Musicandverbalability–atwinstudyofgeneticandenvironmentalassociations

LauraW.Wesseldijk1,2,*,ReynaL.Gordon3,4,5,MiriamA.Mosing1,6,FredrikUllén1

1DepartmentofNeuroscience,KarolinskaInstitutet,Solnavägen9,SE-17177Stockholm,Sweden2DepartmentofPsychiatry,AmsterdamUMC,UniversityofAmsterdam,Meibergdreef5,1105AZAmsterdam,TheNetherlands3DepartmentofOtolaryngology-Head&NeckSurgery,VanderbiltUniversityMedicalCenter4DepartmentofPsychology,VanderbiltUniversity5VanderbiltGeneticsInstitute,VanderbiltUniversityMedicalCenter6DepartmentofMedicalEpidemiologyandBiostatistics,KarolinskaInstitutet,Nobelsv12A,17177Stockholm,Sweden*Correspondingauthor:L.W.Wesseldijk,DepartmentofNeuroscience,KarolinskaInstitutet,Solnavägen9,SE-17177Stockholm,SwedenT:+31620251909.E-mail:laura.wesseldijk@ki.seThelasttwoauthorsshareseniorauthorship.

Theauthorsdeclarenoconflictsofinterestwithrespecttotheauthorshiporthepublicationofthisarticle.

Acknowledgements:ThepresentworkwassupportedbytheBankofSwedenTercentenary

Foundation(M11-0451:1),theSvenandDagmarSalénFoundationandtheMarcusandAmalia

WallenbergFoundation(MAW2018.0017).WeacknowledgeTheSwedishTwinRegistryforaccess

todata.TheSwedishTwinRegistryismanagedbyKarolinskaInstitutetandreceivesfunding

throughtheSwedishResearchCouncilunderthegrantno2017-00641.ReynaL.Gordonwas

supportedbyfundingfromtheNationalInstituteonDeafnessandOtherCommunicationDisorders

andtheOfficeoftheDirectoroftheNationalInstitutesofHealthunderawardnumbers

K18DC017383andR01DC016977.Thecontentissolelytheresponsibilityoftheauthorsanddoes

notnecessarilyrepresenttheofficialviewsoftheNationalInstitutesofHealth.

© 2021, American Psychological Association. This paper is not the copy of record and may not exactly replicate the final, authoritative version of the article. Please do not copy or cite without authors' permission. The final article will be available, upon publication, via its DOI: 10.1037/aca0000401

Abstract

Musicalaptitudeandmusictrainingareassociatedwithlanguage-relatedcognitiveoutcomes,even

whencontrollingforgeneralintelligence.However,geneticandenvironmentalinfluencesonthese

associationshavenotbeenstudied,anditremainsunclearwhethermusictrainingcancausally

increaseverbalability.Inasampleof1,336maletwins,wetestedtheassociationsbetweenverbal

abilitymeasuredattimeofconscriptionatage18andtwomusicrelatedvariables:overallmusical

aptitudeandtotalamountofmusictrainingbeforetheageof18.Weestimatedtheamountof

specificgeneticandenvironmentalinfluencesontheassociationbetweenverbalabilityandmusical

aptitude,overandabovethefactorssharedwithgeneralintelligence,usingclassicaltwinmodelling.

Further,wetestedwhethermusictrainingcouldcausallyinfluenceverbalabilityusingaco-twin-

controlanalysis.Musicalaptitudeandmusictrainingweresignificantlyassociatedwithverbal

ability.Controllingforgeneralintelligenceonlyslightlyattenuatedthecorrelations.Thepartial

associationbetweenmusicalaptitudeandverbalability,correctedforgeneralintelligence,was

mostlyexplainedbysharedgeneticfactors(50%)andnon-sharedenvironmentalinfluences(35%).

Theco-twin-control-analysisgavenosupportforcausaleffectsofearlymusictrainingonverbal

abilityatage18.Overall,ourfindingsinasizeablepopulationsampleconvergewithknown

associationsbetweenthemusicandlanguagedomains,whileresultsfromtwinmodellingsuggested

thatthisreflectedasharedunderlyingaetiologyratherthancausaltransfer.

