I got it! Transient cardiovascular response to the perception of humor

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Reference

I got it! Transient cardiovascular response to the perception of humor

LACKNER, Helmut K., et al.

Abstract

The aim of the present study was to examine the transient cardiovascular response to the perception of humor, that is, the impact of the cognitive process of insight as well as the modulation of the response by the affective appraisal of the humor. To this end transient heart rate, stroke volume, cardiac output, and blood pressure responses were obtained in the immediate context of detecting the punch line in cartoons. Fine-grained analysis of the transient behavior of cardiovascular variables during viewing the cartoons was contrasted to non-humorous cartoon-like pictures. The detection of a punch line was accompanied by relative heart rate acceleration in conjunction with increased cardiac output, which was more pronounced the more amusing the cartoons were perceived. These results provide first evidence of the usefulness of cardiovascular variables for detecting the moment of insight and the quantification of the size of the emotional response accompanying it.

LACKNER, Helmut K., et al . I got it! Transient cardiovascular response to the perception of humor. Biological Psychology , 2013, vol. 93, no. 1, p. 33-40

DOI : 10.1016/j.biopsycho.2013.01.014

Available at:

http://archive-ouverte.unige.ch/unige:98013

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ContentslistsavailableatSciVerseScienceDirect

Biological Psychology

j o u r n al hom ep a g e :w w w . e l s e v i e r . c o m / l o c a t e / b i o p s y c h o

I got it! Transient cardiovascular response to the perception of humor

Helmut K. Lackner

, Elisabeth M. Weiss

, Günter Schulter

, Helmut Hinghofer-Szalkay

, Andrea C. Samson

, Ilona Papousek

aInstituteofPhysiology,MedicalUniversityofGraz,Austria

bInstituteofMedicalEngineering,GrazUniversityofTechnology,Austria

cDepartmentofPsychology,BiologicalPsychologyUnit,KarlFranzensUniversityofGraz,Austria

dDepartmentofPsychology,StanfordUniversity,CA,USA

a r t i c l e i n f o

Articlehistory:

Received20August2012 Accepted21January2013 Available online 1 February 2013

Keywords:

Contrastedtransientresponse Momentofinsight

Positiveemotion Amusement Cartoons

Psychophysiologyofhumor

a b s t r a c t

Theaimofthepresentstudywastoexaminethetransientcardiovascularresponsetotheperceptionof humor,thatis,theimpactofthecognitiveprocessofinsightaswellasthemodulationoftheresponseby theaffectiveappraisalofthehumor.Tothisendtransientheartrate,strokevolume,cardiacoutput,and bloodpressureresponseswereobtainedintheimmediatecontextofdetectingthepunchlineincartoons.

Fine-grainedanalysisofthetransientbehaviorofcardiovascularvariablesduringviewingthecartoons wascontrastedtonon-humorouscartoon-likepictures.Thedetectionofapunchlinewasaccompaniedby relativeheartrateaccelerationinconjunctionwithincreasedcardiacoutput,whichwasmorepronounced themoreamusingthecartoonswereperceived.Theseresultsprovidefirstevidenceoftheusefulnessof cardiovascularvariablesfordetectingthemomentofinsightandthequantificationofthesizeofthe emotionalresponseaccompanyingit.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

Inordertoperceivehumoritisnecessarytodetectaconflict betweentwoinitially incongruentideas,concepts,or situations thatarebroughttogetherinasurprisingorunexpectedmanner.

Thesenseofhavingunderstoodthejoke(themomentofinsight orofhaving“gottenthepoint”)ariseswhenthesurprisingincon- gruitycanberesolvedbyconsiderationofinformationavailable elsewhereinthejokeorcartoon(Suls,1972;Ruch,2001;Ruchand Hehl,2007).Thisprocess,whichresemblesproblemsolving,isfol- lowedbyapositiveemotionalresponse(i.e.,amusement).Thatis,in theimmediatecontextoftheperceptionofhumortwoprocesses arehappening,thecognitiveprocessofinsightandtheaffective experiencefollowingit.Althoughthereisagreatamountoflitera- tureoncardiovascularcontrolinthecontextofcognitiveprocessing andaffectivestates,toourknowledge,wereportforthefirsttime onthedetailedtransientcardiovascularresponsetotheperception ofhumor.

The study of cardiovascular responses to the perception of humorappearstoberelevantparticularlyfortworeasons:first, theyareaninstancefortheprocessof“gettingit”thatalsooccurs

∗Correspondingauthorat:MedicalUniversityofGraz,InstituteofPhysiology, Harrachgasse21/5,A-8010Graz,Austria.Tel.:+433163807626.

E-mailaddress:helmut.lackner@pro.medunigraz.at(H.K.Lackner).

1 Theseauthorscontributedequallytothepaper(design,analysis,manuscript).

during problemsolving or creative thinking. Theperception of humorinvolvesviewingwhatisoriginallyperceivedinone(often serious)sensefromadifferentperspective,inordertodetectthe incongruitybetweenaconcept(orexpectation)andtheobserved objectorsituation(Suls,1972;Ruch,2001).Thatis,itrequiressen- sitivitytodetectnon-prepotentsolutioncandidatesandcognitive switchingfrommorecommonideasorconceptstoonesthatare less apparent(Weiss et al.,in press).Theseprocesses resemble thoseoccurringinthecontextofinsightduringproblemsolving orcreativethinkingwhenindividualsinitiallyfocusonadominant butincorrectassociationandneedtoovercomethisimpasseand switchtothecorrectsolvingstrategytobeabletoreachasudden understandingofthesolution(Bowdenetal.,2005).Ifacharac- teristictransientcardiovascularresponsemaybeidentified,other studiesmay,forinstance,useitforthelocationoftheindividual momentofinsight,inordertouseitasaprecisemarkerforother researchmethodssuchaselectrophysiologicalormagneticreso- nanceimaging,forquantifyingthenumberofnovelideasduring creativethinking,orasanobjectiveindicatorforthetimeittakes participantstofindasolution.

