Exploring the Interactions of Disgust and Fear with Sexual Arousal in Women

23 Pages·2015·1.07 MB·English

RESEARCHARTICLE
Disgust versus Lust: Exploring the
Interactions of Disgust and Fear with Sexual
Arousal in Women
DianaS.Fleischman1*,LisaDawnHamilton2,DanielM.T.Fessler3,CindyM.Meston4
1 DepartmentofPsychology,UniversityofPortsmouth,Portsmouth,Hampshire,UnitedKingdom,
2 DepartmentofPsychology,Mt.AllisonUniversity,Sackville,NewBrunswick,Canada,3 Departmentof
AnthropologyandCenterforBehavior,Evolution,andCulture,UniversityofCaliforniaLosAngeles,Los
Angeles,California,UnitedStatesofAmerica,4 DepartmentofPsychology,TheUniversityofTexasat
Austin,Austin,Texas,UnitedStatesofAmerica
* [email protected]
a11111
Abstract
Sexualarousalisamotivationalstatethatmoveshumanstowardsituationsthatinherently
poseariskofdiseasetransmission.Disgustisanemotionthatadaptivelymoveshumans
awayfromsuchsituations.Incongruentisthefactthatsexualactivityiselementaryto
humanfitnessyetinvolvesstrongdisgustelicitors.Usinganexperimentalparadigm,wein-
OPENACCESS vestigatedhowthesetwostatesinteract.Women(finalN=76)wereassignedtooneoffour
Citation:FleischmanDS,HamiltonLD,FesslerDMT, conditions:ratedisguststimulithenwatchapornographicclip;watchapornographicclip
MestonCM(2015)DisgustversusLust:Exploringthe thenratedisguststimuli;ratefearstimulithenwatchapornographicclip;orwatchaporno-
InteractionsofDisgustandFearwithSexualArousal graphicclipthenratefearstimuli.Women’sgenitalsexualarousalwasmeasuredwithvagi-
inWomen.PLoSONE10(6):e0118151.doi:10.1371/
nalphotoplethysmographyandtheirdisgustandfearreactionsweremeasuredviaself-
journal.pone.0118151
report.Wedidnotfindthatbaselinedisgustpropensitypredictedsexualarousalinwomen
AcademicEditor:MariannaMazza,Catholic
whowereexposedtoneutralstimulibeforeeroticcontent.IntheErotic-before-Disgustcon-
UniversityofSacredHeartofRome,ITALY
ditionwedidnotfindthatsexualarousalstraightforwardlypredicteddecreasedimagedis-
Received:February13,2013
gustratings.However,wedidfindsomeevidencethatsexualarousalincreasedself-
Accepted:January5,2015
reporteddisgustinwomenwithhightraitdisgustandsexualarousaldecreasedself-re-
Published:June24,2015 porteddisgustinwomenwithlowtraitdisgust.Womenwhowereexposedtodisgustingim-
Copyright:©2015Fleischmanetal.Thisisanopen agesbeforeeroticcontentshowedsignificantlylesssexualarousalthanwomeninthe
accessarticledistributedunderthetermsofthe controlconditionorwomenexposedtofear-inducingimagesbeforeeroticcontent.Inthe
CreativeCommonsAttributionLicense,whichpermits
Disgust-before-Eroticconditionthedegreeofself-reporteddisgustwasnegativelycorrelat-
unrestricteduse,distribution,andreproductioninany
edwithgenitalsexualarousal.Hence,intheconflictbetweentheultimategoalsofreproduc-
medium,providedtheoriginalauthorandsourceare
credited. tionanddiseaseavoidance,cuesofthepresenceofpathogenssignificantlyreducethe
motivationtoengageinmatingbehaviorsthat,bytheirnature,entailariskofpathogen
Funding:Reimbursementforparticipantswas
fundedbytheAmericanAssociationofUniversity transmission.
Womendissertationfellowship.Therewasnoother
externalfundingforthisstudy.Thefundershadno
roleinstudydesign,datacollectionandanalysis,
decisiontopublish,orpreparationofthemanuscript.
CompetingInterests:Theauthorshavedeclared
thatnocompetinginterestsexist.
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 1/22
DisgustversusLust
Introduction
Consonantwiththeadaptivesignificanceofavoidingdisease,humansgenerallyshunsitua-
tionsthatpresentcuesofpotentialdiseasetransmission.However,insomecontextssuch
avoidanceisincompatiblewithachievingotheradaptivegoals.Sexualbehaviorisprototypical
inthisregard,asmatingsuccessisanelementarydeterminantoffitness,yetsexinherentlyin-
volvesextensiveexposuretostimulithatindexdiseaserisk.Giventhatemotionsandrelated
motivationalstatescanbeunderstoodasevolvedmechanisms,eachofwhichservesaspecific
adaptivegoal[1,2]itisthereforepossiblethatdisgustandsexualarousalmayconstitutemoti-
vationalenginesthatworkagainst[3–8]oneanother.