Introduction

Musictrainingandmusicalaptitudeshowpositiveassociationswithperformanceonabroadrange

ofcognitivetasks(Schellenberg&Weiss,2013).Musictrainingiscorrelated,asonewouldexpect,

with performance on tests of music cognition (Ullén, Mosing, Holm, Eriksson, & Madison, 2014;

Wallentin,Nielsen,Friis-Olivarius,Vuust,&Vuust,2010),butcorrelationshavealsobeenreported

with,forexample,visuospatial(Hetland,2000;Sluming,Brooks,Howard,Downes,&Roberts,2007)

and mathematical abilities (Hobbs, 1985; Vaughn, 2000). Attention has also been given to the

associationbetweenmusicandthelanguagedomain(Besson,Barbaroux,&Dittinger,2017;Kraus&

White-Schwoch, 2017; Patel, 2007; Peretz, Vuvan, Lagrois, & Armony, 2015). Music training is

associatedwithmeasuresofverbalmemory(Chan,Ho,&Cheung,1998;Schellenberg&M.W.Weiss,

2013),vocabulary(Morenoetal.,2011;Piro&Ortiz,2009),auditorycognition(Parbery-Clark,Strait,

Anderson,Hittner,&Kraus,2011)andreadingskills(Butzlaff,2000;Morenoetal.,2009).Similarly

tomusictraining,musicalaptitudeshowssmalltomodestpositiveassociationswithlanguagetasks,

includingphonologicalawareness(Anvari,Trainor,Woodside,&Levy,2002;Forgeardetal.,2008;

Jones,Lucker,Zalewski,Brewer,&Drayna,2009;Politimou,DallaBella,Farrugia,&Franco,2019),

reading(Anvarietal.,2002;Forgeardetal.,2008),pronunciation(Milovanov&Tervaniemi,2011),

speechencoding(Mankel&Bidelman,2018)andspokengrammar(Gordon,Shivers,etal.,2015).

Further, several studies comparing musicians versus non-musicians reported speech processing

abilities (likevowelperceptionorpitchprocessing) tobehigher inmusicians (Bidelman&Alain,

2015;Magne,Schon,&Besson,2006;Marie,Magne,&Besson,2011;Schon,Magne,&Besson,2004).

However, associations betweenmusic and language have rarely been tested in large population

samples.

Itcouldbethatmusicandlanguageshareevolutionaryroots(Brown,Martinez,&Parsons,2006;

Kotz, Ravignani, & Fitch, 2018; Wallin, Merker, & Brown, 2000), which would be reflected in

phenotypicaswellasgeneticcorrelations.Forinstance,ithasbeenproposedthatarudimentaryform

of singing communication pre-dated language (Brown, 2017; Dissanayake, 2005;Mithen,Morley,

Wray, Tallerman, & Gamble, 2006). Other theorists have suggested that genericmechanisms for

processingofhierarchicalstructuresinthebrainmayhaveplayedakeyroleintheevolutionofboth

musicandlanguage(Fitch,2017;Fitch&Martins,2014).Yetatpresent,thehypothesisthatlanguage

andmusicshareageneticbasisislargelyunexplored.

Tosummarize,eventhoughassociationsbetweenmeasuresofmusictrainingormusicalaptitude,

ontheonehand,andlanguagerelatedcognitiveoutcomes,ontheotherhand,arewell-replicated,less

isknownabouttheirunderlyingcauses.Inaddition,interventionstudieshavealsofoundsignificant

effectsofmusictrainingonverbalperformanceandneuralprocessingoflinguisticstimuli,providing

indicationsthatmusicandlanguagecouldbecausallyrelated(Chobert,Francois,Velay,&Besson,

2014;Morenoetal.,2009;Yuetal.,2017).Thisevidencehaslargelybeeninterpretedinfavorofa

causaltransferhypothesisofexpertisefrommusictrainingtolanguageskills(seeOPERAhypothesis

by Patel, 2014). However, the observed associations could also be driven by genetic liability or

environmentalfactors,ratherthancausaleffectsofoneontheother.Forexample,bothmusictraining

andmusicalaptitudearecorrelatedwithgeneralintelligence(Mosing,Madison,Pedersen,&Ullén,

