Developmental Trajectories of Social Skills during Early Childhood and Links to Parenting ...

14 Pages·2015·0.34 MB·English

RESEARCHARTICLE
Developmental Trajectories of Social Skills
during Early Childhood and Links to Parenting
Practices in a Japanese Sample
YusukeTakahashi1*,KensukeOkada2,TakahiroHoshino3,TokieAnme4
1 GraduateSchoolofEducation,KyotoUniversity,Kyoto,Japan,2 SchoolofHumanSciences,Senshu
University,Kawasaki,Japan,3 FacultyofEconomics,KeioUniversity,Tokyo,Japan,4 FacultyofMedicine,
UniversityofTsukuba,Tsukuba,Japan
* [email protected]
Abstract
ThisstudyuseddatafromanationwidesurveyinJapantomodelthedevelopmentalcourse
ofsocialskillsduringearlychildhood.Thegoalsofthisstudyweretoidentifylongitudinal
OPENACCESS
profilesofsocialskillsbetween2and5yearsofageusingagroup-basedtrajectory
Citation:TakahashiY,OkadaK,HoshinoT,AnmeT approach,andtoinvestigatewhetherandtowhatextentparentingpracticesat2yearsof
(2015)DevelopmentalTrajectoriesofSocialSkills
agepredicteddevelopmentaltrajectoriesofsocialskillsduringthepreschoolperiod.Arela-
duringEarlyChildhoodandLinkstoParenting
tivelylargesampleofboysandgirls(N>1,000)wasassessedonthreesocialskilldimen-
PracticesinaJapaneseSample.PLoSONE10(8):
e0135357.doi:10.1371/journal.pone.0135357 sions(Cooperation,Self-control,andAssertion)atfourtimepoints(ages2,3,4,and5),and
onfourparentingpractices(cognitiveandemotionalinvolvement,avoidanceofrestriction
Editor:MarinaA.Pavlova,UniversityofTuebingen
MedicalSchool,GERMANY andpunishment,socialstimulation,andsocialsupportforparenting)atage2.Theresults
indicatedthatforeachsocialskilldimension,group-basedtrajectorymodelsidentifiedthree
Received:May22,2015
distincttrajectories:low,moderate,andhigh.Multinomialregressionanalysisrevealedthat
Accepted:July21,2015
parentingpracticevariablesshoweddifferentialcontributionstodevelopmentofchildsocial
Published:August12,2015
skills.Specifically,CooperationandAssertionwerepromotedbycognitiveandemotional
Copyright:©2015Takahashietal.Thisisanopen involvement,Self-controlbysocialstimulation,andAssertionbyavoidanceofrestriction
accessarticledistributedunderthetermsofthe
andpunishment.Abundantsocialsupportforparentingwasnotassociatedwithhigherchild
CreativeCommonsAttributionLicense,whichpermits
socialskillstrajectories.Wefoundheterogeneityindevelopmentalprofilesofsocialskills
unrestricteduse,distribution,andreproductioninany
medium,providedtheoriginalauthorandsourceare duringthepreschoolages,andweidentifiedparentingpracticesthatcontributedtodifferent
credited. patternsofsocialskillsdevelopment.Wediscussedtheimplicationsofhigher-qualitypar-
DataAvailabilityStatement:Allrelevantdataare entingpracticesontheimprovementofchildsocialskillsacrossearlychildhood.
withinthepaper.
Funding:ThisresearchwassupportedbyGrants-in-
AidforScientificResearch(B:19330126)toT.A.and
waspartiallysupportedbythePrecursoryResearch
forEmbryonicScienceandTechnology(PRESTO), Introduction
JapanScienceandTechnologyAgency(JST),toT.H.
Socialskillsaredefinedassociallyacceptable,learnedbehaviorsthatenableapersontointeract
Thefundershadnoroleinstudydesign,data
collectionandanalysis,decisiontopublish,or effectivelywithothersandtoavoidsociallyunacceptableresponses[1].Developingsocialskills
preparationofthemanuscript. toenablesuccessfulrelationshipswithothersisoneofthemostimportantaccomplishmentsin
childhood.Conversely,whenchildrenfailtobuildsocialskillsproperly,ortheirskillsdonot
CompetingInterests:Theauthorshavedeclared
thatnocompetinginterestsexist. functioneffectivelyintheearlydevelopmentalphase,theysubsequentlydisplayproblem
PLOSONE|DOI:10.1371/journal.pone.0135357 August12,2015 1/14
SocialSkillsTrajectories
behaviorsandexperiencelatersocialmaladaptation,schoolmaladjustment,andpooracademic
performance[2,3].Therefore,itisimportanttoidentifychildrenwhoaresociallydeficient,to
provideinterventiondirectedatimprovingtheirsocialskills,andtobeproactiveintakingade-
quatepreventionmeasures.
Severallarge-scalelongitudinalprojects,includingtheNationalHeadStart–PublicSchool
EarlyChildhoodTransitionDemonstrationProjectandtheNICHDstudyofEarlyChildCare
andYouthDevelopment,haveidentifiedcharacteristicsofchildren’ssocialskillsdevelopment.
