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Disentanglingthecausesandeffectsofpartisanmediachoiceinapolarizedenvironment:researchtodateandawayforwardDoes media choice cause polarization or does polarization cause media choice? This paper reviews the literature to date on this question, including research on selective exposure and persuasion, as well as on credibility, bias and trust. Establishing the direction of causality has proven empirically challenging, and the extant literature is decidedly mixed on the questions on whether partisan media can change attitudes, or merely reinforce them, as well as the extent to which people selectively expose themselves to news and information that reinforces their preexisting beliefs. Following this review, we identify shortcomings in the extant literature and propose several new methods aimed at moving this research program forward toward ultimately disentangling the relationship between partisan media, individual preferences, persuasion, and political attitudes and behavior.

MatthewA.BaumHarvardUniversity

JustindeBenedictis-Kessner

MIT

AdamBerinskyMIT

DeanKnoxMIT

TeppeiYamamotoMIT

DRAFT-December20,2015

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Introduction

Inrecentyears,pundits,politicians,andordinarycitizenshaveexpressed

growingconcernoverpoliticalpolarizationintheUnitedStates.Ina2013op-ed

article,famedClintonpoliticalguruJamesCarvillewrites,“Ithinkalotofpeoplewill

lookbackatthispointinAmericanpoliticalhistoryandwonderhowthingsgotso

damnscrewedup.”Carville’sexplanation,arguablyreflectingthemostcommon

widespreadconventionalwisdom,isthat:

“…asmuchasanything[it]isthedisturbingfragmentationofthe

media.Today,conservativescangetalltheirinformationfrom

conservativeoutlets,andliberalscangetalltheirinformationfrom

liberaloutfits.Andyoucanspendyourwholelifeneverbeing

challenged,neverhavingtohearorthinkaboutorconfront

viewpointsthataredifferentfromyourown”(Carvill2013).

Theseemingimplicationisthatinaworldoffragmentedmedia,peoples’pre-

existingpoliticalattitudesdeterminetheirchoicesofnewsoutlets.Ifso,thiswould

representaclearexampleofthepsychologicalphenomenonknownasselective

exposure–thetendencytoseekoutinformationwhichreinforcesexistingviews.

Yet,laterinthesamearticle,Carvilleappearstoreversecourse,arguingthat

partisanmedia“makesbothsidesmoredugin.”Theimplicationhereisthatthe

existenceofapartisanmediacause,oratleastexacerbate,polarization.This

perspectiveplacestheblameatthefeetofthemedia;bypresentingone-sided

versionsofissues,partisanmediaoutletslikeFoxNewsontherightandMSNBCon

theleftdriveAmericansapart.Theseslantednewssourcespersuadeindividualsthat

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theparticularone-sidedversionofissuestheyconsumeconsistsoftheunvarnished

truth.Suchaprocessofpersuasionrepresentsaquitedifferentmechanismthan

selectiveexposure.

Thesetwoperspectivesontherelationshipbetweenthemediaandthepublic

standatoddswithoneanother.Dolike-mindedindividualsseekoutpartisannews

sourcesthatsupporttheirpre-existingbeliefs–resultinginatendencytowarda

particularperspectiveamongconsumersofideologicallynarrowpartisanmedia

outletsbyvirtueofself-selection?Orisitthecasethatconsumersofpartisannews

altertheirviewstoreflectthosepresentedinpartisanoutlets,resultinginincreased

polarizationbetweenconsumersofliberalandconservativenews?Intheformer

instance,mediachoicereflectspolarization;inthelatter,mediachoicecausesit.We

arethuslefttoask:ispublicpolarizationacauseoraconsequenceoftheriseofthe

partisanmedia.AsCarville’stwo-sidedtreatmentsuggests,theprocessesof

selectiveexposureandpersuasionareoftenconflated.

Empiricallydistinguishingbetweenthesetwocausalpathwaysischallenging.

Peoplearenotoriouslypooratestimatingtheirownpastbehavior(Prior2009)or

predictingtheirfuturebehavior(Clauson1968).Inthispaper,webegintomove

forwardindisentanglingthetwocausalprocesses.First,wereviewpasteffortsto

disentangletherelationshipbetweenpartisanmediaandpolarizationanddiscuss

theshortcomingsofthatresearch.Second,weproposeasetofnewmethodsto

answerthiscriticalquestion.Inthispaper,wefocusononepieceofthepuzzle,

consideringhowtheeffectsofpartisanmediavarybasedonthepreferencesofthe

viewersofthosestories.Indoingso,wealsoconsidertherelatedquestionofhow

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accuratelyrespondents’statedpreferencespredicttheiractualchoicesin

experimentaltreatmentsdesignedtoteaseoutthecausesandeffectsofpartisan

mediaconsumption.

PolarizationasCauseorEffectofPersuasion?

Awidespreadconcerninsocialscienceresearch,thathasimportant

implicationsforthestudyofmediaeffects,istheproblemofselection.Whenever

socialscientistsobserveatreatmenteffect–thatisadifferencebetweenactors

exposedtodifferentstimuli--intherealworldwhenitisnotpossibletocontrol

whogetsthetreatment,thequestionarisesastowhethertheeffectresultsfromthe

treatmentitself,orfrompre-existingdifferencesintheactorsexposedtodifferent

treatments.Inthiscase,studiesdesignedtodeterminetheeffectsofpartisanmedia

onpolarizationareillequippedtodeterminewhethersomeoralloftheobserved

differencesinattitudesamongindividualsexposedtodifferentpartisaninformation

stemfromdifferencesintheinformationorintheindividualschoosingtoexpose

themselvestoparticularpartisaninformationstreams.

Inrecentyears,manyscholars(e.g.,Levendusky,2013;Arceneauxand

Johnson,2013;Prior,2007)haveexploredthepoliticalconsequencesofincreased

mediachoiceinthe21stcentury.Todate,theresultsfrominvestigationsintothe

questionofwhetherattitudesdriveinformationseeking,oraredrivenbyit,is

decidedlymixed.ThereisnoquestionthatAmericansareincreasinglyableto

consumeunbalancednews.ThetypicalU.S.householdnowreceivesabout190

televisionchannels,morethanatenfoldincreasesince1980andupnearly50%since

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2008.Thisdoesnotincludecountlessofferingsonradio,inprint,and,ofcourse,on

theInternet.Thatsaid,sincemostAmericanscontinuetopredominantlyrelyon

televisionfortheirnews(Pew2014),weprimarilyfocusourdiscussionontelevision.