2016; Mosing, Pedersen, Madison, & Ullén, 2014; Mosing, Verweij, Madison, & Ullén, 2016;

Schellenberg&Weiss,2013),whichinturnisrelatedtoperformanceonessentiallyallcognitivetasks

(McGrew, 2009). We have found, using twin modelling, that shared genes underlie associations

between intelligence and musical outcomes (Mosing, Madison, et al., 2016; Mosing et al., 2014;

Mosing,Verweij,etal.,2016)andahighgeneticcorrelationhasbeenfoundbetweenintelligenceand

language abilities (Plomin & Deary, 2015). Nonetheless, an emerging literature shows that

correlationsbetweenlanguagetasksandmusicaltasks,ormusictraining,remainsignificantwhen

generalintelligenceisheldconstant(Barwick,Valentine,West,&Wilding,1989;Corrigall&Trainor,

2011; Gordon, Shivers, et al., 2015; Lamb & Gregory, 1993; Milovanov & Tervaniemi, 2011;

Swaminathan& Schellenberg, 2019). This suggests that associations betweenmusical and verbal

abilities are likely influenced by more specific factors, over and above the effects of general

intelligence.

Inthisstudy,weanalyzedtheassociationsbetweenmusicalvariablesandverbalability,taking

general intelligence into account, utilizing a large sample of Swedish twins. The study had three

specific aims. First, we test whether, in our population-based twin sample, musical aptitude is

correlatedwithverbalability,evenwhencontrollingforgeneralintelligence.Second,withtheuseof

twindata,wewilltesttowhatdegreetheassociationbetweenmusicalaptitudeandverbalabilityis

influenced by specific genetic factors, over and above the genetic factors shared with general

intelligence. Lastly, we will investigate whether a cumulative measure of music training during

childhoodandadolescenceiscorrelatedwithverbalabilitymeasuredinearlyadulthoodandwhether

thisassociationremainssignificantwithinmonozygotictwinpairs,i.e.aco-twin-controlanalysis,to

testwhethertheassociationisinlinewithacausalhypothesis.

Methods

Participants

In2012-2013,32,000adulttwinsregisteredwiththeSwedishTwinRegistry(STR)from‘theStudy

ofTwinAdults:GenesandEnvironment’(STAGE)wereinvitedtoparticipateinastudycollecting,

amongotherthings,dataonmusictraining,musicalaptitudeandgeneralintelligence.The11,543

twinindividualsthatresponded(4,891males)wereagedbetween27and54years(M=40.7,DS=

7.7)attimeofmeasurement.Ofthe4,891maleparticipants,2,288hadcompletedanintelligence

test,includingaverbalabilitymeasurement,atage18basedonmilitaryconscriptionmeasures.Of

these2,288individuals,1,336individuals(480monozygotic[MZ]twins)haddataavailableon

musicalaptitudeand1,472(525MZtwins)onhoursofmusictraining.Thesewereusedfor

phenotypiccorrelationsandco-twin-controlanalysis.Datafromcompletetwinpairscontributeto

thegeneticanalyses,andwereavailableforverbalabilityfor303pairs(185MZand118dizygotic

[DZ]twinpairs),formusicalaptitudefor373pairs(240MZ,133DZtwinpairs),andforgeneral

intelligencefor507pairs(310MZ,197DZtwinpairs).Intotal,for165completemaletwinpairs

(110MZ,55DZtwinpairs)informationwasavailableonallthreemeasures:verbalability,musical

aptitudeandgeneralintelligence.

Informedconsentwasobtainedfromallparticipants.Thestudywasapprovedbythe

RegionalEthicsReviewBoardinStockholm(Dnr2011/570-31/5,2012/1107-32,2018/1592-32).

Allresearchmethodswereperformedinaccordancewithrelevantguidelinesandregulations.