Forinstance,children’ssocialskills,asperceivedbyparents,increasedfromkindergarten
throughthirdgrade[4].Fromkindergartenthroughfifthgrade,childrenshowedcurvilinear
socialskillgrowth[5,6].Moreover,fromadolescencetoearlyadulthood,youth’sself-reported
prosocialityfollowedahorseshoeshapedtrend:Theoveralllevelofprosocialitydeclineduntil
age17,withasubsequentslightrebounduntilage21[7].However,muchlessisknownabout
thedevelopmentaltrajectoriesofsocialskillsduringearlychildhood,ages2to5.Childrendur-
ingthisperiodareexpectedtobegindemonstratingcooperation,assertivebehavior,andself-
control,whilecopingwithgreaterenvironmentaldemandsbyteachersandpeers[8].Prior
researchhasalsoindicatedthatprosocialbehaviorofmanydifferentsortsappearsinearly
childhood[9,10].Thus,thepreschoolperiodofages2to5isanimportantdevelopmental
stageinwhichchildrenmustacquiresocialskillstopreparefortheirupcomingschoolatten-
danceandtheexpansionoftheirareasofsocialactivity.Fromasocializationtheoryperspective
[10],preschool-agedchildrenlearnwithagehowtobegood;thatis,theyincreasethefre-
quencyofprosocialbehaviors.Atthesametime,thereisevidencethatchildren’ssocialskills
becomedifferentiatedandthusshowheterogeneity[11].Fromthisperspective,itwouldnotbe
surprisingifsomeindividualsorgroupsdemonstrateadeclining(regulated)trendratherthan
ageneralupwardtrend.Indeed,somedevelopmentalprofilesofprosocialbehaviorratedby
teachersdeclinedgraduallyfromkindergartentothirdgrade[4],fromage6to12[12],and
fromage10to15[13].Thefirstgoalofthepresentstudywastoidentifytheheterogeneous
developmentaltrajectoriesofsocialskillsknowntobecomponentsofprosocialbehaviordur-
ingearlychildhoodbyapplyingagroup-basedtrajectoryapproach[14].
Weexpectedthatthenumberoflongitudinalprofilesofchildren’ssocialskillswouldbe
similartotrajectoriesfoundinpriorresearchwithdifferentagedsamples.Someresearchers
havereportedadevelopmentaltrajectoryforchildren’sprosocialbehaviors,abroadconstruct
ofsocialskills.Forinstance,Côté,Tremblay,Nagin,Zoccolillo,andVitaro[15]demonstrated
thatathree-latentclassmodelbestfitteachers’ratingsofchildren’sprosocialbehavior
throughouttheschool-ageperiod.Kokkoetal.[12]obtainedtwotrajectoriesofprosocial
behaviorfromages6to12bymeansofagroup-basedtrajectorymethod.Nantel-Vivieretal.
[13]describedcross-culturaldevelopmentaltrajectoriesofprosocialbehaviorfromages10to
15usingamulti-informantapproach.Theyidentifiedthreetrajectorygroupsfromself-ratings,
fivefrommother-ratings,andthreeorfourfromteacher-ratings.LamontandVanHorn[16]
selectedathree-classsolutionforfoursubscalesofchildsocialskillsfromkindergartentothird
grade.Takentogether,theresultsfromthesepreviousstudiesindicatethatagroup-basedtra-
jectorymethod,orgrowthmixturemodeling,canbeusedtogroupprosocialbehaviorduring
schoolageintotwotofiveseparatelatentclasses.Therefore,wehypothesizedthattwotofive
latentclassescouldbeidentifiedinthedevelopmentaltrajectoryofsocialskillsduringearly
childhood,andthattherewouldbeatleastonelowersocialskillsgroupandatleastonehigher
group,inadditiontosomemiddle-levelgroups.
Thesecondgoalofthepresentstudywastoinvestigatewhetherandtowhatextentparental
andenvironmentalfactorspredicttrajectorygroupmemberships.Thepreviousstudies
reviewedaboverevealedonlythegroupingofdevelopmentaltrajectories,suggestingthatpro-
socialbehaviorduringschoolagecanbegroupedintomultipletrajectories.However,littleis
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SocialSkillsTrajectories
knownabouthowthedifferencesbetweenthedevelopmentaltrajectoriesshouldbecharacter-
ized.Afterthedevelopmentaltrajectoriesareidentified,thefactorsthatinfluencethedevelop-
mentaltrajectoriesofsocialskillscanthenbeidentified.Weexpectthathigherparenting
qualityatanearlydevelopmentalstageactsasagrowth-promotingfactor.Infact,thereexists
anextensivebodyofliteratureshowingthatpositivechild-rearingenvironmentalfactorsare
associatedwithchildren’ssocialdevelopment[6,17].Inareviewofrelevantresearch,Repetti,
Taylor,andSeeman[18]concludedthatpositiveparentalandfamilyenvironmentalcharacter-
isticsarepositivelyrelatedtoindicatorsofchildren’ssocialdevelopment,andviceversa.Parke
andBuriel[19]showedthatsomeaspectsofparentingsuchasemotionalexpressiveness,
responsiveness,andsupporthavebeenstipulatedinanumberofframeworksasmechanisms
thatenablechildrentoacquiresocialskills.AnmeandSegal[20]alsodemonstratedthatglobal
parentingqualitywaspositivelyassociatedwithchildren’ssocialdevelopment,includingsocial
competence,andcommunicationskills.