Secondly,thecomprehensionandappreciationofhumoraddi- tionally requires the integration of these cognitive processes withpositiveaffectiveresponsiveness(Ruch,2001;Shammiand Stuss,2003).Bluntedaffectiveresponsivityingeneralandpositive responsivenessinparticularhasbeensuggestedtoberelevantin psychopathologyaswellas,forinstance,tothepredictionofill- nessoutcomesinthecontextofaffectivedisturbances(e.g.,Bylsma 0301-0511/$–seefrontmatter© 2013 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.biopsycho.2013.01.014

34 H.K.Lackneretal./BiologicalPsychology93 (2013) 33–40

etal.,2008;ChidaandHamer,2008;MathewsandBarch,2010;

Rottenbergetal.,2002).AstudybyRottenbergetal.(2002)sug- gested that the responsivity to positive and negative affective stimulimayhavedifferentfunctionalsignificanceindepression, becauselowerresponsivitytothenegativeaffectivestimuliwas predominantlyrelatedtoconcurrentimpairment,whereaslower behavioralandheartrateresponsivitytopositiveaffectivestimuli specificallypredictedpoorrecoveryfromdepression. Therefore, cardiacresponsestoamusingstimulimayhaveparticularpredic- tivevalueinthiscontext,comparedtobehavioralmeasuresand responsestonegativestimuli.Adifferentiatedanalysisofindividual differencesintransientcardiovascularprocessesintheimmedi- atecontextoftheperceptionofhumormayfurtherimprovesuch predictions.

Consequently,themainquestionsinthepresentresearchwere (a)ifaclearcardiovascularresponsemayoccurintheimmediate contextofdetectingthepunchlineofajoke;(b)iftheimmedi- atetransientcardiovascularresponsetotheperceptionofhumor maybemodulatedbytheaffectiveappraisalofthehumor(i.e.,by theextenttowhichitisperceivedasamusing);(c)tofindaway toquantifyanindividual’simmediateresponsetotheperception ofhumor,inordertoprovideaproperindicatorthatcanbeused instudiesconcernedwithindividualdifferencesintheresponse, forinstance,inconnectionwithpersonalitytraitsorpsychiatric diagnoses.

Numerousstudiesshowedthathighercorticalprocessessuchas variousstagesofinformationprocessingarereflectedintransient changesofcardiacactivity(e.g.Kunieckietal.,2003;Pfurtscheller etal.,2007).Inadditiontolocalregulatorymechanismsoftheheart andbloodvesselsthecardiovascularcontrolinvolvesinputsofthe centralnervoussystemontheeffectorcomponentsofthecardio- vascularsystem(Verberneand Owens,1998).In particular,the genesisofshort-term,beattobeatvariationsinheartratehasbeen describedtobeinfluencedbyautonomicandcentralnervousreg- ulations(TaskForce,1996).Accordingly,avoluminousliterature existsontonicandphasicchangesofheartrateastheyrelateto cognitiveandbehavioralprocesses(Berntsonetal.,1992).Sincethe seminalworkofGrahamandClifton(1966)onthedifferentiation oforientinganddefensereflexes,ithasbeenrepeatedlyreported thatstimulusprocessingandchangesofaffectivestateshavean impactoncardiovascularvariables,particularlytheheartrate(e.g.

Bradleyetal.,2001;BradleyandLang,2001;Codispotietal.,2001;

Lackneretal.,2010; Langet al.,1993).Transientcardiovascular responseshavebeenshowntobeapowerfultoolinthestudyof variousaspectsofcognitiveprocessing(Barry,2006;Kaiseretal., 1999,2001).Arecentstudyshowedsimilaritiesbetweentransient heartrateresponsesandevent-relatedresponsesintheelectroen- cephalogram during cognitive processing (Lawrence and Barry, 2010).Toourknowledge,specificcardiovascularconcomitantsof thedetectionofhumorhavenotbeenreportedyet.Nevertheless, onthebasisoftheexistingliterature,severalexpectationsmaybe derived.

Theimmediate heart rateresponse to thepresentation of a stimulus has been described as the sum of two independent responsecomponents:thefirstcomponentisreflectedinaheart ratedecelerationlastingapproximately2.5sandhasbeenidenti- fiedasstimulusregistrationperse;thesecondcomponent,which isobservableonlyifthestimulusresultsinprocessingdemands, dependsonthelevelofcomplexityofthementalprocesstriggered bythestimulus(Barry,1984,1996).Therefore,aninitialheartrate decelerationcanbeexpectedimmediatelyafterthepresentation ofacartoon.

Thecardiovascularresponsetotheperceptionofhumorshould reflect the effect of the process of insight, which is linked to rewardand pleasure by itself(Shaw, 1999)plus theadditional effectofamusement,whichisastrongapproach-relatedemotion

involvinghigharousal(ChristieandFriedman,2004).Inaddition, thereisevidenceshowingthattransientactivationofthebehav- ioral approach system(produced, e.g., by signals of impending rewardoractualpleasure)isaccompaniedbytransientheartrate acceleration,whichcomesoutespeciallyclearlywhencontrasting ittotheresponsetoneutralstimulation(Bradleyetal.,2001;Fowles etal.,1982).Further,individualsratingstimuliasmorepleasant showeda morepronouncedheart rateacceleration(Aupée and Jönsson,2008).Therefore,thedetectionofthepunchlineshouldbe accompaniedbyatransientrelativeheartrateaccelerationwhich maydependonthelevelofperceivedamusement.

