A multilevel social neuroscience perspective on radicalization and terrorism by Disruptor Institute

2018,VOL.13,NO.5,511–529 https://doi.org/10.1080/17470919.2017.1400462

REVIEW

Amultilevelsocialneuroscienceperspectiveonradicalizationandterrorism

JeanDecetya,b,RobertPapec andCliffordI.Workmana

aDepartmentofPsychology,UniversityofChicago,Chicago,IL,USA; bDepartmentofPsychiatryandBehavioralNeuroscience,Universityof Chicago,Chicago,IL,USA; cDepartmentofPoliticalScience,UniversityofChicago,IL,USA

ABSTRACT

Whyaresomepeoplecapableofsympathizingwithand/orcommittingactsofpoliticalviolence,such asattacksaimedatinnocenttargets?Attemptstoconstructterroristprofilesbasedonindividualand situationalfactors,suchasclinical,psychological,ethnic,andsocio-demographicvariables,have largelyfailed.Althoughindividualandsituationalfactorsmustbeatwork,itisclearthattheyalone cannotexplainhowcertainindividualsareradicalized.Inthispaper,weproposethatacomprehensiveunderstandingofradicalizationandofhowitmayleadtopoliticalviolencerequiresthe integrationofinformationacrossmultiplelevelsofanalysisandinterdisciplinaryperspectivesfrom evolutionarytheory,social,personalityandcognitivepsychology,politicalscienceandneuroscience. Characterizationofthestructural-functionalrelationshipsbetweenneuralmechanismsandthe cognitiveandaffectivepsychologicalprocessesthatunderpingroupdynamics,interpersonalprocesses,valuesandnarratives,aswellasmicro-sociologicalprocessesmayreveallatentdriversof radicalizationandexplainwhysomepeopleturntoextremepoliticalviolence.Thesedriversmaynot beobservablewithinasingleindividuallevelofscientificenquiry.Theintegrative,multilevel approachthatcharacterizessocialneurosciencehasthepotentialtoprovidetheoreticalandempiricalclarityregardingtheantecedentsofradicalizationandsupportforextremeviolence.

Introduction

Politicalviolenceandterrorismarenotnewphenomena. Thepastdecadeshavewitnessedadramatictransformationinthenatureanduseofterrorism,however,which hasforcedintelligence,psychological,andmedical expertstore-evaluatetheirunderstandingofextremism andradicalization(McCauley, 2007).Howcansciencehelp ustounderstandwhycertainpeopledevelopextreme opinionsandbeliefsthat,insomecases,leadtoviolent extremismincludingactsofterrorism?Thisquestionhas capturedtheinterestofscholarsfromvariousdisciplines, particularlythesocialscienceswherethesearchforan elusive “terroristpersonality” beganinthe1970’s.The resultingliteratureisrepletewithfailurestoconstruct terroristprofilesbasedonpersonalitytraits,psychopathology,religiousorientation,orracialand/oreconomicbackground(Atran, 2003;Horgan, 2014;Kruglanskietal., 2014; Victoroff, 2005).Thereisnotypicalsocialandeconomic profileoftheradicalized.Forinstance,individualswho perpetratedrecentattacksinEuropearenotinhabitants oftheGazaStrip,LibyaorAfghanistan.Theyarenot necessarilythepoorest,themosthumiliatedortheleast integrated.Thefactthat25%ofjihadisareconvertsshows thatthelinkbetweenradicalsandtheir “people” isalso

ARTICLEHISTORY

Received15June2017

Revised29September2017

Publishedonline8 November2017

KEYWORDS

Socialneuroscience; politicalneuroscience; radicalization;extremism; politicalviolence;group dynamics;microsociology; terrorism

largelyanimaginaryconstruct(Roy, 2017).Ifa “standard terroristpersonality” doesexistthenitislikelyobscured bythecomplexhistorical,political,andeconomiccontexts intowhichterroristactsareembedded(Horgan, 2014).

Disturbingasitmaybe,individualswhobecomeradicalizedandinvolvethemselveswithterroristorganizationsare,byandlarge,ordinarypeople.These individualshavetypicallyfunctioningbrains;theyare notmadbutarefanatics.Mostarenotpsychopathsand, withtheexceptionof “lonewolf” terroristsarenotespeciallylikelytohavepsychiatricdiagnoses(Horgan, 2014). Violentradicalizationisnotaconsequenceofreligious radicalization,evenifitoftentakesthesamepathsand borrowsfromthesameparadigms.Religiousfundamentalismexists,ofcourse,anditposesconsiderablesocietal problemsbecauseitrejectsvaluesbasedonindividual choiceandpersonalfreedom.Butitdoesnotnecessarily leadtopoliticalviolence(Roy, 2017).Thus,scholarsgenerallyagreethattheoriginsofradicalizationandterrorism arenotnecessarilycausedbybraindisorders.Rather, peoplewhoareotherwisepsychologicallytypicalmay developvaluesandstrongemotionaltiestonarratives andcausesandbecomeradicalized(McCauley, 2007). Manyindividualswhosympathizewithandevenjoin

CONTACT JeanDecety decety@uchicago.edu DepartmentofPsychology,5848S.UniversityAve.,Chicago,IL60637USA

Thisarticlewasoriginallypublishedwitherror.Thisversionhasbeenamended.PleaseseeCorrigendum(http://dx.doi.org/10.1080/17470919.2018.1437883)

terroristorganizationsareeducatedandseemingly rational(Bronner, 2016).Ifordinary,rationalpeopleare capableofholdingextremeviewsandofbecomingradicalized,whythendoextremistscompriseonlyasmall fractionofsociety?Moreover,aretherecharacteristics thatdistinguishindividualswhomerelyholdextreme viewsfromthosewhoactonthoseviewsbyengaging inideologicallymotivatedviolence?

Abetterunderstandingoftheantecedentsofextremism andpoliticalviolencecannotbegleanedsimplybyreexaminingtheextantliteraturesonindividualdispositions, interviews,situationalvariables,andtheirrelationtopoliticalviolenceinhealthyindividuals.Burgeoningevidence (reviewedbelow)suggestsacomprehensiveunderstandingofsociopoliticalattitudesmustincorporateevidence fromthebiologicalscienceswithcognitivescienceand sociologyatmultiplelevelsofanalysis,andcannotrely solelyonpersonality,survey,andotherself-reports. Movingthefieldforwardrequiresatransdisciplinaryperspectivethatemphasizestherelationshipsbetweenneural, cognitive,andsocialprocesses,includingtheintervening information-processingcomponentsandoperationsat boththeneuralandcomputationallevelsofanalysis.This approachhascharacterizedthesocialneuroscienceperspectivesinceitsinception25yearsago(Cacioppo& Berntson, 1992),andhassignificantlycontributedto explainingcomplexsocialbehaviorsandbrain–behavior relationshipssuchasrisk-takingbehaviors(Steinberg, 2008),socialhierarchiesandstatus(Koski,Xie,&Olson, 2015),motivationforjustice(Decety&Yoder, 2017),and socialsupport(Taylor, 2011;Uchino,Smith,Birmingham,& Carlisle, 2011).AspecialissueofthejournalPolitical Psychologypublishedin2003advocatedfortheapplicationofthesocialneuroscienceperspectivetoenrichtheorizingaboutpoliticalpsychology(Cacioppo&Visser, 2003). Subsequenttothispublication, psychological,physiologicalandneurobiologicalevidencehasbeensynthesizedto generateaccountsofpoliticalphenomenathatcouldnot havebeenachievedthroughinvestigationofanyofthese levelsinisolation(e.g.,Hibbing,Smith,&Alford, 2014).The extantevidencestronglysuggestsalinkbetweenbrain structure/functionandthepsychologicalmechanismsthat mediatepoliticalattitudes.Individualdifferencesinneurocognitivestructureandfunctioningareinfactlinkedtoa constellationofsocialandpsychologicalprocessesthat unfoldovertimeandbothreflectandgiverisetothe expressionofpoliticalbehavior(Jost,Nam,Amodio,&Van Bavel, 2014).Inotherwords,theevidencefavorsadynamic, recursivetheoreticalframeworkinwhichtheconnection betweenphysiologicalandpsychologicalfunctioningand

politicalextremismisconceivedofasbidirectional.Linking individualpsychologicaldispositionsanddemographic variablesthatareexpectedtopredictextremismtospecific patternsofbrainactivityandfunctionalconnectivityduring moralevaluations,forexample,couldshedlightonthe cognitiverequirements,affectiveresponses,andcomputationalprocessesthatunderlieradicalization.

Despitetheprogresssocialneurosciencehasafforded politicalscience,thisperspectivehasnotyetbeensystematicallyappliedtothestudyofradicalizationand supportforpoliticallymotivatedviolence.Pessimism towardspsychologicalapproachestounderstanding theantecedentsofradicalizationandsupportfor extremeviolenceisunderstandablegiventhatpsychologicaltheorizinghasnotyetproducedsatisfactoryworkingmodelsdespite40yearsofeffort.Herewearguethat thisstagnationispartiallyattributabletoafailureto capturethe “bigpicture” acrosslevelsofanalysis.