Inthepresentstudy,weassesseddimensionsofparentingpracticesatage2asapredictor
variables.Thedevelopmentoftwo-year-oldchildren―thetimeperiodofage2isthestarting
pointofourcohortstudy,isexplodinginanumberofaspects(e.g.,motorfunctions,language
skills,cognitiveandemotionaldevelopment).Additionally,whenchildrenreachtwoyearsof
age,mostparentsexperienceadifficulttimeduetothefirstrebelliousperiod,anormalstagein
theirchild’sdevelopment.Duringchildren’ssecondyearoflife,theytendtoreactnegatively
againsttheirparents,changemoodeasily,andresorttohavingtempertantrums[21].There-
fore,parentingpracticeatage2isobviouslyimportantforthechilddevelopment.Inthepres-
entstudy,weexaminedthedimensionsofparentingpracticesthathaveanimpactonspecific
dimensionsofchildsocialskills,inordertoexploreinmoredetailthepotentialearlyprotective
factorsthatcaninfluencediversedevelopmentalpathwaysinchildsocialskills.Toachieve
thesegoals,weappliedagroup-basedtrajectorymodelwithpredictorvariables[14].
Insummary,wefirstsoughttoadvanceourunderstandingofchildren’ssocialskilldevelop-
mentbyidentifyingdevelopmentaltrajectoriesofsocialskillsduringearlychildhood,from
ages2to5.Next,weinvestigatedhowparentingpracticesaffecttrajectorygroupmembership.
Althoughpreviousstudieshavealreadyshownthatbetterqualityofparentalcareandfamily
environmentisassociatedwithbetterdevelopmentofchildsocialskills,thepresentstudy
soughttoexamineindetailthespecificparentingfactorsthatcontributetomoresounddevel-
opmentaltrajectoriesofsocialskills.
Methods
Participants
Dataweredrawnfromapopulation-basedstudythatconstitutedpartofanationwideongoing
longitudinalstudyinJapan[20,22].Sixtychildday-carecentersand60childnight-carecenters
authorizedbythegovernmentwereaskedtoparticipateandcooperate,and98agreedtopartic-
ipateinthisstudyatthebeginningofthelongitudinalproject(cooperationrate81.7%).The
participantsinthisstudyconsistedofboysandgirlswhoattendedchildcarecentersandwho
werefirstassessedattheageof2bytheirparentsandbynurserystaffmembers.From2000on,
datawerecollectedwithwritteninformedconsentinthewinterofeachyear.Allstudypartici-
pantsgavewritteninformedconsent,andoneofparentsprovidedwritteninformedconsent
onbehalfofthechildreninvolvedinthestudy.Allresearchprocedureswerereviewedand
approvedbytheinstitutionalreviewboardandethicscommitteeinUniversityofTsukuba.
Thebaselinereturnratewas74.6%forbothparentsandnurserystaff,yieldinginformation
from98childday-carecenters.Parentsweresurveyedregardingtheirparentingpractices(e.g.,
parentalinvolvementandsocialsupportforparenting),andnurserystaffmembersevaluated
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SocialSkillsTrajectories
thesocialskillsdevelopmentofeachchildinthefacility,aswellasaspectsofparentalchild
carequality.Inordertocontrolforethnicandclinicalbackground,childrenwithaparentwho
wasnotborninJapanandchildrenwhodidnotspeakJapaneseasanativelanguage,aswellas
childrenwithdisabilities,wereexcludedfromthesample.Aftertakingtheaboveinformation
intoaccount,thefinalusablesetoffollow-upresponsesofhomogeneousJapanese-speaking
boysandgirlstotaled1,055.AsshowninTable1,thedistributionofboysandgirlswasfairly
even.Anaverageof.49siblingslivedineachhousehold,witharangeofzerotoone(SD=.50).
Whenchildrenwerefirstassessed,amajority(82.6%)wereprimarilylivingwithbothoftheir
biologicalparents.Theremainingchildrenwerelivingwiththeirmotherorfather(14.8%),and
2.7%werelivingwithotherextendedfamilymembers.Inconductingthetrajectoryanalysis,
wedidnotincludecasesthatweremissingpredictororcovariateinformation.Therefore,
amongthe1,055possibleparticipants,1,000forCooperation,997forSelf-Control,and1,026
forAssertionwereavailablebecauseofmissingpredictorvariablesorcovariatesat2yearsof
age.Ofthetotalparticipants,345–376(32.7%-34.8%)providedsocialskillsdataonallfour
assessmentpoints,304–317(28.8%-30.1%)onthree,192–220(18.2%-20.9%)ontwo,and
161–173(15.3%-16.4%)ononlyone.Totesttheeffectofattritionbiasinallfourpossible
groups,weconductedaone-wayANOVA.Therewerenosignificantdifferencesbetweenchil-
drenwhodidanddidnotparticipatecontinuouslyintermsofeachdomainofsocialskillsat
age2:F(3,996)=2.06,p=.10,forCooperation;F(3,993)=1.51,p=.21,forSelf-Control;and
F(3,1022)=.91,p=.44,forAssertion.BymeansofmultiplecomparisonswithBonferronicor-
rection,wealsoconfirmedthattherewerenosignificantdifferences,sothattheseriesofanaly-
sesinthisstudywereconductedunderamissingatrandomassumption.