Heartrate,strokevolume,cardiacoutput,andbloodpressure weremeasuredcontinuouslywhileparticipantswereviewingnon- verbalhumorouscartoons,andtheirtimecoursewasanalyzedin detail.Afterviewingeachcartoon,theparticipantswererequiredto clickabuttonassoonastheyhadunderstoodthepunchlineorwere surethattheydidnotunderstanditandratedthecartoonsforfun- niness.Inordertoanalyzethespecificeffectsoftheperceptionof humor,cardiovascularresponsestothecartoonswerecontrastedto theresponsesduringtheprocessingofnon-humorouscartoon-like controlpictures.Particularfocuswasattachedtothetimeimme- diately beforethe participantsindicatedhavingunderstoodthe punchline,assumingthatitrepresentsthemomentofinsight.

2. Method 2.1. Participants

Thestudywascarriedoutinhealthy,non-medicated(exceptfororalcontra- ceptives)participants.Fifty-sixparticipants(28men,28women)aged18–53years (M=23.9,SD=6.3)completedtheexperiment.Theywererecruitedbyflyersposted ontheuniversitycampus.Participantswererequestedtorefrainfromsmoking, alcohol,aswellascoffeeandotherstimulatingbeveragesfor12hpriortotheirlab appointment,andtocometothesessionwellrested.Thestudywasperformedin accordancewiththe1964DeclarationofHelsinkiandwasapprovedbythelocal ethicscommittee.Participantsgavetheirinformedconsenttoparticipateinthe study.

2.2. Stimulusmaterial

Thestimulusmaterialconsistedofthreetypesofcartoons(“Cartoon”)aswell asnon-humorouscartoon-likepictures(“Control”).Thesecartoon-likepicturescon- tainedanincongruitywhichcouldnotberesolvedmeaningfully,thatis,Controldid notcontainapunchline.Allpictures(CartoonandControl)werelowinaggressive, violent,andsexualcontentandhadbeenusedinpreviousstudies(e.g.,Samsonetal., 2008,2012;SamsonandHegenloh,2010).Allpictures(funnyandnon-funnyones) wereline-drawings.(PleaseseeSamsonetal.,2008,2012forexamplesofhumorous cartoonsandnon-humorouspictures.)Sincethedifferenttypesofcartoonswerenot relevanttotheresearchquestionaddressedinthepresentstudy,thethreetypesof cartoonswerenotanalyzedseparately.

2.3. Physiologicalrecording

Continuous hemodynamic monitoring of blood pressure (BP), heart rate (HR)and thoracic impedance wascarried out with theTaskForce^® Monitor (TFM^®; CNSystems, Graz, Austria). HR was recorded by 3-lead electrocar- diography (ECG; sampling rate=1kHz, fcut-off=0.08–150Hz) using CNSystems ECG-electrodesplacedatthethoracicregion.ContinuousBP(samplingrate=100Hz, BPrange=50–250mmHg,±5mmHg)wasderivedfromthefingerusingarefinedver- sionofthevascularunloadingtechniqueandcorrectedtoabsolutevalueswith oscillometricBPmeasurementonthecontralateralupperarm.Themethodisbased onconcentricallyinterlockingcontrolloopsforcorrectlong-termtracingoffinger BPanddelivers,incontrasttointermittentsetpointre-adjustmentsoftheconven- tionalvascularunloadingtechnique,BPwithoutinterruptions(Fortinetal.,2006a).

Forthoracicimpedancemeasurement,threeCNSystemsshortbandelectrodes(two electrodebandssetatapredefineddistanceontoacommonadhesivemedium;

samplingrate=500Hz,Ieff<400␮A,f=45kHz,Z0,range=10–75,dZ/dt=±10/s) wereplacedontotheparticipant:oneplacedatthenapeoftheneckclosetothe glottis,twoothersplacedonthethoraxclosetothexiphoid(seeFortinetal.,2006b).

2.4. Procedure

Participantswereseatedinanacousticallyshieldedexaminationroom,and electrodeswereattached.Subsequentlyparticipantsreceivedinstructionsforthe taskandweregivenanexampleofthecartoons andtherequiredresponses.

Fig.1.Transientresponsesduringtheprocessingofcartoons:heartrate(HR),strokevolume(SV),andcardiacoutput(CO).RelativechangesofHR,SV,andCOareshown asmean±standarderror,averagedacrossparticipants.Datain0.5stimeintervalsbeginning0.5sbeforeandending6safterpictureonsetwereselected.Cardiovascular changesfollowingthepresentationofapicturewerecalculatedrelativetothemeanofthe0.5sframeprecedingthepictureonset.Therelativechangeswereaveragedacross alltrials,separatelyforCartoon(lightgray)andControl(black).Theresponsesincartoontrialswerecontrastedtothoseincontroltrialsbysubtractingthescoresforcontrol trialsfromthescoresforcartoontrials.