Thereisgeneralagreementthatacoreadaptivefunctionofdisgustistoreducetherisk
ofcontractingdiseasebydistancingtheactorfromcuesofthepresenceofpathogens.Body
odorsandsecretionsnormallyencounteredinsexualcontextsaresomeofthestrongest
disgustelicitors[9].Moreover,sexualbehaviorentailsnotonlyincreasedcontactwithcues
ofdisease,butalsoincreasedvulnerabilitytodisease.Inadditiontothedirectexchangeof
bodilyfluids,theexposureofdelicatemucousmembranes—alongwithpossibleattendant
abrasion—presentsareadyentryopportunityformicroorganisms,whileincreasedrespira-
tioninconjunctionwithcloseproximityenhancestheriskposedbyairbornepathogens.
Byvirtueofthefactthatdisgustmotivatesavoidance,thereisthusaninherentconflictbe-
tweenintrinsicfeaturesofsexualbehaviorandcore,orpathogen-avoidance,disgust[10].
Inthisstudyweinvestigatehowsexualarousalanddisgustinfluenceoneanotherin
women,employingbothself-reportinstrumentsandaphysiologicalmeasureofsexual
arousal.
Pathogenavoidanceorcoredisgusthasbeenfoundbydisgustmeasurestobedistinctfrom
whathasbeencalledthesexualdomainofdisgust[11].Thesexualdomainofdisgustcanbe
understoodasanadaptationservingtheultimatefunctionofreducingsuboptimalmatingbe-
havior[8].Thoughdistinct,sexualdisgust(e.g.thedisgustexperiencedwhenconsideringin-
cest),[8,12]oftenoverlapswithpathogendisgust(e.g.whencuesofinfectionreveallow
geneticquality)[10].However,inthisstudyweexaminetheconflictbetweenpathogen-avoid-
ancedisgustandsexualarousal,ratherthanexaminingtheconflictbetweenuniquelysexual
disgustandsexualarousal.
FunctionalityinWomen’sHeightenedDisgustPropensity
Disgustpropensityisdefinedas“ageneraltendencytorespondwiththeemotionofdisgustto
anygivensituation”[13].Oneofthemostconsistentfindingsinthedisgustliteratureisthat
womentendtohaveaheighteneddisgustpropensityrelativetomen,especiallyinthesexual
domain[3,14–17].Womenalsoaremorelikelytoimplicitlyassociatesexualimageswithdis-
gustthanmen[16].Whileanumberoffactorslikelycontributetothissexdifference,itmay
havenotableadaptivesignificanceinregardtothediseaserisksposedbysexualbehavior.
Womenhaveagreaterareaofmucousmembranesandexperiencemoretissuetraumaduring
coitus,makingthemmoresusceptibletosexuallytransmittedinfectionsthanheterosexualmen
[18].Withregardtoalmostallsexuallytransmittedinfections,womenwhoengageinhetero-
sexualintercoursealsosufferagreaterdiseaseburdenthanheterosexualmen.Progesterone-
drivencyclicreductionsinfemaleinflammatoryresponses,whichreachtheirpeakduringthe
lutealphaseofthemenstrualcycle,increasefemalevulnerabilitytoinfection(reviewedin
[19,20]).Additionally,humanfemaleanatomymakesitpossibleforpathogenicbacteriato
travelthroughthevaginaintotheperitonealcavity,causingpelvicinflammatorydisease(PID);
ofwomenwithasingleepisodeofPID,8%arerenderedinfertile[18]representingoneofthe
mostsevereadaptivecosts.
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 2/22
DisgustversusLust
HowSexualArousalInfluencesDisgustReactions
Todate,fourstudies,twowithmalesamples[21,22],onewithafemalesample[23]andone
withbothmaleandfemaleparticipants[24]havespecificallyinvestigatedwhetherpeoplere-
sponddifferentlytodisgustelicitorswhensexuallyaroused.ArielyandLowenstein[21]found
that,comparedtomenwhoviewedpicturesofclothedwomen,thosewhoviewedpicturesof
nakedwomenweresignificantlymorelikelytoendorseengaginginpotentiallydisgustingsexu-
alsituations,suchaswatchingawomanurinating,havingsexualcontactwithananimal,or
havinganalsex.Stevenson,CaseandOaten[22]useddisguststimulifromeachofthreemodal-
ities(aural,visualandtactile),withonesex-relatedstimulusandonenon-sex-relatedstimulus
presentedineachmodality(e.g.,forthetactilemodality:feelinglubricatedcondomsversus
feelingcoldhamandpeasoup).ConsistentwithArielyandLoewenstein’s[21]findings,com-
paredtomenincontrolconditions,menwhohadbeenexposedtoeroticcontent(photographs
ofnudewomen)showedagreaterdiscrepancybetweendisgustreactionstosexualandnonsex-
ualstimuli.Specifically,sexualarousalreduceddisgustresponsesforsex-relatedstimuli,but
hadnoeffectondisgustreactionstonon-sexualstimuli[22].