Table1. Descriptivestatisticsofallvariables.
variables N Mean SD min max
sex 1,055 0.49 0.50 0 1
sibling 1,055 0.49 0.50 0 1
parentalpracticesatage2
2-yearcognitiveandemotionalinvolvement 1,055 0.29 2.13 –16.24 2.19
2-yearavoidanceofpunishmentandrestriction 1,055 0.14 0.86 –10.05 0.25
2-yearsocialstimulation 1,055 0.06 1.68 –14.07 5.04
2-yearsocialsupportonparenting 1,055 0.15 1.63 –12.55 1.19
childsocialskillsatages2to5
2-yearcooperation 1,000 1.95 3.26 0 16
3-yearcooperation 837 5.63 4.56 0 16
4-yearcooperation 689 9.32 4.81 0 16
5-yearcooperation 378 11.90 4.29 0 16
2-yearself-control 997 6.19 3.97 0 16
3-yearself-control 854 9.94 3.75 0 16
4-yearself-control 698 12.35 3.36 0 16
5-yearself-control 387 13.81 2.84 0 16
2-yearassertion 1,026 13.28 2.70 4 16
3-yearassertion 863 14.73 1.89 4 16
4-yearassertion 701 15.04 1.81 5 16
5-yearassertion 386 15.27 1.63 7 16
Note.Parentingvariableswerestandardizedduetodifferentratingscalesusedforcertainitems.
doi:10.1371/journal.pone.0135357.t001
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SocialSkillsTrajectories
Measures
Socialskills. Socialskillswereassessedbynurserystaffmembersatfourtimepoints(ages
2,3,4,and5).AnadaptedversionoftheSocialSkillsQuestionnaireforPreschoolers(SSQ-P;
[23])wasusedasanindexofobserverratingsofchildsocialskillsateachage.Childsocialskill
scoresmeasuredbytheSSQ-Ppredictinternalizingandexternalizingbehaviorslongitudinally
[23].Becauseoneofthemostwidelyusedsocialskillscales,theSocialSkillsRatingSystem
(SSRS;[24]),whichwasusedintheNICHDstudy(e.g.,[25,26]),shouldbeappliedtochildren
aged3orover,forthisstudyweusedanadaptedversionoftheSSQ-P,whichisappropriatefor
childrenbelowtheageof3years.TheSSQ-Pwasoriginallydesignedtomeasuresocialskills
fromages4to6.Inordertoexpandcoveragetochildrenatages2and3,wefirstanalyzed
whetheranyoftheitemswereinappropriateforyounger-agedchildren.Afteranexploratory
factoranalysisincludingthedatafromchildrenaged2and3,weselected24itemsfromthe
originalform(8itemsforeachsubscale).The24-itemversionincludedthesamethreesub-
scalesusedintheSSRS:Cooperation(e.g.,thechildhelpssomeonevoluntarily),Self-Control
(e.g.,thechildbehaveshim/herselfifthereisaneed),andAssertion(e.g.,thechildinitiates
conversationwithsomeone).Nurserystaffmembersevaluatedhowoftenasocialbehavior
occurredona3-pointscale(0=never,1=sometimes,2=veryoften).Allsubscalesshowed
highinternalreliability,rangingfrom.83–.94forage2,.85–.95forage3,.86–.95forage4,and
.87–.96forage5(Table2).Toconfirmconvergentvalidity,wecomputedcorrelationsbetween
theadaptedversionoftheSSQ-PandtheSSRSteacherformforpreschoolersbyusingasub-
sample.Theresultsindicatedthatthetwoscalesweremoderatelypositivelycorrelatedwith
eachother,rangingfrom.25–.67forage2,.56–.75forage3,.73–.86forage4,and.75–.89for
age5.CorrelationbetweenSSRSCooperationandourscale’sCooperationwassomewhatlow
(r=.25),butthisisprobablybecausetheSSRSpreschoolersversionshouldbeappliedtochil-
drenaged3orover.