Thisexplosionofmediaoutletshasvastlyincreasedthechoicesavailableto

consumersandallowedforthedevelopmentofideological“niche”news

programming(Hamilton,2005).Partisanmediaarewidelyaccessible(Baumand

Groeling2010,Groeling2013)andoftenpresentnewsthatismorebeneficialtoone

partythantheother(BaumandGroeling2008,2010).Forinstance,thepublic

routinelyassociatesFoxNewsandMSNBCasbeingheavilybiasedtowardthe

RepublicanandDemocraticparties,respectively(Ladd2012).Butdopartisan

mediacontributeto,orsimplyreflect,polarizationamongconsumers?Most

researchtodatehaslargelyfailedtoaddress,letaloneresolve,thisquestion.

Therearearguablythreedistinctstrandsofthisresearcharea.Thefirst

focusesonthepossibilitythatmediafragmentationenhancespoliticalpolarization

bytheprocessofpersuasiononthepartofthepartisanmedia.Thesecondtreats

polarizationasprimarily,oratleastsignificantly,asacauseoffragmentation

throughindividuals’decisionstoselectivelyexposethemselvestopartisanmedia.

Thethirdstrandcombineselementsofbothofthefirsttwo,focusingonpotential

effectsonperceptionsregardingthereliabilityandtrustworthinessofthemediain

general,andbeliefsaboutmediabiasinparticular.Indoingso,itconsidersresulting

downstreameffectsonpoliticalattitudesandbehavior.1Wediscusseachstrandof

1Researchonmediatrustmightarguablybemoreaccuratelycharacterizedaseitheramediatorofpersuasionandselection,orevenaneffectthereof.However,

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research,beforeturningtoadiscussionofthepromiseandlimitationsofexisting

researchonthesetopicsandproposingacorrectiveforonesuchlimitation.

SelectiveExposure

Researchdatingbacktothe1940shastheorizedaboutthepotentialroleof

selectiveexposureinexplainingpoliticalattitudes.Thisresearch,–perhapsmost

famouslyLazarsfeld,Berelson,andGaudet’s(1948)studyofthe1940presidential

electionandCampbelletal.’s(1960)theoryofminimalism--foundevidenceofsuch

selectiveexposuretopartisaninformationinmediaconsumptionpatterns.

Sincethe1960s,theliteraturehasgrownexponentially.Manyresearchers

(Stroud2011;Arceneauxetal.2012;GainesandKuklinski2011;IyengarandHahn

2009)haveshownthatDemocratsandRepublicans–especiallythestrongest(Kim

2009;Iyengaretal.2008),andmostpoliticallyengaged(BennettandIyengar2008)

partisans–prefertoconsumenewsthatsupportstheirpre-existingbeliefswhile

avoidingnewsthatchallengesthosebeliefs.Totheextentthatindividualsareself-

consciouslyselectingintoideologicallyfriendlymediaenvironments,itappearsthat

partisanorideologicalpreferencesdrivemediachoice.

Someadditionalresearch,however,hasidentifiedpotentiallimitstoself-

selection.Forinstance,MessingandWestwood(2012)findthatendorsementsfrom

otherpeopleinaperson’ssocialnetworkcancounteracttheselectivityofpartisans

intoideologicallyconsonantnews.GentzkowandShapiro(2010),inturn,findthat

ideologicallyextremepeopleareactuallymore,ratherthanless,likelythantheir

sincethisconcepthasbeenmuchmorewidelyappliedbyscholars,forpurposesofthisreviewwetreatitasananalyticallydistinctcategory.

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moremoderatecounterpartstoencounterideologicallyopposingnewssitesonthe

internet.Ofcourse,televisionandtheInternetdifferinnumerousrespects,

complicatingeffortstogeneralizeacrossthesemedia.

Despitethislatterevidencethatselectiveexposureislessthanubiquitous,a

greatdealofevidencesuggeststhatitisarealphenomenon;onewithpotential

consequencesforthepracticeofpoliticsbecauseitcanleadtoincreasinglyinsulated

partisaninformationsilosamongthepublic.Ifindividualsareonlyexposedtoone

sideoftheargument,compromiseandmoderationofviewsbecomeslessfrequentas

individualsarelesslikelytoencounterinformationchallengingtheirpre-existing

attitudes.Thispossibilityhaspromptednumerousscholarsandpoliticalobserversto

worryabout“mechannels”(Sunstein2001),“thedailyme”(Negroponte1995)–

bothalludingtoself-imposedideologicalstovepipescreatedbyindividuals--and

“filterbubbles”(Pariser2012),wherebynewsproviderscontributetothestovepipe

byobservingusers’newschoicesandthenfilteringtheirofferingstothatindividual

tomatchhisorherrevealedpreferences.Each of these closely related concepts focuses

on the potential dangers associated with individuals’ insulating themselves, or being

insulated by news providers, from opposing viewpoints in their media consumption.

Persuasion

Thesecondschoolofthoughtarguesthatpolarizationresultsfromthe

influenceofmediaexposureonpoliticalattitudes;thatis,throughtheprocessof

persuasion..Thisviewrepresentsafairlyrecentturnintheliterature.Asnoted

above,earlyresearchbysociologists(e.g.,Lazarsfeld,etal.1948,Berelson,

LazarsfeldandMcPhee1954))andsocialpsychologists(Campbelletal.1960)

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advancedtheselectiveexposurehypothesisandconcludedthatpeople’sattitudes

werelargelyimmunetopoliticalpersuasionviathemedia.Severaldecadeslater,the

tideofevidencebegantoturn.Revisionistscholarscounteredthatwhilemedia

exposuremaynotnecessarilychangepeople’sminds,themediacouldstillinfluence

expressedattitudesandbehaviorbychangingwhatpeoplethinkabout,orhowthey

thinkaboutit,throughpriming,framing,andagendasetting(e.g.,Iyengarand

Kinder1987,Druckman2001,ChongandDruckman2007).