Inthispaper,wefirstdescribethesocialneuroscience approachandbrieflyreviewtheoreticaladvancesinpoliticalsciencemadepossiblebythisperspective.Then,we sketchoutaprocessmodelofradicalizationinformedby multiplebiologicalandsocialsciencedisciplines.According tothismodel,radicalization andsupportforideologically motivatedviolenceemergesthroughreciprocalinteractionsbetween1)groupdynamics,2)interpersonaland3) microsociologicalprocesses1 (Figure1).Next,wediscuss neurobiologicalandbehavioralevidenceregardingthe propensitytoengageinviolence.Throughout,wesynthesizekeyfindingsfrommultipledisciplinestoillustratehow socialneurosciencecanadvanceourunderstandingof radicalizationandofsupportforideologicallymotivated violence.Weconcludebyhighlightingthesignificantscholarlyadvancesitislikelytostimulate.

Thesocialneuroscienceperspective

Thecomplexitiesoftherelationbetweenbrainandbehaviorposefundamentalquestionsthatcannotbeanswered byonedisciplinealone.Understandingsocialbehavior requiresintegrativemultidisciplinaryapproachesacross disciplinesandlevels(i.e.,scales)ofanalysis.Socialneuroscienceisaninterdisciplinaryfieldthatinvestigatesthe biologicalmechanismsunderpinningsocialstructures, processesandbehavior,aswellasreciprocalinteractions betweenthesocialandbiologicallevelsoforganization (Cacioppo&Berntson, 1992;Cacioppo&Visser, 2003).In ordertoachieveacompleteunderstandingofsocialphenomena,itisimperativetouseintegrativeanalysesthat encompassdifferentlevelsoforganization,rangingfrom

1Microsociologyisconcernedwiththenatureofeverydayhumansocialinteractionsandagencyonasmallscale,inparticularthe reciprocalrelationshipbetweenevents/actionsandthenatureofthesocietalcontextinwhichtheyoccur.

Figure1. Flowchartofdynamicsocialandcognitiveprocessesinvolvedinradicalization.Atthelevelofgroupdynamics,individuals disconnectgraduallyorabruptlyfromotherformalandnon-formalsocialgroupsthatholdcompetingvalues(e.g.,family,friends, neighbors,hobbies,etc.).Relatedly,isolatedindividualsmayeagerlyseekincorporationintoakinship-likegroup,which,inconjunction withtheassociatedmechanismsofbondingandwiththeunderlyingpsychologyofdesire,mayenableasuicideterroristtoexpectselfsacrificetobenefittheirfictivekinpost-mortem.Socialforcesoperatingattheinterpersonallevelmayacttostrengthenin-group connections(e.g.,throughgroupconformity,obediencetoauthority,and/ordeindividuation)whileincreasingsocialdistancetooutgroups(e.g.,throughdehumanization).Atthemicro-sociologicallevel,fewerconnectionstosocialgroupswithcompetingopinionsand valuesresultsinlessintra-individualcompetitionbetweenbeliefs,values,andideas.Asindividualswhobecomeradicalizedadheremore strictlytoextremistideologies,narratives,andincreasinglylimittheirexposuretocompetingideas,terroristorganizationsareableto exertgreaterinfluenceoverthevaluesandbeliefsoftheirmembers.Themostdangerousextremistideologiesareweaklytranssubjective,orinsufficientlyconvincingtoachievewidespreadacceptancethroughoutapopulation,andsociopathic,orantagonistic towardsdifferentworldviews.Groupdynamics,interpersonalfactors,andmicro-sociologicalfactorsinteractreciprocallytocreatethe conditionsforhyper-altruismtowardsone’sin-groupaswellasviolentactiondirectedatinnocentout-groupmembers.Individual differencesinpropensitytoengageinviolenceoperateatmultiplelevels(genetic,neuroendocrine)mediatingcognitionandbehavior throughspecificneuroanatomicnetworks.Takentogether,interdisciplinarysynergyacrossacademicdisciplinesandlevelsofanalysishas thecapacitytoprovideaclearerunderstandingofhowradicalizationoccurs.

thegeneticthroughtothesociallevels.Molarconstructs usedinsocialscience,suchasradicalization,persuasion, loneliness,empathy,ormorality,provideameansof understandinghighlycomplexprocesseswithoutneeding tospecifyeachindividualprocessbyitssimplestcomponents(Cacioppo,Berntson,&Decety, 2010).However,such constructsarecomposedofprocessesandrepresentations thatworktogethertoserveparticularfunctions (Willingham&Dunn, 2003).Psychologicalmodelsoften usehypotheticalrepresentationsandprocessesthatoperateonthoserepresentations.Forinstance,executivefunctioning,theoryofmind,andempathyareallpsychological constructs,butnoneoftheseconstructscanbedescribed asprimitive(Decety&Jackson, 2004;Miyakeetal., 2000). Thesehigher-levelconstructsneedtobedecomposed intotheirconstituentelements,componentprocesses, representations,andcomputationsthatcanthenbe mappedontoneuralcircuitsusingtechniquesincluding

brainmapping,functionalconnectivity,andlesionstudies (Cacioppo,Cacioppo,Dulawa,&Palmer, 2014;Decety& Cacioppo, 2010).

Multilevelanalysesrequirearangeofexpertisethatis unlikelytobeavailabletoany oneinvestigator,suggesting theneedforteamsofscholarsspanningmultipledisciplines,includingevolutionarybiology,neuroscience,psychology,anthropology,economics,andpoliticalscience.In contrasttomultidisciplinaryresearch,whereexpertiseis aggregatedbutnotsynthesized,interdisciplinaryresearch isnotsimplythesumofitsindividualpartsbutinstead resultsinsynergisticoutcomes(Cacioppoetal., 2007). Socialneuroscienceisnotasubstituteforthebehavioral orsocialsciencesbutratherisaninterdisciplinaryfieldthat drawsonthesedisciplinesaswellasneurosciencetoprovideasingle,integrativeparadigmwithwhichtoinvestigatecomplexhumanbehaviorsacrosslevelsof organization(Cacioppo&Decety, 2011).Importantly,the

best-designedexperimentsaimingtobridgethepsychologicalandneurobiologicallevelsarethosewithclear hypothesesbasedonpre-existingpsychologicalresearch andwithknownorproposedcandidateprocesses.Inaddition,explanationsofresults attheneurallevelarealmost entirelycontingentonhigher-levelvocabularyandconceptsderivedfrombehavioral work(Krakauer,Ghazanfar, Gomez-Marin,MacIver,&Poeppel, 2017).

Multilevelinterdisciplinaryapproacheshavealready gainedtractionelsewhereinpoliticalpsychology, wherescholarsaremerginginformationaboutbrain functioning,individualdispositions(e.g.,beliefs,values, motivations,emotions),andgroupdynamicstoinform theoriesofpoliticalthought(Jostetal., 2014).While politicalbeliefshavelongbeenassociatedwithbroader underlyingcognitive,motivationalandpersonality traits,workthatcombinespsychologyandneurosciencemethodsandtheorizingindicatesthatsome ideologiesareadoptedinpartbecausetheyservethe moregeneralpurposeofreducinguncertainty,ambiguityandthreat(Jost,Glaser,Kruglanski,&Sulloway, 2003).Thereisevidence,forexample,thatliberalsare moretolerantofuncertaintyandcomplexity,whereas conservativesexhibitlesscognitiveflexibilityandless opennesstonewexperiences(e.g.,Gerber,Huber, Doherty,Dowling,&Ha, 2010).Thesefindingsare takentosuggestthatpoliticalattitudesemergefrom generalpsychologicalprocesses,particularlythose involvedinmotivationandself-regulation,andaredeeplyconnectedtobasicbiologicalmechanismsthat servetodefendagainstenvironmentalchallenges (Jost&Amodio, 2012;K.B.Smith,Oxley,Hibbing, Alford,&Hibbing, 2011).Functionalneuroimagingstudiessupportthisinterpretationbyshowing,for instance,thatconflict-relatedactivityintheanterior cingulatecortex(ACC),aregioncriticalforconflict monitoring,isnegativelyassociatedwithpoliticalconservatism(Amodio,Jost,Master,&Yee, 2007).Similarly, conservativesandliberalscouldbedistinguishedby neuralresponsestodisgustingnon-politicalimagesin regionsthatareimplicatedinnegativeaffectivevalence andinteroceptionofdisgust2 andthatservebasic aspectsofattentivesensoryprocessing(Ahnetal., 2014).Anotherstudyinvestigatedwhetheractivityin theneuralcircuitsthatsupportrisk-takingbehaviors differsasafunctionofpoliticalidentity(Schreiber etal., 2013).Althoughnobehavioraldifferenceswere observed,liberalsdemonstratedgreateractivityinthe insulawhereasconservativesdemonstratedgreater activityintheamygdala.Theseregionshavepreviously beenimplicatedinstudiesofaffectiveprocessingand

emotionalsaliency(Cacioppo,Cacioppo,&Petty, 2017; Kaplan,Gimbel,&Harris, 2016).Inparticular,theamygdalaisacriticalhubthatprioritizestheaffectiverelevanceofsensoryinputsforthegoalsandmotivations oftheperceiver(Cunningham,VanBavel,&Johnsen, 2008).Astudyusingneuroanatomicalmeasuresfound thatconservatismwasnegativelyassociatedwithgray mattervolumesintheACCandpositivelyassociated withrightamygdalavolume(Kanai,Feilden,Firth,& Rees, 2011).Arecentstudyreportedincreasedactivity intheinsulaandamygdalainparticipantswhoresisted changingtheirpoliticalbeliefswhenthosebeliefswere challenged(Kaplanetal., 2016).Takentogether,psychologicalprocessesunderpinnedbyspecificneural circuitsrecruitedwhenfacingenvironmentalchallenges appeartoconvergeindiscriminatingpoliticalorientation.Activationintheseregionsseemstodistinguish participants’ politicalorientationevenwhenbehavioral differencesarenotobserved.Interestingly,individual differencesingraymatterdensityininsulaandcingulatecortexpredictindividualdifferencesinaffective andcognitiveempathy,respectively(Eres,Decety, Louis,&Molenberghs, 2015),suggestingthatthese regionsperformdomaingeneralfunctionsthatarenot specifictoprocessingpoliticalinformation.Naturally, theseneurophysiologicaldatacannotdetermine whetheranyofthesebrainregionsplayacausalrole intheformationofpoliticalattitudesandbeliefs.They dosuggest,however,thatsocialneuroscienceprovides aricherperspectiveonpoliticalattitudesbyincorporatinginformationaboutthebiologicalmechanismsassociatedwithcognitions,attitudes,valuesandbeliefs.