Parentingpractices. Toassessseveralparentingpractices,includingparentalinvolve-
ment,parentalstyles,andsocialsupportforparenting,weadaptedthecategoriesusedby
AnmeandSegal[20].Thistoolcontains12items,with6self-reportitemsratedbyparentsand
6other-reportitemsratedbynurserystaff.Itcanbedividedintofourcategories:cognitiveand
emotionalinvolvement(4items;e.g.,readingbooks,singingsongstogether);avoidanceof
restrictionandpunishment(2items,includingparentsbeingtooharshindiscipliningand
parentsexcessivelycontrollingthechild);socialstimulation(3items;e.g.,visitingcoeval
friends’houses,goingtotheparkwiththechild);andsocialsupportforparenting(3items;
e.g.,havingsomeonetoconsultonchildcare,beingsupportedinchildcarebysomeone).To
formcompositescoresindicatinggreaterorlesserqualityofparenting,itemswerez-scored
beforethecompositewascomputedbecauseofthedifferentratingscalesusedforcertain
items.
Covariates. Weselectedchild’ssexandpresenceorabsenceofsiblingsinthefamilyas
covariates.First,severalstudieshaveindicatedthatthechild’ssexhasastronginfluenceon
socialskillsdevelopment(i.e.,girls>boys;[27,28]).Moreover,thesiblingrelationshipislikely
tolastlongerthananyotherrelationshipinone’slifetimeandplaysanintegralpartinthelives
offamilies[29].Whenachildhassiblings,hisorherinterpersonalexperiencesarelikelyto
increase,whichmaybepositivelyassociatedwiththechild’ssocialskillsdevelopment[30].
DataAnalysisPlan
Wefirstcalculateddescriptivestatistics,includingmeans,standarddeviations,range,andcor-
relationsforsocialskillsscoresatdifferentages.Developmentaltrajectoriesofsocialskillswere
estimatedusingagroup-basedtrajectorymodelwithpredictors[14].Thismethodallowedus
PLOSONE|DOI:10.1371/journal.pone.0135357 August12,2015 5/14
SocialSkillsTrajectories
n * * *
ro * * * * *
5-yeaasserti –.22 –.05 .14 .13 .11 .17 (.87)
* * * *
5-yearself-control –*.41 –.07 *.24 .09 *.12 *.23 (.94)*.71
n
o * * * * *
arati * * * * *
er
5-yoope –.20 .05 .15 .09 .04 .16 (.96) .76 .63
c d.
e
n * * * * * at
4-yearassertio –*.18 .03 .05 .07 .07 *.10 (.86)*.56*.65*.84 erecalcul
w
* * * * * * *
4-yearself-control –*.33 –.07 *.11 .06 .07 *.13 (.93)*.66*.70*.88*.65 fiefcients
o
c
on * * * * * * on
arati * * * * * * ati
4-yeooper –.20 .03 .00 –.02 .05 .05 (.95) .69 .55 .78 .64 .52 correl
c c
ori
n * * * * * * * * h
3-yearassertio –*.18 –.02 *.09 *.08 .06 .05 (.85)*.47*.58*.79*.53*.62*.80 ng,polyc
bli
es. 3-yearself-control –**.25 .03 *.07 .02 .05 .01 (.91)**.59**.58**.77**.55**.61**.76**.57 senceofsi
edictorvariabl 3-yearcooperation –**.18 .01 –.01 –.02 .00 –.02 (.95)**.64**.44**.66**.50**.40**.60**.50**.40 ’dssexandpre
Table2.Correlationsbetweenchildsocialskillsandallpr 2-year2-year2-yearcooperationself-assertioncontrol –*–**–**sex(0=girl,.11.18.131=boy) sibling(0=no,.01.05.041=one)–2-yearcognitive.04.03.04andemotionalinvolvement–2-yearavoidance.07.00.04ofpunishmentandrestriction 2-yearsocial.00.03.03stimulation–2-yearsocial.04.01.04supportonparenting 2-yearcooperation(.94)**2-yearself-control.64(.91)****2-yearassertion.37.55(.83)******3-yearcooperation.56.49.40******3-yearself-control.41.65.48******3-yearassertion.23.39.67******4-yearcooperation.46.45.41******4-yearself-control.34.59.48******4-yearassertion.25.40.66******5-yearcooperation.39.42.42******5-yearself-control.33.57.50******5-yearassertion.25.42.70 *<Notep..05**<p.01;forcorrelationsbetweenchildsocialskillsandchil’NumbersinparenthesisshowCronbachsalpha. doi:10.1371/journal.pone.0135357.t002
PLOSONE|DOI:10.1371/journal.pone.0135357 August12,2015 6/14
SocialSkillsTrajectories
toidentifyseparatesubgroupsamongchildrenaged2to5,andtoestimateboththemember-
shipprobabilityofeachtrajectoryandtheeffectofpredictorsonit.Thesoftwareusedtoesti-
matetrajectorieswasaSAS-basedprocedure“proctraj”[31].Acensorednormalmodelwas
fittedtothedata,becausethedatausedtoestimatethetrajectorieswerebasedonpsychometric
scaleswithcensoringatthescaleminimumandmaximum,andthiscensorednormaltrajec-
torymodelingisconsideredtobewellsuitedtoaccommodateacommonfeatureofpsycho-
metricscaledata[14].Additionally,becausethismodelisrepresentedbynotasingle,buta
mixtureofthecensorednormaldistributions,wehavechosentoapplythecensorednormal
model,nottheordinarynormalmodel.Ourselectionoftheoptimalnumberoftrajectory
groupswasbasicallybasedontheBayesianinformationcriteria(BIC).Themodelallowsusto
calculateposteriorprobabilitiesofgroupmembership,whichestimateseachindividual’sprob-
abilityofbelongingtoeachofthetrajectorygroups.Amorecomprehensivediscussionofthe
technicaldetailsofthisapproachcanbefoundelsewhere[14,31].Afterestablishingthetrajec-
tories,wethensoughttoanswerthenextresearchquestion:Howdoparentalandenvironmen-
talfactorspredictchildren’ssocialskillstrajectories?Withcovariatesandparentingpractices
fortrajectorygroupmembership,themodelallowedustocomputetheeffectofpredictorvari-
ablesontheprobabilityoftrajectorygroupmembership.Amultinomiallogisticfunctionwas
usedtospecifythisprobabilityfunction.Byestimatingageneralizedmodelinwhichprobabil-
ityoftrajectorygroupmembershipwasconditionalonindividualcharacteristicsandthetrajec-
toriesthemselveswerejointlyestimated,weavoidedbiasesinstatisticaltestsdueto
classificationerrorsintrajectorygroupmembership.Intrajectoryanalysis,subjectswithsome
missinglongitudinalvariableswereincludedintheanalysis,sincethesewereassumedtobe
missingatrandom.Maximumlikelihoodestimationwasusedtoestimatethemodel
parameters.