Questionnairesthatarenotrelevantfortheresearchquestionswereadministered followedbyarestingperiodof10min.Subsequently,thehumorparadigmwas applied.Atotalof96pictureswerepresented,dividedintothreeblocksof32 pictureseach.Withineachblock,thepictures(24cartoonsand8non-humorous pictures)werepresentedinrandomorder.A10minbreakwasprovidedbetween theblocks.Theorderofblockswascounterbalanced.Theexperimentwasrunusing aMatlab(TheMathWorksInc.)scriptdesignedforthisstudy.Eachpicturewaspre- sentedfor6s,alongwithtwobuttonsatthebottomofthescreen(“notunderstood”,

“understood”).Participantswereinstructedtoclicktheappropriatebuttonwiththe computermouseassoonastheyhadunderstoodthepunchlineorweresurethat theydidnotunderstandit.Afterpresentationofeachpicture,ascaleappearedfor4s onwhichtheparticipantsratedviamouseclickthefunninessofeachcartoon,from 1(notfunny)to6(veryfunny).Theexperimenterremainedoutsidetheexamina- tionroomduringthewholeexperiment;theparticipantsweremonitoredthrough aone-waywindowandanintercom.

2.5. Dataextractionandanalysis

Dataoftrialsinwhichparticipantsfailedtoindicatewhetherornottheyhad understoodthepunchlinewereexcludedfromfurtheranalysis.Onaverage,M=65.6 (SD=4.9)trialsforCartoon(91%)andM=20.5(SD=3.1)trialsforControl(85%)were valid.94percentofthepunchlineswereratedasunderstood.

Toobtainheartrate,bloodpressure,strokevolumeandcardiacoutputtime serieswithequidistanttimesteps,beat-to-beatvalueswerere-sampledwith4Hz usingpiecewisecubicsplineinterpolationafterartifactcorrection.Singleartifacts werereplacedbyinterpolation.Thedatainthetimewindowbeginning0.5sbefore pictureonsetandending6safterpictureonsetwereanalyzed.Cardiovascular changesfollowingthepresentationofthepicturewerecalculatedrelativetothe meanofthe0.5sframeprecedingthepictureonset.Subsequently,foreachpartici- pant,therelativechangesofcardiovascularvariableswereaveragedacrossalltrials ofallblocksforCartoonandControl,respectively.

Forthestatisticalanalysesofthetimecourseofthecardiacresponseduring theprocessingofcartoons,weextractedtherelativecardiovascularvaluesforevery 0.5swithintheselectedtimewindowof6.5s,resultingin13timepointsforCartoon andControl,respectively.

Toanalyzetheimmediateresponsestothedetectionofthepunchline,relative cardiovascularchangesoccurringduringthe0.5simmediatelyprecedingthecom- prehensionratingcomparedtothemeanofthe0.5sprecedingthegivenpicture onsetwerecalculated.Thiswasdoneforeachparticipantbasedontheparticipant’s averagedresponsetimetothecomprehensionratingincartoonandcontroltrials, respectively.Inordertopreciselylocatethetimepointasamplingrateof8Hzwas usedfortherelativecardiovascularvalues.Inaddition,duetopossibledifferences intheresponsetimesincartoonandcontroltrials,datafromthesame0.5stime frameasselectedforcartoontrialswereusedtocalculatetherespectivescoresfor controltrials.

Inaddition,weanalyzedtheinter-individualandintra-individualcorrelations betweenthelevelofperceivedamusementandtheimmediatecardiovascular responsetotheperceptionofhumor.Inthefirststep,foreachofthe56participants cardiovascularchangesineachofthe72cartoontrialswerecalculatedforthe0.5s

frameimmediatelyprecedingtheparticipant’sresponseindicatinghavingunder- stoodthepunchlinerelativetothemeanofthe0.5sframeprecedingthecartoon onset.Thiswasdoneusingasamplingrateof8Hz.Inthesecondstep,cardiovas- cularchangesrelativetotherespectivemeanofControlwerecalculatedbasedon eachparticipant’saveragedresponsetimetothecomprehensionratinginCartoon.

Inthethirdstep,thecoefficientsofapolynomialP(X)(X...perceivedamusement) offirstorder,thatfitsthedataY(Y...relativecardiovascularchanges)bestina least-squaressense,werecalculated(a)foreachcartoon,toanalyzetheassocia- tionsofinter-individualdifferencesintheelicitedamusementtothecardiovascular response;(b)foreachparticipant,toanalyzetheassociationofintra-individualdif- ferencesintheperceptionofdifferentcartoonstothecardiovascularresponse.Inthe fourthstep,theestimatedcardiovascularresponseforeachamusementlevelwas calculatedbasedonthepolynomialcoefficientsfor(a)eachcartoonand(b)each participant.Thisway,for(a)eachcartoonand(b)eachparticipantthebestesti- mationinaleast-squaresenseforeachamusementlevelwasobtainedforfurther statisticalanalysis.Thisapproachwaschosen,becausenotallparticipantsexploited thefullrangeoftheratinganditseemedthemostreliablewaytoestimateallvalues overthefullrange.Thus,itmadeitpossibletoanalyzethescoresforallparticipants inthesameway.

Therespiratorysignalwasderivedfromtherawdataofthoracicimpedance (Ernstetal.,1999;Houtveenetal.,2006).Inadditiontothebreathingrate(cycles perminute),theproportionofregularbreathingcycleswerecomputed.

2.6. Statisticalanalysis

Dataarepresentedasmean±standarddeviation,relativetothebaselinepre- ceding eachpictureonset.Repeatedmeasuresanalysesofvariance(ANOVAs) wereusedtoexaminetimecourseresponsesacrosstrialsusingCondition(Car- toon,Control)andTime(13timepoints)aswithin-subjectsfactors.Ifnecessary, Greenhouse-Geisser correctionswere usedto adjustfor non-sphericityofthe variance–covariancematrices.

