Viewing sexual images is associated with reduced physiological arousal response to gambling loss

14 Pages·2017·1.55 MB·English

RESEARCHARTICLE
Viewing sexual images is associated with
reduced physiological arousal response to
gambling loss
MingLui1*,MingHsu2
1 DepartmentofEducationStudies,HongKongBaptistUniversity,HongKong,China,2 HaasSchoolof
Business,UniversityofCalifornia,Berkeley,California,UnitedStatesofAmerica
*[email protected]
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a1111111111 Abstract
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Eroticimageryisonehighlysalientemotionalsignalthatexistseverywhereindailylife.The
impactofsexualstimulionhumandecision-making,however,hasrarelybeeninvestigated.
Thisstudyexaminestheimpactofsexualstimulionfinancialdecision-makingunderrisk.In
eachtrial,eitherasexualorneutralimagewaspresentedinapicturecategorizationtask
OPENACCESS beforeagamblingtask.Thirty-fourmenmadegamblingdecisionswhiletheirphysiological
Citation:LuiM,HsuM(2018)Viewingsexual arousal,measuredbyskinconductanceresponses(SCRs),wasrecorded.Behaviorally,
imagesisassociatedwithreducedphysiological theproportionofgamblingdecisionsdidnotdifferbetweenthesexualandneutralimagetri-
arousalresponsetogamblingloss.PLoSONE13
als.Physiologically,participantshadsmallerarousaldifferences,measuredinmicro-siemen
(4):e0195748.https://doi.org/10.1371/journal.
perdollar,betweenlossesandgainsinthesexualratherthanintheneutralimagetrials.
pone.0195748
Moreover,participants’SCRstolossesrelativetogainspredictedtheproportionofgambling
Editor:EldadYechiam,TechnionIsraelInstituteof
decisionsintheneutralimagetrialsbutnotinthesexualimagetrials.Theresultswerecon-
Technology,ISRAEL
sistentwiththehypothesisthatthepresenceofemotionallysalientsexualimagesreduces
Received:August5,2017
attentionalandarousal-relatedresponsestogamblinglosses.Ourresultsareconsistent
Accepted:March28,2018
withthetheoryoflossattentioninvolvingincreasedcognitiveinvestmentinlossescompared
Published:April12,2018 togains.Thefindingsalsohavepotentialpracticalimplicationsforourunderstandingofthe
Copyright:©2018Lui,Hsu.Thisisanopenaccess specificrolesofsexualimagesinhumanfinancialdecisionmakingineverydaylife,suchas
articledistributedunderthetermsoftheCreative gamblingbehaviorsinthecasino.
CommonsAttributionLicense,whichpermits
unrestricteduse,distribution,andreproductionin
anymedium,providedtheoriginalauthorand
sourcearecredited.
DataAvailabilityStatement:Allrelevantdataare
withinthepaperanditsSupportingInformation Introduction
files.
Inthepastdecades,theroleofemotionsinchoicebehaviorshasbeenahottopicinthedeci-
Funding:ThisworkwassupportedbytheHong
sion-makingresearchcommunity.Eroticimagesareemotionalsignalsfrequentlyencountered
KongBaptistUniversityFacultyResearchGrants
indailylife,suchasinadvertisements,websites,TVshows,andmovies.Likehungerandthirst,
(FRG1/14-15/067)giventoML.Thefunderhadno
sexualdesirecreatesoneofthestrongestmotivationsforhumanbehaviors,alongwithother
roleinstudydesign,datacollectionandanalysis,
decisiontopublish,orpreparationofthe appetitivefunctionsinthebrain[1].Nevertheless,fewstudieshaveexaminedhowsexualstim-
manuscript. ulationinfluenceshumandecision-makingbehaviorallyandphysiologically.Inastudyby
ArielyandLoewenstein(2006)[2],meninasexuallyarousedstatehadahighertendencyto
Competinginterests:Theauthorshavedeclared
thatnocompetinginterestsexist. acceptunsafesexandmorallyquestionablebehaviors.Anotherfieldstudy[3]showedthat
PLOSONE|https://doi.org/10.1371/journal.pone.0195748 April12,2018 1/14
Sexualimageandarousalresponsetogamblingloss
youngmaleskateboarderstookhigherphysicalriskofcrashlandingsinthepresenceofan
attractivefemalecomparedtoalessattractivefemale,aneffectassociatedwithanincreased
leveloftestosterone.Inadditiontoriskysexualandphysicalactivities,evidencehasaccumu-
latedregardingtheeffectofsexualstimulionfinancialdecision-makingsuchasdelayeddis-
counting[4,5],theultimatumgame[6],theIowaGamblingTask[7],andfinancialrisk-taking
[8].