Results
DescriptiveResults
Themeans,standarddeviations,andrangesforallpredictorandoutcomevariablesarepro-
videdinTable1.Intercorrelationsamongchildsocialskillsandpredictorvariablesarepre-
sentedinTable2.AsthemeansshowninTable1indicate,therewasageneraltrendforeach
child’ssocialskillstoincreasewithage.Thecorrelationsamongchildsocialskilldimensions
weremoderatelypositive,bothconcurrentlyandacrosstime.Table2alsoindicatesthatthe
polychoriccorrelationsbetweenchild’ssexandsocialskilldimensionswerealwayssignifi-
cantlynegative,meaningthatgirlsconsistentlyshowedhighersocialskillsthanboys.Thepoly-
choriccorrelationsbetweenthepresenceofsiblingsinthefamilyandsocialskilldimensionsin
Table2werenotsignificantinanycase.
DevelopmentalTrajectories
Weidentifiedgroupsofchildrenshowingdistinctlongitudinalprofilesofsocialskillsovertime
usingagroup-basedtrajectorymodelwithpredictorvariables.Inordertodeterminetheopti-
malnumberoftrajectoriesneededtodescribethetransitionofsocialskillsdevelopmentfrom2
to5yearsofageforthissample,wefittedmodelswithtwo,three,four,andfiveprofiles,based
onBIC.ForCooperation,theBICwas–6734.30fortwotrajectories,–6712.30forthree,–
6719.87forfour,and–6724.92forfive.ForSelf-Control,theBICwas–7349.24fortwotrajec-
tories,–7290.40forthree,–7277.74forfour,and–7293.24forfive.ForAssertion,theBICwas
–4990.72fortwotrajectories,–4945.61forthree,–4945.56forfour,and–4954.23forfive.By
usingtheBICcriterion,athree-groupmodelwasselectedforCooperationandfour-group
modelsforSelf-ControlandAssertion.However,althoughthefour-groupmodelsforSelf-
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SocialSkillsTrajectories
ControlandAssertionshowedgreaterBICs,thethree-groupmodelsforthesetwodimensions
alreadysubdividedmodestsizegroupswithhigherlevelsofchildsocialskillsintosmaller
groupsthatdidnotdiffersubstantively[32].Thus,forallthreedimensionsofchildsocialskills,
themodelwiththreetrajectorieswasidentifiedasthebestfittingandmostparsimonious.Fur-
ther,inordertojudgeobjectivelytheadequacyofthefinalthree-groupmodels,theaverage
posteriorprobabilitiesforeachgroup(i.e.,themeangroupassignmentprobabilities,condi-
tionalonassignmentbythemaximumlikelihoodprobabilityrule)werecalculated.Theaverage
posteriorprobabilityofgroupmembershipmeasurestheprobabilitythatanindividualwitha
specificprofilebelongstoeachofthemodel’strajectorygroups.ForCooperation,group1aver-
ageposteriorprobability=.81,group2=.85,andgroup3=.83;forSelf-Control,group1=
.87,group2=.85,andgroup3=.86;andforAssertion,group1=.88,group2=.85,andgroup
3=.78.Inallcases,theaverageposteriorprobabilitiesweregreaterthan.70,avaluethatNagin
[14]assumedtoimplyagoodmodelfittothedata.AspresentedinthepanelAofFig1,the
threetrajectoriesforCooperationfromages2to5andtheestimationoftheproportionofthe
samplefollowingeachtrajectorywereasfollows:low(9.2%),moderate(66.2%),andhigh
(24.6%)groups.Thelowgroupfollowedatrajectoryreflectingaslightincreaselaterinthepre-
schoolage.Themoderategroupshowedthesharpestincrease,movingfromalmostthesame
levelasthelowgroupatage2tothelevelofthehighgroupbyage5.Thehighgroupfolloweda
trajectoryreflectingalinearincreaseastheygrew.ThepanelBinFig1depictsthethreetrajec-
torygroupsofSelf-Control,alongwiththeestimatedproportionofchildrenineachgroup.