Measures

Musicalaptitude.MusicalaptitudewasmeasuredusingtheSwedishMusicalDiscriminationTest

(SMDT)(Ullénetal.,2014).TheSMDT,administeredonline,consistsofthreesubtests:apitch,

melodyandrhythmdiscriminationtest.Thethreediscriminationscoresencompassdifferenttrials

rangingfrom18to27trials.Cronbach’salphavalueswereintherange.79–.89forallscales;see

Ullénetal.(2014)foramoredetaileddescriptionandpsychometricvalidationoftheSMDT.Here,

themeanofthethreestandardizedsubtestscoreswasusedasanoverallmusicalaptitudescore.

Generalintelligence.PsychometricintelligencewasmeasuredwiththeWienerMatrizenTest(WMT)

(Formann&Piswanger,1979),whichisavisualmatrixtestsimilartoRaven’sstandardprogressive

matrices.WMTscorescorrelatehighlywithRaven’sSPM(r=0.92)andaCronbach’salphaof.79

showsarelativehighreliabilityofthescale(Ullénetal.,2012).The25-minutelongtestconsistsof

24multiplechoiceitemsandcorrectlyanswereditemsarescoredasoneandsummed,while

incorrectormissingitemsarescoredaszero.

Verbalability.TheSwedishmilitaryserviceexaminesmenbeforethebeginningoftheirconscription.

TheSwedishEnlistmentBattery(Carlstedt&Mårdberg,1993;Mårdberg&Carlstedt,1998)includes

acognitiveability(IQ)testthatconsistsoffourdifferentpartsthatmeasurelogical(40items),

spatial(25items),verbal(40items)andtechnicalabilities(52items).Theverbalabilitysubtest

measuredverbalcomprehensionandwasadministeredintwodifferentversions.Onewasaconcept

discriminationtestinwhichparticipantshadtoselectwhichworddoesnotfitwiththeothers

conceptually,outofalistoffivewords;intheotherversion,participantshadtoselectthesynonym

toawordfromfouralternatives.Normedscoresfromthetwoversionswerepooledinthepresent

analyses.Previousstudiesindicatethattheverbalsubscaleloadssubstantiallyonbothasecond-

orderverbal-crystallizedintelligencefactor(Gc)andgeneralintelligence(g)(Carlstedt&Mårdberg,

1993).ACronbach’salphaof.88hasbeenreportedfortheverbalsubscale(Rönnlund,Carlstedt,

Blomstedt,Nilsson,&Weinehall,2013).Instructionsaregivenpriortoeachsubtestandparticipants

areaskedtoproceedasfastaspossible.Resultsofthedifferenttestsperformedaresummedintoa

9-pointscale,1to9.

Musicaltraining.Participantsthateverplayedaninstrumentwereaskedtoindicatedtheyearsthey

playedandthenumberofhoursperweektheypracticedmusic(in10categoriesrangingfrom0,

over6-9,tomorethan40hours)duringfourageintervals(ages0-5,6-11,12-17and18yearsuntil

timeofmeasurement).Fromtheseanswers,ascorereflectingcumulativemusictrainingfromthe

momenttheystartedpracticinguntilage18wascalculated(Mosing,Madison,Pedersen,Kuja-

Halkola,&Ullen,2014).

Allvariablesincludedintheanalyseswerestandardizedwithameanofzeroandastandard

deviationofone.

Statisticalanalyses

Phenotypicassociations

Correlationsbetweenverbalability,musicalaptitude,musictrainingbeforetheageof18,and

generalintelligencewerecalculatedinSTATA.Additionally,wecalculatedpartialcorrelations

controllingforgeneralintelligence.

Geneticandenvironmentalinfluencesontherelationshipbetweenmusicalaptitudeandverbalability

