carolyn m. parkinson1* 2 3 - biorxiv · carolyn m. parkinson1*, adam m. kleinbaum2, and thalia...
TRANSCRIPT
SpontaneousNeuralEncodingofSocialNetworkPosition
CarolynM.Parkinson1*,AdamM.Kleinbaum2,andThaliaWheatley3
1DepartmentofPsychology,UniversityofCalifornia,LosAngeles,1285FranzHall,Box
951563,LosAngeles,California,USA90095
2TuckSchoolofBusiness,DartmouthCollege,100TuckHall,Hanover,NewHampshire,USA
03755
3DepartmentofPsychologicalandBrainSciences,DartmouthCollege,6207MooreHall,
Hanover,NewHampshire,USA03755
*Correspondingauthor:
CarolynM.Parkinson,Ph.D. Telephone:(310)206-8177
DepartmentofPsychology Fax:(310)206-5895
UniversityofCalifornia,LosAngeles E-mail:[email protected]
1285FranzHall,Box951563
LosAngeles,CA90095
Keywords:socialnetworkanalysis,socialperception,functionalMRI,multi-voxelpattern
analysis
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SpontaneousNeuralEncodingofSocialNetworkPosition
Humansformcomplexsocialnetworksthatincludenumerousnon‐reproductivebondswithnon‐kin.Navigatingthesenetworkspresentsaconsiderablecognitivechallengethoughttohavecomprisedadrivingforceinhumanbrainevolution.Yet,littleisknownabouthowandtowhatextentthehumanbrainencodesthestructureofthesocialnetworksinwhichitisembedded. By combining social network analysis and multi‐voxel pattern analysis offunctional magnetic resonance imaging (fMRI) data, we show that social networkinformation about direct relationships, bonds between third parties, and aspects of thebroadernetworktopologyisaccuratelyperceivedandautomaticallyactivateduponseeingafamiliarother.
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Unlikemanyotherspeciesthatenactsocialbehaviorinlooseaggregations(e.g.,
swarms,herds),humansformgroupscomprisedofmanylong-term,intense,non-
reproductivebondswithnon-kin1.Thecognitivedemandsofnavigatingsuchgroupsare
thoughttohavecomprisedadrivingforceinhumanbrainevolution2.Yet,littleisknown
abouthowandtowhatextentthehumanbrainencodesthestructureofthesocial
networksinwhichitisembedded.Here,wecharacterizedthesocialnetworkofan
academiccohort(N=277),asubsetofwhom(N=21)completedafunctionalmagnetic
resonanceimaging(fMRI)studyinvolvingviewingvideosofindividualswhovariedin
termsof“degreesofseparation”fromthemselves(socialdistance),theextenttowhich
theyarewell-connectedtowell-connectedothers(eigenvectorcentrality–EC),andthe
extenttowhichtheyconnectotherwiseunconnectedindividuals(brokerage).
Understandingtheseaspectsofothers’socialnetworkpositionsrequirestrackingnotonly
directrelationships,butalsobondsbetweenthirdpartiesandthebroadernetwork
topology.Pairingnetworkdatawithmulti-voxelpatternanalysis,weshowthatsocial
networkpositioninformationisbothaccuratelyperceivedandspontaneouslyactivated
uponencounteringfamiliarindividuals.Thesefindingselucidatehowthehumanbrain
encodesthestructureofitssocialworld,andunderscoretheimportanceofintegratingan
understandingofsocialnetworksintothestudyofsocialperception.
Relationshipsareintrinsictohumanbehavior.Everydayinteractionsareshapednot
onlybyourownrelationships,butalsobyknowledgeofbondsbetweenthirdpartiesand
thebroadersocialnetworksinwhichweareembedded.Well-connectedindividualscan
effectivelythreatenorbolsterone’sreputation3,thosewhobridgeotherwisedisparate
groupscanefficientlyseekandspreadinformation4,andknowledgeofmutualties
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influencesinformation-sharingandtrust5.Humansocialintelligencerests,inpart,ona
calculusthatinheresinanunderstandingofsocialnetworkstructure.
Isknowledgeaboutothers’socialnetworkpositionsactivatedonlywhenexplicit
goalsrequireit,orspontaneously,wheneverweencounterfamiliarindividuals?Itmaybe
efficienttoprocesssuchinformationonlywhenourgoalsrequireit(e.g.,determininghow
toobtaininformation;forecastingtherepercussionsofasocialmisstep).Alternatively,it
maybebeneficialtoactivatesuchknowledgespontaneouslywhenencounteringothers,
giventheimportanceofsocialnetworkpositiontomanyaspectsofbehaviorandto
impressionsofstatusandcompetence3,6.Humansspontaneouslyregisteragreatdealof
informationwhenperceivingotherpeople(e.g.,intentions,traits,emotions7,8),presumably
tofacilitateappropriate,beneficialsocialinteractions.Thus,thebrainmayrunseveral
social“daemons”–efficient,backgroundprocessesthatspontaneouslyregisterinformation
usefulforpredictingthesocialrepercussionsofpotentialactions,and,morebroadly,to
informcognitionandbehavior.
Totestwhetherthebrainspontaneouslyencodesthesocialnetworkpositionsof
familiarothers,wescanned(fMRI)membersofarealworldsocialnetwork(seeFig.1;
Methods)astheyviewedbriefvideosof12classmates(Fig.2).Theonlytaskwasto
indicatewhenthesamevideowaspresentedtwiceinarow(seeMethods)inorderto
ensureattentionwithoutanyinstructionstoretrievesocialrelationshipknowledge,or
personknowledgemoregenerally.Therefore,weconsideranysocialnetworkposition
informationencodedwhileparticipantsperformthistasktoberetrievedspontaneously
(i.e.,withoutinstruction).
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Eachclassmateineachparticipant’sstimulussetwascharacterizedaccordingto
threemetricsderivedfromthesocialnetworkdata:geodesicsocialdistancefromthe
participant;EC;andconstraint,aninversemeasureofbrokerage.Geodesicsocialdistance
referstotheminimumnumberofintermediarysocialtiesrequiredtoconnecttwo
individuals.ECisaprestige-basedcentralitymetricthatconsidersnotonlyhowmany
connectionsagivenindividualhas,butalsothecentralitiescharacterizingeachcontact9.