Thelowgroup(2.2%)includedchildrenwithlowerlevelsofthisdimension.Themoderate
group(51.7%)comprisedapproximatelyhalfofthechildren.Thehighgroup(46.1%)included
childrenwhoshowedhigherlevelsduringearlychildhood.Allthreetrajectoriesincreasedline-
arlyfromages2to5.ThepanelCinFig1illustratesthetrajectoriesontheAssertiondimen-
sionforlow(3.8%),moderate(58.3%),andhigh(37.9%)groups.Forthelowgroup,thetrends
canbedescribedasalineargrowingtrajectory,whereasforthemoderateandhighgroups,the
trendswerestableovertimeandremainedatarelativelyhighlevel.
PredictorsforSocialSkillsTrajectoryMembership
Wenextexaminedthecontributionsofallpredictorvariablesindistinguishinggroupmember-
shipsforchildsocialskillstrajectories.Weexaminedtherelativecontributionsoffour
Fig1.Developmentaltrajectoriesofsocialskilldimensionsfromages2–5.(A)Developmental
trajectoriesonCooperationdimension.(B)DevelopmentaltrajectoriesonSelf-controldimension.(C)
DevelopmentaltrajectoriesonAssertiondimension.
doi:10.1371/journal.pone.0135357.g001
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SocialSkillsTrajectories
Table3. Multinomiallogisticanalysesforpredictingsocialskillstrajectorygroupmembershipsbycovariatesandfourcategoriesofparenting.
PredictorVariables LowVs.Moderate LowVs.High
B WaldTest p B WaldTest p
Cooperation
Sex –.51 –1.29 .20 –1.36 –3.53 .00
Sibling –.09 –.24 .81 .20 .56 .57
2-yearcognitiveandemotionalinvolvement .19 2.22 .03 .14 1.76 .08
2-yearavoidanceofpunishmentandrestriction .22 1.45 .15 .02 .16 .87
2-yearsocialstimuli .01 .13 .89 .04 .43 .67
2-yearsocialsupportonparenting –.06 –.60 .55 –.05 –.53 .60
Self-Control
Sex –.79 –1.15 .25 –1.88 –2.78 .01
Sibling –.52 –.83 .41 –.23 –.37 .71
2-yearcognitiveandemotionalinvolvement .06 .58 .56 .16 1.47 .14
2-yearavoidanceofpunishmentandrestriction .20 1.29 .20 .14 .90 .37
2-yearsocialstimuli .30 2.15 .03 .29 2.12 .03
2-yearsocialsupportonparenting .20 1.47 .14 .19 1.41 .16
Assertion
Sex –1.02 –2.01 .04 –1.56 –3.13 .00
Sibling .08 .19 .85 .16 .38 .70
2-yearcognitiveandemotionalinvolvement .19 2.24 .03 .15 1.84 .07
2-yearavoidanceofpunishmentandrestriction .33 2.59 .01 .27 2.20 .03
2-yearsocialstimuli .09 .92 .36 .14 1.33 .18
2-yearsocialsupportonparenting –.13 –1.13 .26 .03 .26 .79
doi:10.1371/journal.pone.0135357.t003
parentingpracticesatage2:cognitiveandemotionalinvolvement,avoidanceofpunishment
andrestriction,socialstimulation,andsocialsupportforparenting.Thechild’ssexandthe
presenceofsiblingswereenteredascovariatesinordertocontrolfortheseeffectsonchild
socialskillsdevelopment.Inthemultinomiallogisticanalysis,allgroupswerecomparedtothe
lowgroup(Table3).Whenallpredictorswereenteredtogetherinthemodels,severalchild
andfamilialcharacteristicsemergedassignificantfactors.Thechild’ssexmostconsistentlydis-
tinguishedsocialskillsgroupmembership:Beingagirlwasassociatedwithhigherlevelsof
socialskillsdevelopment(B=–1.36,p<.01forCooperation;B=–1.88,p=.01forSelf-Con-
trol;B=–1.56,p<.01forAssertion)andthechild’ssexeffectgavesomeindicationofdistin-
guishingbetweenthelowandmoderategroupforAssertion(B=–1.02,p=.04).Thesecond
strongestassociationwithdifferentialtrajectorymembershipswascognitiveandemotional
involvement.Thistendedtoincreasethelikelihoodofmembershiptothemoderateandhigh
groups(B=.19and.14,p=.03and.08,respectively).ForAssertion,cognitiveandemotional
involvementalsodistinguishedbetweenthelowgroupandboththemoderateandhighgroups
intheexpecteddirection(B=.19and.15,p=.03and.07,respectively).Socialstimulationsig-
nificantlydistinguishedbetweenthelowandboththemoderateandhighgroupsontheSelf-
Controldimension(B=.30and.29,p=.03and.03,respectively).ForAssertion,socialstimula-
tionshowedsomeindicationofdistinguishingthelowfromthemoderate(B=.33,p=.01)and
fromthehighgroups(B=.27,p=.03).Finally,withinamultivariateframework,thepresence
ofsiblingsandsocialsupportforparentingdidnotdistinguishbetweenanypairsoftrajectory
groups.