Morerecently,evidenceforpersuasionhasbeguntoemerge.Forinstance,in

hisseminalstudyofpublicopinionZaller(1992)arguedthatthelackofevidencefor

persuasionresultedfromresearcherslookinginthewrongplaces.Zallerfoundthat

mediaexposurehaslimitedeffectontheattitudesoftheleast-andmost-politically

awareindividuals,albeitfordifferentreasons.Theleastpoliticallyaware

individualstendednottoreceivepoliticalmessagesfromthemedia,whilethemost

highlyawareindividualspossessedsufficientconsiderationsregardingmostissues

thattheywereabletosuccessfullycounter-argueanydissonantmessagestowhich

theywereexposed.Thisleftthemoderatelypoliticallyawaremostamenableto

persuasion:theypayenoughattentiontobeexposedtopoliticalmessagesbutlack

sufficient“ammunition”(intheformofconsiderationsaboutissues)tobeatback

informationtheyencounteredthatchallengedtheirpre-existingbeliefs.Notably,

however,anyresultingpolarizationeffectsfromtheprocessthatZaller’sRAS

(receive-accept-sample)modeldescribesdonotdependonthepartisanorientation

oftheoutletpresentingtheinformation.Partisansarecapableoffilteringoutpro-

andcounter-attitudinalinformationcontainedwithinagivennewsitemthatmay,in

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thenet,beideologicallybalanced.Zaller’smodelissimilarinmanyrespectstothe

theoryofmotivatedreasoning,wherebyindividualsare“motivated”toacceptpro-

attitudinal,orconsonantinformation,whilerejectingcounter-attitudinal,or

dissonantinformation.Theformerissimplyeasiertoprocess,requiringless

cognitiveeffort,thanthelatter.

BuildingonZaller’swork,otherscholarshavesearchedforevidenceof

persuasioneffectsfrompartisanmedia.Forinstance,Levendusky(2013)findsthat

newsattributedtoright-leaningFoxNewsismorelikelythannewsattributedto

left-leaningMSNBCtopersuadeconservatives(forcomparablefindings,seealso

e.g.,Feldman2011b,Bullock2011,JeritandBarabas2012).Thatsaid,some

evidencehasemergedsuggestingthatAmericansarenotyetentirelyensconcedin

impenetrableinformationsilos.Forinstance,Dilliplane(2013)reportsevidence

thatinformationfromcounter-attitudinalmediamaypersuadeevenstrong

partisansandthehighlypoliticallyaware.Alongtheselines,Feldman(2011a)finds

thatbothpro-andcounter-attitudinalvisualmediacaninfluencepolitical

ideologues.However,theevidenceonwhenpartisanmediaarepersuasiveismixed.

Additionalresearchappearstosuggestthatpartisanmediacanproduce

tangiblepersuasioneffects.Forinstance,withrespecttoclimatechange,countless

pundits,particularlyontheleft,haveblamedFoxNewsforthewidespreadbelief,

primarilythoughbynomeansexclusivelyamongRepublicans,thateitherclimate

changeisnotreal,orifitisrealthathumansarenotcontributingtoit(Meyer2012).

Hmielowksi,Feldman,Myers,andLeiserowitz(2013:13),inturn,concludeinpartthat

“themoreAmericansuseconservativemedia,thelesscertaintheyarethatglobal

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warmingishappening.”Theclearimplicationoftheirfindingsisthatpartisanmedia

havewidened,ifnotcreatedinthefirstinstance,thedivideonclimatechangebetween

DemocratsandRepublicans,primarilybydissuadingRepublicansofitsvalidity.

MediaTrustandPoliticalAttitudesandBehavior.

Thisthirdpredominantstrandofpolarizationresearchisarguablyan

extensionofthepriortwo,ratherthanaseparateenterprise.Thatsaid,because

scholarshaveinvestigatedthecausesandeffectsoftrustinnumerousdomains

beyondpersuasionandselectiveexposure,wetreatithereasaseparatecategory

(thoughwealsopointouthowtrustmediatesthepriortworesearchstrandswe

havediscussed).

So,inthepresentcontext,wefocusourattentiononscholarlyeffortsto

delineatetheeffectsofmediachoiceonpolarizationofattitudestowardsthemedia.

Asnotedabove,confidenceintraditional(TV,newspaper)andnew(Internet)media

outletsreachedall-timelowsin2014.Indeed,accordingtoGallup,between1976

and2014,thepercentageofAmericansexpressing“greatdeal”or“afairamount”of

trustinthemediaoverallfellfrom72to44percent.Aconsequenceofthisdistrust

wereonfulldislpayinthe2016Republicanprimarydebates–particularlythe

October28,2016CNBCdebate--wherecandidatesfromTedCruztoMarcoRubioto

BenCarsonandDonaldTrumpearnedamongtheirstrongestliveaudienceand

(fellowpartisan)voterapprobationwithaccusationsofmediabiasagainst

themselvesandtheirparty.Indeed,attacksonthemediaasbiasedandunreliable

emergedasamongthemostreliableapplauselinesamongRepublicanand

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Independentvotersinthe2016primarycampaign.

Thatsaid,objectivelyestablishingthepresenceorabsenceofpartisanbiasin

newscontenthasprovendifficult.Self-describedmediawatchdoggroupssuchas

theMediaResearchCenter(MRC),theCenterforMediaandPublicAffairs(CMPA),

andFairnessandAccuracyInReporting(FAIR)claimtoobjectivelyanalyzemedia

content,yettheyroutinelydisagreeontheincidence,severity,anddirectionofbias

inthemedia.Scholarlyattemptstoassessmediabiasaresimilarlyinconclusive(e.g.,

Efron,1971;Patterson,1993;Sutter,2001).Amongtheprincipaldifficultiesin

establishingthepresenceorabsenceofmediabiasisestablishingacleardefinition

ofwhatexactlyconstitutesbias.Severalrecentstudies(Groseclose2011,Groseclose

&Milyo,2005;Gentzkow&Shapiro,2006,Baum&Groeling2008,Hamilton2003)

havesoughttoempiricallymeasuremainstreamnewsmediacontentagainst

variousstandards,buthavecometoverydifferentconclusions.