HighECimpliesthatanindividualiswell-connectedtowell-connectedothers;lowEC
impliesthatanindividualhasfewfriendswhotendtobeunpopular.Prestige-based
centralitymetricsareparticularlyusefulforcharacterizingsocialstatus,giventhatbeing
namedasafriendbyapopularindividualshouldincreaseone’ssociometricstatus(i.e.,the
extenttowhichsomeoneislikedbyothers)morethanbeingnamedbysomeoneless
popular9.Individualswhoconnectotherswhowouldnototherwisebeconnectedoccupy
networkpositionslowinconstraint,andhavethecapacitytoserveas“brokers”of
resources(e.g.,information)inthenetwork.Becauseofthestructureoftheirlocalsocial
ties,brokerscancoordinatebehaviorandtranslateinformationacrossstructuralholesin
networks4.
Toprobeforthespontaneousencodingofsocialnetworkpositioninformation,we
usedrepresentationalsimilarityanalysis(RSA),whichdistillsfMRIresponsepatternsinto
representationaldissimilaritymatrices(RDMs)thatindicatethedegreetowhichparticular
brainregionsdistinguishbetweensetsofstimuliormentalstates10.BecauseRDMsare
abstractedawayfromthespatiallayoutofneuroimagingdata(i.e.,theyareindexedby
experimentalcondition;Fig.3),RSAaffordstheevaluationofthedegreetowhichsimilarity
structurescontainedinparticularbrainregionsreflectthoseofdataacquiredusingother
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modalitiesofmeasurementorcomputationalmodels10(here,thesocialnetworkdata).
Specifically,inthecurrentstudy,weusedagenerallinearmodel(GLM)decomposition
searchlightapproach11.NeuralRDMswereiterativelyextractedwithin9-mmradius
spherescenteredateachpointineachparticipant’sbrain.Withineachparticipant,each
localneuralRDMwasmodeledasaweightedcombinationofRDMsbasedonpropertiesof
thesocialnetworkpositionsoftheindividualsinthatparticipant’sstimulusset(Fig.3).
Usingthistechnique,participants’brainsweremappedintermsofthedegreetowhichthe
representationalcontentoflocalneuralresponsestofamiliarotherscouldbeexplainedby
thoseindividuals’positionsintheirsocialnetwork,andintermsofwhereinformation
aboutspecificsocialnetworkpositioncharacteristicwascarriedreliablyacross
participants(Fig.4).
Wehypothesizedthatgeodesicsocialdistancewouldbespontaneouslyencoded,
giventheimportanceofthisinformationfordeterminingself-relevance.One’simmediate
socialtiesareobviouslymostself-relevant.Giventheimportanceofreputation
managementforhumanbehavior12,individualstwo“degreesaway”mayberelatively
importanttoidentifyandmonitor:Negativeinteractionswithsuchindividualscould
damagerelationshipswithone’sdirectconnections.Similarly,sharingmutualfriendsmay
enhancetrust,giventhepotentialreputationcostsofbadbehavior5.Associaldistance
betweenpeopleincreases,theirrelevancetoeachotherdecreases.Wepredictedthatsocial
distance-relatedinformationwouldbecarriedinthelateralsuperiortemporalcortex
(STC)andinferiorparietallobule(IPL),aswellasthemedialprefrontalcortex(MPFC),
givenpastresearchimplicatingtheseregionsinencodingsocialdistance13andself-
relevancemoregenerally14.
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Socialdistancewasreliablysignaledinalargeclustercenteredinthelateral
posteriorSTCandextendinginferiorlythroughoutposteriorlateraltemporalcortex(LTC),
andsuperiorlytotheanterioraspectoftheIPL(seeFig.4;TableS1).Pastresearch
demonstratedthatmulti-voxelresponsepatternsinthisregionencodeegocentricspatial
andabstract(e.g.,social)distanceswhenexplicitlyjudging14ormentallynavigating15such
distances14;thecurrentfindingssuggestthatthisregionalsoencodesegocentricdistances
spontaneously(i.e.,intheabsenceofanyexplicitdistancetask).Thus,whenencounteringa
familiarindividual,knowledgeofagent-to-agentrelationshipsappeartobespontaneously
retrieved,suchthatrepresentationsofotherpeopleinthisregionareorganizedintermsof
whethersomeoneisafriend,afriend-of-a-friend,orfartherremovedfromoneselfinsocial
ties.Ithasbeensuggestedthatsomeregionswithinposteriorparietalcortex,suchasthe
anteriorIPL,whichhavewell-establishedrolesinrepresentingandnavigatingphysical
space,analogouslyrepresentmoreabstractrelationships(e.g.,socialtiesbetween
agents)16,17.Thecurrentresultssuggestthatwhenencounteringfamiliarindividuals,
humansmayspontaneouslyretrieveknowledgeofwheretheyarelocated,relativeto
oneself,inamentalmapof“socialspace”.
AlthoughtheLTCandIPLregionsthatcarriedinformationaboutsocialdistance
herehavepreviouslyimplicatedinencodingsocialdistance13,14,someregionspreviously
implicatedinsignalingsocialdistancewerenotimplicatedinthecurrentstudy.For
instance,previousresearchhasimplicatedMPFCindistinguishingfriendsfromstrangers13,
andarecentstudyimplicatedthehippocampusandposteriorcingulatecortex(PCC)in
trackingsocialdistancesbetweenparticipantsandcharactersinaninteractivegame18.
Differencesbetweenthecurrentresultsandthoseobservedinpreviousinvestigations
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likelyreflectdifferencesindataanalyticapproachesandinhowsocialdistancehasbeen
operationalized.Inthecurrentstudy,participantsonlysawpersonallyfamiliarindividuals,
andsocialdistancewasoperationalizedintermsofgeodesicdistanceintheirreal-world
socialnetwork.Inpreviousneuroimagingstudies,theterm“socialdistance”hasbeen
operationalizedinwidelyvaryingways,suchasthepresenceofsocialties13,thestrengthof
socialties14,anddistancefromoneselfinatwo-dimensional(affiliationxstatus)
representationalspace18.Giventhatthesevariableslikelyhavedifferentialconsequences
forsocialcognitionandbehavior,itisnotsurprisingthattheyareencodedbyatleast
partiallydistinctneuralsubstrates.
Whereassocialdistanceisinherentlyrelativetotheperceiver,otheraspectsof
familiarothers’socialnetworkpositions,suchasthedegreetowhichone“bridges”
differentareasofthenetworkandthenumberoffriendssomeonehas,areincreasingly
thoughttobelargelystable,possiblyheritable,dispositionaltendenciesthatshapesocial
behavior19,20.Therefore,wehypothesizedthatECandconstraintwouldbeencodedin
brainregionsinvolvedinencodingothers’traitsandbehavioraltendenciesmoregenerally,
suchastheMPFC,whichiswidelyimplicatedininferringandencodingperson
knowledge21andinintegratingknowledgeofpersonalitytraitsinordertosignalindividual
identity22.