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SocialSkillsTrajectories
Discussion
Inthepresentstudy,weanalyzedlongitudinaldatacollectedthroughoutJapaninorderto
describethepatternsofconsistencyandchangeinthedevelopmentofsocialskillsforpre-
schoolers.Wealsoexaminedthelinksbetweenthedevelopmentalpatternsofchildren’ssocial
skillsandparentingpracticesatanearlydevelopmentalphase.
Althoughtherehavebeenseverallongitudinalstudiesandreviewsofthecourseofprosocial
developmentduringthepreschoolperiod[10,27,28],fewlongitudinalstudieshavefocusedon
thespecificcourseofsocialskills.Thepresentstudyprovidedthreeimportantcontributionsto
thestudyofpreschoolers’socialskillsdevelopment.Thefirstconcernsthedevelopmentalpro-
filesofpreschoolers’socialskills.Hay[28]mentionedthatitisduringthepreschoolperiod
thatchildrenlearnhownottobegood,quotingaphraseinMachiavelli’sThePrince:“Aprince
mustlearnhownottobegood.”However,fromasocializationtheoryperspective[10],pre-
schoolagedchildrenlearnhowtobegoodwithage;namely,theyshowanincreaseinthefre-
quencyofprosocialbehaviors.Thepresentresultssupportthisperspective.Children’ssocial
skillsdemonstratedanupwardtrendoneverydimensionduringthepreschoolperiodofages2
to5(Table1).Ourresultsindicatethatevenduringthepreschoolperiod,childrenlearnand
buildtheirsocialskills,whicharetheveryfoundationsofprosocialbehaviors.
Oursecondcontributionistheidentificationofthreedevelopmentaltrajectoriesforeachof
thethreesub-dimensionofsocialskills,low,moderate,andhigh,usinggroup-basedtrajectory
models.Ashypothesized,thesedescriptionsoflongitudinalprofilesweresimilartoprior
researchthatexaminedtrajectoriesofchildren’sprosocialdevelopment[7,12,13,15].Inaddi-
tion,asmallpercentageofchildreninthepresentstudyshowedlowlevelsofsocialskillsfrom
ages2to5.Inpreviousstudiesthatexaminedthetrajectoriesofprosocialbehaviorsfromchild-
hoodtoearlyadolescence,thepercentagesoflowsocialskillsgroupsrangedfrom7%to53%;
however,inthepresentstudy,10%orlessofpreschoolagedchildrendisplayedachronically
lowlevelofsocialskills.Thissmallerpercentagesuggeststhatwemaybeabletoidentifya
groupofchildrenininneedofsocialskillstraining.Italsosuggeststhatweneedtoidentify
potentialprotectivefactorsthatdistinguishchildreninachronicallylowgroupfromthosewho
displaymoderateorhighlevelskillsduringearlychildhood.
Ourthird,andmostimportant,findingwasthelinksbetweenparentingpracticesatage2
andchildsocialskillsdevelopment.Pastresearchhasshownthatpositiveparentingcanpredict
latersoundsocialdevelopmentofchildren[18,19,20],andnegativeparentingcanalsopredict
children’ssubsequentproblembehaviorsandinterpersonalconflict[6,17].Asshownin
Table2,eachparentingpracticewasbasicallypositivelyassociatedwithchildren’ssocialskill
subscalescores.Itisinterestingtonotethatcorrelationsofparentingpracticesatage2and
children’ssocialskillsscoresatage2aresmallbutincreaseasthechildrengetolder.Thisindi-
catesthatparentingpracticesatage2maynotconferashort-termbenefittochildren,but
ratherbearfruitovertime.
Weconductedmultinomiallogisticanalysestoexaminetowhatextenteachdimensionof
parentingpracticesaffectschildsocialskillsdevelopment.Theresultsindicatethatcognitive
andemotionalinvolvementtendstostimulatethedevelopmentofCooperationandAssertion,
thatavoidanceofrestrictionandpunishmentencouragesachildtoincreaseAssertion,and
thatsocialstimulationdrivesdevelopmentofSelf-control.Theseresultssuggestthatchild
socialskillsdevelopmentisdomain-specificallyassociatedwithparentingpractices.Thatis,
Cooperation(aswellasAssertion)wasenhancedbycognitiveandemotionalinvolvement,
Self-controlbysocialstimulation,andAssertionbyavoidanceofrestrictionandpunishment.It
isreasonabletomentionthattreatingachildwithemotionalwarmthhelpsthechildacquire
skillsforactingcooperativelytoavoidconflictwithothersandtointeractwellwithothers.
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