ToevaluatewhethertherelativecardiovascularresponsesdifferbetweenCar- toonandControlintheimmediatecontextofdetectingthepunchline,thatis,in closeproximitytotheperceptionofhumor,onewayANOVAswereused.Thiswas done(a)fortherelativecardiovascularchangescalculatedforeachparticipantbased ontheparticipant’saveragedresponsetimetothecomprehensionratingincartoon andcontroltrials,and(b)duetopossibledifferencesintheresponsetimesforthe relativecardiovascularchangesincartoonandcontroltrialsforeachparticipant calculatedbasedontheparticipant’saveragedresponsetimetothecomprehension ratinginCartoon,asdescribedinSection2.5.

Forthosecardiovascularvariablesforwhichaneffectofthedetectionofthe humorcouldbedemonstrated(i.e.,asignificantdifferencebetweenCartoonand Controlcouldbeobserved),one-wayANOVAswereusedtoevaluatetheeffects ofinter-individualdifferencesintheelicitedamusementonthecardiovascular responsesforeachcartoonbasedontheregression-basedvalues,asdescribedin Section2.5.Toevaluatetheeffectsofintra-individualdifferencesintheelicited amusementonthecardiovascularresponses,equivalentonewayANOVAswere used.

36 H.K.Lackneretal./BiologicalPsychology93 (2013) 33–40

Fig.2. Transientresponsesduringtheprocessingofcartoons:systolic,diastolicandmeanarterialbloodpressure(SBP,DBP,andMAP).RelativechangesofSBP,DBP,and MAPareshownasmean±standarderror,averagedacrossparticipants.Datain0.5stimeintervalsbeginning0.5sbeforeandending6safterpictureonsetwereselected.

Cardiovascularchangesfollowingthepresentationofapicturewerecalculatedrelativetothemeanofthe0.5sframeprecedingthepictureonset.Therelativechangeswere averagedacrossalltrials,separatelyforCartoon(lightgray)andControl(black).Theresponsesincartoontrialswerecontrastedtothoseincontroltrialsbysubtractingthe scoresforcontroltrialsfromthescoresforcartoontrials.

Atwo-tailedsignificancelevelof˛=.05wasusedforallanalyses.Bonferroni correctionformultiplecomparisonsyieldedcriticalp-valuesofp<.016toindicate statisticalsignificanceintheanalysisofHR,SV,andCOaswellasbloodpressure variables,respectively.Estimatesofeffectsizearereportedusingpartialeta-squared (²_p),whichgivestheproportionofvarianceafactororinteractionexplainsofthe overall(effect+error)variance.

3. Results

The participantsindicated having understood or having not understoodthepunchlineM=3.3s(SD=0.5s)afterpictureonsetin cartoontrialsandM=3.8s(SD=0.5s)afterpictureonsetincontrol trials(F(1,55)=73.9,p<.001,²_p=.57).Thefunninessofthepicture wasratedM=3.5,SD=0.7(Cartoon)andM=1.8,SD=0.5(Control) aftertheonsetoftheratingscale(F(1,55)=574.4,p<.001,²_p=.91).

3.1. Timecourseofthecardiacresponseduringtheprocessingof cartoons

Heartrate,strokevolume,andcardiacoutput.Themeanresponses in the Cartoon and Control conditions as well as the differ- encebetweenthetwoconditionsforHR,SV,andCOareshown in Fig. 1. The ANOVAs yielded a significant main effect of Time for all variables (HR, F(12,660)=127.9, ε=0.18, p<.001, ²_p=.70,SV,F(12,660)=58.8, ε=0.16,p<.001,²_p=.52,and CO, F(12,660)=97.6,ε=0.18,p<.001,²_p=.64).ThemaineffectofCon- ditionwassignificantforHR(F(1,55)=10.4,p<.01,²_p=.16)and CO (F(1,55)=9.2, p<.01, ²_p=.14),but not for SV (F(1,55)=1.8, p=.19,²_p=.03).TheinteractionCondition×Time,indicatingadif- ferent course of the response in cartoon versus control trials, wassignificantfor heart rate(F(12,660)=10.3, ε=0.28, p<.001, ²_p=.16), SV (F(12,660)=6.6, ε=0.13, p<.01, ²_p=.11), and for CO(F(12,660)=5.2,ε=0.31,p<.01,²_p=.09).Bonferronicorrected post hoc tests indicated that significant differences between cartoon and control trials did only occur from 2.5s (HR; SV:

4.5s,CO:2.5s),afterthebeginning ofthetrialonwards.Before that, theresponses to cartoon and control trials did not differ significantly.

Bloodpressurevariables.Theaveraged responsesfortheCar- toon and Control conditions as well as thedifference between

the two conditions for blood pressure variables are shown in Fig. 2. The ANOVAs yielded a significant main effect of Time for all variables (SBP, F(12,660)=39.9, ε=0.16, p<.001, ²_p= .42, MAP, F(12,660)=39.2, ε=0.13, p<.001, ²_p=.42, and DBP, F(12,660)=63.3, ε=0.13, p<.001, ²_p=.54). The main effect of ConditionwassignificantforDBP (F(1,55)=7.4, p<.01, ²_p=.12) but not for SBP (F(1,55)=0.01, p=94) and MAP (F(1,55)=2.0, p=.17).ThemostrelevanteffectCondition×Timewassignificant forDBP(F(12,660)=5.3,ε=0.17,p<.01,²_p=.09)butnotforSBP (F(12,660)=0.3,ε=0.14,p=.69)andMAP(F(12,660)=3.2,ε=0.12, p=.06).