InformationaboutECwasreliablycarriedinbrainregionsthatencodeindividual
identitywhenimaginingothers’actions22(i.e.,MPFC)andviewingfaces23,24(e.g.,temporal
pole;fusiformgyrus;seeFig.4andTableS2),suggestingthatsociometricstatusmay
compriseadimensionofmeaningfororganizingmentalrepresentationsofothers.ECwas
alsoencodedinmedialparietalcortex(precuneus,PCC),aregionpreviouslybeenshownto
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encodeextraversion22,whichismodestlycorrelatedwithEC25,suggestingthatthisregion
mayencodedispositionaltendenciescommontobothextraversionandEC.Inaddition,
recentworkhasalsoshownthatthemedialparietalcortex,aswellasotherregions
involvedininferringothers’mentalstates,intentions,andtraits(e.g.,MPFC;
temporoparietaljunction),respondspreferentiallytowell-likedindividuals,whichis
thoughttoreflectperceiversbeingpreferentiallymotivatedtounderstandtheinternal
statesofpopularothers26.Thecurrentfindingsareconsistentwiththenotionthatbrain
regionsthatrepresentothers’internalstatesandbehavioraltendencies(e.g.,PCC,MPFC)
tracksociometricstatus,andsuggestthatlikeotherfacetsofsocialstatus(e.g.,
dominance27,prestige28),ECmaymodulateattentiontotheinternalstatesofothers.Future
behavioralstudiesshoulddirectlytesttheimpactofEConsocialattention.
InformationaboutECwasalsoreliablycarriedinunexpectedregions,suchas
extrastriatevisualcortex(EVC).Thisresultisunlikelytobeduetolow-levelvisual
characteristicsofstimuli,aseachparticipanthadauniquestimulusset,andbecausevideos
correspondingtoeachindividualineachstimulussetwerehorizontallymirroredonhalfof
trials(seeMethods).However,thisfindingmaynonethelessreflecttheeffectsofsocial
statusintermsofsocialtiesonvisualattention.Peopletendtopreferentiallyorienttoward
high-statusindividualsandtothelocioftheirattention,presumablytoobtainbehaviorally
relevantinformationaboutoursurroundings28–30.GiventhatECisreliablysignaledinEVC
responsepatterns,futureresearchshouldtestifvisualattentionisalsopreferentially
allocatedtocentralactorsinone’ssocialnetwork.
EC-basedRDMswerealsosignificantlyrelatedtoneuralRDMsinbrainareas
previouslyimplicatedinevaluatingsocialstatusintermsofdominance,prestige,and
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morality,suchastheventralMPFCandventrolateralprefrontalcortex(VLPFC)31–33.The
involvementoftheventralMPFCinsocialstatusencodinghasbeensuggestedtoreflecta
moregeneralroleinassessingthevalueofstimuli32,whereastheVLPFChasbeen
suggestedtoencodesocialstatusinordertoappropriatelymodulatebehavioral
responding,whichisthoughttobeaprimaryfunctionofstatuscues31.Wesuggestthat
theseregionslikelyencodeECforsimilarreasons,ashighECindividualshavehigh
behavioralrelevanceandvalueassocialpartners.Forexample,individualsconnectedto
well-connectedothersmaybeprotectedfrommistreatmentbecausetheyaremorelikely
tobedefendedbyothers,whothemselvesaremorelikelytobedefended.Lessriskis
associatedwithwrongingalowECindividual,giventhatlowECindividualshavelittle
influenceonthespreadofinformationandotherresources3.
Thecurrentresultssuggestthatwhenencounteringafamiliarindividual,the
degreetowhichthatindividualiswell-connectedtowell-connectedothersshapes
processesrelatedtovaluation,behavioralmodulation,attention,andencodingothers’
internalstates,dispositionalcharacteristics,andidentities.Manyofthesefindingsechothe
knowneffectsofotherdimensionsofsocialstatus(e.g.,statusconferredbydominance).
Althoughagreatdealofpastpsychologicalandneuroimagingresearchonsocialstatushas
focusedonphysicaldominance,wenotethatovertphysicalviolenceisrelativelyrarein
contemporaryhumangroups34andthatsocialsupportandreputationmanagementare
centraltoeverydayhumanlife12.Socialpowerinsuchgroupsmayberelativelyless
contingentonindividualstrengthandphysicalaggression,andmoredependentongroup
dynamicsandaffiliativerelationshipmaintenance.Thus,sociometricstatusislikely
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especiallyrelevanttomodernhumans,andmeritsfurtherattentioninsocialperception
andneuroscienceresearch.
InadditiontosocialdistanceandEC,diverseaspectsofsocialcognitionand
behavior(e.g.,decidinghowtoeffectivelyseekorspreadinformation;trustdecisions)
wouldbenefitfromencodingnetworkconstraint.Lowconstraintindividualscanbroker
theflowofinformationbetweengroups,andthus,exertadisproportionateinfluenceonthe
flowofideasandresources4.Additionally,individualsinrelatively“closed”localnetworks,
characterizedbyhighconstraint,suffergreaterreputationcostsforbadbehavior;
correspondingly,constraintcanfostertrustandcooperation4.Giventhedearthofprevious
researchinvestigatingtheperceptionofconstraint,wemadenospecificpredictionsabout
whichbrainregionswouldbeinvolvedinencodingthisfacetofsocialnetworkposition.
LargeclustersspanningbothrightandleftlateralSTCcarriedinformationabout
constraint(TableS3),asdidasmallerclusterinthesupplementarymotorarea(SMA).
AlthoughthelateralSTCandSMAareimplicatedinbiologicalmotionprocessing35and
actionunderstanding36,respectively,thisfindingwasnotattributabletotheamountof
movementinvideos(seeSI).Aperceiver’sknowledgeofthenetworkconstraintofan
individual,orofassociateddispositions,mayimpacthowthatperceiverattendstothat
individual’smovements.Forexample,becausebrokersmaybeperceivedasexceptionally
charismaticorinteresting(e.g.,becausetheyoftenserveassourcesofnovelinformationor
opportunities4),theymaycommanddifferentialamountsofattentiontotheirexpressions
andgestures.Brokersmayalsodifferintheamountofsocialmeaningcarriedintheirfacial
andbodilymovements(e.g.,fidgetingaimlesslyvs.usingmovementtoexpressoneself
coherently).ThelatterexplanationwouldbeconsistentwithevidencethattheSTS
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respondstothesocialmeaning,ratherthanamount,ofmovementindynamicdisplays37.