Bivariateclassicaltwinmodelling–aCholeskydecomposition–inOpenMx(Bokeretal.,2011)was

performedtoexplorethegeneticandenvironmentalinfluences,ontheassociationbetweenmusical

aptitudeandverbalability,whilecontrollingforgeneralintelligence.Therefore,inthemodel,we

enteredaresidualscoreformusicalaptitudeandaresidualscoreforverbalability,afterhaving

regressedgeneralintelligenceout.Inthisgeneticstructuralequationmodel,theobserved

phenotypicvariance(basedonthecorrelationsbetweentwin1andtwin2forthestudiedtraits)as

wellasthephenotypiccovariance(basedonthecross-twin-cross-traitcorrelationsbetweenthe

traits)canbepartitionedintoadditivegenetic(A),commonenvironmental(C)andnon-shared

environmental(E)components.Thisispossiblebecauseoftheavailabilityofdatafromtwotypesof

twins:MZtwinswhoshare100%oftheirgeneticmaterialandfamilyenvironment,andDZtwins

whoshare,onaverage,50%oftheirgenesand100%oftheirfamilyenvironment(Verweij,Mosing,

Zietsch,&Medland,2012).WeestimatedtheACEinfluencesontheassociationbetweenmusical

aptitudeandverbalability,controllingforgeneralintelligence.ThesignificanceoftheseACE

influencesontheassociationwastestedusingthelikelihood-ratiotest,bycomparingamodelwith

thegeneticorenvironmentalfactorfreelyestimatedtoamodelwiththegeneticorenvironmental

factorconstrainedtozero.Inthelikelihoodratiotest,thenegativelog-likelihood(-2LL)andthe

degreesoffreedom(df)ofthemoreconstrainedmodelaresubtractedfromthe-2LLanddfofthe

moregeneralmodel.Achisquaretestthenshowswhethertheconstraintsignificantlydeteriorates

thefitofthemodel(p<.01).

Testingpotentialcausalityofeffectsofmusictrainingonverbalability

Co-twincontrolanalysesinMZtwinswereconductedtotestwhethertheassociationbetweenmusic

trainingbeforetheageof18andverbalabilitymeasuredatconscriptionremainedsignificantwhen

controllingforsharedgeneticandsharedenvironmentalfactorsinfluencingbothtraits.SinceMZ

twinssharetheirgeneticmake-upaswellastheircommonfamilyenvironment,associationswithin

suchpairsareintheoryfreefromfamilialconfounding.Incaseofacausalassociation,thetwinwith

moremusictrainingwouldbeexpectedtoalsoscorehigheronverbalabilitythanhisorherco-twin,

whotrainedless.Within-pairlinearregressionanalyseswereconductedusingthextregfe

statementinSTATAtostratifybytwinpair.OnlycompleteMZtwinpairsdiscordantinmusic

trainingandverbalabilitycontributetothewithin-pairanalyses.Theanalyseswereadjustedfor

generalintelligence.

Results

Phenotypicassociations

InTable1,abovethediagonal,weshowthecorrelationsbetweenmusicalaptitude,verbalability,

musictrainingandgeneralintelligence.Belowthediagonal,partialcorrelations,i.e.controlledfor

generalintelligence,aredisplayed.SupplementaryFigure1showstheassociationsbetweenmusical

aptitudeandverbalability(r=.36),musictrainingandverbalability(r=.11)andtheirbestlinear

fitwhenadjustingforgeneralintelligence(.25and.08respectively).Foracompletecorrelation

tableofallmeasuredvariables(musicalaptitudesubscales,othersubtestsoftheconscriptionIQ

test),seeSupplementaryTable1.

Geneticandenvironmentalinfluencesontherelationshipbetweenmusicalaptitudeandverbalability

Twincorrelationsandtheir95%confidenceintervalsareshowninSupplementaryTable2.Forall

traits,MZcorrelationswerehigherthanDZcorrelations,suggestingtheinvolvementofadditive

geneticfactors.TheDZcorrelationswerelargerthanhalfoftheMZcorrelations,alsosuggestinga

roleforthecommonenvironment.

BasedontheCholeskydecomposition,wecalculatedthepercentageoftheassociation

betweenmusicalaptitudeandverbalabilityexplainedbygeneticandenvironmentalinfluences.Of

thephenotypiccorrelationbetweenmusicalaptitudeandverbalability(r=.25;whencontrolling

forgeneralintelligence),50%ofthevariancewasexplainedbygeneticfactors,15%bycommon

environmentalfactorsand35%byuniqueenvironmentalfactors.