Processmodelofradicalizationandsupportfor violence

Theoriesexplainingradicalizationtoterrorismabound butarelimitedbyadearthofsolidexperimentalevidence,whichisunderstandablegiventhecomplexityof thephenomenonandthedifficultyofobtainingempiricaldata.Furthermore,numerousstudieshavereliedon anecdotalratherthanempiricalevidenceoroninterviewsthataresusceptibletobiasessuchasconfirmationbias.Thisconstrainstheorizingaboutterrorist psychology(Horgan, 2014).Ifweaccepttheviewthat mostterroristsareordinarypeople,howcanwereconcilethiswiththerealitythatmostordinarypeopleare unwillingtosacrificeinnocentlivestosupportthe causestheyholddear?Inotherwords,acomprehensivetheoryofterroristpsychologymustbesensitiveto thefeaturescommontoextremistsyetspecificenough

2Interoceptiveawarenessisthesensitivitytostimulioriginatingwithinthebody.

todistinguishbetweenextremistswhowillandwillnot goontocommitactsofpoliticalviolenceandfrom otherordinarypeople.

Althoughsocioeconomicstatus,ethnicbackground, education,relativedeprivation,religiousaffiliation,poverty,andthedesireforpersonalsignificance,forexample,maycontributeinvaryingdegreestoindividual pathwaystowardsradicalizationandterrorism,they areneitherspecificenoughnornecessary,letalone sufficienttobecategorizedasrootcauses(Roy, 2017; Victoroff, 2005).Inordertoprovideatheoreticalscaffoldinguponwhichtoorganizerelevantdatafrom multiplescalesofanalysesandacademicdisciplines, aswellashelptomovethefieldforward,webuildon currentknowledgefromgroupdynamics,interpersonal processesandmicro-sociologytoproposethatradicalizationemergesfromcomplexinteractionsacrossthese levels(see Figure1).Inthefollowingsections,we synthesizekeyfindingsfrompsychologyandneuroscienceinrelationtoeachlevelwithaviewtowards providingpreliminarydescriptionsoftheneurocognitivemechanismsthatmayunderpinradicalizationand supportforideologicallymotivatedviolenceand,where applicable,wepointtooutstandinggapsintheliteraturethatfutureresearchshouldaddress.

Groupdynamicsleadstobothcooperationand competition

Homosapiens isanultra-socialspecies.Weareinterdependent,obtainthemajorityofourresourcesthrough cooperation(e.g.,hunting,buildingshelters,protection againstpredators,childrearing),andcooperatetoan extraordinarydegree.Humansengageinhighlycomplex coordinatedgroupactivitieswithpeoplethatarenot theirkin(Tomasello, 2009).Theymayrushtodefend absolutestrangersoneday,orjoinforceswithunrelated individualstowagemercilesswarsagainsttheircompetitorsthenext.Socialitycanbenefitindividualsbecause itprovidesgreaterprotectionfrompredators,enhances successinlocatingormaintainingaccesstoresources, createsmatingopportunities,andreducesvulnerability toinfanticide.Socialitycanalsobecostly,however,by increasingcompetitionforaccesstoresourcesandmatingopportunities,increasingexposuretoinfection,and potentiallyincreasingconspicuousnesstopredators (Marean, 2015).Mathematicalmodelingofsocialevolutioncombinedwitharchaeologicalevidenceoncauses ofdeathduringthelatePleistoceneshowsthatanoptimalconditionunderwhichgeneticallyencodedhyperprosocialitycanpropagateis,paradoxically,whengroups areinconflict.Groupsthathavehighernumbersof prosocialpeoplewillworktogethermoreeffectively

andthusoutcompeteothersandpasstheirgenesfor thisbehaviorontothenextgeneration,resultinginthe spreadofhyperprosociality.Furthermore,suchcooperativebehaviorspreadsbestwhenitbeginsinasubpopulation,competitionbetweengroupsisintenseandwhen overallpopulationsizesaresmall,liketheoriginalpopulationof Homosapiens inAfricafromwhichallmoderndaypeoplearedescended(Boyd&Richerson, 2009). Additionally,thereisstrongempiricalevidencethat humansarehelpfulorhurtfultowardsothersbasedon perceivedsimilaritytothemselves(Hare, 2017).Thislikemepsychologymanifestsitselfinahighdegreeoftolerancetowardin-groupmembersthatfacilitatesunique formsofcollaborationandconformity(Burton-Chellew& West, 2012;Kurzban,Burton-Chellew,&West, 2015).In contrast,ostracismandlethalaggressionamonghuntergatherersprimarilytargetsnonconformistorout-group members(Boehmetal., 1993).Violentpropensitieslike intraspecifickillingoccurinavarietyofspeciesandhave beenselectedamongmalechimpanzeesandhumans. Likewise,propensitiesforparticulartypesofaltruisticand cooperativebehaviorhaveprobablyalsoevolved throughselection,andareneithermorenorlessimportantbiologicallythanviolence(Wrangham, 1999).This typeofantisocialoragonisticresponseisfacilitatedby thereadinessofhumanstodehumanizeout-group members(Kteily,Hodson,&Bruneau, 2016).Thus, humansarethemostultra-socialspeciesonearthbut alsothemostruthless.Overall,evolutionarytheorysupportstheviewthatanyintensificationofout-group aggressioncouldbeaby-productofselectionfor intragroupprosocialitylateinhumanevolution(Hare, 2017).In-groupfavoritismincombinationwithoutgrouphostilityseemstohaveemergedsimultaneously ashighlysuccessfulstrategies(Choi&Bowles, 2007).

Asaspecies,grouplivinghashadtheconsequenceof fosteringobligatoryinterdependence – thatis,long-term survivalispredicatedonthewillingnesstoshareinformation,resources,andhelpwithothers.Atafundamental level,humansexperiencethestrongneedtocreateand fostersocialbonds(Baumeister&Leary, 1995).Ourcognitive,emotional,andmotivationalfacultieshavebeen shapedbythedemandsofthissocialinterdependence. Indeed,humanshavehardwiredcapacitiesforin-group favoritism,enhancedself-esteem,enhancedgroup boundaries,groupnorms,scripts,schemas,conformity, symbolicimmortality,anddistinctempathicandhelping behaviorsforin-groupcomparedtoout-groupmembers (Mesoudi, 2009).Humanbeingshaveanaturalproclivity tomakedistinctionsbetween “us” and “them”,whichhas aclearsurvivalvalue,butisalsoasourceofbiasand prejudice(Diesendruck, 2013).Thesegroupbiasesmanifestearlyindevelopmentandcarrywiththem

expectationsofbehaviorandconstrainthepossible actionsindividualsbelieveotherswillengagein,suchas whethertwopeoplewillbefriendsorfoes,willcooperate orcompete,orwillhelporharmothers(Rhodes&Chalik, 2013).Forinstance,preschoolersreliablyexpectagents fromonegrouptoharmmembersoftheothergroup (ratherthanmembersoftheirown)butexpectagentsto helpmembersofbothgroupsequallyoften(Rhodes, 2012).Stronglyheldbiasestypicallyemergearound groupsintimatelytiedtosocietallyreinforcedstereotypes, makingthemparticularlysusceptibletoindividualdifferencesinlifeexperiences(Hirschfeld, 2013).

Asenseofkinshipmaydriveindividualstotakegreat risksandeventosacrificethemselvesinorderto increasethefitnessoftheirfamilymembers,tribes, cliques,ethniccommunities,andnationalgroups (Trivers, 1985).Thefundamentalneedtoestablishsocial bondsthatisexperiencedfrombirthmayencourage humanbeingstoseek “fictivekin,3” andeventosacrificeforthem(Tobeña, 2009).Throughtheprocessof radicalization,individualsestablishkinship-likerelationshipswithextremistorganizationsandmayeven engageinself-sacrificialbehaviors,suchasactsofmartyrdom,thatareexpectedtoenhancethefitnessofthe communityandcollectivecauseitclaimstosupport. Indeed,theIslamicStateandmanyoftheworld’sdeadliestterroristgroupsorganizearoundkin-likecauses. Fictivekinshipisoneofmanysocialforcesthatemerge duringtheprocessofradicalization.Assuchsocial bondsdeepen,isolationfromgroupswithcompeting valuesandthedevelopmentofextremebeliefsfacilitateinterpersonalprocessessuchasobedience,conformity,deindividuation,anddehumanizationwhich, takentogether,maysetthestageforviolencetowards innocentindividuals(Table1 fordefinitions).