Futurestudiescouldarbitratebetweenthesehypothesesbytestingifstrangersareableto
differentiatebetweenindividualshighandlowinconstraintbasedontheirobserved
movements.Ifso,thiswouldsuggestthatnetworkconstraintisencodedinlateralSTC
becausethisaspectofsocialnetworkpositionisapparentinhowindividualscarry
themselves.Ifnot,thiswouldbeconsistentwiththeinterpretationthatperceivers’
knowledgeofanindividual’snetworkconstraint,orofqualitiesrelatedtothisaspectof
socialnetworkposition,influenceshowperceiversattendtothatindividual’sexpressions,
gestures,andbodilymovements.
Afterscanning,participantswereaskedabouttheirperceptionsofeachSNA-
derivedmetricofinterestforeachindividualintheirstimulusset(seeSI).Thisallowedus
totesttheaccuracyofparticipants’perceptionsofothers’socialnetworkpositions,andto
evaluatehowwellparticipants’perceptionsmatchedthedatausedtoconstructtheir
stimulussets.Post-scanratingsindicatedthatparticipants’explicitperceptionsofthe
socialnetworkpositionsoftheindividualsintheirstimulussetscloselymatchedreality.
Veridicalconstrainthadasignificanteffectonperceivedconstraint(ß=19.44SE=2.01,p<
.0001),andveridicalEChadasignificanteffectonperceivedEC(ß=14.95,SE=0.93,p<
.0001).Further,subjectiveratingsofsocialcloseness(ß=-31.00,SE=1.62,p<.0001),
proportionofsocialtimespenttogether(ß=-22.74,SE=1.84,p<.0001),andfrequencyof
discussions(ß=-33.77,SE=1.89,p<.0001)variedasafunctionofgeodesicnetwork
distance(seeMethodsandFig.5).
Althoughparticipantshadconsciouslyaccessibleknowledgeofthesocialnetwork
positioncharacteristicsstudiedhere(Fig.5),thetaskusedinthefMRIstudy(aone-back
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memorytask)didnotrequireparticipantstoretrievesocialrelationshipknowledge,and
fromparticipants’perspectives,thesocialnetworkquestionnaireandfMRIstudywere
ostensiblyunrelated.Nevertheless,upto40%ofthevarianceinsimilaritystructuresof
localfMRIresponsestopersonallyfamiliarotherscouldbeexplainedmerelyby
characteristicsofthoseindividuals’positionsintheperceiver’ssocialnetwork(Fig.4b).
Thesefindingsareconsistentwithbehavioralevidencethathumansspontaneously
activateknowledgeaboutotherpeopleuponencounteringtheminordertoinform
cognitionandbehavior7,8,andsuggestthathumansspontaneouslyactivatecomplex
knowledgeaboutotherpeople’spositionsintheirsocialnetworkswhenviewingthem.
Thesefindingsareconsistentwithpsychologists’mountingappreciationforthe
importanceofbothdirectandindirectrelationshipknowledgetoeverydaycognitionand
behavior.Everydayinteractionsareinfluencednotonlybyinformationthatwouldbe
availabletoanyobserver,butalsobypatternsofpersonalandthird-partyrelationships.By
adoptinganinterdisciplinaryapproachcombiningtheoryandmethodsfromneuroscience,
psychology,andSNA,wecanbegintouncoveradeeperunderstandingofhowthehuman
brainnegotiatestheintricaciesofeverydaysociallife.
Methods
Part1:Socialnetworkcharacterization
Participants.ParticipantsinPart1ofthestudywere275first-yearMastersof
BusinessAdministration(MBA)studentsataprivateuniversityintheUnitedStateswho
participatedaspartoftheircourseworkonleadership(91females;184males).Thetotal
classsizewas277students;twostudentsfailedtocompletethequestionnaire(i.e.,
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responserate=99.3%).Allprocedureswerecompletedinaccordancewiththestandardsof
theDartmouthCommitteefortheProtectionofHumanSubjects.
Socialnetworkcharacterization.Tocharacterizethesocialnetworkofallfirst-year
students,anonlinesocialnetworksurveywasadministered.Participantsfollowedane-
mailedlinktothestudywebsitewheretheyrespondedtoasurveydesignedtoassesstheir
positioninthesocialnetworkoffirst-yearstudentsintheiracademicprogram(seeSI).The
surveyquestionwasadaptedfromBurt38andhasbeenpreviouslyusedinthemodified
formusedhere25,39.Itread,“Considerthepeoplewithwhomyouliketospendyourfree
time.Sinceyouarrivedat[institutionname],whoaretheclassmatesyouhavebeenwith
mostoftenforinformalsocialactivities,suchasgoingouttolunch,dinner,drinks,films,
visitingoneanother’shomes,andsoon?”
Aroster-basednamegeneratorwasusedtoavoidinadequateorbiasedrecall.
Classmates’nameswerelistedinfourcolumns,withonecolumncorrespondingtoeach
sectionofstudentsintheMBAprogram.Nameswerelistedalphabeticallywithinsection.
Participantsindicatedthepresenceofasocialtiewithanindividualbyplacingacheckmark
nexttohisorhername.Participantscouldindicateanynumberofsocialties,andhadno
timelimitforresponding.
SocialnetworkanalysiswasperformedusingtheRpackageigraph40,41.Threesocial
network-derivedmetricswereextractedforeachnode:constraint,ECandgeodesic
distancefromeachclassmate,asdescribedingreaterdetailbelow.
Constraint.Theconstraintofactoriisgivenbythefollowingequation,wherePij
correspondstotheproportionofi'sdirectsocialtiesaccountedforbyhis/hertietoactorj.
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Theinnersummationapproximatestheindirectconstraintimposedonibyotheractors,q,
whoaresociallyconnectedtobothiandj(i.e.mutualfriendsofiandj):
𝑪𝒐𝒏𝒔𝒕𝒓𝒂𝒊𝒏𝒕𝒊 = (𝑷𝒊𝒋 + 𝑷𝒊𝒒𝒏
𝒒~𝟏𝑷𝒒𝒋)𝟐
𝒏
𝒋~𝟏
Anunweighted,undirectedgraphwasusedtoestimateconstraint;i.e.,thepresence
ofanysocialtie,irrespectiveofitsdirection,wasusedtocomputetheconstraintofeach
node.Constraintisaninversemeasureofnetworkbrokerage.