Figure1showsthepathestimatesandtheirconfidenceintervalsforthebivariatemodel

includingmusicalaptitudeandverbalabilitycontrolledforgeneralintelligence.Non-significant

pathsaredashedandpathestimatesfortheuniqueenvironmentalinfluencesaredisplayedinlight

grey.Eventhoughgeneticfactorsexplainedthemajorityofthecovariancebetweenmusicalaptitude

andverbalability,significancetestingshowedthatthegeneticpathwayfrommusicalaptitudeto

verbalability,denotingsharedgeneticfactorsindependentofgeneralintelligence,couldbe

constrainedto0withoutsignificantdeteriorationofmodelfit(χ20.83(1),p=.36).Theshared

environmentalpathwaysfrommusicalaptitudetoverbalabilitywasalsonon-significant(χ20.09

(1),p=.76).

Testingpotentialcausalityofeffectsofmusictrainingonverbalability

Within-pairlinearregressionsinidenticaltwinpairs(co-twincontrolanalyses)showedno

significanteffectofmusictrainingonverbalability(β=.05,p=.56),whenadjustingforfamiliar

factors.Whenaddinggeneralintelligencetotheanalysestheresultsdidnotchange(β=.07,p=.42).

Table1.Correlations(n)betweenmusicalaptitude,verbalability,musictrainingbefore18andgeneralintelligence.Rawcorrelationsareshownabovethediagonalandpartialcorrelations,controllingforgeneralintelligence,areshownbelowthediagonal.

**p<.001,*p<.05.

Musicaptitude Verbalability Musictraining Generalintelligence

Musicalaptitude - .36**(N=1,336)

.35**(N=1,742)

.38**(N=2,830)

Verbalability .25**(N=1,334)

- .11**(N=1,305)

.38**(N=1,689)

Musictraining .35**(N=1,740)

.08*(N=1,007)

- .07*(N=2,187)

Figure1.ThebivariateCholeskydecompositionformusicalaptitudeandverbalability,adjustedforgeneralintelligence.A1andA2aretheadditivegeneticfactorswiththeirpathwayestimates;C1,C2,E1 and E2 are the common (C) and unique (E) environmental factors, respectively. Dashed linesindicatenon-significantpaths.Thesampleofcompletemaletwinpairswithdataavailableformusicalaptitude,verbalabilityandgeneralintelligencewasn=165.

Discussion

Here,wetestedthreehypothesesconcerningtheassociationsbetweenmusicalaptitude,music

trainingandverbalabilitiesinalargepopulation-basedsample(N=1,336maleindividualsinthe

SwedishTwinRegistry).Insupportofourfirsthypothesis,wefoundthatmusicalaptitudeand

musictrainingwereassociatedwithverbalability,evenwhencontrollingforgeneralintelligence.

Second,weusedtwinmodellingtotestwhethertheassociationbetweenmusicalaptitudeand

verbalabilitydependsonspecificgeneticfactors,overandaboveinfluencesfromgeneral

intelligence.Thishypothesiswaspartlyconfirmedbythedata:thepartialassociationbetween

musicalaptitudeandverbalabilitywasmostlyexplainedbygeneticinfluences.However,this

findingdidnotreachstatisticalsignificance.Thirdly,wetestedifmusictraininginchildhoodand

adolescencehasacausalinfluenceonverbalabilitymeasuredatage18.Co-twincontrolmodelling

providednosupportforthishypothesis.

Thecorrelationbetweenmusicalaptitudeandverbalabilitywasmoderate(.36)andlargely

remainedwhencontrollingforgeneralintelligence(.25).Theseresultsconvergewithfindingsfrom

avarietyofneuropsychologicalstudiesshowingassociationsbetweenmusicandlanguagerelated

traits,whilecontrollingforintelligence(Barwicketal.,1989;Corrigall&Trainor,2011;Gordon,

Shivers,etal.,2015;Hille,Gust,Bitz,&Kammer,2011;Lamb&Gregory,1993;Milovanov&

Tervaniemi,2011;Swaminathan&Schellenberg,2019).Surprisingly,generalintelligenceonly

slightlyattenuatedthecorrelations,whileweexpectedalargerroleforIQinexplainingcovariance

betweenlanguageabilitiesandmusicalaptitudebasedonthewell-establishedassociationbetween

musicandIQ(Schellenberg&Weiss,2013).