Anotherstudydidnotfindthatsexuallyarousedmenreportedadecreaseindisgust.Lee
etal.[24]conductedanonlinestudyexamininghowmenandwomenrespondedtotheThree
DomainsofDisgustScale(TDD;[11])inasexuallyarousedstate,aphysiologicallyaroused
stateoracontrol(noarousal)state.Participantsachievedsexualarousalintheirpreferredway
athome.Thesexualarousalconditiondidnotreducethedisgustofmaleparticipantsinanyof
thethreedomainsofdisgust(pathogendisgust,sexualdisgustormoraldisgust)[24].Thisfind-
ingisatoddswithpreviousstudies[21,22]perhapsindicatingthatyoungmendidnotcomply
withinstructionstojustachievesexualarousalandnotorgasmbeforereturningtothesurvey.
Inlightoftheabovefindingsinmen,andgiventheadaptiveconsiderationsdiscussedearli-
er,itisplausibletoexpectsexualarousaltoinfluencewomen’sreactionstodisgust-elicitingsti-
muli.Borg&deJonglookedathowwomenrespondtoengagingindisgustingtaskswhenin
oneofthreemood-inductiongroups:positivearousal,negativearousal,andsexualarousal
[23].Womenwatched5minutesofvideointendedtoelicitoneofthesethreestatesandthen
conducted2of16disgustingtasks(ratherthanactuallydoingthetask,participantscouldalso
choosetoimagineengaginginit).Thisprocedure(5minutesofvideoand2newdisgusting
tasks)wasrepeateduntileachparticipanthadbeenexposedtoall16disgustingtasks.Com-
paredtowomeninboththepositivearousalandthecontrolconditions,womeninthesexual
arousalconditionreportedlessdisgustatengagingin(orimaginingengagingin)thesexualdis-
gustingtasks(e.g.,lubricatingavibrator,handlingapairofstainedunderwear),thusreplicat-
inginwomenStevensonetal.'s[22]findingsinmen.Additionally,BorganddeJong[23]
foundanearlysignificantdifferenceindisgustreactivityforthenonsexualdisgustingtasks
(e.g.,insertingapinintoacoweyeball),suchthatwomeninthesexualarousalconditionre-
portedlessdisgustthanthoseinthepositivearousalcondition.Thisstudyalsofoundthat
thoseinthesexualarousalconditioncompletedthemostdisgustingtaskscomparedtotheneu-
tralorpositivearousalconditionregardlessofwhetherthesetasksweresexualinnature.This
studyprovidesevidencethatbothpathogendisgustandsexualdisgustmaybeattenuatedby
sexualarousal.
Leeetal.[24]foundthesameeffectasBorg&deJong[23]withregardstosexualdisgust
buttheoppositeeffectforpathogendisgustintheironlinestudy.ReplicatingBorg&deJong,
sexuallyarousedwomenreportedbeinglessdisgustedatcontextsinthesexualdomainofthe
TDDscale(e.g.“Findingoutsomeoneyoudon’tlikehassexualfantasiesaboutyou”)than
womeninthephysiologicallyarousedandcontrolconditions.However,sexuallyaroused
womenreportedsignificantlymoredisgustatthepathogendisgustcontextsintheTDD(e.g.
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 3/22
DisgustversusLust
“Steppingondogpoop”)thanwomeninthephysiologicallyarousedconditionandmarginally
morepathogendisgustthanwomeninthecontrolcondition.
HowDisgustInfluencesSexualArousal
Therehavebeenstudiesofhowtraitdisgustinfluencessexualarousalandfunctioning(e.g.
[16,25])butnostudieshavereallyexaminedhowelicitingdisgustdirectlyinfluencessexual
arousal.KoukounasandMcCabe[26]foundthatwomenreportedmoredisgustthanmenat
eroticvideosandthatthesedisgustratingswereassociatedwithsignificantlylowerself-re-
portedsexualarousal.However,thisresultdoesnotdistinguishbetweencoredisgustand
moraldisapprovalexpressedasdisgust,animportantconfoundgiventhatdisapprovalofpor-
nographyingeneral,orofgenderrolesdepictedtherein,couldalsocreatethiseffect.Malamuth
andCheck[27]askedmaleparticipantstoreadstoriesofsexualencountersinwhichthedegree
offemalearousalandconsentdepictedweremanipulated,findingthatvignettesinwhichthe
womanwasdescribedasdisgustedwerelesssubjectivelyarousingthanthoseinwhichshewas
describedassexuallyaroused.However,thisstudyaddressesobserveddisgustinanotherparty
ratherthanowndisgust,whiletheabsenceofaneutralconditionmakesitimpossibletodeter-
minewhetherobserveddisgustexercisesauniqueeffectonparticipantarousal.Vonderheide
andMosher[28]foundthatthemoredisgustwomenreportedwhenimagininginsertingacon-
traceptivediaphragm,thelesssexualarousaltheyreportedwhileimaginingasubsequentsexu-
alinteraction.However,thesamestudysuggeststhatboththeeliciteddisgustandthe
associatedreducedarousallikelyreflectunderlyingnegativeattitudestowardsexuality.Ethno-
graphicaccountsdescribeaninverserelationshipbetweendisgustandsexualarousalamong
theMangaiansofPolynesia[29]andtheBengkuluofSumatra[30],butitisimpossibletodis-
tinguishpersonalexperiencefromfolkmodelsinsuchreports.Disgusthasalsobeenfoundto
haveaneffectonhypotheticaldecisionmakinginasexualcontext:participantsexposedtothe
smelloffecesreportedbeingmorelikelytousecondoms[31].Murray,Jones&Schaller[32]
foundacorrelationbetweenself-reportedvulnerabilitytodisease,lowernumberofdesiredfu-
turesexualpartnersandreducedfuturepromiscuity.Thiscorrelationwasstrongerinagroup
ofwomenwhohadbeenexposedtodiseasecues.However,bothresultsrevealchangesinsexu-
al-decisionmakinginthepresenceofdiseasecuesratherthanadecreaseofsexualarousalper
se.Hence,todate,therehavebeennodirecttestsoftheeffectsofexperimentallyeliciteddisgust
onsubsequentsexualarousal.