Interpersonalprocesses

Humanbehaviorisinfluenced,directlyandindirectly,by thepresenceand/orbehaviorofothers.Thisismanifested inmanyphenomenastudiedbysocialpsychologysuchas socialinfluence,conformity,obedience,orcompliance.As demonstratedinnowclassicalworkonobedienceto authorityconductedbyMilgramandZimbardo,almost anyonecanbeledtoperpetrateactsofviolenceorabuse undertherightcircumstancesandsocialpressures.Twothirdsofparticipantsadministeredwhattheybelieved werelethalelectricshockstosomeonewhofailedamemorytestwhenaskedtodosobyaresearcherinalabcoat (Milgram, 1963).Theselevelsofobedienceandof

disobediencehaveremainedstableinthe50yearssince Milgram’soriginalstudy(Dolińskietal., 2017).Athirdof collegestudentsassignedtoplayprisonguardshumiliated andabusedstudentsplaying prisonersinasimulation (Haney,Banks,&Zimbardo, 1973).Thesefindingsmake cleartheimportanceofsituationalfactorsandgroup dynamicsincreatingthecircumstancesunderwhichordinarypeoplemaycarryoutacts ofviolence.Importantly, however,theunwillingnessofsomeparticipantstoact violentlyorabusivelydespitetheircircumstancessuggests dispositionalfactorsshouldnotbeignored.

Consistentwiththisview,recentstudiesreportthata varietyofindividualdispositionspredictthewillingness ofindividualstoadministerhigh-intensityelectrical shocksinadaptedversionsoftheMilgramobedience paradigm(Bègueetal., 2015).Inonestudy,obedience waspositivelyassociatedwithtraitconscientiousness andagreeableness,whichreflectself-disciplineand senseofdutyaswellasthedesiretoavoidviolating socialnorms,respectively.Obediencewasfurtherinfluencedbypoliticalorientation,whichisconsistentwith previousresearchlinkingconscientiousnessandagreeablenesstopoliticalideology(Hirsh,DeYoung,Xu,& Peterson, 2010;Mondak&Halperin, 2008).Relatedly, anotherstudyusingasimilarparadigmfoundthat obediencewasassociatedwithauthoritarianismand hostility(Dambrun&Vatiné, 2009).Takentogether withmeta-analyticresultsshowingparticipantsin Milgramdisobedienceexperimentsaremostlikelyto disobey(36.88%)whentheindividualreceivingshocks requestsrelease(Packer, 2008),behavioralresearch clearlyindicatesthatbothsituationalanddispositional factorsareindispensableforunderstandingwhatdrives actsofextremeviolence.

Functionalneuroimagingresearchpointstoempathy asanadditionaldispositionmediatingobedienceto authority.Individualswhounderwentscanningwhile completingavirtualrealityadaptationoftheMilgram experimentdemonstratedincreasedactivationinregions includingtheventrolateralprefrontalcortexandamygdala whileviewingvirtualavatarsinpain(Cheetham, 2009). Thispatternofactivationwasfurtherassociatedwith traitpersonaldistress,whichistheemotionalcomponent ofempathyandindexessensitivitytodiscomfortoranxietywhenobservingthenegativeexperiencesofothers. Anotherstudyreportedthatindividualswhoreactedto self-relevantmoralstatementswithbluntedactivationof themedialprefrontalcortexweremorelikelytoharmoutgroupmemberswhencompetingonateam(Cikara, Jenkins,Dufour,&Saxe, 2014).Relatedly,individualswho

3Thenotionoffictivekinreferstopeoplewhoareregardedasbeingpartofafamilyeventhoughtheyarenotrelatedbyeither bloodormarriagebonds.Fictivekinshipmaybindpeopletogetherintiesofaffection,concern,obligationandresponsibility.

Table1. Interpersonalprocessesinfluenceandalterindividualperceptions,motivations,attitudes,andsocialbehavior. Socialinfluence Description

Conformity Adoptingtheopinions,attitudes,and/orbehaviorsofmembersofagrouptowhichonebelongsorwishestobelong DehumanizationDenyingapersondignity,individuality,andautonomy,ensuringthatone’smoralstandardsarenotapplied DeindividuationReferstolossofidentityanditsautomaticlinktoirresponsibleandantisocialbehaviors DepersonalizationOccurswhenoneviewsoneselfasanarchetypalmemberofasocialgroupratherthanasauniqueindividualwithinthatgroup Diffusionof responsibility Whenonefeelslessresponsiblefortakinganactionwhileinthepresenceofotherpeople

Essentializing Attributingnatural,essentialcharacteristicstomembersofspecificallydefinedgroups ObediencetoauthorityComplyingwithcommandsgivenbyanauthorityfigure

respondedtomoraldilemmasindicatingtheywerewilling tosacrificethelivesofout-groupmembers(e.g.,the homeless)tobenefitthein-groupactivatedmedialprefrontalcortexaswellasorbitofrontalcortexanddorsolateralprefrontalcortex(Cikara,Farnsworth,Harris,&Fiske, 2010).Themedialprefrontalcortexispartofanetwork includingthesuperiortemporalsulcus(pSTS/TPJ)which playsafundamentalroleintheattributionofintentions, beliefs,andemotionstooneselfandothers(see Figure2).

Sociallyconnectedindividualshavebeenshownto dehumanizeout-groupmembersandaremorewilling toendorseharmsagainstdehumanizedothers(Waytz& Epley, 2012).Individualswhowereshownstimuli depictingdehumanizedoutgroupmembersresponded withincreasedactivationofamygdalaandinsula,consistentwithdisgust,aswellasbluntedventromedial prefrontalcortexactivation(Harris&Fiske, 2006).The

corticalnetworkinvolvedintheattributionofmental statesallowsindividualstocomparetheirownthoughts andfeelingstothoseofothersandiscentraltogeneratingbothcaringanddehumanizingresponses. Perceivingvideosdepictingdrugaddictsexperiencing physicalpainisassociatedwithsignificantlylessneural responsethanvideosdepictingcontrolsubjects, althoughthelevelofpainexpressedinthevideosis exactlythesame(Decety,Echols,&Correll, 2010).When otherhumansareperceivedashavinggoodintentions (beingwarm)andhavingthecapabilitytocarrythem out(beingcompetent),themedialprefrontalcortex modulatesempathicresponses.

Whensubjectswereallowedtopunishin-groupand out-groupmembersfornormviolations,punishmentofingroupmemberswaslesslikelyandwasassociatedwith heightenedactivityandconnectivitybetweenthemedial

Figure2. Brainregionsimplicatedinsocialcognitionanddecision-making.Convergingevidencefromsocialneuroscienceindicates that brainregionsassociatedwithsocialcognitionarewidelydistributedandsharecomputationalresourceswithcircuitscontrolling othercapacitiessuchasemotionalsaliency,mentalstateunderstanding,valuationofrewards,anddecision-making.Theseregions includetheventromedialprefrontalcortex(vmPFC),dorsolateralprefrontalcortex(dlPFC),dorsomedialprefrontalcortex(dmPFC), anteriorcingulatecortex(ACC),posteriorsuperiortemporalsulcus(pSTS)/temporoparietaljunction(TPJ),amygdala,anteriorinsula (aINS),striatum,andperiaqueductalgray(PAG).ThevmPFCplaysacriticalroleinsocialdecision-making.ItsconnectivitywithPAG, hypothalamus,striatum,amygdala,pSTS,allowsfortheencodingofvalueandmodulationofaffectiveresponses.ThedlPFChas consistentlybeenimplicatedinexecutivefunctioning,workingmemory,andresponseselection,whereasthedmPFCisinvolvedin evaluatingsocialinformationaboutrelevantmentalstates,socialnorms,andcontextualfactors.TheACCisabroadswathofmedial cortexthatisthoughttoperformvariousfunctionsrangingfromconflictmonitoring(dorsalACC)torepresentingself-consciousand affiliativeemotion(pre-andsubgenualACC).ThepSTS/TPJareconcernedwithrepresentingthebodilystates,intentionsandbeliefs ofothers.Theamygdalaprioritizestheaffective(positiveandnegative)relevanceofsocialstimuli.Theinsulaisassociatedwith emotionalawarenessandempathy,andthestriatumisknowntoplayaroleinrewardandpleasureprocesses.ThePAGisthesite ofintegratedautonomic,behavioral,andantinociceptivestressresponses.

prefrontalcortexandpSTS/TPJ.Theoryofmindregions becomemoreactive,suggestingthatpeoplewerejustifyingtheirgroupmates’ infractions;thesameregionswere notasactivewhenout-groupmembersmadethesame transgressions(Baumgartner,Schiller,Rieskamp,Gianotti,& Knoch, 2014).Whenthereisdecreasedactivityinthis mentalizingnetwork,peoplearemoreeasilyabletodehumanizeothersandarelesslikelytoshowempathy,tolerance,orprosociality(Cikaraetal., 2014;Harris&Fiske, 2006; Waytz&Epley, 2012).Interestingly,recentworksuggests dehumanizationmayenablemorallyobjectionableactsof violencewhenthesearemotivatedbyadesiretoobtain instrumentalbenefits(Rai,Valdesolo,&Graham, 2017).