Nevertheless,astheassociationbetweenmusicalaptitudeandverbalabilityremainedsignificant

aftercontrollingforgeneralintelligence,wewereabletoinvestigateitsunderlyinggeneticand

environmentalinfluences.Theassociationbetweenmusicaptitudeandverbalabilitywasmostly

drivenbygeneticfactors;however,thiseffectwasnon-significant.Itisimportanttonotethough

thatthelackofstatisticalsignificanceislikelyduetothesmallsamplesizeofcompletemaletwin

pairswithdataavailableforallthreetraits(N=165twinpairs).Thesizeofthepathestimates

indicatedthatthemostprominentinfluenceonthepartialvariance(correctedforgeneral

intelligence)wasthatofthegeneticfactor.Therefore,itseemsthatformusicalaptitudethereare

specificgeneticinfluences,overandabovethegeneticinfluencessharedwithgeneralintelligence,

thatexplaintheassociationwithverbalability.Thiscouldimplythatindividualswithagenetic

predispositionformusicarealsomorelikelytohaveapredispositionforbetterlanguageskills.

Notably,wealsofoundasignificantnon-sharedenvironmentalcomponentintheassociation,

suggestingthattheremayalsobeoverlappingenvironmentalinfluencesonmusicalandverbal

ability.Tofurtherinvestigatesuchenvironmentalfactors(e.g.,geneticnichepicking)willbean

interestingtopicforfurtherresearch.

Thelasthypothesiswaswhethertherewasapotentiallycausalinfluenceofmusictraining

onverbalability.First,wefoundthatmusicpracticeinchildhoodandadolescenceisslightlybut

significantlyassociatedwithverbalability(r=.11or.08whencontrolledforgeneralintelligence).

Thisfindingalignswithasubstantialbodyofevidenceshowingthatindividualswhopracticemusic

tendtohavebetterabilitiesandsensitivitiesforspeechandlanguage(i.e.,Brod&Opitz,2012;Marie

etal.,2011;Schonetal.,2004).Onepossibilityisthatthiswouldrepresentcausaltransfereffects

frommusictrainingtolanguageskills(seee.g.OPERAhypothesis,Patel,2014).However,the

presentco-twincontrolanalysisshowedthatmusictrainingduringchildhoodandadolescence,

whencontrollingforfamilialconfounding,didnotpredictverbalabilityatageofconscription.This

suggeststhattheassociationbetweenmusicpracticeandverbalabilityislargelydrivenbyfamilial

factors,whichisinlinewithfindingsfromSwaminathanandSchellenberg(2019).Moreover,adding

generalintelligencetotheanalysisdidnotchangetheseresults.Therefore,inearliercorrelational

work(i.e.,Musacchiaetal.,2007;Marieetal.,2011;Bidelman&Alain,2015),associationsbetween

voluntarymusictrainingandverbalabilitiesarelikelytobeinfluencedbyfamilialfactorsmaking

individualsandtheirfamilieswhoseekmusictrainingmorepredisposedtobettermusicand

speech/languageacquisitionskills(Mankel&Bidelman,2018,Schellenberg,2015).

Thisstudyhasseverallimitations.First,ourdataonverbalabilitywerelimitedtomen

enrolledintheSwedishmilitaryservicebeforethebeginningoftheirconscription.Therefore,itis

possiblethatindividualsmayhavepurposefullyunderperformedintheteststoavoidconscription,

whichwouldresultinincreasederrorandassuchinreducedassociationswiththelatercollected

phenotypes.Moreimportantly,thissamplethereforeonlyincludesmales;futureresearchshould

testwhetherourfindingsreplicateforfemales.Second,asmentionedearlier,thesampleof

completemaletwinpairswithdataavailableformusicalaptitude,verbalabilityandgeneral

intelligencewassmall(N=165pairs)–presumablyanimportantexplanationforthenon-significant

pathwaysinourgeneticmodel.Third,thehoursofmusictrainingvariablewasbasedonself-report

dataandthiscouldintroduceabias.Anotherimportantpointisthatwestudiedtheamountofany

kindofvoluntarymusictrainingwhichcanvarylargelydependingone.g.whetheranindividual

singsortheinstrumenttheindividualplays.Possibly,focusedandcontrolledtrainingofspecific

musicaltasksinthecontextofanintervention,asforexampleinthestudybyFrancois,Chobert,

Besson,andSchon(2013),couldhavedifferentandlargereffectsonlanguagetaskperformance.