Clinically,traitdisgusthasbeenshowntohaveimplicationsforwomen’ssexualfunction-
ing.Womenwithvaginismus(aconditioninwhichvaginalspasmsmakeintercoursedifficult
orimpossible)werefoundtohavegreateroveralldisgustpropensity(asmeasuredusingthe
DisgustScale(DS)–[14])thanwomenwithdyspareunia(genitalpainrelatedtointercourse)
andwomenwithoutsexualcomplaints[33].Surprisingly,thisstudyshowednooveralldiffer-
encesbetweengroupsonratingsfromaSexualDisgustQuestionnaire(e.g.,“Towhatextent
areyouwillingtoliebeneathbedclothesinahotelthatlookunwashed,andbelowwhichprevi-
ousguestsmayhavehadsexualintercourse?”)[33].Afollow-upstudyfoundthatwomenwith
vaginismusanddyspareuniabothshowedgreaterimplicitdisgustassociationstosexualsti-
muli,andthatwomenwithvaginismusshowedgreaterfacialmuscleactivationreflectingdis-
gustwhenviewinganeroticfilm[25].
Researchershavealsolookedattherelationshipbetweentraitdisgustandsexualfunctioning
innonclinicalsamples.vanOverveldetal.[34]foundthata)lowerwillingnesstohandlesexual
itemsfromafamiliarsource,andb)greaterdisgustathandlingsuchitemssignificantlypre-
dictedlowerratingsonthesubjectivearousalandlubricationsubscalesoftheFemaleSexual
FunctioningIndex.Grauvogletal.[16]reanalyzedthisdata[34]findingthatthosewomen
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 4/22
DisgustversusLust
withgreaterdisgustpropensityacrossdomainsalsoreportedexperiencingmorepainduring
intercourseandhadmoredifficultyachievingorgasmwhereasformentraitdisgustwasnot
associatedwithsexualfunctioning.Inafurtherstudy,Grauvogletal.[16]brought19men
and24womenintothelaboratory.Theylookedattheassociationbetweengenitalsexual
arousal(measuredwithpsychophysiologicalinstruments)andthreedisgustmeasures:im-
plicitassociationbetweensexualstimulianddisgust,disgustpropensityandthetendencyto
findtheemotionofdisgustunpleasant.Theydidnotfindanyassociationbetweendisgust
measuresandgenitalsexualarousalinwomen.Surprisingly,theyfoundthathigherdisgust
propensityandunpleasantnesswasassociatedwithgreatergenitalarousalinmalepartici-
pants.Thus,theredoesnotseemtobegoodevidencethattraitdisgustreducesgenitalre-
sponsetosexualstimuli.
FearandSexualArousal
Althoughtheeffectsofeliciteddisgustonsexualarousalhavenotbeendirectlyexamined,the
effectsofanxietyandstresshave.Areviewofthisliteratureinformspredictionsforthefear
conditionthatweemployasanegatively-valencedcontrolconditioninthepresentstudy.