Thesestudiesrevealedthatsexualstimuliwereassociatedwithheighteneddesireforimme-
diatereward[4]andahighertendencytowardrisk-taking[8].Findingsontheeffectofsexual
arousalonfinancialdecision-makinghaveremainedscarce,andnoneofthepaststudieshas
examinedlossaversion.LossaversionwasfirstdescribedbyKahnemanandTversky[9]asthe
overweightingoflossescomparedtoequallylargegains[10],andisthoughttobeahallmark
ofirrationaldecision-makingthatinvolvesemotionalprocesses.Inadditiontobehavioral
findings(e.g.[11]),therewerephysiological(suchaspupildiameter,heartrate,andskincon-
ductance)andbrainimagingdatademonstratingthatlosseshadalargerimpactthangainson
ouremotionalandcognitivesystems(e.g.[10,12]).Theconceptoflossaversionisdistinct
fromrisk-seeking,whichischaracterizedbyincreasedmarginalutilityofmoney.Somepast
findingssuggestthatlossaversionhasastrongereffectonmodulatingdecision-makingbehav-
iorthanrisk-seeking(see[13]forareview).However,thereisalsoevidenceshowingnoloss
aversionamongaveragedecisionmakers[14,15,16],evenwiththepresenceofheightened
physiologicalresponses(suchaspupildilationandincreasedheartrate)tolossescompared
withgains[17,18].Giventheinconsistentfindings,YechiamandHochman[18]haverecently
proposedanattentionalmodeloflossregardingtheimpactoflossonbehavioraldecisionsand
physiologicalarousal(e.g.[17]).Themodelproposesthatlossesleadtoincreasedphysiological
arousalaswellasvigilancetotask,causinganincreaseinsensitivitytotheoutcomesofdeci-
sionsincludingbothlossesandgains.Thisinturnspromotesbehavioralresponsesaccording
tothereinforcementstructureandreducesrandombehaviors.
Regardingtheeffectofsexualstimuliondecisionmaking,somepaststudieshaveshown
thatsexualstimuliinterfereswithattentionandleadstodistractionfromthetaskrequirements
[19,20],therebyreducingthementalresourcesforprocessingemotionalresponsesassociated
withgainandlossoutcomes[21,22].Ontheotherhand,neuroscientificfindingshaveshown
thatsexualstimuliactivatethedopaminergiccircuitryofthebrainrewardsystem,suchasthe
nucleusaccumbens,similarlytoothertypesofrewardssuchasmoneyanddrugs[23].Dopa-
mineinthenucleusaccumbensisresponsibleformotivationalandapproachbehaviorfor
reward-seeking(see[24]forareview).Theactivationoftheappetitiveneuralsystembysexual
stimulimayaccountfortheheighteneddesireforimmediatemonetaryreward[4]anda
highertendencyoffinancialrisktaking[8]whenpeoplearesexuallyaroused,asfoundinpre-
viousstudies.Giventhatpastfindingsoftheeffectsofsexualarousalondecision-making
behaviorsremainscarce,ourstudyaimstofillthisresearchgapbyexaminingtheeffectofsex-
ualimagesondecision-makingunderrisk.Theprospecttheoryproposesthatpeoplemake
real-lifedecisionsbasedonthepotentialvaluesoflossesandgainswhentheprobabilitiesof
outcomesareknown[9].Inourexperiment,participantswereinformedthattheirdecisionsto
gamblewouldresultin50%chanceofmonetarygainand50%chanceofmonetarylossof
knownvalues.Immediatelybeforethisgamblingtask,participantswererequiredtoevaluate
pictureswitheithereroticorneutralcontent,whichwasdesignedtomanipulateparticipants’
levelofsexualarousal.Theyweretoldthatthetwotaskswereseparateexperiments.Ourstudy
adoptedawithin-subjectrepeated-measuresdesignbecauseofthelargebetween-subjectvaria-
tionsinriskattitude,whichcansubstantiallyreducethepowerofstudies.Infact,within-sub-
jectdesignshavelongbeenusedbydecision-makingresearcherstomitigatethisvariationand
havealsobeenincreasinglyrecommendedinotherareasofpsychology(Normand,2016).