Empathyisapowerfulmotivationalforcethatfostersbondsandcaringbetweenconspecifics,andinhibitsaggressiontowardsin-groupmembers(Decety, Norman,Berntson,&Cacioppo, 2012 ).Ithasadark sidetoo.Peopleoftenfeellessempathyandmotivationtoactprosociallytowardsindividualsthatbelong todifferentethnic,political,orsocialgroups(Decety &Cowell, 2014).Longitudinalincreasestoempathyin Muslimimmigrantyouthswhounderwentresilience trainingaimedatstrengtheningself-esteem,agency, andempathywereassociatedwithincreasednegativeattitudestowardsideology-basedviolence (Feddes,Mann,&Doosje, 2015).Conversely,lower traitcognitiveempathy(i.e.,perspectivetaking)was positivelyassociatedwithdogmatism,oranunwaveringsteadfastnessinone’sbeliefsthatisresistantto updatingwithnewinformation,accordingtoarecent study(J.P.Friedman&Jack, 2017).Thissamestudy foundthatdogmatismwasnegativelyassociatedwith analyticthinking.Activit ywithinanetworkofbrain regionsincludingtheACC,anteriorinsula(aINS),and periaqueductalgray(PAG)wassignificantlydecreased whenhealthyvolunteerssawphysicalpaininstrangerscomparedtoloved-ones(Cheng,Chen,Lin, Chou,&Decety, 2010).Relatedly,activitywithinthe ACCwasbluntedinbothCaucasianandChinese participantswhenviewingracialout-groupmembers inpaincomparedtoracialin-groupmembers(Xu, Zuo,Wang,&Han, 2009).Activitywithinthisnetwork wassignificantlylowerinparticipantswhoviewed clipsofpainedfacialexpressionsinpeoplewhohad contractedAIDsfromillici tdruguseratherthanfrom ataintedbloodtransfusion,eventhoughtheclips werecarefullymatchedonfacialexpressionintensity, indicatingthat apriori implicitattitudestowardconspecificsmodulateresponsestoperceptionsofdistress(Decetyetal., 2010).Anotherstudyfoundthat greaterrival-specificaggressionwasassociatedwith elevatedactivityintheventralstriatum,abrain regionimplicatedinrewardandpleasure,when

watchingrivalsfail,evenagainstathirdparty (Cikara,Botvinick,&Fiske, 2011 ).

Oxytocin,aneuropeptidewithwidespreadtargetsin boththebrain(includingtheanteriorcingulatecortex andamygdala)andperiphery,isasilentdriverofflexible empathicrespondingandthelackthereof.Oxytocinhas beenimplicatedintheregulationofvariousbehaviors rangingfrombondingandattachmenttoallyselection andintergroupcooperationbymakingsocialinformation moresalient(Bartz&Hollander, 2006).Oxytocinincreases eyecontact,trustandsocialbondingbutalsoamplifiesingroupfavoritism.Forinstance,individualsadministered intranasaloxytocinaremorelikelytohumanizein-group ratherthanout-groupmembersbyattributinghumanuniqueemotionstothein-groupmembersandshowing increasedpositiveevaluationsofthem(DeDreu,Greer, VanKleef,Shalvi,&Handgraaf, 2011).Inbehavioraleconomicgames,oxytocinreducesthelikelihoodthatmale participantswillcooperatewithout-groupmembers whentheyareperceivedasathreattoin-groupmembers (DeDreuetal., 2011;DeDreu&Kret, 2016).Importantly, individualdifferencesindispositionalempathyaswellas sympatheticnervoussystemresponsesarepredictedby variantsoftheoxytocinreceptorgene(Smith,Porges, Norman,Connelly,&Decety, 2014).Takentogether,ordinarypeopleexhibitin-groupfavoritismcoupledwitha bluntedordiminishedempathicresponsestoout-group members,atendencythatispartlydrivenbyindividual differencesatthemolecularlevel,thatappearstooperate outsideofconsciouscontrolandthatmayevenmotivate harmtowardsrivals.

Micro-sociologicalprocesses

Narratives,sacredvalues,andthequestfor significance

Ineverydaylife,humansconstructrichnarrativesthat representcausalconnectionsbetweendifferentevents andsoimbuetheseconnectionswithmeaningorpurpose.Indeed,oneofthewaysinwhichhumansunderstandthemselvesisbygeneratingautobiographical stories,ornarrativeidentities,thatrepresenttheselfin past,present,andimaginedfuturecontexts(McAdams, 2013).Coherentself-identitiesemergegraduallythrough adulthoodfromtheintegrationofsuchnarratives,which maythemselveschangeovertime,withsocialroles,psychologicaldispositions,motivations,andvalues (McAdams&McLean, 2013).Withtherightpsychological ingredientsinplace,narrativescanmakebadideas appearattractiveandgoodideaswhollyunappealing.Of particularrelevancetothestudyofradicalizationare victimizationnarratives,ornarrativesthatframe

individualsorsocialgroupsasthevictimsofintentional harm(s)(Pemberton&Aarten, 2017).Attemptstounderstandexperiencesofvictimization,toassigntheseexperiencesmeaning,andtoreconciletheseexperienceswith one’spre-existingidentitymayleadtotheemergenceof newnarrativeidentities(Crossley, 2000).InPalestinian andDutchMuslimyouths,forexample,perceivingoneself orone’sgroupasthevictimofinjusticeswasassociated withgreatersupportforviolenceandradicalism(Doosje, Loseman,&vandenBos, 2013;Victoroffetal., 2011).Itis thusnotsurprisingthatpropagandamaterialsproduced anddistributedbyviolentextremistorganizationsinan efforttogarnersupportandtomobilizerecruitsroutinely employsuchvictimizationnarratives.Theyareapowerful meansfortransmittingemotionsandvalues.

Justicemotivation,thecapacityforperceivinginjusticetowardsoneselforothersandpreferencesregardingwhethertoacttorestorejustice(Decety&Yoder, 2017),playsacentralroleinvictimizationnarratives. Theperceptionthatone’sgrouphasbeenthevictim ofinjustices,whetherpolitical,economic,orreligious,is believedtoplayacriticalroleinmotivatingactsof terrorism.Forinstance,Palestinianyouthswhofeltas thoughtheirgrouphadreceivedunjusttreatmentalso reportedgreatersupportforreligio-politicalaggression (Victoroffetal., 2011).PerceivedinjusticewasalsoassociatedwithsocietaldisconnectednessandwasadeterminantofaradicalbeliefsysteminyoungDutch Muslims(Doosjeetal., 2013).Whileconcernforjustice isapartofhumannatureandemergesearlyinontogeny,someindividualsarehighlysensitivetoinjustice. Individualsthatareparticularlysensitivetoinjustices aremotivatedbyjusticeprinciplesratherthanemotionalcontagionandpersonaldistress(Decety& Yoder, 2016).Justicesensitivityhasbeenassociated withbrainactivationinregionsthoughttoperform higher-ordercomputationalfunctions,suchasmental stateevaluationandgoalunderstanding.Individualdispositionsinjusticesensitivitypredictedneuralresponse indorsolateralprefrontalcortex(dlPFC),dorsomedial prefrontalcortex(dmPFC),andposteriorsuperiortemporalsulcus(pSTS)inparticipantswhowereaskedto ratescenariosdepictingofinterpersonalassistanceor harmaseithermorallygoodorbad(Decety&Yoder, 2017;Yoder&Decety, 2014).Neuralactivityinthese regionspredictedparticipants’ praiseandblameratings whentheywereevaluatingprosocialandantisocial behavior.Bothempathyandjusticemotivationare topicsofgrowinginterestinsocialneuroscience,and validatedbehavioralmeasuresofempathyandjustice sensitivityaswellasnormativefunctionalneuroimagingdatadescribingtheirneuralsubstratesareavailableforuseinfuturestudiesofvulnerabilityto

radicalization(Chengetal., 2010;Cikaraetal., 2011; Decety&Yoder, 2016, 2017;Decetyetal., 2010;Xu etal., 2009;Yoder&Decety, 2014).

Experiencesofvictimizationthroughinjusticemay occurwhenonefeelsasthoughtheirsacredvaluesor theirgroup’ssacredvalueshavebeenviolated.Sacred valuesaredistinguishablefrominstrumentalormaterial valuesinthattheyincorporatemoralandethicalprinciples and,assuch,areinsensitivetotrade-offswithothervalues (Atran,Axelrod,&Davis, 2007;Atran&Ginges, 2012). Sacredvaluesmayinteractwithotheraspectsofindividual andgroupidentitytoproduceawillingnesstomakecostly sacrificesinsupportofone’sgrouporcause.Forinstance, inMoroccanslivinginneighborhoodsassociatedwithmilitantjihad,awillingnesstoengageincostlysacrificefor ShariawasespeciallypronouncedinindividualswhoconsideredShariaasacredvalue(Atran,Sheikh,&Gomez, 2014).Sacredvaluesmayalsocomplicateattemptsatconflictresolution – IsraelisandPalestinianswhowerepresentedwithhypotheticalIsraeli-Palestinianpeacedeals weremorestronglyopposedwhenthesedealsincluded materialincentivesbutoppositiondecreasedwhenadversarieswerewillingtomakesymbolicconcessionsrelating totheirsacredvalues(Ginges,Atran,Medin,&Shikaki, 2007).Arecentfunctionalneuroimagingstudyreported thatsacredvalues,operationalizedasvaluesparticipants wereunwillingtosacrificeinexchangeformaterialgain, wereassociatedwithactivation inventrolateralprefrontal cortexandlefttemporoparietaljunction(Bernsetal., 2012). Interestingly,activationwasnotobservedintypicalvalue encodingregionswhichmightbeexpectedifindividuals processsacredvaluesintermsofutility.Theauthorsinterpretedtheneuralresponseasreflectingtheencodingand retrievalofdeonticrules,whichtheyarguesuggestssacred valuesareconcernedwithwhatisrightorwrongrather thanwithoutcomes(Bernsetal., 2012).Violationsof sacred,moralvaluesmaytriggerdisgustand/oranger responses(Rozin,Lowery,Imada,&Haidt, 1999;Seidel& Prinz, 2013)thatmaysetthestageforideologically-motivatedviolence.