“Stress”isfairlylooselydefinedintheliteratureand,consistentwiththislackofprecision,
hasbeenshowntohaveavarietyofeffects.Hoon,Wincze,andHoon[35]foundthataphysi-
ologicalmarkerofsexualarousalwaselevatedwhenaneroticfilmclipwaspresentedafteran
anxiety-inducingclip(depictingdyingvictimsintheaftermathofanautomobileaccident)
comparedtowhentheeroticclipwaspresentedafteraneutralclip.PalaceandGorzalka[36]
replicatedthesefindingswithtwopairsoffilms:aneutralfilmfollowedbyaneroticfilm,and
ananxiety-inducingfilmfollowedbyaneroticfilm;womenshowedmorevasocongestion
(indicativeofarousal)duringtheeroticfilmshownaftertheanxiety-inducingfilm.Instudies
whereastressorleadstoincreasedphysiologicalarousal,thefacilitatoryeffectislikelydueto
increasesinsympatheticnervoussystemactivity,whichhasbeenshowntoenhancesubse-
quentarousal[37,38].However,self-reportedsexualarousalappearsnottofollowthesame
pattern.PalaceandGorzalka[36]foundthat,ratherthanreportingmoresexualarousalfol-
lowingexposuretoanxiety-inducingstimuli,womeninthisconditionreportedlessarousal,
whileotherstudiesshowactivationofthesympatheticnervoussystemdoesnotchangeself-
reportedarousal[37,38].Theformerpatternispotentiallyexplicableintermsofsubjective
misattribution[39]apossibilitythat,aswediscussbelow,hasimportantmethodologicalim-
plications.Incontrasttothesefindings,stressthatentailsthethreatofharmhasbeenshown
todecreasesexualarousal.Forexample,womenwhoweretoldthattheyhada60%chanceof
receivingapainfulelectricshockshowedlowergenitalarousalthandidwomeninacontrol
condition[40].Frustration,suchasacognitivelyfrustratingtaskwitharesearcherpresent,
alsolowerssexualarousal[41].Importantly,allofthemyriadfearandanxietyinduction
methodsemployedbypreviousinvestigatorsdiffersubstantiallyfromthestimulithatwe
employ.Inordertoinvokeanegatively-valencedemotionalstatethatisfunctionallydiver-
gentfromdisgust,wespecificallyselectedimagesofsituationsthatcanplausiblybepresumed
tohavepotentialadaptivesignificanceforahumanobserver,yetdonotincludecuesof
theriskofdiseasetransmission(e.g.,predators,precipitousheights,naturaldisasters,
weapons).
Candisgustalsobeconstruedasastressor?Disgustappearstoinvolvecoactivationofthe
sympatheticandparasympatheticnervoussystems,ratherthanexclusiveactivationofthefor-
mer[42].Hence,incontrasttothepredictionsoftheadaptationistaccountpresentedearlier,at
aproximatelevel,thepotentialimpactofdisgustonsexualarousalisunclear,assuchinfluence
maydependontheratioofSNStoPNSactivation.
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 5/22
DisgustversusLust
TheCurrentStudy
Herewepresentthefirststudytodirectlymeasuretheimpactofdisgustonsexualarousaland
viceversausingbothself-reportofsexualarousalandphysiologicalindicesofsexualarousal.Pre-
viousstudieshavegenerallyusedameasureofsubjectivesexualarousal.Self-reportmeasuresof
women’ssexualarousaloftenshowlowcorrelationwithgenitalmeasuresofsexualarousal(i.e.,
vaginalpulseamplitude,themeasureusedinthisstudy)[43]orevenanegativecorrelation[16].
Self-reportedsexualarousalmayrepresenthigher-orderconsciousappraisalofsexualcues,while
genitalmeasuresmaybetheproductofmoreimmediateandunconsciousprocessing[44,45].
Giventhatself-reportedsexualarousalmaythusreflectagreaterinfluenceoftheculturalmean-
ingofparticularsexualcues,whilegenitalarousalmayreflectmoreelementaryfeaturesofbio-
logicalresponsestosuchstimuli,itispossiblethatgenitalarousalwillmoreclearlyrevealthe
tracesofevolvedmechanismsdesignedtoweighthecompetingadaptivegoalsofreproduction
anddiseaseavoidance.Bymeasuringbothgenitalandself-reportedsexualarousal,thepresent
studyallowsforamorecomprehensiveviewoftherelationshipbetweendisgustandsexual
arousalinwomen.
PredictionsandRationales
Because,overevolutionarytime,theexperienceofdisgusthasbeenareliableindicator
thatapropitiousmatingisunlikely,wepredictthatdisgustwilldecreasesexualarousal,
andhencethatparticipantsinwhomdisgustiselicitedpriortosexualarousalwillshow
thelowestsexualarousal.Disgustpropensityappearstobecalibratedtocurrentimmune
vulnerability[46]andthuswithincreasedprobabilityofcontagionduringsexualcontact.
Wethereforepredictthatbaselinedisgustpropensitywillpredictloweroverallsexual
arousalinourparticipants.Becausephysiologicalmeasuresofsexualarousalrepresenta
morebasicandunconsciousprocessingoferoticcues,wepredictthatthismeasurewillbe
moresusceptibletotheeffectsofdisgustinductionthanwillsubjectiveindicatorsofsexual
arousal.
WithregardtotheeffectsofsexualarousaloncoredisgustinwomenBorganddeJong
[23]foundthatsexualarousalsignificantlydecreasedcoredisgustreactionsincomparisonto
aneutralcondition.Leeetal.[24]foundthatsexualarousalincreasedpathogendisgustin
womenrelativetoaphysiologicallyarousedcontrolcondition.However,bothgroupsofin-
vestigatorsmeasuredsexualarousalthroughself-report,leavingopenthequestionoftheex-
tenttowhichthesepatternsreflectsymbolicmeaningsversusmorephysiologically-driven
processes.Here,wepittwopredictionsagainstoneanother.Ontheonehand,sexualarousal
coulddecreasepathogen-avoidancedisgustbecausetheultimateadaptivefunctionthat
sexualarousalserves—achievingreproductivesuccessthroughmating—canonlybeachieved
throughintimatecontactwithcuesofpathogenpresence.Ontheotherhand,because
sexualarousal(especiallywhenmeasuredintermsofvasodilation,explainedbelow)poten-
tiallycorrespondswithincreasedriskofcontagion,sexualarousalcouldincreasedisgust
reactivity.