Irrespectiveofthe“truth,”fromanormativeperspective,mediatrustis

criticalbecausepeoplewhodistrustthemediamayconcludeitcannotreportinan

unbiasedmannerandsodismissitscontentasunreliablealtogether.Moreover,

ordinarycitizensmayalsobegintoseebiasinwhatisactuallyobjectiveand

balancedpoliticalreporting.Numerousstudieshavefoundevidenceofthisso-called

hostilemediaphenomenon(Valloneetal.1985,Giner-SorollaandChaiken1994,

Peffleyetal.2001,GuntherandSchmitt2004,MorehouseMendez2004,Baumand

Gussin2008),wherebytypicalindividualstendtoviewthemediaasbiasedagainst

theirownviews.Asaresult,citizensmayincreasinglybecomesuspiciousofand

antagonistictowardthenewsmediamoregenerally(Arceneauxetal.,2012;Ladd,

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2012).Ladd(2012),infact,findsempiricalevidencethatrisingpublicdistrustinthe

mediahasreducedpublicwillingnesstoacceptinformationfromthemediaas

reliable.Instead,partisanpredispositionsincreasinglydrivepublicbeliefsand

votingbehavior.

Thatsaid,agrowingbodyofresearchshowsthatpeoplereactdifferentlyto

identicalcontentdependingonwhetherornottheyconsiderthesourcetrustworthy

andcredible(BaumandGussin,2008;Druckman,Fein,andLeeper,2012;

Levendusky2013,BaumandGroeling2010).Inparticular,partisanreputation

interactswithperceptionsofcredibilitytomediatethepersuasivenessof

informationappearingonpartisanoutlets.Alongtheselines,BaumandGroeling

(2009)conductedanexperimentinwhichtheyexposedparticipantstoanews

reportaboutacongressionalhearingonnationalsecurityinwhichoneortheother

partypraisedorcriticizedtheBushAdministration’spolicies.Theymodifiedthe

reporttoappearalternatelyasappearingonCNNorFoxNews.Theyfoundthat

participantswhosawcriticismoftheRepublicanpresident’spoliciesonFox,

downgradedtheirassessmentsofthepresident’sperformanceonnationalsecurity.

ThesamewasnottrueofthosewhosawtheidenticalcriticismonCNN,The

oppositepatternemergedforpraiseofthepresident’spolicies.Theauthorsargue

thatthispatternisaresultofcalculationsamongthepublic.Foraconservative

outlet(Fox)tocriticizeaRepublicanpresidentiscostlyrhetoric(thatis,contraryto

Fox’sperceivedinterests),whileforthemoreliberalCNNsuchcriticismisperceived

ascheaptalk.Conversely,respondentsperceivedpraiseofaRepublicanonCNNas

costly,whilethesamepraisetheyviewedthesamepraiseappearingonFoxas

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cheaptalk.Thisimpliesthatexposuretopartisanmediacaninfluenceattitudes,

albeitdependingonwhetherviewersperceivethecoverageinquestionascostlyor

cheaptalk.

Additionalresearchshowsthatwhenindividualsencountercounter-

attitudinalinformation,itcanproduceabacklash,resultinginevenmorepolarized

opinions(Zaller1992)andgreaterhostilitytowardthemedia(Arceneaux,Johnson,

andMurphy2012).Theselectionofindividualsintoconsumingmediathat

reinforcestheiropinionscouldthusdrivegroupsfurtherapartbothintheir

attitudestowardissuesandpeoplewhodisagreewiththem.Indeed,some

additionalevidencesuggeststhatstrongideologueswhoselectintopartisannews

sourcesbecomemoreideologicallyextreme(Bullock2011,Feldman2011,Jerritand

Barabas,2012),implyingthatexposuretopartisaninformationstreamscan,via

persuasion,increasepolarization,evenamongalready-somewhat-polarized

partisans.Theselatterfindings,alongwiththoseofBaumandGroeling(2010)and

researchonthehostilemediaphenomenon,combinetosuggestanindirectpathway

topolarization.Thatis,thesefindingsraisethepossibilitythatbothselective

exposureandpersuasionmaycontributetopolarizationdirectly,throughtheir

independenteffectsonmediaconsumers,andalsoindirectly,throughtheeffectof

initialtrustandperceivedbiasontheselectionandacceptanceofmediacontent.

Conroy-KrutzandMoehler(2014),inturn,showthatpeoplewillbemore

easilypersuadedbyopposingmediawhenpoliticalcleavagesarelessclearinless

polarizedmediaenvironments(thatis,non-overtly-partisannewsoutlets).

Furthermore,individualswhoarewillingtowatchcounter-attitudinalmediaare

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alsolikelytobepersuadedbyit(Levendusky2013).Thereasonmaybethat

relativelyopen-mindedindividualsaremorelikelytobeinclinedtoexpose

themselvestocounter-attitudinalmedia.Ifso,thispatternwouldbedrivenmoreby

selectionthanpersuasion.Ingeneral,whenindividualsperceiveoppositionalmedia

ascredible,theymayalsofinditpersuasiveregardlessofitsperspective

(Levendusky2013b,BaumandGroeling2008).Thisresearchsuggeststhatevenin

aneraofmediaconsumptionincreasinglycharacterizedbypartisanself-selection,

andevenamongstrongpartisans,theremaystillexistthepotentialformoderation

ofextremeideologicalviews.