3.2. Immediateresponsetothedetectionofthepunchline

Heart rate, stroke volume, andcardiac output. The decline of HR (Cartoon: M=−5.1bpm, SD=2.8bpm;Control: M=−6.0bpm, SD=2.7bpm) and CO (Cartoon: M=−0.41l/min, SD=0.25l/min;

Control:M=−0.47l/min,SD=0.23l/min)inthetimeframeimmedi- atelyprecedingthemouse-clickindicating(non-)comprehension ofthepunchlinewassignificantlysmallerincartoontrialscom- paredtocontroltrials–indicatingarelativelyhigherHRandCO incartoonthanincontroltrials(F(1,55)=15.1,p<.001,²_p=.22, F(1,55)=9.9,p<.005,²_p=.15,respectively).Nosignificantdiffer- encewasobservedforSV(F(1,55)=5.9,p=.02).

Theanalysis ofthe responseusing thesame time framefor controltrialsasforcartoontrialsconfirmedtheseobservations.

The decline of HR (Cartoon: M=−5.1bpm, SD=2.8bpm; Con- trol:M=−5.7bpm,SD=2.6bpm)andCO(Cartoon:M=−0.41l/min, SD=0.25l/min; Control: M=−0.47l/min, SD=0.22l/min) was significantly smaller in cartoon trials compared to control tri- als (F(1,55)=8.5, p<.005, ²_p=.13, F(1,55)=7.6, p<.01, ²_p= .12, respectively). Again, no difference was observed for SV (F(1,55)=0.8,p=.38,²_p=.01).

Blood pressure variables. The DBP responses differed between cartoon and control trials (Cartoon: M=−0.4mmHg, SD=1.1mmHg; Control: M=−1.0mmHg, SD=1.6mmHg;

F(1,55)=13.4, p<.005, ²_p=.20). No differences in SBP (F(1,55)=0.2, p=.67, ²_p=.00) and MAP ((F(1,55)=5.7, p=.02, ²_p=.09)wereobserved.

However, using the same time frame for control trials as for cartoon trials, no difference was observed for DBP (Car- toon: M=−0.4mmHg, SD=1.1mmHg; Control: M=−0.7mmHg, SD=1.4mmHg,F(1,55)=4.1,p=.05,²_p=.07).Therefore,theblood pressureeffectcannotbesecuredagainstthepotentialimpactof thedifferentanswertimesinCartoonandControl.Nodifferences wereobservedforSBPandMAP.

3.3. Effectsofthelevelofperceivedamusement

ThefollowinganalyseswereperformedforHRandCO,which showedcleareffectsoftheperceptionofthehumorinthecartoons inthepreviousanalyses.

Inter-individualdifferences.The ANOVAs yieldeda significant effectofperceivedamusementforHR(F(5,355)=12.5,p<.001,²_p= .15)andCO(F(5,355)=7.9, p<.001,²_p=.10).Thelinearregres- sionshowedonaverageanincreaseofM=0.3bpm,SD=0.7bpm (HR)andM=0.02l/min,SD=0.06l/min(CO)peramusementlevel increase (see Fig. 3). The analysis of the relative cardiovascu- larresponsesbasedonthesametimeframeforcontroltrialsas forcartoontrialsconfirmedtheseobservations(HR,F(5,355)=7.7, p<.001,²_p=.10); CO(F(5,355)=5.4, p<.001, ²_p=.07).Thelin- ear regression showed on average an increase of M=0.2bpm, SD=0.7bpm (HR) and M=0.02l/min, SD=0.06l/min (CO) per amusementlevelincrease.

Intra-individual differences. TheANOVAs yielded a significant effectofperceivedamusementforHR(F(5,275)=29.9,p<.001,²_p= .35andCO(F(5,275)=29.6,p<.001,²_p=.35).Thelinearregres- sionshowedonaverageanincreaseofM=0.6bpm,SD=0.8bpm (HR)andM=0.05l/min,SD=0.07l/min(CO)peramusementlevel.

Duetostatisticalreasons,theresultsfortheanalysisoftherelative cardiovascularresponsesbasedonthesametimeframeforcontrol trialsasforcartoontrials(resultingonlyinalevelshiftcompared tothevaluesabove)wereequivalent(HR(F(5,275)=29.9,p<.001, ²_p=.35andCO(F(5,275)=29.6,p<.001,²_p=.35).

3.4. Respiration

Breathingratedidnotdifferbetweencartoon(M=18.2min⁻¹, SD=2.1min⁻¹)andcontroltrials(M=18.0min⁻¹,SD=2.1min⁻¹; t(55)=1.4,ns.).Respirationdidnotsynchronizewiththepaceof theexperimentaldesignwhichwouldhaveresultedinabreathing rateof6min⁻¹(0.1Hz).Thepercentageofregularbreathingcycles didnotdifferbetweencartoon(M=86.6%,SD=14.1%)andcontrol trials(M=85.8%,SD=18.1%;t(55)=0.7,ns.).Furthermore,nocorre- lationbetweenthepercentageofregularbreathingcyclesandthe contrastedheartrateresponsewasfound(r=.167,ns.).

4. Discussion

The aimof thepresent studywas toexamine thetransient cardiovascularresponsestotheperceptionofhumor,thatis,the impactofthecognitiveprocessofinsightaswellasthepotential modulationoftheresponsebytheaffectiveappraisalofthestimuli.