Finally,becausepreviouswork,characterizedbyheterogeneousmethodsanddivergentsti-
muli,documentsmixedeffectsofstressandanxietyonsubsequentsexualarousal,wehaveno
discretepredictionsregardingtheeffectsoffearinductioninthisregard.Rather,wetreatour
fearconditionasanegatively-valencedcontrolforourdisgustcondition,withtheunderstand-
ingthattheformerisitselfexploratoryinnature.
DataArchiving
DataforallstudiesdescribedinthispaperarearchivedattheDryadDigitalRepository.
PLOSONE|DOI:10.1371/journal.pone.0118151 June24,2015 6/22
DisgustversusLust
Method
EthicsStatement
TheresearchwasapprovedbyboththeethicsboardsattheUniversityofTexasatAustinand
thatatMountAllisonUniversity.Duringscreening,informedverbalconsentwasobtained
fromparticipants.Onthedayoftheexperiment,informedwrittenconsentwasobtainedfrom
allparticipants.Writtenconsentformswereretainedandlockedinasecurecabinet.
ScreeningParticipants
Potentialparticipantswerescreenedbyphoneusingthefollowingeligibilitycriteria:a)female
overage18,b)heterosexual,andc)experiencingregularmenstrualcycles.Exclusionarycriteria
wereasfollows:a)self-reportedsexualaversionordistressrelatedtosexualabuse,b)nothav-
ingconsistentmenstrualcycles(e.g.,pregnant,menopausal),c)breastfeedingwithinthelast3
months,d)anyuntreatedendocrinedisease,ande)takingmedicationsthatcouldinterfere
withthestudy,includingDHEA,SSRIsorbetablockers.Womenonhormonalcontraception
participatedinthestudy.Aftertheinitialphonescreening,participantswerescheduledto
comeintothelabbetweendays5–10oftheirmenstrualcycleinordertostandardizemenstrual
cycleeffects.
Participants
ParticipantsweremembersoftheundergraduatepsychologysubjectpoolataNorthAmerican
university,receivingcoursecreditinexchangeforparticipation,orwerecompensatedvolun-
teersfromNorthAmerica,recruitedviaCraigslist.orginexchangefor$15.Eighty-fourwomen
participatedinthestudy.Weexcludeddatafromthoseparticipantsforwhomwewereunable
toobtainavalidvaginalpulseamplitude(VPA)reading(n=6),onewomanwhowasanoutli-
er(discussedlater),andonewomanwhosufferedconjunctivitisatthetimeofparticipation,
leaving76participantstotal.Participantsrangedinagefrom18–42(mean=23.55,SD=5.44).
Thefinalsamplewas55%White,14.5%EastAsian,9.2%AfricanAmerican,and10.5%Latina,
6.6%MixedLatinaandWhite;additionally,thereweretwoSouthAsianparticipants,andone
participantwhodidnotindicateherethnicity.Thesampleconsistedof48womennotusing
hormonalcontraceptives,27womenusinghormonalcontraceptives,andonewomanwhodid
notanswerthisquestion.
Pre-ExperimentMaterials
Questionnairesandbackgroundmaterials. Allquestionnaireswerecompletedbeforethe
experimentbegan.Individualdifferencesinpathogen-avoidancedisgustpropensitywereas-
sessedusingasix-questionsubsetoftheThreeDomainsofDisgustScale(TDD;[11]).Weused
thistruncatedversionoftheTDDbecausewedidnotwanttoelicitstrongdisgust—especially
sexualdisgust—inparticipantsbeforetheexperimentbegan.Thesix-questionsubsetexhibited
areasonablygoodalphainthepresentstudyα(76)=.72,akintothat(alphaα[1064]=.78)
characterizingtheseitemsintheoriginalTyburetal.[15]studyinwhichtheTDDwasdevel-
oped[47].ParticipantsalsofilledouttheFemaleSexualFunctionIndex[48],aswellasques-
tionnairesregardingtheirhealth,positioninthemenstrualcycle,andrelationshipstatus.
Additionalquestionnaires,addressingothertopics,werealsoadministeredbutarenotdis-
cussedhere.
ExperimentalDesign
ThestudydesignisillustratedinFig1.
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DisgustversusLust
Fig1.Fourconditionswereemployed,asfollows(clockwisefromtheupperlefthandcorner).Disgustaffectssexualarousal:Womenrated18
disgust-inducingpicturesandthenwatchedaneroticfilm;Sexualarousalaffectsdisgust:Womenwatchedtheeroticfilmfirst,thenrated18disgust-
inducingpictures;Sexualarousalaffectsfear:Womenwatchedtheeroticfilmandthenrated18fear-inducingpictures;Fearaffectssexualarousal:
Womenrated18fear-inducingpicturesandthenwatchedtheeroticfilm.Thetwofearconditionscontrolforthecontributionsofnegativevalence,anattribute
sharedbydisgustandfear.
doi:10.1371/journal.pone.0118151.g001
Films
Neutralfilm. Theneutralfilmwasa3-minuteclip,includingaudio,fromadocumentary
aboutthesearchforthenavalshipPT-109;theclipfeaturesmostlyfootageofboats,alongwith
someinterviews.