EC.Agraphconsistingofnodesconnectedbyedgescanbecharacterizedbyan
adjacencymatrixA,populatedbyelementssuchthataij=1ifnodesiandjaredirectly
connected,andaij=0ifthesenodesarenotconnected.TheECofeachnodeisgivenbythe
eigenvectorofAinwhichallelementsarepositive.Therequirementthatallelementsof
theeigenvectormustbepositiveyieldsauniqueeigenvectorsolution(i.e.,that
correspondingtothegreatesteigenvalue).Here,whencomputingEC,thedirectionalityof
thegraphwaspreserved;intheeventofasymmetricrelationships,onlyincoming,rather
thanoutgoing,tieswereusedtocomputeEC.
Socialdistance.Geodesicsocialdistancereferstothesmallestnumberof
intermediarysocialtiesrequiredtoconnecttwoindividualsinanetwork.Individualswho
aparticipantnamedasfriendshaveadistanceofonefromhim/her.Individualswhoma
participant’sfriendsnamedasfriends(butwhowerenotnamedasfriendsbythe
participant)haveadistanceoftwofromtheparticipant.Individualswhowerenamedas
friendsbyclassmatesatadistanceoftwofromtheparticipant(butnotbytheparticipant
orhis/herfriends)haveadistanceofthree,andsoon.
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15
Part2:Neuroimagingstudy
Participants.AsubsetofindividualswhohadcompletedPart1participatedina
subsequentneuroimagingexperiment.Participantswereinformedduringclassaboutthe
opportunitytoparticipateinanfMRIstudythatwasostensiblyunrelatedtotheonline
questionnaireinPart1,andthattheywouldreceive$20/hourascompensationandimages
oftheirbrains.Allparticipantswereright-handed,fluentinEnglish,andhadnormalor
corrected-to-normalvision.Participantsprovidedinformedconsentinaccordancewiththe
policiesoftheDartmouthCollegeCommitteefortheProtectionofHumanSubjects.
Twenty-fourparticipants(12females)completedthefMRIstudy.Thesamplesizewas
chosenbasedonpreviousfMRIstudiesusingsimilarparadigmsandRSAmethods11,42.One
participantwasexcludedduetoimageartifact,andtwowereexcludedbecausetheyscored
lessthan65%correctontheone-backmemorytaskusedinthescanner(thisthreshold
wasbasedonwhathasbeenusedpreviouslyinsimilarstudies43).Consequently,we
analyzeddatafrom21participants(10females,aged25-33,M=27.95,SD=2.16).Asa
within-subjectsdesigninvolvingnogroupallocationwasused,blindinginvestigatorsto
between-subjectsconditionsandrandomassignmentofparticipantstoconditionswere
notapplicable.
Imageacquisition.ParticipantswerescannedattheDartmouthBrainImaging
Centerusinga3TPhilipsAchievaInterascannerwitha32-channelheadcoil.Anecho-
planarsequence(35msTE;2000msTR;3.0mmx3.0x3.0mmresolution;80x80matrix
size;240x240mmFOV;35interleavedtransversesliceswithnogap;3.0mmslice
thickness)wasusedtoacquirefunctionalimages.Functionalrunsconsistedof180
dynamicscans,foratotalacquisitiontimeof360sperrun.Ahigh-resolutionT1-weighted
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anatomicalscanwasacquiredforeachparticipant(8.2sTR;3.7msTE;240x187FOV;
0.938mmx0.938mmx1.0mmresolution)attheendofthescanningsession.Foam
paddingwasplacedaroundsubjects’headstominimizemotion.
Stimuli.Eachparticipant’scustomizedstimulussetconsistedofshortvideosoffour
individualsateachofthreegeodesicdistances(i.e.,one,two,andthree)fromthe
participantinthesocialnetworkoffirst-yearMBAstudents.ThetwohighestandlowestEC
individualsateachsocialdistancewereincludedinthestimulusset(Fig.2).
Thevideosusedasstimuliconsistedofindividualsintroducingthemselves(e.g.,“Hi
mynameis[firstname],andyoucancallme[firstname/nickname]”).Avideoofthiskind
wasmadeinvolvingeachstudentatthebeginningoftheacademicyearasaresourcefor
otherstudentsandfaculty.Videosweretruncatedto2s,beginningwhenthesubjectbegan
tosaytheword,“Hi,”andwerepresentedwithoutsound.PriortoenteringthefMRI
scanner,participantswereshowneachvideowithsoundtofamiliarizethemselveswiththe
stimuli.
fMRIparadigm.ThefMRIstudyconsistedof10runsandfollowedarapidevent-
relateddesignwithaninter-trialintervalconsistingof4soffixation(Fig.2c).Fournull
events,eachconsistingofanadditional2soffixation,wererandomlyinsertedintoeach
run.Ineachrun,fourrepetitionsof14eventcategories(12identities;1nullevent;1catch
trial)werepseudo-randomizedsuchthattherewerenoconsecutiverepeatsofthesame
category.Horizontalmirroringwasrandomlyappliedtohalfthepresentationsofeach
stimuluswithineachruntoreducesimilaritieswithinidentitiesduetolocallow-level
visualfeatures.Catchtrialsinvolvedseeingthesamestimulusatthesamemirroringlevel
astheimmediatelypreviousstimulus(ortwotrialsbackifacatchtrialfollowedanull
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17
event).Participantswereinstructedtopressabuttonwhenanidenticalvideowas
presentedtwiceinarow(i.e.,forcatchtrials).
Post-scanquestionnaire.Afterscanning,participantswereaskedabouttheir
subjectiveperceptionsofeachsocialnetworkmetricofinterestforeachindividualintheir
stimulusset,aswellasquestionsassessingtiestrength(seeSI).Becausetheconstraint
questionaskedaboutbrokerage(i.e.,whichindividualswerelowinnetworkconstraint),
responsestothisitemweremultipliedby-1.Toalleviateskewinthenetworkdata,
eigenvectorcentralitiesandnetworkconstraintvalueswerelog-transformedpriorto
analysis.
Thecorrespondencebetweenparticipants’post-scanratingsandthesocial
networkpositioncharacteristicsoftheindividualsintheirstimulussetswasassessed
usinglinearmixedmodelsusingtheR40packagelme444.Foreachofthefivequestions(see
SI),amodelwasconstructedwithparticipants’ratingsasthedependentmeasureandthe
relevantsocialnetworkpositioncharacteristicasafixedeffect,aswellasrandom
interceptsandslopesforeachparticipant.Totestthesignificanceoftherelationship
betweenparticipants’ratingsandsocialnetworkdata,p-valueswerecomputedusing
Satterthwaite’sapproximationfordegreesoffreedom45asimplementedinlmerTest46.
fMRIdatapreprocessing.ForfMRIdataanalysis,datawerepreprocessedand
averagevoxel-wisehemodynamicresponsestoeachidentitywereestimatedusingAFNI47.