Whencontrastedtocardiacactivityduringtheprocessingofnon- humorouscartoon-likepictures,apronouncedcardiacresponseto theperceptionofhumorwasobserved.Intheimmediatecontextof detectingthepunchlineinthecartoons,transientcardiacactiva- tionoccurred,reflectedinarelativeincreasedheartrateandcardiac outputtocartoons ascomparedtonon-humorouspictures.The particularlycleareffectintheheartrateisinagreementwithother indicationsthattheheartrateisanespeciallypowerfulcardiovas- cularvariableinthecontextofpsychologicalprocesses(Berntson etal.,1992).Thecardiacoutputmirroredthebehavioroftheheart rate.Nosignificanteffectoftheperceptionofhumorwasobserved

for stroke volume,suggesting that the relative increase in car- diacoutputisrelatedtotheheartrateacceleration.Asforblood pressurevariables,aneffectoftheperceptionofhumorcouldbe observedfordiastolicbutnotforsystolicbloodpressure.Referring todynamic controlprocessesand interactions amongvariables, thebeattobeatchangeofheartratecausesaresponseinblood pressure,asthemeanarterialpressureistheprimaryregulated variable(Julius,1998;Hinghofer-Szalkayetal.,2004).However,it shouldbetakenintoaccountthatthebloodpressurehasafun- damentalfrequencyofapproximately0.1Hz,thatis,itshows10-s rhythms.Consequently,thedesignofthehumorparadigm,with 6spicturepresentationfollowedby4sfortheamusementrating mayhaveproducedoverlapping timecourses ofbloodpressure changesand,thus,noclear-cutbloodpressureresponsetotheper- ceptionofhumoremerged.Thesystolicbloodpressureisalsomore stronglyaffectedbyrespirationthanthediastolicbloodpressure (Lackneretal.,2011).However,theuseofrelativechangescom- paredtotheactivitypriortothepictureonsetinconjunctionwith therelativeshorttimeintervalshouldhaveruledoutsignificant influencesofrespirationonbloodpressure.Fromtheanalysisof breathingpatternsitcanbeconcludedthatthedifferencesincar- diovascularvariablesbetweencartoonandcontroltrialswerenot duetoinfluencesofmarkedchangesinrespiration.Italsoindicated thatthecartoonswerefunnyenoughtoproduceamusementand perhapssmiles,butthattheydidnotproduceovertlaughter.

Psychologicallyviewed,thecardiovascularresponsethatwas observed in closeproximity tothedetection of thepunch line shouldreflecttheeffectoftheprocessofinsight.Themomentof insight,whenthesolutiontoapuzzle-orthepunchlineinjokes- becomessuddenlyclear,isanactivatingexperienceandislinkedto intrinsicrewardandpleasure(Shaw,1999;Suls,1972;Ruch,2001, 2007;RuchandHehl,2007).Inlinewiththis,studieshavedemon- stratedthattransientactivationofthebehavioralapproachsystem, producedbysignalsofimpendingrewardoractualpleasurewas accompaniedbytransientheartrateacceleration.Similarlytothe present study, this response could be demonstrated especially clearlywhencontrastingittotheresponsetoneutralstimulation (Bradleyetal.,2001;Fowlesetal.,1982).Relatedtothat,onestudy showedashortheartrateaccelerationafterparticipantshadsolved aninsightproblem(JauˇsovecandBakracevic,1995).

Thecardiacactivationinproximitytothedetectionofthepunch linefollowedaninitialperiodofcardiacdeactivationthatcanbe attributedtostimulusprocessing (De Pascalis etal.,1995), and wasobservedinallcardiovascularvariablesascouldbeexpected (e.g.Ruiz-Padialetal.,2011).Thisdeactivationwasobservedin parallelforcartoonsandnon-humorouspictures,confirmingthat theprocessingof thestimuliwassimilarfor both typesofpic- turesuntilthehumorwasdetected(ortheparticipantsdecided thattheycouldnotdetectthepunchline).Afterthisinitialperiod, cardiacaccelerationwasobservedinalltrials.Thetimecourseof theresponses inthepresent studysomewhat differsfromthat reportedinstudiesusingclassicalparadigmstoevoketransient heartrateresponses.Thereareimportantdifferencesbetweenthe experimentalparadigmsthatmayexplaintheinconsistencies.In studiesofBarry,shortstimuliwereusedaspromptstocount,not requiringanymorestimulusprocessingbutspecificcognitiveoper- ationssuchasmemoryretrievalandupdating(e.g.,Lawrenceand Barry,2010).Bycontrast,inthepresentstudyprocessingofthe stimuluswastotheforeuntilthepunchlinewasdetectedinthe cartoon(i.e.,atleastfor3s),andthecognitiveoperationsaccom- panyingit(resemblingproblemsolving)verymuchdifferedfrom that inBarry’s paradigm.Therelevanceofthedifferencein the paradigmsissupportedbyastudyshowingthatduringwordtrans- lationtasksthatcannotberesolved,thatis,wheretheattemptto solvetheproblemdoesnotcometoanendduringtherecording timeofatrial,onlyheartratedeceleration(withoutsubsequent

38 H.K.Lackneretal./BiologicalPsychology93 (2013) 33–40

Fig.3. Associationsbetweeninter-individualdifferencesintheestimatedcardiacresponsestotheperceptionofhumorandthelevelofperceivedamusement.Estimated relativechangesofHRandCObasedontheregressionofthecontrastedcardiovascularchangesontheamusementratingsareshownasmean±standarderror,averaged acrosscartoons.

acceleration)wasobserved(Pfurtschelleretal.,2007).Intheexper- imentsofLang’s group,emotional pictures(IAPSpictures)were typicallyused,withunequivocalpositiveornegativevalence(e.g., Codispotietal.,2001).Thatis,ifapicturewaspleasant,thiswas immediatelyevident. By contrast, in the paradigmused in the presentstudy,thestimulusonlybecomespleasantthemoment thatthepunchlineisdetected.Thismayexplainwhytheheart rateaccelerationfollowingtheinitialdecelerationappearstobe delayedascomparedtothefindingsofLang’sgroup.Actually,it seemslikelythattheoveralltimecourseoftheresponsesinthe cartoonparadigmwouldhaveresembledthoseofLang’sgroup(but spreadapart),iftheinterstimulusintervalwouldhavebeenlonger and,thus,thetimecourseoftheheartratewouldnothavebeen interruptedbythepresentationofthenextstimulus.