LimitationsandPromiseofExistingResearch

Todate,whenattemptingtoisolatethecausalstoryunderlyingthese

hypothesizedeffectsofmediafragmentation,scholarshavestruggledtoresolvethe

underlyingselectionproblem.Inotherwords,wheneversocialscientistsobservea

differenceintherealworldbetweenindividualsexposedtodifferenttreatments,

thequestionarisesastowhethertheeffectresultsfromthetreatment,orfrompre-

existingdifferencesintheindividualsexposedtodifferenttreatments.Inthiscase,

evencontrolledexperimentsdesignedtodeterminetheeffectsofpartisanmediaon

polarizationareillequippedtodeterminewhethersomeoralloftherealworld

observeddifferencesinattitudesamongindividualsexposedtodifferent

informationstemfromdifferencesintheinformationorintheindividualschoosing

toexposethemselvestoparticularinformationstreams.Mappingfromthe

laboratorytotherealworldintroducessomedifficultinferentialproblems.

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Typicalexperimentsbeginbyassessingparticipants’politicalpartisanship

andideology.Researchersthenpresentparticipantswithoneoftwosetsof

treatments:(a)multiplenewsitemsfromwhichtochoose,or(b)asinglerandomly

assignednewsitem,withparticipantssubsequentlyaskedtheiropinionsononeor

moreissuesoverwhichpartisansusuallydisagree.Theformerdesignallows

investigatorstodeterminetheextenttowhichparticipantschooseinformation

sourcescompatiblewiththeirpreexistingbeliefs,aswellastomeasuredifferences

inattitudesbetweenparticipantsexposedtodifferentinformationsources.The

latterdesignallowsforinvestigationofpersuasioneffectsforthesinglesource,but

doesnotaccountfortheself-selectionthattakesplaceintherealworld.

Forinstance,Feldman(2011a)exposedparticipantstooneofthreenews

clipsrelatedtohealthcarereformfromleft-leaning(CountdownwithKeith

Olbermann),right-leaning(GlennBeck),andcentrist(NewsHourwithJimLehrer)

outlets.Shethenassessedattitudechangeamongparticipants,dependingontheir

partisanorientation.Thisstudyiswellsuitedtomeasuretheattitudinaleffectsof

exposuretoaparticularinformationstream.Yetbecauseitcannotaccountforthe

heterogeneityintroducedbyself-selectionintomediasources,itdoesnotaddress

thepossibilitythattheobservedtreatmenteffectsmaybeover-statedbyvirtueof

forcingparticipantstowatchaparticularnewsitem,irrespectiveoftheir

preferences.Numerousstudies(e.g.,Levendusky2013;Taniguchi2011;Feldman

2011b;JeritandBarabas2012;BaumandGroeling2009;SlothuusanddeVreese

2010haveemployedsimilardesignstoinvestigatevariationsonasimilartheme:

thesestudiesalltakeupthequestionofhowmucheffectdoesexposureto

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informationhaveonindividuals’attitudes,conditioningontheirpartisanship,

ideology,orpoliticalawareness.

Studiesthataccountforself-selectionthroughtheseconddesignarerelatively

rare.OnerecentexampleisEllithorpeetal.(2013),whostudytheeffectsofdifferent

mediaenvironmentsonnewsconsumptionandattitudes,findingthatthechoice

environmentplaysanimportantroleinmediatingtheeffectsofmediaconsumption

onpoliticalattitudes.NatalieStroud(Stroud,2011),inturn,invitedexperimental

subjectstoparticipateinalaboratorystudy.Inthewaitingroom,whilethey

nominallywaitedtobeginthestudy,shepresentedthemwithavarietyofnewsand

entertainmentmagazinesthatweresimplyplacedonatablenearwheretheywere

sitting.Sheobservedtheirmagazinechoicesandtheamountoftimetheyspentwith

eachmagazinetoestimatetheamountofselectiveexposurebehavior.

KevinArceneauxandhiscolleagues(ArceneauxandJohnson,2013;

Arceneauxetal.,2012)offeravariationonthisthemethatrepresentsanimportant,

yetincomplete,stepforward.Inbothstudies,Arceneauxandhiscolleaguesconduct

aseriesofexperimentsaimedinpartataddressingtheselectionproblemin

polarizationandpersuasionresearch.Inonesetofstudies,themethodology

approximatestheforcedexposuredesignthatexperimentersstudyingmotivated

reasoningandpersuasiontypicallyutilize.Asdescribedabove,theexperimenters

presentaliberal,conservative,orentertainmentnewsstorytoarespondent,and

thenobservetheeffectsofthattreatmentonsubsequentattitudes(seeStudy1in

Figure1,below).Arceneauxandhiscolleaguesgoonestepfurther,however,by

conductingparallelexperimentsinwhichtheyallowedparticipantstochoosefrom

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amenuofoptions–asistypicalforexperimentsinvestigatingselectiveexposure--

includingbothpartisannewsfromtheleftandrightandseveralentertainment

programs(seeStudy2inFigure1,below).

Bycomparingtheobservedattitudinaleffectsacrossstudies,Arceneauxand

hiscolleaguessoughttoestimatetheextenttowhichobservedtreatmenteffects

resultedfromeitherselectiveexposure(attitudesdrivingexposure)orpersuasion

(exposuredrivingattitudes).Theirprimaryconclusionisthatpartisanattitudes

drivemediaexposuremuchmorethanexposuredrivesattitudes.

TheWayForward

SortingOutCauseandEffect

WhileArceneauxandhiscolleagueshavetakenasignificantstepforward,

theirapproachcannotfullyresolvethedirectionofcausalityproblem,asitdoesnot

allowrandomassignmentacrosschoiceselectionconditions.Nordoesitcorrectfor

theeffectsofbiasedestimatesofsubjects’truemediapreferencesandresulting

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over-orunder-estimatesofthetruelikelihoodofexposure.Consequently,wehave

nowayofknowingwhetherrespondentswhowatched,say,FoxNewsbecausethey

choseitwerecomparabletotheircounterpartswhowereassignedtowatchFox

News.

