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图contagion黑客链接Structuraldiversityinsocialcontagion

发布时间:2021-10-12 11:03:16 阅读: 来源:渔坠厂家

Structuraldiversityinsocialcontagion

JohanUgandera,LarsBackstromb,CameronMarlowb,andJonKleinbergc,1

a

CenterforAppliedMathematicsandcDepartmentofComputerScience,CornellUniversity,Ithaca,NY14853;andbFacebook,MenloPark,CA94025

EditedbyRonaldL.Graham,UniversityofCaliforniaatSanDiego,LaJolla,CA,andapprovedFebruary21,2012(receivedforreviewOctober6,2011)

Theconceptofcontagionhassteadilyexpandedfromitsoriginalgroundinginepidemicdiseasetodescribeavastarrayofprocessesthatspreadacrossnetworks,notablysocialphenomenasuchasfads,politicalopinions,theadoptionofnewtechnologies,and?nancialdecisions.Traditionalmodelsofsocialcontagionhavebeenbasedonphysicalanalogieswithbiologicalcontagion,inwhichtheprobabilitythatanindividualisaffectedbythecontagiongrowsmonotonicallywiththesizeofhisorher“contactneighborhood”—thenumberofaffectedindividualswithwhomheorsheisincontact.Whereasthiscontactneighborhoodhypothesishasformedtheunderpinningofessentiallyallcurrentmodels,ithasbeenchallengingtoevaluateitduetothedif?cultyinobtainingdetaileddataonindividualnetworkneighborhoodsduringthecourseofalarge-scalecontagionprocess.HerewestudythisquestionbyanalyzingthegrowthofFacebook,arareexampleofasocialprocesswithgenuinelyglobaladoption.We?ndthattheprobabilityofcontagionistightlycontrolledbythenumberofconnectedcomponentsinanindividual’scontactneigh-borhood,ratherthanbytheactualsizeoftheneighborhood.Sur-prisingly,oncethis“structuraldiversity”iscontrolledfor,thesizeofthecontactneighborhoodisinfactgenerallyanegativepredictorofcontagion.Morebroadly,ouranalysisshowshowdataatthesizeandresolutionoftheFacebooknetworkmakepossibletheidenti?-cationofsubtlestructuralsignalsthatgoundetectedatsmallerscalesyetholdpivotalpredictiverolesfortheoutcomesofsocialprocesses.

socialnetworks

systems

S

ocialnetworksplayhosttoawiderangeofimportantsocialandnonsocialcontagionprocesses(1–8).Themicrofounda-tionsofsocialcontagioncan,however,besigni?cantlymorecomplex,associaldecisionscandependmuchmoresubtlyonsocialnetworkstructure(9–17).Inthisstudyweshowhowthedetailsofthenetworkneighborhoodstructurecanplayasigni?-cantroleinempiricallypredictingthedecisionsofindividuals.WeperformouranalysisontwosocialcontagionprocessesthattakeplaceonthesocialnetworkingsiteFacebook:theprocesswherebyusersjointhesiteinresponsetoaninvitatione-mailfromanexistingFacebookuser(henceforthtermed“recruitment”)andtheprocesswherebyuserseventuallybecomeengagedusersafterjoining(henceforthtermed“engagement”).AlthoughthetwoprocesseswestudyformallypertaintoFacebook,theirdetailsdifferconsiderably;theconsistencyofourresultsacrossthesedifferingprocesses,aswellasacrossdifferentnationalpopulations(MaterialsandMethods),suggeststhatthephenomenaweobservearenotspeci?ctoanyonemodalityorlocale.

Thesocialnetworkneighborhoodsofindividualscommonlyconsistofseveralsigni?cantandwell-separatedclusters,re?ectingdistinctsocialcontextswithinanindividual’slifeorlifehistory(18–20).We?ndthatthismultiplicityofsocialcontexts,whichwetermstructuraldiversity,playsakeyroleinpredictingthedecisionsofindividualsthatunderliethesocialcontagionprocesseswestudy.Wedevelopmeansofquantifyingsuchstructuraldiversityfornetworkneighborhoods,broadlyapplicableatmanydifferentscales.Therecruitmentprocesswestudyprimarilyfeaturessmallneighborhoods,buttheon-siteneighborhoodsthatwestudyinthecontextofengagementcanbeconsiderablylarger.Forsmallneighborhoods,structuraldiversityissuccinctlymeasuredbythenumberofconnectedcomponentsoftheneighborhood.Forlargerneighborhoods,however,merelycountingconnectedcomponents

5962–5966|PNAS|April17,2012|vol.109|no.16

failstodistinguishhowsubstantialthecomponentsareintheirsizeandconnectivity.Todeterminewhetherthestructuraldiversityofon-siteneighborhoodsisastrongpredictorofon-siteengagement,weevaluateseveralvariationsoftheconnectedcomponentcon-ceptthatidentifyandenumeratesubstantialstructuralcontextswithinlargeneighborhoodgraphs.We?ndthatallofthedifferentstructuraldiversitymeasuresweconsiderrobustlypredicten-gagement.Forbothrecruitmentandengagement,structuraldi-versityemergesasanimportantpredictorforthestudyofsocialcontagionprocesses.Results

UserRecruitment.TostudythespreadofFacebookasitrecruits

newmembers,werequireinformationnotjustaboutFacebook’susersbutalsoaboutindividualswhoarenotyetusers.Thus,supposethatanindividualAisnotauserofFacebook;itisstillpossibletoidentifyasetofFacebookusersthatAmayknowbecausetheseusershaveallimportedA’se-mailaddressintoFacebook.Wede?nethissetofFacebookuserspossessingA’se-mailaddresstobeA’scontactneighborhoodinFacebook.ThiscontactneighborhoodisthesubsetofpotentialfuturefriendshiptiesthatcanbedeterminedfromthepresenceofA’se-mailaddress(Fig.1A).WhereasAmayinfactknowmanyotherpeopleonFacebookaswell,suchadditionalfriendshiptiesre-mainunknownforindividualswhodonotchoosetoregisterandsocannotbestudiedasapredictorofrecruitment.Thee-mailcontactneighborhoodswestudyaregenerallyquitesmall,typi-callyontheorderof?veorfewernodes.

扩展:social contagion / contagion in bank / unity in diversity

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