The “significancequest” modelprovidesaframework throughwhichsomevictimizationnarratives,suchas thoseconstructedaroundviolationsofsacredvalues, canbeunderstoodasriskfactorsforradicalization (Kruglanskietal., 2014;Pemberton&Aarten, 2017).The significancequestreferstotheuniversalneedtomakea difference,tobenoteworthy,andtofindone’spurpose. Onthisview,theradicalizationprocessrequiresthedesire forsignificance,theidentificationofideologically-motivatedviolenceasthemostappropriatemeansbywhich toachievesignificance,andthedevaluationofcompeting goalsanddesires.Victimizationnarrativesmaydampen feelingsofpersonalsignificanceandconsequentlyleadto

disconnectionsbetweenindividualnarrativeidentities and “master” societalnarratives(Pemberton&Aarten, 2017).Individualswhofeeltheirlifestoriesareatodds withsocietalnarrativesoftenseekunderstandingthrough interactionswithindividualsorgroupsthathavehad similarvictimizationexperiences(Pemberton&Aarten, 2017).Thesepeopleorgroupsprovidealternative “master” narrativesthatmayaccordbetterwithindividuals’ personalnarratives.Anindividualwithextremeviewson religiousfundamentalism,forexample,mightfindthe prospectofjoiningaviolentextremistorganizationattractiveifthisorganizationsharestheirviews,andifitcan provideameansbywhichtoachievesignificance.How, though,doindividualsgoaboutdevelopingthekindsof narrativesthatcoincidewiththe “master” narratives offeredupbysuchorganizations?Inorderwords,how dopeopledevelopextremeviews?

Extremeviews

Itiscriticalistoexaminehowindividualsdevelopextreme opinionsandbecomeradicalized,increasingtheprobabilityofpoliticalviolence.Extremeviewsrequireunconditionaladherencesuchthatotheraspectsofone’slifeare madesubordinate(Bronner, 2016).Theprocessofradicalizationrequiresstrictadherencetoextremethoughts, beliefs,andworldviews(Horgan, 2014),andindividuals whobecomeradicalizedmaysacrificethingstheyonce consideredprecious(e.g.,career,family,friends,freedom), oreveninnocentlives,insupportoftheirviews.Contraryto folkwisdom,however,extremistideologiesareoftenperfectlyrational.Extremistsadhereuncompromisinglyto theirmoralworldviews.Thisstrictmoraldualism,according towhichthedistinctionbetweenrightandwrongisunambiguous,underpinsextremeviewsandprovidesarationale forusingviolenceasameansofre-establishingthebalance betweengoodandevil.Ordinarypeople,ontheother hand,maycompromisetheirmoralvalueswhenthissuits theirinterests – thatis,theyaresufficientlymentallyflexible toholdcontradictorybeliefs(Bronner, 2016).Importantly, thecapacityfortolerancetowardspotentialinconsistencies andambiguitiesrequiresmentalflexibility,whichrefers heretotheabilitytorepresentknowledgefromdifferent perspectivesandtoshiftbetweensometimesmutually contradictoryviews.Whenindividualsbelongtomany differentgroups,eachofthesegroupsinfluencesitsmembers’ beliefs,values,andbehaviors.Competitionbetween thediversevaluesheldbydifferentgroupsreducesthe powerofanyonegroupoveritsmembers.

Valuesaremotivationalconstructscomprisedofbeliefs imbuedwithemotionthat,whenactivated,mayexert attractiveorrepulsiveforces(Eccles&Wigfield, 2002). Socialvalueshavebeenshowntoemergefromco-

activationofneuralstructuresthatrepresentsocialconcepts(rightsuperioranteriortemporallobe)andemotionalstates(fronto-mesolimbicareas)(Zahnetal., 2009).Thereisahedonicelementtovalues,where approachandavoidancemodulatemotivationsto engageinbehaviorsaimedatachievingdesirablegoals. Motivationincludesaglobalenergizationfactorthatvariesindependentlyofcontroldemandsandbehaviordirection(Duffy, 1962).Computationalneurosciencework indicatesthatreward-basedenergizationofhighercognitiveresourcesindependentofcognitivedemandsand behaviordirectionisacentralcomponentofhumanmotivation(Kouneiher,Charron,&Koechlin, 2009).Thismotivationalfunctionincludesdistinctincentivelevelsthatare intimatelyrelatedtocognitivestagesofdecision-making.

Functionalneuroimagingstudiesconsistentlyimplicatethenucleusaccumbensinmotivationalsalience andrewardprocessingacrossdomains.Religious experience(i.e., “feelingtheSpirit”),forexample,was foundtobeassociatedwithactivationofthenucleus accumbensandventromedialprefrontalcortexina smallsampleofdevoutMormons(Fergusonetal., 2016).Importantly,threedistinctparadigmsrevealed nucleusaccumbensactivationthatprecededpeakspiritualfeelingsbyseveralseconds,whichsuggestsdoctrinalconceptsmaybecomeintrinsicallyrewardingand motivatebehaviorinindividualswhovaluereligious experience.Relatedly,individualswithgeneticmarkers indicativeofgreaterdopamineavailabilityweremore likelytoholdunfoundedbeliefs(e.g.,suspicious thoughts,beliefintheparanormal)(Schmacketal., 2015).Dopamineneurotransmissionisvitalforpleasure andreward-relatedcognitiveprocesses,withthedopaminergicprojectionsthatcomprisethemesolimbic pathwayterminatingatthenucleusaccumbens. Values,then,reflectreasonablystableattributionsof worthassignedtosacredandnon-sacredpeople, places,objects,andevents,andallindividualshold numerousvalueswithdifferingsubjectiverankings.

Individualswhobecomeradicalizedbyviolentorganizationsusuallywithdrawfromorcompletelyterminate socialconnectionswithformalandinformalgroupsand socialnetworksthatholdcompetingvalues.Theyestablishexclusivebondswithothermembersoftheterrorist groupwhoseideas,experiencesandidentitiesaresimilar,andmembersmaybecometightlyknittotheextent thatthegroupservesasasurrogatefamily.Asaconsequence,terroristgroupswieldenormousinfluenceover thebondsandvaluesofradicalizedindividuals(see Figure1).Extremismingeneral,whetherrelatedtoanimalrights,aestheticpreferences,orpoliticalattitudes,is characterizedbyanunconditionalrelationshipbetween valuesandbeliefs(Bronner, 2015).Theaverageperson,

however,onlyadheresunconditionallytovaluesthat requireminimalsacrifice – forexample,oppositionto childmolestation.Thesevaluesare “trans-subjective” in thattheycanbeapplieduniversallyandwithoutdamage tothecollectivewell-being(Bronner, 2016).Onthecontrary,extremeviewsareweaklytrans-subjective,inthat theyareunlikelytobeperceivedasconvincingenough topropagatethroughoutapopulation,andpossibly sociopathic,inthattheyrejectcompetingworldviews. Bothofthesecharacteristicsarepresentinthemost dangerousextremeviews.

Neurobehavioralbasesofviolenttendencies

Oneoftenoverlookedaspectofthefamousearlysocial psychologyexperimentsonobedienceandauthority describedearlieristhatanontrivialproportionofparticipantsrefusedtocommitviolentorabusiveacts (Haneyetal., 1973;Milgram, 1963).Whilegroup dynamicsandsituationalfactorsundoubtedlyfacilitate theemergenceofviolence,vulnerabilitytothesefacilitatorsislikelycontingentonindividualdispositions.It isbeyondthescopeofthispapertoprovideathorough reviewofallindividualdispositionsthatmaybeuseful inunderstandingradicalizationandsupportforideologicallymotivatedviolence.Preliminaryevidence,however,pointstoanumberofcognitive,emotional,and motivationalfactorsthatmayreciprocallyinteractwith groupandsituationalfactorstofacilitateextremist valuesandbeliefsandviolentbehavior.Theextentto whichemotionalandmotivationalfactorsbecome interconnectedwithextremebeliefsmaydistinguish