Morerecently,we(Benedictis-Kessner,Baum,Berinsky,andYamamoto

2016)attempttoaddressthisdilemmabyintegratingbothchoiceconditionsintoa

singledesign.Inthisstudy,followingapre-test,participantsarerandomlyassigned

toeitheraforcedchoiceorfreechoicetreatmentcondition,wherethetwo

conditionsapproximatetheaforementionedfirstandseconddesigns,respectively,

employedbyArceneauxandhiscolleagues.Participantsinbothconditionswatched

anewsreportongas/oilpricesfromFox(BillO’Reilly)orMSNBC(RachelMaddow),

oranentertainmentsegment(fromJaimeOliver:Jaime’sKitchenorDirtyJobs).This

design–illustratedinFigure2--makesitpossible,toagreaterextentthaninprior

research,todisentangleselectionandpersuasion.

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Ultimately,wefindclearevidenceofbothselectiveexposureandpersuasion

amongrespondentsexposedtobothtreatments.Whilemostrespondents,giventhe

opportunity,dosortintoviewingnewsfromtheirsideoftheideologicalspectrum,

themajorityofpeople–bothpartisansandindependents–expressapreferencefor

entertainmentratherthanpartisannewsshows.Thismajorityalsoappeartobe

persuadable,aswatchingpartisannewsproducedsubstantivechangesintheir

opinions.

ReliabilityofPreferenceClaims

Inthesamestudy(Benedictis-Kessneretal.2016),wealsodevelopan

uncertaintycorrectionproceduretoestimatetheeffectsofrespondentsmisstating

theirtruemediapreferences.Thisallowstheresearcherstoestimatethesampling

errorintheirdata.Theproblemisthat,forwhateverreason,somerespondents’

truepreferencesmaydifferfromtheirstatedpreference.Throughanovel

applicationofapatientpreferencetrial(PPT),describedindetailinaseparate

paper(Knox,Yamamoto,Baum,andBerinsky2015),thisprocedure,illustratedin

Figure3,estimatesminimumandmaximumerrormarginsinrespondents’stated

preferences.2

2ThePPTapproachhasbeenutilizedinpriorsocial(e.g.,GainesandKuklinski,

2011;Arceneaux,JohnsonandMurphy,2012)andmedical(Kingetal.,2005;

HowardandThornicroft,2006)scienceresearch.

20

FIGURE3.DiagramofPPTDesign

Note:blueboxesrepresentrandomassignment;dashedboxindicatesoptionalcomponent.

Themethodologyconsistsoftwoparts.Participantsfirststatetheir

preferences–inthisinstanceovermediaoutlets--inapre-treatmentsurvey(Si).

Followinganoptional“washout”period,theexperimentthenconsistsof

randomizingthemintooneoftwodesignconditions(Di):eitherastandardRCT

design(Di=0)orintoaself-selectioncondition(Di=1),inwhichtheycanchoose

fromamenuofmediaoutlets.Theirstatedpreferencesdonotinfluencetheir

assignedcondition.Theexperimentersthenassesstheoutcomemeasure(Yi).

Thenoveltyofthedesignisthatitallowstheexperimenterstomeasurethe

extenttowhichexantestatedpreferencespredictexpostactualtreatment(media

outlet)choices.Inparticular,weimplementasensitivityanalysistoestimatethe

assumedinformativenessofsubjects’statedpreferencesrelativetotheirrevealed

preferences.Wethenusethisanalysistoassesstheeffectsonthequantityof

interest(inthiscaseattitudesregardingseveralpoliticalissues)asthisparameter

varies.Theendresultisanimprovedestimateoftherelationshipbetweenmedia

consumption(thetreatment)andpoliticalattitudes(theoutcomevariables).Figure

21

4presentsanillustrativeexampleoffindingsfromapilotstudyimplementedvia

AmazonMechanicalTurkandbasedontheaforementioneddesignfromBenedictis-

Kessneretal.(2016)employingthisprocedure.

Figure4comparestheresultsfrompointestimates,assumingnosampling

error(thickbars),withthosefromconfidenceintervalboundsthattakesampling

errorintoaccountviabootstrapping,andemployingtheaforementionedcorrection

procedure(thinbars).Theoutcomevariableinthisinstanceisthepropensityof

participantstoindicatethattheywouldsharethestorysegmenttheywatched(via

emailorsocialmedia).Thisresultcomparesthedifferenceinpropensitytosharea

pro-attitudinalnewsstory(e.g.,aRepublicanwatchingFoxoraDemocratwatching

MSNBC)withthepropensitytoshareanentertainmentstory,amongparticipants

whoexpressedapreferenceforpro-attitudinalnews,counter-attitudinalnewsor

entertainment.Theseresultsshowastrongpositiveincreaseinthepropensityto

sharethestoryamongindividualswhopreferredapro-attitudinalvideoandwere

22

assignedthepro-attitudinalvideo,regardlessofassumptionregardingconfidence

intervals.However,amongindividualswhopreferredacounter-attitudinalvideo

butwereassignedapro-attitudinalvideo,thepointestimatesurprisinglysuggestsa

(marginally)significantlygreaterpropensitytosharethenewsstoryrelativeto

respondentswhopreferredanentertainmentvideo.Thisrelationshipdisappears

withtheerrorcorrectionprocedure.Inshort,oncethepropensityofrespondentsto

incorrectlypredicttheirownbehavioristakenintoaccount,thisseeminglycounter-

intuitivepatterndoesnotemerge.

Conclusion

Scholarsfromnumerousacademicdisciplines,rangingfromsociologyto

psychologytoeconomicstopoliticalsciencetocommunications,havedevoted

considerableattentionthroughoutthepost-WorldWarIIeratounderstandinghow

consuminginformationviathemediainfluencespublicopinion.Theexplosionof

consumerchoiceoverthepastseveraldecadesandwithittheresurgenceofan

Americanpartisanpress,emergingintandemwithaparallelriseinpartisan

polarizationandpoliticalgridlockinWashingtonD.C.,hasrenewedscholarly

interesttothisresearchagenda.Todate,scholarshavemadeconsiderableprogress

inunderstandingtheroleofpartisanmedia,inparticular,inshapingpolitical

attitudesanddiscourse.Gettingthisstoryrightseemsparticularlyimportantinthe

currentera,wherebuildingcoalitionsacrosspartisanandideologicallinesseems

evermoreelusiveandcitizensincreasinglyquestionthecapacityofourleadersto

overcomepartisanpolarizationinorderaddressthemanyimportantissues

23

confrontingthenation.Togoverneffectively,policymakersneedscholarshipthat

willhelpthemdeterminewhenandhowtheymightbridgethesedivides.Accurately

assessingthemediaconsumptionchoicesofcitizensandanyresultingattitudinal

effectsrepresentsonestepindiscerningapotentialresponsetothisquandary

facingtoday’spoliticiansandpolicymakers.