Pre-processingstepsincludedapplyingAFNI’s3dDespikefunctiontoremovetransient,
extremevaluesinthesignalnotattributabletobiologicalphenomena,slice-timing
correctiontocorrectforinterleavedsliceacquisitionorder,alignmentofthelastvolumeof
thefinalruntothehigh-resolutionanatomicalscan,registrationofallfunctionalvolumes
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18
totheanatomical-alignedfinalfunctionalvolumeusinga6-parameter3-Dmotion
correctionalgorithm,spatialsmoothingusinga4-mmfull-widthathalf-maximumGaussian
kernel,andscalingeachvoxeltimeseriestohaveameanamplitudeof100.Priorto
regression,consecutivevolumeswheretheEuclideannormofthederivativesofthemotion
parametersexceeded0.3mmwereexcludedfromfurtheranalysis,aswerevolumesin
whichmorethan10%ofbrainvoxelswereidentifiedasoutliersbytheAFNIprogram
3dToutcount.
ParameterestimateswereextractedforeachvoxelusingaGLMthatconsistedof
gamma-variateconvolvedregressorsforeachof13predictors(oneforeachofthe12
identitiesintheparticipant’sstimulusset;oneforcatchtrials),aswellas12regressorsfor
eachofthesixdemeanedmotionparametersextractedduringvolumeregistrationand
theirderivatives,andthreeregressorsforlinear,quadratic,andcubicsignaldriftswithin
eachrun.Thisprocedureremovedvariancecausedbyregressorsofnointerest,and
resultedinanestimateoftheresponseofeachvoxeltoeachtrialtype.
GLMdecompositionsearchlight.UsingPyMVPA48andSciPy49,aGLMdecomposition
searchlight11wasperformedwithineachparticipant’sdata.Asphere(radius=3voxels)
wasmovedthroughouteachparticipant’sbrain.Ateachpointinthebrain,thelocal
distributedpatternsofneuralresponsestoeachpersoninthestimulussetwereextracted
withinaspherecenteredonthatpoint,andthepairwisecorrelationdistancesbetween
themwerecalculatedtoconstructalocalneuralRDM(Fig.3a-c),whichwasdecomposed
intoaweightedcombinationofpredictorRDMsusingordinaryleastsquares(OLS)
regression(Fig.3d).TherewerethreepredictorRDMs,onecorrespondingtoeachsocial
networkpositionmetricofinterest.PredictorRDMswereconstructedbytakingthe
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19
Euclideandistance(i.e.,theabsolutevalueofthenumericaldifference)betweenthe
relevantsocialnetworkpositionmetricsforeachpossiblepairofidentitieswithineach
participant’sstimulusset.EachpredictorRDMforeachparticipantwasthenz-scored.Next,
foreachRDM(e.g.,theEC-basedRDMforagivenparticipant),thevarianceaccountedfor
bytheremainingtwopredictorRDMs(e.g.,thesocialdistanceandconstraint-basedRDMs
forthatparticipant)wasremovedusingOLSregression.Thus,theresultantpredictor
RDMsweremadeorthogonaltooneanotherpriortoperformingtheGLMdecomposition
searchlight.
Ateachsearchlightcenter(i.e.,ateachvoxel),theGLMdecompositionprocedure
yieldedaβvaluecorrespondingtoeachsocialnetworkderivedmetricofinterest,aswell
asanR2valuecorrespondingtohowmuchthevarianceinthesimilaritystructureoflocal
neuralresponsepatternscouldbeexplainedbythesocialnetworkpositionsofthe
individualscomprisingagivenparticipant’sstimulusset.
Groupanalysis.Eachsubject’smapsofregressioncoefficientsandR2valueswere
transformedtostandard(Talairach50)spaceusingAFNI:Anatomicalscanswerelinearly
alignedtotheTalairach50templateusingthe@auto_tlrcalgorithminAFNI,andthesame
transformwasusedtoaligneachparticipant’ssearchlightresultstostandardspaceprior
togroupanalysis.Toidentifyareasthatreliablycontainedinformationabouteachspecific
aspectofsocialnetworkpositionacrossparticipants,theregressioncoefficientsforeach
socialnetworkposition-derivedRDMweretestedagainst0acrossparticipantsusingone-
tailedone-samplet-tests.Morespecifically,FSL’srandomise51,52programwasusedto
performpermutationtestsandtogenerateanulldistributionofclustermassesformultiple
comparisonscorrection(cluster-formingthreshold:p<.01,two-tailed;5,000
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20
permutations;10-mmvariancesmoothing).Allreportedresultshavebeenthresholdedata
family-wiseerrorrateof5%.
Dataandcodeavailability:Thedatathatsupportthefindingsofthisstudyareavailable
fromthecorrespondingauthoruponrequest.Thecodeusedfortheanalysesalsois
availableuponrequest.
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21
Acknowledgements
ThisworkwassupportedbyagraduatefellowshipfromtheNeukomInstitutefor
ComputationalScienceandaDartmouthGraduateAlumniResearchAward.Theauthors
wishtothankWillHaslettforassistancewiththeopticalflowanalysis.
AuthorContributions
CP,AMKandTWconceivedofanddesignedthestudy.CPandAMKcollectedthedata.CP
analyzedthedata.CP,AMK,andTWwrotethepaper.
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22
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Figure1.Socialnetworkcharacterization.Thesocialnetworkofafirst-yearcohortofMBA
studentswasreconstructedbasedonresponsestoonlinequestionnairesadministeredto
allmembersof the class (N=275;99.3%response rate).Nodes indicate students; lines
indicate reported social ties between them. For ease of visualization, only mutually
reportedsocialtiesareillustrated.AsubsetofthesestudentsparticipatedinanfMRIstudy.
Orangenodes indicate fMRI studyparticipants; graynodesdenoteothermembersof the
graduateprogram.Nodesizeisproportionaltoeigenvectorcentrality.