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Sexualimageandarousalresponsetogamblingloss
Regardingthedependentvariables,participants’behavioralresponses(decisionsofgam-
blingandreactiontime)andphysiologicalresponses(skinconductanceresponses;SCRs)were
measured.Weexaminedboththedecisionsandthereactiontimesbecausewebelievedthat
sexualstimulationmayaffectparticipants’decisionstogambleandthetimerequiredforthe
decisionstobemade.Reactiontimereflectsthelevelofmentalconflictbetweengamblingand
notgamblingduringthedecisionmakingprocess[25].SCRisanindexofautonomicarousal
triggeredbythesympatheticnervoussystemandwemeasuredparticipants’arousalresponses
tosexualimageviewingandtotheoutcomeofgambling(i.e.monetarygainsandlosses)
throughthemeasurementsofSCRstime-lockedtotheonsetsofthesestimuli.
Intermsofbehavioralresults,wehypothesizedthatsexualstimuliwouldactivatethe
rewardsystemandstimulatetheappetitivemotivationtoseekpotentialrewards,whichwould
manifestasahigherproportionofgamblingdecisionsinsexualimagetrialsforallriskratios.
Increasedappetitivemotivationwasconsistentlyfoundtocausepeopletohavediminished
sensitivitytorisks;forexample,drugaddictsduringcraving(Naqvietal.,2014)andriskysex-
ualbehaviors(Ariely&Loewenstein,2006).Therefore,weproposedthatpeoplewoulddem-
onstrateahigherproportionofgamblinginallrisk-ratios.Second,theincreasedappetitive
motivationinsexualtrialsmayleadtoareductioninthementalconflictsbetweenthedeci-
sions(gamblingornotgambling)[25],whichmayinturncauseafasterreactiontimeinsexual
imagetrialsrelativetoneutralimagetrials.Third,wehypothesizedthatsexualstimulation
wouldattenuateparticipants’emotionstriggeredbygamblinglossesrelativetogains:they
wouldhavelowerSCRstogamblinglossesrelativetogainsinsexualthaninneutralimagetri-
als.Thishypothesiswasbasedontheneuroscientificfindingsthatsexualstimuliareassociated
withthereleaseofendogenousopioids[26],leadingtoaeuphoricstateandthusmightbuffer
againstthenegativeemotionalarousaltriggeredbymonetarylossfromgambling.Inother
words,wehypothesizedthatsexualstimulationwouldreducelossaversion,bothbehaviorally
andphysiologically.Finally,wehypothesizedthatparticipants’SCRstolossesrelativetogains
wouldpredictgamblingdecisions,thatis,participantswhohadhigherphysiologicalarousalto
lossesrelativetogainswouldgambleless,basedonSokol-Hessneretal.(2009)’sfindingofcor-
relationbetweenbehaviorallossaversionandSCRstolossesrelativetogains[12].
Materialsandmethods
Participants
Thirty-eightheterosexualmalesparticipatedintheexperiment.Fourparticipants’datawere
excludedbecauseoflackofSCRresponsesduringthedeep-breathtest(N=3),oratechnical
error(N=1).Thefinaldatasetcontains34subjects,agedbetween18and27years(M=21.5;
S.D.=2.3),reportingnoneurologicalorpsychiatricconditions.Allparticipantswereconsid-
eredright-handedbasedontheEdinburghHandednessInventory[27].Beforetheparticipants
joinedtheexperiment,theycompletedanonlineversionoftheAutismSpectrumQuotient
(AQ)[28],whichisaself-administeredinstrumentformeasuringthedegreeofautismtraits
amongadultswithnormalintelligence.Sincetherewasevidenceshowingdiminishedneural
andbehavioralresponsestomonetaryrewardamongindividualswithautismtraits(e.g.[29]),
onlyparticipantswithAQlowerthan30wereincludedinthisstudy.Dataofparticipantswith
highAQwereanalyzedseparatelytobeincludedinanotherstudy.
OurstudyhasreceivedapprovalfromtheCommitteeontheUseofHumanandAnimal
SubjectsinTeachingandResearch(HASC)atHongKongBaptistUniversity(approvalnum-
ber:FRG1/14-15/067).Allproceduresperformedinthisstudywereinaccordancewiththe
ethicalstandardsofHASCandwiththe1964Helsinkideclarationanditslateramendmentsor
comparableethicalstandards.Writteninformedconsentwasobtainedfromallparticipants.