However,beforesuchastepcanbesuccessfullytaken,thisresearch

continuestoconfrontimportanthurdles,suchasaddressingtheproblemof

selectionanditsimplicationsforthedirectionofcausality.Inthisreviewwethus

tracedrecenttrendsinscholarlyresearchandproposedseveralpotential

methodologicalimprovementsaimedatachievingbetterestimatesofthecausesand

effectsofmediachoiceinthecontemporaryera.Thenextstepistoimplementthese

methodsforavarietyofoutcomevariablesandonmorerepresentativepopulation

samples.

24

References

Arceneaux,K.andJohnson,M.(2013).ChangingMindsorChangingChannels?

PartisanNewsinanAgeofChoice.UniversityofChicagoPress,Chicago.

Arceneaux,K.,Johnson,M.,andMurphy,C.(2012).Polarizedpolitical

communication,oppositionalmediahostility,andselectiveexposure.Journalof

Politics,74(1),174–186.

Baum,M.andGroelingT.J.(2008).NewMediaandthePolarizationofAmerican

PoliticalDiscourse.PoliticalCommunication25:4:345-65.

Baum,M.andGroeling,T.J.(2010)WarStories:TheCausesandConsequencesof

PublicViewsofWar.Princeton:PrincetonUniversityPress.

Baum,M.andGroeling,T.J.(2009).Shotbythemessenger:partisancuesandpublic

opinionregardingnationalsecurityandwar.PoliticalBehavior,31,157–186.

Baum,M.andGussin,P.2008.“IntheEyeoftheBeholder:HowInformation

ShortcutsShapeIndividualPerceptionsofBiasintheMedia.”QuarterlyJournal

ofPoliticalScience3:1:1-31

Benedictis-Kessner,Justin,MatthewA.Baum,AdamBerinsky,andTeppeiYamamoto.2016.

DisentanglingSelectiveExposureandMediaPersuasion.WorkingPaper.

Berelson,BernardR.,andF.Paul."Lazarsfeld,andWilliamN.McPhee.1954."Voting:

Astudyofopinionformationinapresidentialcampaign(1963).

Bullock,J.(2011).Eliteinfluenceonpublicopinioninaninformedelectorate.

AmericanPoliticalScienceReview,10(3),496–515.

Campbell,Angus,PhilipEConverse,WarrenMillerandDonaldStokes.1960.The

AmericanVoter.Chicago:UniversityofChicagoPress.

25

Carville,James.2013.“Opinion:Disturbingpolarizationinmediaworsenspolitical

partisanship.”TheHill(10/15/13).Availableat:

http://thehill.com/opinion/columnists/james-carville/328731-polarization-in-

media-worsens-partisanship(accessedon10/15/15).

Chong,D.andDruckman,J.N.(2010).Dynamicpublicopinion:Communication

effectsovertime.AmericanPoliticalScienceReview,104(04),663–680.

Chong,Dennis,andJamesN.Druckman."Framingtheory."Annu.Rev.Polit.Sci.10

(2007):103-126.Clausen,AageR.1968.“ResponseValidity:VoteReport.”Public

OpinionQuarterly32(4):588–606.

Conroy-Krutz,Jeffrey,andDevraMoehler.EthnicCuesandBallotDesign.Working

Paper,UniversityofPennsylvania.(January3,2014),2014.

Druckman,JamesN."Onthelimitsofframingeffects:whocanframe?."Journalof

Politics63.4(2001):1041-1066.

Druckman,JamesN.,JordanFein,andThomasJ.Leeper."Asourceofbiasinpublic

opinionstability."AmericanPoliticalScienceReview106.02(2012):430-454.

Ellithorpe,M.E.,Holbert,R.L.,andPalmer-Wackerly,A.L.(2013).Procrastination

andtheshiftingpoliticalmediaenvironment:Anexperimentalstudyofmedia

choiceaffectingademocraticoutcome.CommunicationStudies,64(5),561–578.

Feldman,L.(2011a).Theopinionfactor:Theeffectsofopinionatednewson

informationprocessingandattitudechange.PoliticalCommunication,28(2).

Feldman,L.(2011b).Partisandifferencesinopinionatednewsperceptions:Atestof

thehostilemediaeffect.PoliticalBehavior,33(3),407–432.

Gaines,B.J.andKuklinski,J.H.(2011).Experimentalestimationofheterogeneous

26

treatmenteffectsrelatedtoself-selection.AmericanJournalofPoliticalScience,

55(3),724–736.

Gallup(2014).Americansconfidenceinnewsremainslow.

http://www.gallup.com/poll/171740/americansconfidence-news-media-

remains-low.aspx.

Gentzkow,Matthew,andJesseM.Shapiro.Ideologicalsegregationonlineandoffline.

No.w15916.NationalBureauofEconomicResearch,2010.

Gentzkow,Matthew,andJesseM.Shapiro.Whatdrivesmediaslant?Evidencefrom

USdailynewspapers.No.w12707.NationalBureauofEconomicResearch,2006.

Giner-Sorolla,Roger,andShellyChaiken."Thecausesofhostilemediajudgments."

JournalofExperimentalSocialPsychology30.2(1994):165-180.

Groeling,Tim."Mediabiasbythenumbers:Challengesandopportunitiesinthe

empiricalstudyofpartisannews."PoliticalScience16.1(2013):129.

Groseclose,Tim.Leftturn:HowliberalmediabiasdistortstheAmericanmind.Macmillan,2011.

Groseclose,Tim,andJeffreyMilyo."Ameasureofmediabias."TheQuarterlyJournal

ofEconomics(2005):1191-1237.

Gunther,AlbertC.,andKathleenSchmitt."Mappingboundariesofthehostilemedia

effect."JournalofCommunication54.1(2004):55-70.