Eroticfilm. Theeroticfilmwasan8-minuteclipdrawnfromtheFemaleSexualPsycho-
physiologyLaboratoryfilmlibrary.Allfilmsinthislibraryhavebeenstandardizedintermsof
thelengthofdifferenttypesofsexualscenes(i.e.,foreplay,oralsex,andvaginalintercourse).
Noneofthefilmsshowsexualviolenceorfellatio.Thesefilmswereselectedfromeroticfilms
producedanddirectedbywomen,andareintendedtobesexuallyappealingtowomen.Partici-
pantswereeachshownonesuchfilm.Wechosetousefilmsratherthanstillimagesbecause
audiovisualdepictionsofintercoursehavebeenshowntoelicitgreatergenitalarousalin
womenthanstillimagesofnudemenandwomen[43].
DisgustandFearInduction
Creatingthestimuliset. Stimuliintendedtoelicitfearanddisgustweretakenfrominter-
netsearches,theimagesintheCurtisdisgustinventory[3]andtheInternationalAffectivePic-
tureSystem[49].Fourraters(twomenandtwowomen)eachrated194imageswithregardto
howfrightening,enjoyable,sexual,anddisgustingeachwasonascalefrom1–9.Weexcluded
imagesthatwererankedasbothhighlydisgustingandhighlysexualbecausewewantedtoen-
surethatthedisguststimuliwouldneitherarouseparticipantsnorspecificallyelicitsexualdis-
gust.Wethensubtractedthefearratingfromthedisgustrating,yielding18imageswiththe
highestdisgustratingindependentoffearrating.Weperformedasimilarassessmentoffear
images,subtractingdisgustratingfromfearratings,andselectingthose18imageshavingthe
highestfearratingsindependentofdisgustratings.
Descriptionoffearanddisgustinducingstimuli. Theimagesinthedisgustslideshow
comprised9photographsofinfected,diseased,orinjuredhumansorhumancorpses,3photo-
graphsoffeces,5picturesofdeadandrottinganimalsoranimalparts,andonephotographof
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DisgustversusLust
ahumanvomiting.Theimagesinthefearslideshowcomprised7photographsofweaponsor
violenthumans,7photographsofdangerousanimals(e.g.wolves,sharks),and4photographs
ofhazardousenvironments(e.g.heights,fire,tornado).Wechosetousestillimagesbecause
theyofferedabreadthofdisgustinductionandbecause,asfarasweareaware,thereisnoevi-
dencethatfilmsarebetteratinducingdisgustthanstillimages.Twoparticipantsdidnotfill
outtheimageratingsatall,andtwoparticipantsonlyfilledoutimageratingsfortwooutofthe
fourvalenceoptions.Theseparticipantsareexcludedonlyforthosecorrelationsinwhichtheir
datawasmissing.Themeandisgustratingofthedisgustimagesforthose43womeninthetwo
disgustconditionswas4.88(1.50)outofapossible9,andthemeanfearratingofthefearim-
agesforthose32womeninthetwofearconditionswas3.92(1.52)outofapossible9.
Imageratings. PictureRatingSheet-Participantsviewedeachdisgust-orfear-inducing
imagefor8seconds,thenhad8secondstorecordtheirevaluationofitonapre-printedpaper
ratingsheet,using1–9scales.Theyratedeachimageonhowfearful,disgusting,sexual,anden-
joyableitwas.
MeasurementofSexualArousalDuringtheEroticFilm
Apparatusforvaginalmeasures. VaginalPhotoplethysmograph.Genitalarousalinre-
sponsetoallfilmswasmeasuredusingavaginalphotoplethysmograph[50],aclearacrylic
tampon-shapeddevicethatcontainsaninfraredlight-emittingdiodeasalightsource,anda
photosensitivelightdetector.Themeasureofinterestfromthephotoplethysmographisthe
vaginalpulseamplitude(VPA),whichisreceivedthroughtheA/Csignalandbandpassfiltered
at.5to30Hz.VPAwassampled80timespersecond.Resultsaremeasuredinmillivolts(mV).
VPAdatawereacquiredusingthesoftwareprogramAcqKnowledgeIII,Version3.7.3(BIO-
PACSystems,Inc.,SantaBarbara,CA)andaModelMP100WSdataacquisitionunit(BIOPAC
Systems,Inc.,SantaBarbara,CA)foranalog/digitalconversion.