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Sexualimageandarousalresponsetogamblingloss
Thepaymentschemewasexplainedtotheparticipantsthoroughlybeforetheexperiment,and
allparticipantswerereimbursedaccordingly.
Psychophysiologicalmeasures
Participants’skinconductanceresponses(SCRs)wererecordedbytheeegosportsystem(ANT
NeuroLtd.)connectedtoalaptopcomputer.Triggersweresentfromthestimuluspresenta-
tionprogram(Eprime)ofonecomputertotheSCRsignalrecordingsoftwareinanothercom-
puter.ElectrodesmadeofAg-AgClwereattachedtothepalmarsurfaceofparticipants’index
andmiddlefingertipsoftheirlefthand.TheSCRdatawereevent-relatedmeasures,which
weretime-lockedtothetriggerssentattheonsetoftheimagesandofthegamblingoutcomes.
TheSCRdataweresampledat500Hz,low-passfiltered(20Hz),smoothed(9samplekernel),
transformedfromkOhmtomicro-siemens(μS),andsquare-rootedusinganin-house
MATLABscript.TheSCRswerethebaseline-to-peakamplitudedifferenceinthe0.5-sto5-s
timewindowfromthestimulus-onset.Thephysiologicaldataof4participantswhohad
extremelylowgamblingresponses(<=15%)wereexcludedbecauseoftoofewtrialspercon-
ditionforanalysis.These4participants’behavioraldata,includingdecisionsandreaction
times,wereincludedinthebehavioraldataanalysisonly.
Procedure
Atthebeginningoftheexperiment,participantsweretoldthattheywouldperformtwosepa-
rateexperiments;onewasapicturecategorizationtask,andtheotherwasafinancialdecision
task.Inthepicturecategorizationtask,participantssawpicturesofyoungwomen.Thefemale
pictureswereselectedbasedonratingspreviouslygivenby20maleheterosexualcollegestu-
dents(meanage=22.4)whodidnotparticipateinthiscurrentdecision-makingexperiment.
Themeanarousalratings(witha9-pointLikertscale)ofsexyandneutralpictureswere6.21
(S.D.=.25)and1.71(S.D.=.26)respectively.Theproportionsofsexualandneutralfemale
pictureswereequal(.5vs.5)andtheorderofpresentationwasrandomized.Witharesponse
box,participantspressedthe“+”buttoniftheyregardedthepictureassexy;theypressedthe
“0”buttoniftheyregardedthepictureasneutral.Positionsofthebuttonswerecounterbal-
ancedacrossparticipants.Theywereinstructedtopressthebuttonwitharesponseboxwithin
atimelimitof1.5seconds.Responsesmadebeyondthetimelimitwerenotrecorded.
Forthefinancialdecisiontask,beforethestartoftheexperiment,participantsweregiven
HKD$50cashforgamblingandweretoldtoputitintheirwallet.Duringthetask,thepartici-
pantswererequiredtochoosebetweentwooptionsthatinvolveddifferentlevelsoffinancial
risk.Referringtoanexampleofgain-losstrial(Fig1leftpanel),participantsweretoldthatif
theychosetheleftoption,therewasa50%chanceofgainingthemonetaryamountshownat
theupperleftcorneranda50%chanceoflosingtheamountshownatthelowerleftcorner.If
theparticipantchosetherightoption,itwas100%certainthattheywouldreceivetheamount
indicatedontheright,whichcouldbezeroorapositivenumber(pleaserefertoS1Fileofsup-
portinginformationforthecompletesetofinstructions).Table1showthepossiblegainand
losscombinationsofall72trials.Seventy-twotrialsweregain-losstrials(Table1)inwhich
therewasa50%chanceoflosingorgainingmoneyiftheparticipantchosetheleftoption(Fig
1leftpanel).Tocomparethesamechoiceoptionsunderdifferentconditionsofsexualarousal,
eachgain-losscombinationwaspresentedtwice,onceafterasexualimageandonceaftera
neutralimage.The36combinationsthereforeresultedin72gain-losstrials(Table1).There
wereeightgain-onlychoices(i.e.8choicesx2conditions=16trials)inwhichtheleftoption
ledtoeitherapositiveorzerooutcome(50%chance),andtherightoptionledtoa100%
chanceofgain(Fig1rightpanel).Thegain-losstrialsandgain-onlytrialswererandomly
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Sexualimageandarousalresponsetogamblingloss
Fig1. (Leftpanel)Thetwooptionsingain-losstrials.Theparticipantschoseeithertheleftorrightoption.Inthisexample,thereisa50%chanceofgainingHKD$64
anda50%chanceoflosingHKD$96iftheleftoptionischosen.Iftherightoptionischosen,therewillnotbeanylossorgain.(Rightpanel)Thetwooptionsinthe
gain-onlytrials.Inthisexample,thereisa50%chanceofgainingHKD$44anda50%chanceofgainingnothing($0)iftheleftoptionischosen.Iftherightoptionis
chosen,theoutcomeisacertaingainofHKD$15.
