisedwhentheyheartherepairstheyhavemadeand arehardputtoexplainthem,althoughtheycanidentifythemwhenaskedto judgewhatotherpeoplesay.Yetlinguistsandpsychologistshavefoundhidden treasuresinstudyinghowspeakersidentify,produce,andexplainself-repairs, correctingtheirspeechoutputastheygoalong.From6to7yearsofage,childrencan detect differentkindsofspeechrepairs,butexplicitcontrolandprovisionofverbalexplanationsfortheserepairstakeuntiladolescencetoacquire. Withage,childrendevelopincreasingawarenessaboutdifferentaspectsoflanguage(seeChapter 6).Forexample,theywillrecognizethat,inthecaseof hair/hare,thesamestringofsoundshastwodifferentmeaningsandisspelled intwodifferentways.Yetnumerousfeaturesremaininaccessibletoconsciousness,whilesomerequiretheinterventionofthewrittenmodalitytobeaccessed. InChapters 6 and 7,wediscusshowformalinstructionmodifieschildren’slinguisticinput,enablingthemtoreflectonlanguageandpromotingmetalinguistic understanding.
1.3 Thebrainthatdoeslanguage—alongwitheverythingelse
AlkmaionKrotonietes,Pythagoras’syoungdisciple,wasthefirsttosuggestthat thebrainisthelocusofourmind,whereasAristotlebelievedthehearttoplaythis role.Nowadays,scholarsandlay-peoplealikerecognizethatwethinkwithour brains.8 Wecanevenexplainwhycertaintasks—likeproducingasentencewith severaldependentclausesorcomposinganessaythatmakessensefrombeginning toend—aremoredemandingthanothers.
Whatarethepropertiesofthisdevicethatgeneratesthehumanmind?How doesit do language?AndhowdothesepropertiesexplainwhatThomas Suddendorf(2013) definesas“thepeculiarityofthehumanmind:…ouropen-ended capacitytocreatenestedmentalscenariosandourdeep-seateddrivetoconnectto
otherscenario-buildingminds”(p.276).Toaddressthesequestions,wealignwith theneuro-constructivistviewthatunderstandingcognitivedevelopmentrequires knowinghowtheneuralsubstratasupportingmentalrepresentationsareshaped (Westermannetal.,2006).
Recentdecadeshaveseenimpressiveadvancesintechniquesforpinpointingthe structuralandfunctionalcharacteristicsofthebrainatdifferentspaceandtime scales,atrestandwhenperformingvarioustasks.Someapproaches,underthe umbrella-term neuro-emergentism,addressdevelopmentalconcernsbymeansof imagingprocedurestoclarifythebasesoflanguageandcognitioninthebrain (Hernandezetal.,2019).Ofthese,neuro-constructivismfocusesonfactorsthat impingeontheemergenceanddevelopmentof representations inthebrain—as patternsofneuralactivationthatcontributetotheindividual’sadaptivebehaviorin theenvironment.Thismeansthatdevelopmentofneuralsystemsisconstrainedby multipleinteractingfactors,bothintrinsicandextrinsic,thataffectthedeveloping organism(Westermannetal.,2006).
Althoughcastinadifferentterminology,thisconceptualframeworkechoesa majorthemeoftheSwissepistemologistJeanPiagetbackin 1936,thatcognitive development—thedevelopmentof intelligence inPiagetianterms—proceedsas aninteractionbetweenbiologicalendowmentandenvironment(Piaget,1952). ForPiaget,cognitivestructuresareneitherinnatenortheunconstrainedresultof experience;theyareconstructedinteractively.Twobiologicalprocesses,present ineverylivingorganism—assimilationandaccommodation, andtheequilibrium betweenthem—explainbothcognitivegrowthandcognitivestability.
• assimilation istheprocessbywhichanaspectoftheenvironment(aperturbation,anewobject,ornovelsituation,say)isintegrated,combinedwith, orabsorbedintoanexistingscheme(physiological,metabolic,muscular, sensorimotor,perceptual,reflexive,etc.);
• accommodation istheprocessbywhichaschemeorstructure(physiologicalorcognitive)ismodulatedortransformedtosubsumeanasyetnot assimilatedaspectoftheenvironment;
• equilibration istheprocessbywhichagivencognitiveorbiological organization—asaresultofprocessesofassimilationandaccommodation— reachesanewformoforganizationalstability.
Neuro-constructivismrecapturestheinteractionsproposedbyPiaget.Itconceives ofdevelopmentasapathor trajectory shapedbyinteractingconstraintsatdifferentlevelsoftheorganism,fromgenestoculturalsettings.Neuralactivityyields behaviorthatmodifiesthephysicalandsocialenvironment,leadingtonewexperiencesandinvokingnewpatternsofneuralactivity.Cognitivedevelopmentcan
becharacterizedinessenceas mutuallyinducedchanges betweenthebrainand themind.
Thisviewcallsintoquestiontwoideasrootedintwentieth-centurylinguisticsandcognitivescience:David Marr’s(2010) notionofindependentlevelsof descriptionandtheideathatlanguagelearninganduseissupportedexclusively byprespecifiedbrainregionsthatrespondselectivelytoverbalinput.
Marr,aBritishneuroscientistwhoworkedonvision,conceiveditasaninformationprocessingsystemthatcanonlybeunderstoodifanalyzedatthefollowing threelevels:
• computational:whatdoesthesystemdo,whatproblemsdoesitsolve?
• algorithmic(orrepresentational):howdoesthesystemdowhatitdoes,what representationsdoesituse,andwhatprocessesdoesitemploy?
• implementational(orphysical):howisthesystemphysicallyrealized,what neuralstructuresandactivitiesimplementthesystem?
Marr’slevelsofanalysisunderliethecommondistinctionbetweenbehavioral, psychological,andbiologicallevelswhich,inmarkedcontrasttoaneuroconstructivistview,haspermeatedthestudyoflanguagedevelopmenttothis day.
In 2012,thirtyyearsafterthepublicationofMarr’s Vision,hiscoauthorTomaso Poggioaddedtwofurtherlevelstoexplainhowprocessingsystemsfunction:a leveloflearninganddevelopmentandalevelofevolution. Poggio(2012) argued thatitisnotenoughtoknowhowtransistorsandsynapseswork,andwhichalgorithmsareusedforcomputations;wealsoneedtounderstandhowachildcan learnthealgorithmsandhowtheselearningmechanismsemergedinthecourse ofevolution.Developmentintheindividualandevolutioninthespeciesmust bothbetakenseriouslytounderstandthefunctioningofend-stateorganisms,or ofanyprocessingsystemforthatmatter.
Thesecondideathatisqueriedbyneuro-constructivismisofspecificareasof thebrainthatsupportlanguage.Fromaneuro-constructivistview,circumscribed regionsofthebrainhaveabiologicallydetermined readiness toprocessacertain input(inthiscaselanguage)ratherthanafixedprespecifiedfunction(Elsabbagh &Karmiloff-Smith,2006).Withdevelopment,thankstointeractionwithspecific inputs,thisinitialreadinessbecomesincreasinglyspecialized.Again,development isnecessarytounderstandanend-state,inthiscase,thespecializationofcortical regionstoperformaparticularfunction.
Belowwediscusstheanatomicalandfunctionalpropertiesofourinformation processingsystemandillustratehowthesepropertiesmayvarydevelopmentally. Figure 1 displaysthebrainsiteswementionintherestofthischapter,asdetailed inGlossaryIandII.