Thus,cognitiveflexibilityisapsychologicaltraitthat appearstoplayakeyroleintheradicalizationprocess (Hogg,Kruglanski,&vandenBos, 2013).Individualswho arecognitivelyinflexibleandintolerantofambiguitymay becomecaptiveaudiencesforideological,political,orreligiousextremistswhosesimplisticworldviewsglossover nuance.Indeed,cognitiveinflexibilityhasbeenpositively associatedwithauthoritarianaggression,racism,andethnocentrism(Victoroff, 2005).Therelatedmotivationalconstructofneedforcognitiveclosure,orthedesiretoreduce ambiguityanduncertainty(Webster&Kruglanski, 1994), hasbeenlinkedtoincreasedfavoritismtowardsin-group members(Federico,Hunt,&Fisher, 2013)andhostility towardsout-groupmembers(DeZavalaetal., 2010). Executivefunctions,ofwhichcognitiveflexibilityisone aspect,facilitatetheselectionofactionsinresponseto competinginternalgoalsandaresubservedbyspecific regionsoftheprefrontalcortex(Miyakeetal., 2000).In particular,cognitivecontrolandmotivationareintegrated viareciprocalconnectionsbetweenthelateralprefrontal cortex,wherecontrolsignalsarerepresentedinagraded fashionalongananterior-posterioraxis,andmedialprefrontalcortex(Koechlin&Summerfield, 2007;Kouneiher etal., 2009).Interestingly,arecentstudyreportedthat lesionstothedorsolateralprefrontalcortexwereassociatedwithfundamentalistbeliefs,andthatthisrelationshipwasmediatedbycognitiveflexibilityandtrait openness(Zhong,Cristofori,Bulbulia,Krueger,& Grafman, 2017).FunctionalneuroimagingstudiesofcognitiveinflexibilityandotherexecutivefunctionsalsoconsistentlyimplicatetheACC(Shackmanetal., 2011). Individualswhoweregiventheopportunitytoexplain awaythreateninginformationaboutafavoredpolitical candidate,forexample,demonstratedincreasedactivation inACCaswellasventralstriatum(Westen,Blagov, Harenski,Kilts,&Hamann, 2006).TheACCisakeynode inneurobiologicalmodelsofaggressionandviolence (Siever, 2008)anderror-relatedactivityinthisregionpredictsfutureantisocialbehavior(Aharonietal., 2013). Althoughtheneuralunderpinningsofextremism remainelusive,politicalneuroscienceresearchsuggests politicalengagementandradicalismareassociatedwith distinctivepatternsofneuralactivation.Politically engagedindividualsperceivedcongruentpoliticalattitudesasmoreemotionallyintenseandpositivecomparedtoindividualswhoarenotpoliticallyengaged (Gozzi,Zamboni,Krueger,&Grafman, 2010). Furthermore,interestinpoliticsinthatstudywasassociatedwithgreateractivationinamygdalaandventral striatumwhenreadingcongruentpoliticalopinions,suggestingpoliticalengagementrecruitsemotion-and reward-relatedbrainareas.Anotherneuroimaging experimentfoundthatindividualspresentedwithpoliticalstatementsstructuredcomplexpoliticalbeliefsalong threeindependentdimensionsthatwerereflectedin distinctivepatternsofneuralactivation(Zambonietal., 2009).Individualism,whichreflectsthespectrumfrom individualismtocollectivism,wasassociatedwithactivationofthemedialprefrontalcortexandposteriorsuperiortemporalsulcus,whereasconservatism,whichreflects thespectrumfromconservatismtoliberalism,wasassociatedwithactivationofthedorsolateralprefrontalcortex.Incontrast,theradicalismdimension,which includeditemssuchas “Peopleshoulduseviolenceto pursuepoliticalgoals”,wasrelatedtoincreasedactivationoftheventralstriatumandposteriorcingulate. Takentogether,thereexistsareciprocalrelationship betweensmallgroupdynamics,whentiestogroups withcompetingvaluesaresevered,andindividualdispositions,suchaslackofmentalflexibilityorintolerance inresponsetoambiguity,infacilitatingextremebeliefs andopinions.Preliminaryempiricaldatafurthersuggest extremebeliefsrecruitbrainareasimplicatedinemotion andreward-processing.

thosewhomerelyexperiencesympathyforanextremistcausefromthosewhobecomemotivatedtoacton itsbehalf.Itislikelythattheemotionalandmotivationalfactorsthatdriveradicalization,however,are heterogeneousandmultifaceted.Forexample,the inherentrisksorpromiseofexhilarationassociated withterrorismmayappealprimarilytoindividuals highintraitnoveltyseekingorimpulsivity(Victoroff, 2005).Ofnote,threeyearoldchildrenwhowere “under-controlled” (e.g.,impulsive,distractible)were morelikelytobeinvolvedwithcrimeat21-yearsof age(Caspi,Moffitt,Newman,&Silva, 1996).

Multipleneurochemicalsystemsinadditionto MAOAhavebeenimplicatedinaggressiveantisocial behavior(reviewedinNelson&Trainor, 2007). Serotonergichypofunctionisperhapsoneofthemost reproduciblecorrelatesofaggression(Moore,Scarpa,& Raine, 2002).Acutelyimpairingserotonergicfunction withacutetryptophandepletionorbyloweringplatelet serotoninlevelsincreasedaggressiverespondingto unfairoffersintheultimatumgame(Crockett,Clark, Lieberman,Tabibnia,&Robbins, 2010;Emanuele, Brondino,Bertona,Re,&Geroldi, 2008).Impairingserotoninfunctioningalsoincreasedimpulsivity(Crockett, Clark,Liebermanetal., 2010).Conversely,serotonergic enhancementwithanacutedoseofaselectiveserotonin-reuptakeinhibitorincreasedacceptanceofunfair offersinhealthyvolunteers(Crockett,Clark,Hauser,& Robbins, 2010).Importantly,thesesameparticipants judgedmoralharmsaslessacceptable,suggesting thatserotoninregulatestheaversivenessofaggressive responding.Themechanismsbywhichserotoninmodulatessuchcognitionsandbehaviorsarenotwell understoodbutareseeminglycontingentonindividual differencesinimpulsivity,emotionregulation,and socialabilities(Krakowski, 2003).Serotoninmodulates factorsattheindividualpsychologicallevelthatmay havedownstreamconsequencesforgroupdynamics, and socialfactorsinfluenceserotonergicfunctioning (Krakowski, 2003).Again,acompleteunderstandingof vulnerabilitytoideologicallymotivatedviolencewillnot bepossiblewithoutconsideringeachoftheselevels andinteractionsbetweenthem.

Atthelevelofthebrain,severalstudieshave describedneuralcircuitslinkedtoobservingandimaginingactsofviolence.Inonestudy,forexample, participantsviewedaseriesofshortvisualscenarios depictingintentionalharmingorhelpingbehaviors whileundergoingfunctionalneuroimaging(Decety& Porges, 2011).Toexaminetherelationshipofagency (whichreferstothefeelingofcontroloverone ’s actionsandtheirconsequences)totheneuralcircuitry engagedinaggression,participantswereaskedto imaginethemselvesaseithertheperpetratororrecipientoftheseactions.Bilateralamygdaladeactivation wasdetectedwhenparticipantsimaginedharming otherscomparedtobeingharmed.Decreasedconnectivitybetweenamygdalaandventromedialprefrontalcortexwasalsoobserved,aswellas increasedactivationofsecondaryvisualcortex,

Thereexistmanypathwaystoradicalizationsuch thatsearchingforauniversalterroristprofileisunlikely toyieldfruitfulresults.Hopeisnotlost,however – even ifasingleuniversalprofileisunlikelytoexist,thereare undoubtedlyclustersofrecurrentdispositionsthatmay predictvulnerabilitytodifferentradicalizationavenues andbehavioraloutcomes.Apropensitytomeetconflict withviolence,forexample,mayreflectonesuchrecurrentdisposition.Agrowingbodyofresearchdescrobes molecular,neurobiological,andbehavioralpredictorsof futureaggressionandviolence(Glenn&Raine, 2013). Aggressivebehaviormeasuredinchildrenasyoungas twohasbeenshowntopredictfutureaggression (Cummings,Iannotti,&Zahn-Waxler, 1989;Huesmann, Eron,Lefkowitz,&Walder, 1984).Similarfindingshave beenreportedinsamplesbothinsideandoutsidethe USandirrespectiveofdemographicvariablessuchas gender(Kokko,Pulkkinen,Huesmann,Dubow,&Boxer, 2009).Thissuggestsaggressionandviolencearestable dispositions.Indeed,stronglinksbetweengeneticmarkersandaggressive,antisocialbehaviorarewelldocumentedintheliterature(Glenn&Raine, 2013;Raine, 2013).Alargestudyofapproximately1.3millionadopteesandnon-adopteesfoundthatadopteesweremore likelytocommitviolentcrimesiftheirbiologicalparentshadahistoryofcriminalviolence(Hjalmarsson& Lindquist, 2013).Maltreatedchildrenwhocarryalleles associatedwithlowmonoamineoxidaseA(MAOA) activityaremorelikelytodevelopantisocialbehaviors laterinlife(Caspietal., 2002).Crucially,thiseffectwas notobservedinchildrenwhosegenotypeisassociated withhighlevelsofMAOA,suggestinggeneticriskfactorsforviolenceinteractwithenvironmentalfactors. Thisjustoneofoverahundredstudiesprovidingevidenceforsuchinteractionsingivingrisetoantisocial behavior(Raine, 2013).Thisliteratureunderscoresthe pointthat,sinceriskfactorsforextremeviolencemay emergethroughinteractionsacrosslevelsoforganization,amultidisciplinaryperspectiveisurgentlyneeded tounderstandvulnerabilitytoradicalization.Animportantdirectionforfutureresearchwillbetoinvestigate howapropensitytoengageinviolent,antisocialbehaviorinteractswithotherdispositions(e.g.,cognitive inflexibility)andwithotherlevels(e.g.,neurochemical) toincreasevulnerabilitytodevelopingextremeviews andtobecomingradicalized.

posteriorthalamus,andstriatum.Thisdecreasein ventromedialprefrontalcortexactivationisconsistent withchangesinpatternsofresponsesreportedin previousstudiesofimaginedaggression(Pietrini, Guazzelli,Basso,Jaffe,&Grafman, 2000).ThevmPFC iscriticalregionforsocial,motivationalandemotional processing(Grafman&Litvan, 1999)anddecisionmaking(Levy&Glimcher, 2016).Itisdenselyinterconnectedtoemotionprocessingregionsincluding amygdala,periaqueductalgray,temporalpoles,and rewardprocessingareassuchasthestriatum (Carmichael&Price, 1996;Kondo,Saleem,&Price, 2003).ThereisalargebodyoffMRIandelectrophysiologyevidencethattheventromedialprefrontalcortexcarriesinformationaboutthepersonalsubjective valueofstimulioractions(Fellows, 2006). Interestingly,increasedactivationofthalamusand striatumanddecreasedventromedialprefrontalcortexactivationhavebeenreportedtoreflectenjoymentofaggressioncoupledwithadiminished capacityforcontrollingaggressivebehavior(Decety, Michalska,Akitsuki,&Lahey, 2009;Decety&Porges, 2011;Murray, 2007).