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Figure2.Stimulussetconstructionandparadigmforneuroimagingstudy.(A)Thegeodesic
distancebetweeneachfMRIstudyparticipantandeveryotherstudentinthenetworkwas
characterized. An alternative visualization of the network is shown in which nodes are
organized intohorizontal layersaccording todistance fromaparticularparticipant.Each
participant’sstimulussetwascomprisedof12ofhisorherclassmates:thetwolowestand
twohighesteigenvectorcentralityindividualsatdistancesofone,two,andthreefromthe
participant in the network (e.g., the classmates signified by the two smallest and two
largest nodeswithin each layer in (A)). (B) During the fMRI study, participants viewed
brief(2s)videosofthe12individualsintheirstimulussetsseparatedby4-6soffixation.
Inordertomaintainattention,aone-backtaskwasused(i.e.,participantswereinstructed
touseabuttonpress to indicatewhenan identicalvideowaspresented twice inarow).
Frames from this participant’s video clip are reproduced with permission from the
individual.
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Figure 3. GLM decomposition searchlight. (A) A spherical searchlight was moved
throughouteachparticipant’sbrain.(B)Ateachpointinthebrain,distributedpatternsof
neuralresponsestoeachindividualintheparticipant’sstimuluswereextractedwithina9-
mmradiusspherecenteredonthatpoint.(C)Ateachsearchlightcenter,aneuralRDMwas
generatedbasedonpairwisecorrelationdistancesbetweenlocalneuralresponsepatterns
toeachclassmateintheparticipant’sstimulusset.(D)EachlocalneuralRDMwasmodeled
asaweightedcombinationofRDMsconstructedbasedonthepairwiseEuclideandistances
(i.e.,theabsolutevalueofnumericaldifferences)betweenindividualsineachparticipant’s
stimulussetintermsofsocialdistance,eigenvectorcentrality,andnetworkconstraint.
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Figure4.Neuralencodingofsocialnetworkposition.(A)Distinctbrainregionsencodedifferentpropertiesofpeers’socialnetworkpositions(socialdistance=purple;eigenvectorcentrality=orange;constraint=green).Betavaluesindicatetheextenttowhichtheinformationcontainedinlocalmulti-voxelresponsepatternstoparticipants’classmatescouldbepredictedbasedonpropertiesofthoseindividuals’socialnetworkpositions;p<.05,FWE-corrected.(B)TheR2valuecorrespondingtotheGLMdecompositionperformedateachsearchlightcenterindicatestheextenttowhichtheinformationcontainedinlocalmulti-voxelresponsepatternscanbeexplainedbythesocialnetworkpositionsoftheclassmatesbeingviewed.Voxel-wiseR2valuesaveragedacrosssubjectsaredepicted;redcontoursindicateclustersofvoxelsthatreliablysignaledoneormoreofthetestedaspectsofsocialnetworkpositionacrossparticipants.ResultsareprojectedontoacorticalsurfacemodeloftheTalairach50N27brainusingPySurfer(https://github.com/nipy/PySurfer).
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Figure5.Associationsbetweenperceivedandactualsocialnetworkcharacteristics.Blackdashedlinesdepicttherelationshipsbetweenperceivedandactualsocialnetworkcharacteristicsacrossallparticipants(fitusinganordinaryleastsquareslinearmodel).Solidpurple,orangeandgreenlinesdepicttheserelationshipsforeachsubjectforsocialdistance,eigenvectorcentrality,andconstraint,respectively.(A)Neuroimagingstudyparticipants’subjectiveratingsofsocialcloseness,proportionofsocialtimespenttogether,andfrequencyofdiscussionswiththeindividualsintheirstimulussetsvariedaccordingtogeodesicnetworkdistancefromtheminthenetwork(allp’s<.0001,seemaintext).(B)Participants’estimatesoftheeigenvectorcentralityoftheindividualsintheirstimulussetswerecloselyrelatedtothoseindividuals’actualeigenvectorcentralities(p<.0001,seemaintext).(C)Participants’estimatesofthenetworkconstraintofindividualsintheirstimulussetswerealsoassociatedwiththeactualconstraintofthoseindividuals’positionsinthesocialnetwork(p<.0001,seemaintext).Asdescribedinthemaintext,self-reportdatawasobtainedafterscanning;networkconstraintandeigenvectorcentralitywerelog-transformedpriortoplottingandanalysistoalleviateskew.Perceivednetworkconstraintratingsweremultipliedby-1priortoplottingbecausetherelevantquestionaskedparticipantstorateperceivedbrokerage(whichisinverselyrelatedtonetworkconstraint).Analysesofbehavioralratingswereconductedusinglinearmixedmodelsthatincludedby-subjectrandomslopesandintercepts.
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SupplementaryInformation
I.Opticalflowanalysis
Toquantifytheamountofmovementwithineachvideoclipusedasastimulusin
theneuroimagingexperiment,theaverageopticalflow(i.e.,thepatternofapparentmotion
betweenconsecutivevideoframes)wascomputedforeachvideothatwasshowninthe
fMRIstudy.Giventhatthevideosusedasstimuliwererecordedbyastablecameraagainst
aplain,staticbackground,opticalflowestimatesforthesevideoscaptureoftheamount
thateachindividualmovedhisorherfacialfeaturesandheadinthevideoclip.Farneback’s
algorithmformotionestimation1asimplementedinOpenCV2wasusedtoestimatethe
averagemagnitudeofopticalflowineachvideo.Thismethodextractsapixel-wisemotion
vectorforeachpairofsequentialframesinwhicheachpixelischaracterizedbya
magnitudeandadirection.Toestimatethemagnitudeofmotionwithineachframepair,
themagnitudevalues(withoutrespecttodirection)weresummedacrosspixels.To
computethemeanmagnitudeofopticalflowforagivenvideo,themotionmagnitude
estimateswereaveragedacrossframeswithinthatvideo.
Inordertotestwhetherornotindividualdifferencesinnetworkconstraintare
relatedtomovementinthevideosusedasstimuli,thecorrelationbetweennetwork
constraintandaveragemotionmagnitudewasassessedamongthe88individualswhose
videoswereusedasstimuliinthefMRIstudy.Giventhatdistributionsofbothvariables
werehighlyskewed,datawerelog-transformedpriortoanalysis.Theresultsofthis
proceduresuggestthatinthestimuliusedinthecurrentstudy,networkconstraintand
amountofmovementwerenotsignificantlycorrelated,r=-0.12,p=0.28(seeFig.S1).
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II.Post-scanquestionnaire
Participantsperformedthepost-scanquestionnaireona13”MacBooklaptopusing
Psychopy3.Participantsfirstviewedaninstructionscreenthatread,“Nowyouwillseethe
samepeoplewhoyousawinthescanner.Youwillbeaskedquestionsabouteachperson.