Lastly,itisimportanttoemphasizethatverbalabilitymeasuredinthisstudyreflectslexicalaccess

andsemanticrelationships,whichisonlyonecomponentofthemuchbroader‘languageconstruct’.

Itwouldbevaluableifinthefuture,otheraspectsoflanguage(forexamplegrammaror

phonologicalawareness)inrelationtomusicalaptitudewouldalsobeexploredingenetically

informativesamples.Thestrengthofthisstudyisthatwehadalargepopulation-basedsamplein

whichwewereabletoinvestigatenotonlythephenotypicassociationbetweenmusicalaptitude,

musictrainingandverbalability,butalsotestwhetherthisassociationcouldbecausal,bytaking

geneticandfamilialconfoundingintoaccount.

Toourknowledge,thepresentstudyisthefirstgeneticallyinformativepopulation-based

studythathasnowdemonstratedthatmusicalaptitudeandmusictrainingareindeedassociated

withverbalabilitiesinapopulation-basedsample,evenwhencontrollingforgeneralintelligence.

Bothgeneticandnon-sharedenvironmentalfactorsareinvolvedinthepartialassociation,corrected

forinfluencesfromgeneralintelligence,betweenmusicalaptitudeandverbalability.Ratherthan

findingacausaleffectofmusictraining,ourfindingssuggestthattheassociationbetweenmusic

trainingandverbalabilityislikelyduetosharedunderlyingaetiology.

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SupplementaryMaterial

SupplementaryTable1.Correlationsbetweenmusictraining,musicalaptitude,melodydiscrimination,pitchdiscrimination,rhythmdiscrimination,verbalability,spatialability,logicalabilityandtechnicalability.Abovethediagonalfullcorrelationsandbelowthediagonalpartialcorrelationswhilecontrollingforgeneralintelligence.

**p<.001,*p<.05.Notethatmelody,pitchandrhythmdiscriminationformpartoftheoverallmusicalaptitudescore.

SupplementaryTable2.Twincorrelationsperzygositygroupformusicalaptitude,verbalability,musictrainingandgeneralintelligence.

Musictraining

Musicalaptitude

Melodydiscrimination

Pitchdiscrimination

Rhythmdiscrimination

Verbalability

Spatialability

Logicalability

Technicalability

Generalintelligence

Musictraining - .35** .27** .33** .18** .11* .07* .09** .08* .07*Musicalaptitude

.35** - .79** .75** .76** .36** .31** .39** .33** .38**

Melodydiscrimination

.27** .78** - .41** .42** .24** .21** .24** .21** .27**

Pitchdiscrimination

.33** .73** .36** - .33** .25** .22** .30** .28** .30**

Rhythmdiscrimination

.17** .73** .37** .26** - .33** .27** .37** .26** .31**

Verbalability .08* .25** .16** .15** .24** - .48** .68** .45** .38**Spatialability .02 .14** .10** .07* .13** .35** - .58** .54** .54**Logicalability .06 .24** .12** .16** .25** .60** .41** - .52** .55**Technicalability

.05 .20** .12** .17** .15** .33** .41** .38** - .45**

Musicalaptitude

Verbalability

Musictraining

Generalintelligence

MZmaletwins .72(.65-.77) .74(.67-.79) .59(.51-.66) .63(.56-.69)DZmaletwins .53(.40-.62) .46(.32-.58) .38(.23-.51) .39(.28-.49)

SupplementaryFigure1.Therelationshipbetweenmusicalaptitudeandverbalability(r=.36),musictrainingandverbalability(r=.11)andtheirbestlinearfitwhenadjustingforgeneralintelligence(r=.25and.08respectively).