Ahandfulofneuroimagingstudieshavebegun sheddinglightonhowsituationalfactorsandgroup dynamicsshapeattitudestowardskillingandhowthis isrepresentedinthebrain.Indeed,althoughharming conspecificsismorallyprohibited,therearecircumstanceswheretheseprohibitionsmayberelaxed,as inwarfarewherekillingenemysoldiersisconsidered justified.IndividualswhounderwentfMRIscanning whileimaginingcarryingoutunjustifiedactsofkilling (e.g.,shootingcivilians)comparedtojustifiedkilling (e.g.,shootingenemysoldiers)showedincreasedactivationintheorbitofrontalcortexwithincreasedcouplingtothetemporoparietaljunction(Molenberghs etal., 2015 ).Furthermore,activationoftheorbitofrontalcortexwaspositivelyassociatedwithfeelingsof guiltaboutengaginginactsofunjustifiedkilling. Relatedly,greaterneuro-hemodynamicactivitywas detectedintheorbitofrontalcortex,aswellincreased couplingbetweentheorbitofrontalcortexandamygdalaandinsula,whenindividualsviewedharmful behaviorsperpetratedbyout-groupmembersagainst in-groupmembers(Molenberghs,Gapp,Wang,Louis, &Decety, 2016).Futurestudiesshouldinvestigate whetheractivationofandconnectivitytotheorbitofrontalcortexcapturesindividualdifferencesinthe processingofextremeviolence.Beyonddescribing theneuralcorrelatesofobservingorimaginingviolence,tworecentstudieshaveusedneuroimaging measuresinanattempttopredictfutureantisocial behavior.Error-relatedactivityintheACCdetected

withfunctionalMRIwasshowntopredictfutureantisocialbehaviorinahigh-riskpopulation(Aharoni etal., 2013).Relatedly,increasedaggressionandviolenceinadultmenwaspredictedbyloweramygdala volumesasmeasuredthreeyearsprior(Pardini,Raine, Erickson,&Loeber, 2014).Animportantavenuefor futureresearch,then,willbetoinvestigatewhether andwhichneuralmarkersarecapableofpredicting vulnerabilitytoradicalization.

Movingbeyondmetaphors

Socialneuroscienceisimportantforunderstandingthefull rangeofcollectivesocialbehaviors,whetherpositive(e.g., cooperationandaltruism)ornegative(e.g.,conflict,war andviolence).Thisperspectiveshouldappealtoanyacademicwhowishestobetterunderstandtheworkingsof theterroristmind,suchasanthropologists,psychiatrists, economists,orpoliticalscientists.Asconceptualclarify improves,sotoowillthedesignofinterventions,thestructuringofstudies,theselection offutureresearchquestions, thespecificationofhypotheses,andtheselectionofsuitableanalytictechniques.Psychologists,intelligenceexperts, andlawenforcementpersonnelinparticularcouldcapitalizeonanimprovedunderstandingofthecomplexinterplaybetweenindividualdispositionsandgroupdynamics torefineprophylacticstrategies,toinformcounter-terrorismefforts,toencouragedisengagementfromterrorist organizations,andtoimprove rehabilitationstrategies.

Acomprehensiveunderstandingofradicalizationand ofterroristpsychologymorebroadlywillnotbepossible, however,withoutfirstintegratingtop-downapproaches, accordingtowhichthecausesofterrorismarepolitical, social,andeconomic,withbottom-upapproaches, accordingtowhichterrorismisbestunderstoodwith referencetothecharacteristicsofterroristgroupsandof theindividualsthatcomprisethem.Althoughtheliteratureisbrimmingwiththeoriesandmodelsofradicalizationandofterrorism,manyofwhicharecouchedin catchymetaphors(e.g.,the “StaircasetoTerrorism” ; Moghaddam, 2005),thesewereintendedtoprovidegeneralframeworksfororganizingknowledgeinterrorist psychology.Incontrast,thecomprehensiveapproach weareadvocatingmayeventuallyproduceworkingmodelscapableofpredictingbehavior.

Thisendeavorischallenging.Itismadenolesssoby therealitythat,tounderstandhowsocial,cognitive, emotional,andmotivationalprocessesinteract,wewill eventuallyneedacomputationalaccountthatacknowledgestheadaptivenatureofradicalizationandofpoliticalviolence.Theresultingmodelmaylookentirely differenttoanythingwemightanticipatebasedon ourintuitionsorontheextantliterature.Iftrue,this

wouldnotnecessarilymeanthattheneuralprocesses thatgiverisetosocialcognitionanddecision-makingin thecontextofradicalizationandterrorismareinherentlymoredifficulttocharacterizethanotheraspects ofcognitionorperception.Rather,theproblemlies withour “folk” psychology.Ontheonehand,ourintuitiveunderstandingoftheworldgroundspsychological theorizing.Thereasonsocialneuroscienceisatall understandableisbecauseitusesconceptsthatare continuouswithourcommonsenseunderstandingof ourmindsandofthemindsofothers.Ontheother hand,ourintuitionssometimesgetitwrong.Itisintuitive,forexample,thatpsychopathyshouldbeaprerequisiteforcarryingoutterroristattacksthattarget innocentpeople.Howelsecouldsomeonedosuch terriblethingswithoutexpressinganyremorseor guilt?Aswehavediscussed,however,thepsychopathy accountofterrorismislimitedatbest.

Puttingthepiecestogether

Inthispaper,weprovideanoverviewoftheputative processesinvolvedinradicalizationandextremepolitical violence,andintroduceanewframework,whichcaptures themostcriticalelementsthatcontributetoresearchand theoryconcerningthischallengingissue.Onecentralidea developedhereinisthatmostpeoplewhobecomeradicalizedandresorttoextremeviolencearerationaland shouldnotbeconsideredpsychiatricpatients.Thatis, ordinarypeoplecanholdextremesviewswithoutbecomingterrorists.Thus,thereareintra-individualcharacteristicsatthemolecularandbrainorganizationlevelsthat mustbetakenintoaccountinexplainingwhysome individualsturntoviolence.Asecondcentralideaisthat nosinglelevelofanalysis,beitmolecular,developmental, orsociological,canaloneaccountforradicalizationand propensitytocommitactsofterror.Futureresearchneeds toincorporateasmanylevelsofenquiryaspossible.The utilizationofthecomplementaryinformationprovidedby perspectivesonindividualdifferences,socialscience,and neurosciencewillenhancetheidentificationofdeterminantsandfacilitatorsofradicalization.Thesedifferent theoreticallevelsandapproachestomeasurementcan becompressedwithmathematicalmodelsandcomputer algorithms.Suchinformationcompressionhastheadvantageofreducingcomplexityofalargeproportionofthe interindividualvariabilityacrosslevelsofanalysisand allowsfortheexaminationoftheextenttowhichradicalizationisdrivenbyalimitednumberoffactors,aswellas therelationsbetweenvariables.Undoubtedly,individual differencesacrosslevelsoforganizationmoderatethe efficacyofrehabilitationstrategies.Identifyingclustersof recurringfactorslinkedtosusceptibilitytoradicalization,

then,willinformtailoringofrehabilitationstrategiesto thecharacteristicsofradicalizedindividuals.Molecular, neuroendocrine,andneurocognitivemarkerswillincrease confidenceinwhichstrategiesarelikelytobeefficacious. Thevalueofanyscientificundertakinghingesonits relevancetopressingsocialproblemsandmentalhealth issues.Althoughsocialneurosciencealoneisneithernecessarynorsufficienttoaddressradicalizationandpolitical violence,itrepresentsamethodologicalandtheoretical advancethatcreatesanopportunitytoaddressoldquestionsinnewwaysanduncovernewquestionsaboutbrain function,cognitionandbehavior.Whenneuroimaging dataarecombinedwithfine-grainconceptualanalyses, connectivityanalyses,quantitativemeta-analyses,lesion studies,andothersourcesofinformation(e.g.,genetics, hormones,electrophysiology)acrossdisciplines(e.g., anthropology,sociology,politicalscienceandbehavioral economics),theycansignificantlyadvancetheorizing aboutthehumanmindandsocialbehavior(Decety& Cacioppo, 2010).Theoryguidesscientistswhentheyselect researchquestions,structurestudies,specifyhypotheses, chooseanalyses,anddesigninterventions,anditconnects thedotsinordertorevealthebiggerpicture(Gray, 2017). Additionalclaritycanbeachievedbycomplementingtheorizingwithunconstrained,bottom-upapproachesaccordingtowhichthelatentdriversofradicalizationemerge frominteractionsbetweenbasicpsychologicalprocesses, representationsandmotivations.Mappingthecomplex cognitive,motivationalandsocialprocessesontobrain mechanismsthatmediateordriveradicalizationand potentialviolentoutcomesisaniterativewaytomake progress,bootstrappingourunderstandingwithimprovementsoccurringineachsuccessiveiteration.

Disclosurestatement

Nopotentialconflictofinterestwasreportedbytheauthors.

Funding

ThisworkwassupportedbyagrantfromtheUSDepartment ofDefense-OfficeofNavalResearch(FP060231-01-PR).

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