https://doi.org/10.1371/journal.pone.0195748.g001
presentedforeachparticipant.Thegain-onlytrialswereforidentifyingthemodelparameters
tocaptureriskaversion.TheywereincludedforaclosereplicationofthechoicesinSokol-
Hessneretal.(2008),whichmeasuredlossaversionandcognitiveregulation.Wedidnot
includeanyanalysisonthesegain-onlytrialsbecausethepresentstudyfocusedonmodel-free
comparisonandthegain-onlytrialsarenotdirectlycomparablewiththegain-losstrials.
PleaserefertoFig2forthetimingsofeventsineachtrial.Participantswererequiredto
respondwithina4.5-secondtimewindow;however,theywerenottoldtorespondasfastas
possible.Responsesmadebeyondthetimelimitwerenotrecorded.Iftheparticipantdidnot
respondwithinthetimelimit,theoutcomescreenwouldshowthefeedback“Youweretoo
slow”.Theoutcomeofeachparticipant’sdecisionwasshownafteraperiodofwaiting(7.5–7.8
s).Notethatatimegapwasinsertedbetweenthefinancialdecisionscreenandtheoutcome
screen,aswellasbetweentrials(6.5–6.8s).Thiswassothattheskinconductancelevelcould
returntothebaselinebeforetheonsetofthenextstimulus.
Beforetheexperiment,theparticipantswereclearlyinformedthataftertheycompletedall
88trials,eightofthetrialswouldberandomlyselectedforcalculationofthefinalamountof
paymenttheywouldreceive.Thenetgainorlossfromtheeightselectedtrialswouldbeadded
Table1. Gain-losstrials:Combinationsofpossiblegainsandlossesleadingtodifferentriskratios. Eachgain-loss
combinationwaspresentedtwice,onceafterasexualimageandonceafteraneutralimage.The36combinationscon-
tributedto72gain-losstrials.
PossibleGain
Riskratio 44 48 52 56 60 64
0.25 -11 -12 -13 -14 -15 -16
0.5 -22 -24 -26 -28 -30 -32
0.75 -33 -36 -39 -42 -45 -48
1 -44 -48 -52 -56 -60 -64
1.25 -55 -60 -65 -70 -75 -80
1.5 -66 -72 -78 -84 -90 -96
https://doi.org/10.1371/journal.pone.0195748.t001
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Sexualimageandarousalresponsetogamblingloss
Fig2.Stimuluseventsinasingletrial.
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toorsubtractedfromtheHK$50cashtheyreceivedatthebeginning.Ifthenetamountwas
lessthanzero,theyonlyneededtoreturnalltheHK$50andnoextramoneywouldbe
requested.Accordingtothiscalculationmethod,themaximumpossiblemonetaryrewarda
participantcouldreceivewasHK$586andtheminimumwasHK$0.Attheendoftheexperi-
ment,theparticipantswereaskedthefollowingfourquestionsinaninterview:1)Doyouhave
anyideasaboutthesetwoexperiments?2)Whatdoyouthinkaretheobjectivesoftheseexper-
iments?3)Whatstrategyhaveyouappliedinthefinancialdecision-makingtask?4)Haveyou
everparticipatedinasimilarexperiment?Ifso,pleasedescribetheprocedures.
Results
Behavioralfindings
Asamanipulationchecktoseewhetherparticipantsfoundthesexualimagessexyandtheneu-
tralimagesneutral,participants’responsestothepicturecategorizationtaskwereanalyzed.
Thirty-oneoutofthe34participantsratedover80%ofthesexualimagesassexyandover80%
neutralimagesasneutral.Weanalyzedthebehavioralandphysiologicaldataexcludingthe
threeparticipantswhodidnothaveover80%responsesconsistentwiththeintendedstimulus
manipulations.Thepatternsofresultswereidenticaltotheanalyseswithallparticipants’data
included.Wethereforeincludedallparticipants’datainthestatisticalanalyseswithoutexclu-
sionbasedonresultsofthepicturecategorizationtask.