Hamilton,JamesT.2003.AlltheNewsThat’sFittoSell.Princeton:Princeton

UniversityPress.

Hamilton,J.T.(2005).Themarketandthemedia.InG.OverholserandK.H.

Jamieson,editors,ThePress.OxfordUniversityPress,Oxford.

Hmielowski,J.D.,Feldman,L.,Myers,T.A.,Leiserowitz,A.,andMaibach,E.(2014).

27

Anattackonåscience?mediause,trustinscientists,andperceptionsofglobal

warming.PublicUnderstandingofScience,23(7),866–883.

Howard,LouiseandGrahamThornicroft.2006.“Patientpreferencerandomised

controlledtrialsinmentalhealthresearch.”TheBritishJournalofPsychiatry

188(4):303–304.

Iyengar,S.andHahn,K.S.(2009).Redmedia,bluemedia:evidenceofideological

selectivityinmediause.JournalofCommunication,59,19–39.

Iyengar,S.,Hahn,K.S.,Krosnick,J.A.,andWalker,J.(2008).Selectiveexposureto

campaigncommunication:Theroleofanticipatedagreementandissuepublic

membership.TheJournalofPolitics,70,186–200.

Iyengar,Shanto,andDonaldR.Kinder."Newsthatmatters:agendasettingand

priminginatelevisionage."NewsthatMatters:Agenda-SettingandPrimingina

TelevisionAge(1987).

Jacobson,G.C.(2014).Partisanmediaandelectoralpolarizationin2012:Evidence

fromtheamericannationalelectionstudy.ConferenceonAmericanGridlock.

Jerit,J.andBarabas,J.(2012).Partisanperceptualbiasandtheinformation

environment.TheJournalofPolitics,74(3),672–684.

Kim,Y.M.(2009).Issuepublicsinthenewinformationenvironment:Selectivity,

domainspecificity,andextremity.CommunicationResearch,36,254–284.

Knox,Dean,TeppeiYamamoto,MatthewA.Baum,andAdamBerinsky.2015.Design,

Identification,andSensitivityAnalysisforPatientPreferenceTrials.Paper

originallypreparedforthe2014SocietyforPoliticalMethodologySummer

MeetingandMacMillan-CSAPWorkshopatYaleUniversity(updatedNov2015).

28

King,M.,Nazareth,I.,Lampe,F.,Bower,P.,Chandler,M.,Morou,M.,Sibbald,B.,and

Lai,R.(2005).Impactofparticipantandphysicianinterventionpreferenceson

randomizedtrials:asystematicreview.JourmaloftheAmericanMedical

Association,293(9),1089–1099.

Ladd,J.M.(2012).WhyAmericansHatetheMediaandHowItMatters.Princeton

UniversityPress,Princeton.

Lazarsfeld,PaulFelix,BernardBerelson,andHazelGaudet."Thepeopleschoice:

howthevotermakesuphismindinapresidentialcampaign."(1968).

Levendusky,M.S.(2013).Whydopartisanmediapolarizeviewers?American

JournalofPoliticalScience,57(3),611–623.

Messing,Solomon,andSeanJ.Westwood."Selectiveexposureintheageofsocial

media:Endorsementstrumppartisansourceaffiliationwhenselectingnews

online."CommunicationResearch(2012):0093650212466406.

Meyer,Frederick.2012.StoriesofClimateChange:CompetingNarratives,theMedia,

andU.S.PublicOpinion2001-2010.ShorensteinCenterontheMedia,Press,and

PublicPolicy,DiscussionPaper#D-72(February).

MorehouseMendez,Jeanette."Killingthemessenger:Anexperimentalanalysisof

thehostilemediaeffect."meetingoftheSouthernPoliticalScienceAssociation,

NewOrleans,LA.2004.

Negroponte,Nicholas."BeingDigital-ABook(p)review."Wired.com3(1995).

Pariser,Eli.FilterBubble:WiewirimInternetentmündigtwerden.Hanser,2012.

Peffley,Mark,JasonGlass,andJamesAvery."Publicperceptionsofbiasinthenews

media:Takingacloserlookatthehostilemediaphenomenon."Meetingofthe

29

MidwestPoliticalScienceAssociation,Chicago,IL.2001.

PewResearchCenter.2014.StateoftheNewsMedia2014.Availableat:

http://www.journalism.org/packages/state-of-the-news-media-2014/(Accessed

12/21/15).

Prior,M.(2007).Post-BroadcastDemocracy:HowMediaChoiceIncreasesInequality

inPoliticalInvolvementandPolarizesElections.CambridgeUniversityPress,

Cambridge.

Prior,Markus.2009.“TheImmenselyInflatedNewsAudience:AssessingBiasin

Self-ReportedNewsExposure.”PublicOpinionQuarterly73:1–14.Rosenbaum,P.

R.(2002).ObservationalStudies.Springer-Verlag,NewYork,2ndedition.

Slothuus,R.anddeVreese,C.(2010).Politicalparties,motivatedreasoning,and

issueframingeffects.TheJournalofPolitics,72(3),630–645.

Stroud,N.J.(2011).ThePoliticsofNewsChoice.OxfordUniversityPress,Oxford.

Sunstein,Cass.2001.Republic.com.Princeton:PrincetonUniversityPress.

Taniguchi,M.(2011).Theelectoralconsequencesofcandidateappearancesonsoft

newsprograms.PoliticalCommunication,28(1).

Vallone,RobertP.,LeeRoss,andMarkR.Lepper."Thehostilemediaphenomenon:

biasedperceptionandperceptionsofmediabiasincoverageoftheBeirut

massacre."Journalofpersonalityandsocialpsychology49.3(1985):577.Weprin,

A.(2013).Billclintonturnsmediacriticoncnn.Online,TheBlaze.com.

Yamamoto,T.(2012).Understandingthepast:Statisticalanalysisofcausal

attribution.AmericanJournalofPoliticalScience,56(1),237–256.

Zaller,John.1992.TheNatureandOriginsofMassOpinion.Cambridge:CambridgeUniv.Press.