Thesequestionsrelateonlytothisperson’sinteractionswithinthe[institutionname]MBA
cohort.Weunderstandthatpeoplehavemanysocialcirclesthattheyparticipatein(perhaps
includingfamily,friendsoutsideof[theinstitution],othercontacts,etc.).Forthesequestions,
pleasejustconsiderinteractionswithintheMBAcohort.Youwillbepresentedwitha
continuousratingscaleforeachquestion.Youcanchooseanypointalongthecontinuumto
respond.Pressanykeytocontinue.”Duringthesurvey,videosofthe12individualsfromthe
participant’sstimulussetwerepresentedinarandomorder.Participantsrespondedtoall
questionsaboutagivenindividualsequentially,andthesamevideothathadplayedinthe
scannerrepeatedonaloop(withoutsound)abovethequestiontextandresponsescale
(seeFig.S2).
Participantswerepresentedwithquestionsconcerninglaydefinitionsof
eigenvectorcentrality(“Insocialnetworkanalysis,scientistsassessaconstructthat
measureshowmanyfriendsapersonhas,andhowmanyfriendsaperson’sfriendshave.How
wouldyouratethispersononthisconstruct?”Responsesrangedfrom“Low(fewfriendswho
havefewfriends)”to“High(manyfriendswhohavemanyfriends)”)andconstraint(“Social
networkanalystsalsoassessaconstructcalled‘brokerage’thatmeasureshowmuchaperson
connectsgroupsofpeoplewhowouldn’totherwisebeconnected.Usingthisdefinition,how
highisthisindividualin‘brokerage’?”Responsesrangedfrom“Low(thispersonnever
connectsdistinctgroupsofpeople”to“High(Thispersonoftenconnectsdistinctgroupsof
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people)”).Responsestotheitemassessingbrokeragewerereversescoredinorderto
estimateperceivednetworkconstraint.
Participantswerealsopresentedwiththenamegeneratorthathadoriginallybeen
usedtoconstructthenetwork(“Considerthepeoplewithwhomyouliketospendyourfree
time.Duringthelastmonth,isthisoneoftheclassmateswhoyouhavebeenwithmostoften
forinformalfriendshipactivities,suchasgoingouttolunch,dinner,drinks,films,visitingone
another’shomes,andsoon?”Responsesrangedonacontinuumfrom“Noneofmysocial
activitiesinthepastmonthhaveincludedthisperson”to“Allofmysocialactivitiesinthepast
monthhaveincludedthisperson”),aswellasquestionsdesignedtoassesstiestrength
(“Howcloseareyouwiththisperson?”Responsesrangedfrom“Distant”to“Lessthanclose”
to“Close”to“EspeciallyClose”)andfrequencyofinteractions(“Onaverage,howoftendoyou
talktothisperson(anysocialorbusinessdiscussion)?”Responsesrangedfrom“Lessoften”
to“Monthly”to“Weekly”to“Daily”).
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References1. Farnebäck,G.inImageAnalysis:LectureNotesinComputerScience(eds.Bigun,J.&
Gustavsson,T.)2749,363–370(SpringerBerlinHeidelberg,2003).2. Bradski,G.TheOpenCVLibrary.DrDobbsJ.Softw.Tools25,120–125(2000).3. Peirce,J.W.PsychoPy-PsychophysicssoftwareinPython.J.Neurosci.Methods162,
8–13(2007).
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Figure S1.Relationshipbetweennetwork constraint andmovementduring videos.
Theamountofmovementofthe88individualswhosevideoswereusedasstimuliwasnot
significantly related to the constraint characterizing those individuals’ positions in the
socialnetworkoffirst-yearMBAstudents,r=-0.12,p=0.28.
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Figure S2. Post-scan questionnaire. Following scanning, participants responded to
questions about their subjective perception of each aspect of social network position of
interest for each individual in their stimulus set. A screenshot of the question
correspondingtonetworkconstraint(reverse-scored)isshown.
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Table S1: Brain regions where local neural information content is associated with the social distance of the individuals being viewed. Hemi Size
(mm3) COG x
COG y
COG z
Location
R 4,397 49.6 -46.6 7.6 IPL (SMG), STG, STS, MTG Hemi = hemisphere; COG = center of gravity; L = left; R = right; IPL = inferior parietal lobule; SMG = supramarginal gyrus; STG= superior temporal gyrus; STS = superior temporal sulcus; MTG = middle temporal gyrus. All reported results are significant at a statistical threshold of p < .05, FWE-corrected. All coordinates are in Talairach space.
Table S2: Brain regions where local neural information content is associated with the eigenvector centrality of the individuals being viewed. Hemi Size
(mm3) COG x
COG y
COG z
Location
L 24,483 -42.4 -18.5 33.6 IPL, IFG, Ins., pre-central gyrus R 8,768 21.7 26.8 -4.9 MPFC, IFG, aIns., ant. PHG, TP L 7,716 -32.7 12.9 -6.1 aIns., IFG L, R 7,552 -9.4 -41.8 40.4 PCC, precuneus R 6,802 20.4 -48.0 -2.8 PHG, LG, FG R 6,065 48.0 -29.4 38.4 IPL, precuneus, post-central gyrus L, R 5,233 -0.8 -44.4 65.4 Precuneus, post-central gyrus L, R 4,961 -0.6 -83.3 28.5 EVC
Hemi = hemisphere; COG = center of gravity; L = left; R = right; a = anterior; IPL = inferior parietal lobule; IFG = inferior frontal gyrus; Ins. = insula; MPFC = medial prefrontal cortex; PHG = parahippocampal gyrus; TP = temporal pole; PCC = posterior cingulate cortex; LG = lingual gyrus; FG = fusiform gyrus; EVC = extrastriate visual cortex. All reported results are significant at a statistical threshold of p < .05, FWE-corrected. All coordinates are in Talairach space.
Table S3: Brain regions where local neural information content is associated with the constraint of the individuals being viewed. Hemi Size
(mm3) COG x
COG y
COG z
Location
R 11,872 51.5 -16.0 -3.0 STS, STG, MTG, ITS, pIns. L 7,739 -51.6 -38.5 7.1 STS, STG, MTG, pIns. R 4,363 11.5 -5.7 58.4 SMA, dorsal premotor cortex Hemi = hemisphere; COG=center of gravity; L = left; R = right; STS = superior temporal sulcus; STG = superior temporal gyrus; MTG = middle temporal gyrus; ITS = inferior temporal sulcus; pIns. = posterior insula; SMA = supplementary motor area. All reported results are significant at a statistical threshold of p < .05, FWE-corrected. All coordinates are in Talairach space.
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