Theoutcomesofgainsandlosseswerefullyrandomizedacrosssexualandneutralimage
trialsbythestimuluspresentationsoftware.The34participantsgambledin1185trialsoutof
the2445gain-losstrials.Thenumbersofgainandlossoutcomesinsexualandneutralimage
trialswere285(gainsinsexualtrials),317(lossesinsexualtrials),296(gainsinneutraltrials)
and287(lossesinneutraltrials)respectively.Thechi-squarestatisticwas1.39(p=.24),show-
ingnosignificantdifferenceintheproportionsofgainsandlossesinthesexualandneutral
imagetrials.
Theproportionsofgamblingdecisionsforchoiceswithriskratiosof.25,.5,.75,1,1.25and
1.5were.91,.70,.56,.37,.21,and.16respectively(averagingacrossthesexualandneutraltri-
als).Thelowproportions(.56,.37,.21,and.16)ofgamblesintrialswithriskratiosof.75and
higherindicatedlossaversionamongparticipants.Two-wayrepeated-measuresANOVAs
wereconductedtoexaminetheeffectsofimage(sexualvs.neutral)andriskratios(fiveratios
from.25to1.50)ongamblingdecisionandreactiontime.Greenhouse-Geissercorrections
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Sexualimageandarousalresponsetogamblingloss
wereappliedtoeffectswithsignificantresultsofMauchly’sTestofSphericity.Forgambling
decisions,therewasasignificantmaineffectofriskratio(F(2.81,92.68)=61.93,p<.001,par-
tialη2=.65).Pairwisecomparisonsshowedthatparticipantshadsignificantlyfewergambles
inthetrialswithhigherriskratioscomparedtotrialswithlowerriskratios(ps<.001),except
forthecomparisonbetween1.25and1.5riskratio(Fig3).Theeffectofimage(sexualvs.neu-
tral)wasnotsignificant(p=.25),norwastheinteractionbetweenimageandriskratios(p=
.15).ReferringtoFig3,itisapparentthatparticipantsmadesimilarproportionsofdecisions
togambleintrialswithallriskratiosexceptforthehighestriskratio,1.5.Pairedsamplet-tests
(withBonferronicorrections)showedthatthenumberofgamblesdidnotdifferbetweensex-
ualimagetrialsandneutralimagetrialsforallriskratios;thedifferencewasclosetothepoint
ofsignificancefortrialsatthehighestriskratioof1.5(t(33)=2.70,uncorrectedp-value=.011,
correctedp-value=.066,partialη2=.18).
Therewasasignificantmaineffectofriskratioforreactiontime(F(3.10,102.32)=3.75,p=
.013,partialη2=.10).Descriptivestatisticsshowedthatparticipantsrespondedthefastest
(M=1.05s;SD=.043)intrialswiththelowestriskratioof.25,andtheyrespondedtheslowest
intrialswithariskratioof.75(M=1.24s;SD=.070).Noothermaineffectorinteractionwas
significant.
Physiologicalfindings
Physiologicalarousalresponses(intermsofμS/$)totheoutcomeofgamblingweremeasured
bythebaseline-to-peakamplitudedifferenceinthe0.5-sto5-stimewindowfromtheonsetof
thegamblingoutcomescreen.Toexaminetheeffectofsexualstimulionphysiologicalarousal
togamblingoutcome,atwo-wayrepeated-measuresANOVAwasconductedwithimage(sex-
ualvs.neutral)andoutcome(lossesvs.gains)asthefactors(Fig4).Therewasasignificant
maineffectofoutcome:theparticipantshadsignificantlylargerarousaltogamblinglosses
thantogamblinggains(F(1,29)=16.92,p<.001,partialη2=.37).Therewasatrendthatpar-
ticipantshadsmallerarousaltogamblingoutcomeinsexualthaninneutralimagetrials(F(1,
29)=3.69,p=.065,partialη2=.11).Theinteractionbetweenimageandoutcomewassignifi-
cant(F(1,29)=4.21,p=.049,partialη2=.13).Apost-hocpairedsamplest-testshowedthat
participantshadsignificantlysmallerarousaldifferencebetweenlossesandgainsinsexual
thaninneutralimagetrials(t(29)=2.05,p=.049,partialη2=.13).Toexaminewhetherthe
effectfoundwasduetodifferencesintheinitialskinconductancelevelattheonsetofgam-
blingoutcome(thebaseline),apairedsamplet-testwasconducted.Nosignificantdifference
wasfoundbetweensexualandneutralimagetrialsatbaseline(t(29)=.11,p=.915).Theresult
suggestedthatthesmallerarousaldifferencebetweenlossesandgainsinthesexualthaninthe
neutraltrialswasnotduetoanyinitialdifferenceinskinconductancelevelatthebaseline(i.e.
theonsetofreleaseofgamblingoutcome).