Self-reportmeasuresofarousal. Self-reportSexualArousal.Self-reportsexualarousalwas
continuouslymonitoredthroughoutthedurationoftheeroticfilmusingadeviceconsistingof
acomputermousemountedonatracknumberedfrom0to7;thedevicewaspositionedona
smalltableacomfortabledistancefromthesideoftheparticipant'schair.Theparticipant
beganwiththedevicesetatzeroandmovedthemouseupordowntoindicateincreasingorde-
creasingself-reportedarousalduringtheeroticfilmpresentation.Theparticipantwasin-
structedthatthedevicewasusedtomeasuretheirpsychologicalarousal,andthatzero
indicatednoarousal,and7indicatedintensesexualarousal.Thelevelsofsexualarousalindi-
catedandtheamountoftimespentateachlevelofarousalwererecordedandanalyzedusing
theMatlabsoftwarepackage(studentversion,release12).Theoutputforthis“arousometer”is
measuredasaproportionofthemaximum.Weextractedthreevariablesfromthesedata:the
meanlevelofself-reportsexualarousalduringtheeroticfilm,themaximumlevelofself-report
sexualarousalachievedduringtheeroticfilm,andthelengthoftimeittookparticipantsto
achievetheirpeakself-reportedsexualarousal.
Procedures
Thestudyprocedureswereexplainedtotheparticipant,includingtheproperinsertionofthe
vaginalphotoplethysmographandtheplacementofelectrodewires.Aftertheparticipantread
andsignedtheconsentform,threeelectrodeswereappliedtoherskinforelectrocardiography
(toaidinanalysisofVPA),andtheparticipantwasleftalonetoinsertthephotoplethysmo-
graphandfilloutthesurveys.Allfurthercommunicationwiththeparticipanttookplacevia
intercom.Participantsviewedtheexperimentalstimuliona42-inchplasmascreentelevision
mountedonthewall.Allfourexperimentalconditionsequenceswereapproximately15
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DisgustversusLust
minuteslong,andallbeganwithaoneminutedisplayoftheword“Relax”onablackscreen,
followedbythreeminutesoftheneutralfilm,andthentheremainderoftheexperimentalpro-
tocoldescribedabove.
DataAnalysis
Preprocessing. VPAData.VPAdatawerereducedbycalculatingthetotalchangeinam-
plitudeforeachheartbeat.Thiswasdonebyfindingthepeakandnadirforeachpulsewave
andcomputingthedifferencebetweenthetwotoobtaintheamplitudeforeachpulsewave,
usingAcqKnowledgesoftware.Artifactsinthedatawereidentifiedvisuallybytheresearcher
andremovedmanually.VPAisarelativemeasurewithnotruezero.Thus,inkeepingwithpre-
viousinvestigations(e.g.[51,52])VPAwasaveragedacrosseachconditionandthenascorefor
eachparticipantforeachconditionwascalculatedaspercentchangeduringtheexperimental
filmrelativetotheneutralfilmthatfollowedit.Thisvariablewillbereferredthroughoutthe
paperasVPApercentchange.
Results
Exclusions
Oneoutlierwasremovedfromthestudy:aparticipantintheDisgust-before-Eroticcondition
showedapercentchangeof178.55.Thiswas3.97standarddeviationsfromthemeanforthe
sampleasawholeand4.08standarddeviationsfromthemeanwithintheDisgust-before-
Eroticcondition.Twootherparticipants,bothintheFear-before-Eroticcondition,showed
percentchangegreaterthan3standarddeviationsfromthemeanforthesampleasawhole.
However,thesepercentchangeswereonly2.4and2.3standarddeviationsfromthemean
withintheFear-before-Eroticcondition,andhencedatafromtheseparticipantswerenot
excluded.
TDDScale
ThreeparticipantsdidnotcompletetheTDDsubset.ScoresontheTDDsubsetdidnotdiffer
significantlyacrossconditionsbothwhenallfourconditionswereexaminedseparatelyF(3,68)
=2.36,p=.08andwhenthetwoneutralconditions(Neutral-before-Erotic)werecombinedF
(2,69)=2.31,p=.11.TheTDDscoresforthetwodisgustconditionswerenearlyidenticalto
oneanother(seeTable1).WefoundtheTDDsubscaleofdisgustpropensityweusedtobe
highlycorrelatedwithdisgustimageratingsr(39)=.44,p<.01,thusvalidatingthemeasure.
BecausedifferencesinvaluesontheTDDsubscalesaresoclosetosignificant,resultscontrol-
lingforTDDarealsoreportedwhereappropriate.
CorrelationofSelf-ReportedArousalandVPAPercentChange
Self-reportsexualarousalwasnotrecordedfor13participantsinthefinalsample.Ninepartici-
pantsforgottousethearousometeroruseditincorrectly,inthreecasestheequipmentfailed,
andinonecaseitisunclearwhyresultswerenotrecorded.Amongthe64participantsfor
whomsuchdatawererecorded,weassessedthreedifferentmeasures:averageself-reported
arousalacrosstheentireeroticfilmclip,maximumself-reportedsexualarousal,andelapsed
timetopeakself-reportedsexualarousal.Thedescriptivestatisticsfortheself-reportedsexual
arousalratingsarepresentedinTable1.Similartootherstudies,self-reportedarousaldidnot
correlatesignificantlywithgenitalarousal[43].Acrossthetwocontrolconditions(wherenei-
therfearinducingstimuliordisguststimuliwerepresentedbeforethearousingfilmclip)corre-
lationsbetweenVPApercentchangeandself-reportedarousalwerepositive:averageself-
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