Inordertoapplythetransientheartrateresponsefortheloca- tionof theindividualmomentofinsight,therelativeheartrate changes(relativetoabaselinebeforestimuluspresentation)dur- ingtheexperimentalconditionmaybecontrastedtotherelative heartratechangesduringacontrolconditioninwhichinsightisnot requiredornotpossible.Intheresultingdifferencecurve(suchas theonethatisshowninFig.1,butforeachindividualseparately), themomentofrelativeheartrateacceleration(insightversusnon- insighttrials)canbeidentified.

Theoretically,asthedetectionofthepunchlineinjokesisfol- lowedbyamusement,whichisastrongapproach-relatedemotion involvinghigharousal(ChristieandFriedman,2004),thetransient cardiovascularresponsetotheperceptionofhumorshouldnotonly comprisetheeffectofthesuddeninsight,butalsotheadditional effectofthepositiveemotionalarousal.Previousresearchshowed that, afterthe usualinitial deceleration, highly arousingpleas- antpicturesproducephasicheartrateacceleration(e.g.Bradley andLang,2000;Bradleyetal.,2001).Individualswhoperceived stimuliasmorepleasantshowedamorepronouncedheartrate acceleration(Aupéeand Jönsson,2008).Consequently, thecar- diovascularresponsetotheexperienceofinsightmaybefurther modulatedbytheextenttowhichthejokeisperceivedasamusing.

Thiswasconfirmedbytheassociationofhigherlevelsofamuse- mentwithgreatercardiacresponsestotheperceptionofhumor, particularlyoftheheartrateinconjunctionwithcardiacoutput.

Thisrelationshipwasshown inter-individually(i.e.,participants experiencingmoreamusementexhibitinggreaterresponses)and intra-individually(i.e.,cartoonsexperiencedasmoreamusingpro- ducinggreaterresponses).Therefore,thefindingssuggestthatthe sizeoftheimmediatecardiacresponsetotheperceptionofhumor (particularlytheheartrateresponse)indicatesanindividual’spos- itive affectiveresponsiveness (when evaluatinginter-individual differences),aswellas(inintra-individualcomparisons)theaffec- tiveimpactofaparticularstimulus.

Thus,thepresentstudydemonstratesthattherelativediffer- encebetweentheheartrateresponseintheimmediatecontextof theperceptionofhumorandtheheartratedataselectedfromthe respectivetimeintervalofacontrolconditionisavalidindicator oftheimpactthattheperceptionofhumorhasonanindividual.

Consequently,whentheresearchquestionofastudyinvolvesthe examinationofindividualdifferencesintheperceptionofhumor (or,moreprecisely,inthecardiacresponsestotheperceptionof humor),wesuggesttopreparethedataasdescribedinthepara- graphontheanalysisoftheimmediateresponsestothedetection ofthe punchlineinSection 2.5 andtocomputethe difference betweenthescoreforcartoontrialsminusthescoreforcontrol trials,inordertogaina“ContrastedTransientResponse”scorefor eachindividual.Higherpositivevaluesinthisscoreindicateamore pronouncedcardiacresponsetotheperceptionofhumor.Thefine- grainedanalysisoftheimmediatebehaviorofthecardiovascular variables incloseproximity tothemomentof insightmakes it possibletotakeinter-individualdifferencesintheresponselaten- ciesintoaccount,that is,foreach individualthecardiovascular changesintheimmediatecontextofhisorherparticularmoment ofinsight areanalyzed.In addition,thetime coursesofcardio- vascularvariablesduringviewingcartoonsversusnon-humorous picturessuggestthatitissensibletoalsoconsiderthedifference intheresponsetimesbetweentherelevantconditionandthecon- trolcondition.Thiswasaccomplishedbyrelatingthedatafromthe timeframeimmediatelyprecedingthebehavioralresponseincar- toontrialstodatafromtheverysametimeframeincontroltrials.

Thishastheadvantagethatitcanberuledoutthattheparam- eteris corruptedbydifferences intheresponse times(a larger responselatencymightprolongthecourseoftheinitialheartrate decelerationthatisrelated totheprocessingofthestimulus).A corruptionofthepresentfindingsandtheproposedparameterby apotentialimpactofthemotorresponseonthecardiacvariablesis alsounlikely.Ifpreparationofthemotorresponsehadaneffect,it wouldbeadditionalheartratedeceleration(e.g.,Pfurtschelleretal., 2007).Intheusedtimeframe,thedataextractedfromcartoontri- alswerethoseimmediatelyprecedingpressingofthebutton,but duringcontroltrialsthebuttonwaspressedlater and,thus,the motorresponsewasnotyetprepared.Consequently,preparation ofthemotorresponsemighthavereducedtheheartrateincartoon trials(butnotincontroltrials),therebypossiblyreducingthecon- trastedresponsetotheperceptionofhumor(butnotproducingan artifact).

Alimitationoftheexperiment isthat itwasnot possibleto obtainexplanations of why the participantsfound thecartoon funnyafterviewingeachcartoon,inordertogaindirectevidence ofthevalidityofthejudgmentsofhavingunderstoodthejokes.

This would have interrupted the continuous progress of the