Furthermore,linearregressionanalyseswereconductedtoexaminewhethertheSCRs(in
termsofμS/$)tolossesrelativetogainspredictedparticipants’proportionofgamblingdeci-
sionsmadeinneutralandsexualimagetrials.TheSCRstolossesrelativetogainswerecalcu-
latedbySCRstolossesdividedbySCRstogains.TheSCRstolossesrelativetogains
significantlypredictedtheproportionofgamblingdecisionsintheneutralimagetrials(stan-
dardizedcoefficientsβ=-.50,t=-3.07,p=.005;AdjustedR2=.23)butnotinthesexualimage
trials(standardizedcoefficientsβ=-.13,t=-.70,p=.49;AdjustedR2=-.018).
Finally,toinvestigatehabituation,wesplitthetrialsintofirsthalfandsecondhalftocheck
whethertherewasanychangeinparticipants’behavioraldecisionsandSCRsovertime.For
thebehavioraldecisions,therewasaninteractionbetweenimage(sexualvs.neutral)andhalf
(firstvs.second)(F(1,33)=5.78,p=.022,partialη2=.15).Thereweresignificantlymore
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Sexualimageandarousalresponsetogamblingloss
Fig3.Proportionsofgamblingdecisionsmadeintrialswithdifferentriskratios(.25–1.5)undersexualandneutralconditions.
https://doi.org/10.1371/journal.pone.0195748.g003
gamblesinthesexual(M=.50)thanintheneutral(M=.45)imagetrialsforthesecondhalf(F
(1,33)=7.56,p=.010,partialη2=.19)butnotforthefirsthalfoftrials(p=.37).Thephysio-
logicaldatashowedthattherewasnodifferenceinSCRtooutcomeofgamblingbetweenthe
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Sexualimageandarousalresponsetogamblingloss
Fig4.Skinconductanceresponses(inmicro-siemenperdollar)tooutcomeofgamblinglossesorgainsundersexualorneutralimagetrials.
https://doi.org/10.1371/journal.pone.0195748.g004
firstandsecondhalfoftrials(p=.65),indicatingnohabituationofphysiologicalarousal
responsesovertime.Therewasnointeractionbetweenthefactorsofimageandhalf(p=.65).
Therewashoweveramaineffectofimage:theSCRstogamblingoutcomesweresignificantly
lowerinsexualimagetrialsthaninneutralimagetrialsinboththefirstandsecondhalfofthe
trials(F(1,29)=4.90,p=.035,partialη2=.15).
Finally,theSCRstime-lockedtotheonsetsofsexualandneutralimageswithinthetime
windowof0.5–5swereanalyzed.Nosignificantdifferencewasfoundbetweensexualandneu-
tralimagetrials.
Discussion
Consistentwithpriorstudies[10,13,15],participantsinourstudyshowedlossaversion
behaviorally:ourparticipantshadlowproportionsofgamblesatthetrialswithriskratiosof
.75andhigher,indicatinganoverweightingoflossesrelativetogains.Theslowestreactionin
trialswithariskratioof.75indicatedlargermentalconflictsexperiencedbyparticipantsin
decidingwhethertogambleornot[25],comparedtotrialswithotherriskratios.Physiologi-
cally,participants’SCRsinresponsetogamblinglossesweresignificantlyhigherthanthoseto
gamblinggains.Theincreasedarousaltolossesrelativetogainisconsistentwithpreviousfind-
ings(e.g.[17])suggestingthatpeoplehaveincreasedcognitiveinvestmentwithlossescom-
paredtogains,resultinginheightenedattentionandarousalresponses.Importantly,wefound
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Sexualimageandarousalresponsetogamblingloss
thatsexualstimulireducedthearousaldifferencebetweenlossesandgains.Inourexperimen-
taldesign,thetimegapsbetweenthesexual/neutralimagesandthegamblingoutcomeswere
settobelong(about10–12seconds)suchthattheSCRstriggeredbytheimageshadreturned
tobaselinebeforethegamblingoutcomeswerereleasedtotheparticipants.Thiswascon-
firmedbythestatisticalresultshowingthattheskinconductancelevelsattheonsetofthegam-
blingoutcomeweresimilarinsexualandneutralimagetrials.Therefore,thesmaller
differencesinSCRstogamblinglossesandgainsinsexualthaninneutralimagetrialswere
notduetoanybaselinedifferencesbecauseoftheimagespresented.Analternativepossibility
isthatthepositiveemotionstriggeredbysexualstimuli,whichwereassociatedwithreleaseof
endogenousopioids[26],ledtoaeuphoricstateamongtheparticipants,whichmayinturn
bufferagainstthenegativeemotionalarousaltriggeredbygamblinglosses.Anotherpossibility
isthatsexualimagescompetewithgamblinglossesforattentionandarousalresponses.The
presenceofasexualimagemighthavecausedthelossestobelesssalientforattention.Also,a
previousexcitationofthesympatheticnervoussystembyasexualimage(apositivestimulus)
maycauseahigherthresholdforsubsequentexcitationbyagamblingloss(anegativestimu-
lus),causingpeopletobecomearousedlesseasily.Theadditionalsourceofattentionand
arousalcompetitionbetweensexualimageandgamblingoutcomewasabsentinneutraltrials.
Furtherstudiesareneededtoexaminethispossibility.
Anotherimportantobservationdemonstratingtheimpactofsexualstimulusondecision-
makingwasthatparticipants’physiologicalresponsestolossesrelativetogainspredictedgam-
blingdecisionsonlyforneutralimagebutnotforsexualimagetrials.Thepatternofresults
foundinneutralimagetrialssuggestedthatphysiologicalarousalguidesdecision-making
behavior[30,31],whichiscongruentwiththeclassicsomaticmarkerhypothesis[32].Interest-
ingly,inthesexualimagetrials,physiologicalresponsestomonetarylossesrelativetogainsdid
notpredictbehaviors,suggestingadecouplingbetweenphysiologicalstatesandbehaviors.
Theresultscouldbeexplainedbytheattentionalmodelofloss[18]:sexualstimulimayoppose
theattentionenhancementeffectofgamblinglosses,leadingtodistractionfromthetask
requirements[19,20]anddeviationfromthedecisionalgorithmbasedonoutcomes.
Intermsofbehavioralfindings,however,ourdatadidnotsupportthefirsthypothesisthat
participantswouldhaveahigherproportionofgamblingdecisionsinthesexualthaninthe
neutralimagetrialsforallriskratios.Theeffectofsexualstimuliongamblingdecisionswas
closetosignificance(aftercorrectionsformultiplecomparisons)onlyfortheriskiesttrials
(whentheriskratio=1.5).Ourhypothesiswasbasedontheevidencethatsexualstimulation
facilitatesdopaminetransmissionandenhancesactivityinthenucleusaccumbens(NAcc)[8,
33],whichisthoughttoreflectreward“wanting”.Additionally,greaterNAccactivityisrelated
toastrongersaliencyofincentives[34]suchasmoney.Ourresultsmayimplythattheactiva-
tionoftherewardsystembysexualstimuliwasnotsufficienttocounteracttheeffectofloss
aversioninlow-riskgamblingtrials.However,inhigh-riskgambling(suchaswhenrisk-
ratio=1.5),participants’decisionmaybemoresusceptibletotheeffectofsexualstimuli,
becauseoftheleveloftestosterone,whichisfoundtoincreaseunderconditionsofsexually
arousal[3].Testosteronelevelispositivelyassociatedwithrisk-takingbehaviorsinfinancial
decision-making[35–38].Ourfindingattrialswitharisk-ratioof1.5wasonlyclosetosignifi-
canceandfurtherstudymayrequirealargersampleandtrialswithawiderrangeofriskratios
(upto2)toexaminetheeffectofsexualstimuliinhigh-riskgambling.
Finally,theSCRstime-lockedtoonsetsofsexualandneutralimageswerenotsignificantly
different.Webelievethatthiswasbecausethefinancialdecisiontaskwaspresentedsoonafter
theimages,whichwaswithinthetimewindow(0.5–5s)inwhichtheSCRstoimageswere
measured(Fig2).Thearousaltriggeredbythefinancialdecisiontaskoverlappedwiththe
arousaltriggeredbythesexualimages,therebyreducingthedifferencesbetweentrialswith
PLOSONE|https://doi.org/10.1371/journal.pone.0195748 April12,2018 10/14