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Voice pitch modulation in human mate choice
Article (Accepted Version)
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Pisanski, Katarzyna, Oleszkiewicz, Anna, Plachetka, Justyna, Gmiterek, Marzena and Reby, David (2018) Voice pitch modulation in human mate choice. Proceedings of the Royal Society B: Biological Sciences, 285 (201816). pp. 1-8. ISSN 0962-8452
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Voicepitchmodulationinhumanmatechoice
Katarzyna Pisanski1,2*, Anna Oleszkiewicz2,3, Justyna Plachetka4, Marzena Gmiterek2,
& David Reby1
1 – School of Psychology, University of Sussex, UK
2 – Institute of Psychology, University of Wroclaw, Poland
3 – Taste and Smell Centre, Department of Otorhinolaryngology, Technische Universität
Dresden, Germany
4 –SWPS University of Social Sciences and Humanities, Wroclaw, Poland
* Corresponding author: K. Pisanski (e-mail: [email protected])
Running head: Voicemodulationinhumanmatechoice
Word count: 5702 (incl. everything except Tables)
Abstract
Inter-individualdifferencesinhumanfundamentalfrequency(F0,perceivedasvoice
pitch)predictmatequality,reproductivesuccess,andaffectlisteners’social
attributions.Althoughhumanscanreadilyandvolitionallymanipulatetheirvocal
apparatusandresultantvoicepitch,forinstanceintheproductionofspeechsounds
andsinging,littleisknownaboutwhetherhumansexploitthiscapacitytoadjustthe
nonverbaldimensionsoftheirvoicesduringsocial(includingsexual)interactions.
Here,werecordedfull-lengthconversationsofthirtyadultmenandwomentakingpart
inrealspeeddatingevents,andtestedwhethertheirvoicepitch(mean,range,and
variability)changedwiththeirpersonalmatechoicepreferencesandtheoverall
desirabilityofeachdatingpartner.Within-individualanalysesindicatedthatmen
loweredtheminimumpitchoftheirvoiceswheninteractingwithwomenwhowere
overallhighlydesiredbyothermen.Menalsoloweredtheirmeanvoicepitchondates
withwomentheyselectedaspotentialmates,particularlythosewhoindicateda
mutualpreference(matches).Interestingly,althoughwomenspokewithahigherand
morevariablevoicepitchtowardmentheyselectedaspotentialmates,women
loweredbothvoicepitchparameterstowardmenwhoweremostdesiredbyother
womenandwhomtheyalsopersonallypreferred.Between-individualanalyses
indicatedthatmeninturnpreferredwomenwithlower-pitchedvoices,wherein
women’sminimumvoicepitchexplainedupto55%ofthevarianceinmen’smate
preferences.Theseresults,derivedinanecologicallyvalidsetting,showthatindividual
andgroup-levelmatepreferencescaninteracttoaffectvocalbehaviour,andsupport
thehypothesisthathumanvoicemodulationfunctionsinnonverbalcommunicationto
elicitfavourablejudgmentsandbehavioursfromothers,includingpotentialmates.
Keywords:matechoice,sexualselection,speeddating,nonverbalcommunication,
fundamentalfrequency,vocalcontrol
Thehumanvoiceconveysevolutionarilyandsociallyrelevantinformationthataffects
theoutcomesofmatechoiceandintrasexualcompetition.Todate,mostresearchinthis
areahasfocusedonmen,whosefundamentalfrequency(F0,perceivedaspitch)
appearstohavebeenshapedbysexualselectiontocommunicatemasculinity,physical
formidability,andgeneticquality[1].Menwithlow-pitchedvoicestypicallyhave
higherlevelsofpubertal[2]andcirculating[3,4]testosterone,andareperceivedas
moremasculineanddominantthanaremenwithhigher-pitchedvoices[5forreview].
Lowpitchvariability,perceivedasamonotonevoicequality,alsopredictsmen’s
formidability[6].Inturn,alargeliteraturedemonstratesthatwomengenerallyprefer
menwithrelativelylow-pitchedvoices,particularlyinthecontextofashort-term
relationship,andthatsuchmenreportmoresexualpartnersandhavemoreoffspring
thantheirhigher-pitchedcounterparts[7].Infact,menwithlow-pitchedvoicestendto
havehighersuccessinarangeofsocialcontexts,frommatingtosocioeconomicand
political[5,7].
Amongwomen,between-individualdifferencesinvoicepitchareunderstudied,but
appeartoindicatereproductivestatus(e.g.,pre-pubertalandpost-menopausalstages
offertility)andsexualreceptivity[7,8].Womenwithrelativelyhigh-pitchedvoicesare
typicallyperceivedasmorefeminine,younger,andmoreattractivethanarewomen
withlow-pitchedvoices[9–12].However,severalstudiessuggestthatalowerpitchin
womenisperceivedasattractiveor‘sexy’[13–16],whileothersfailtoidentifyany
relationshipbetweenfemalevoicepitchandjudgmentsofattractiveness[6].In
contrast,womenwithlow-pitchedvoicesareconsistentlyjudgedasmoredominant,
competent,andmature,andasbetterleadersthanwomenwithahighervoicepitch
[12,17,18].Thetrade-offimpliedbythisdichotomysuggeststhatwomenmay
volitionallyraisetheirvoicepitchtosignalyouthandfemininity,butlowertheirpitch
incontextswheretheywishtobetakenseriously,ortoindicatesexualinteresttoa
listener(seee.g.,[13]).
Lowfrequencyvocalisationssignaldominance,notonlyinhumans,butinawiderange
ofanimals.Manyspeciesvocalisewithalowervoicepitchduringagonisticinteractions,
therebycommunicatingaggressionandthreat,andinsomespecies(e.g.,reddeer
Cervuselaphus,andkoalasPhascolarctoscinereus),malesextendthelengthoftheir
vocaltractbyloweringtheirlarynx(andthustheirformantfrequencies),thereby
portrayingalargerbodysizetoothermalesincompetitivecontexts,aswellasto
potentialfemalemates[19,20].Importantly,suchfrequencychangesobservedinthe
callsofmostnonhumanmammals,includingprimates,typicallyoccurinresponseto
physiologicalorenvironmentaltriggers.Humans,incontrast,arereadilycapableof
volitionally(i.e.,voluntarily)manipulatingtheirvocalapparatus,owingtoincreased
neuralcontrol[21,22].Perhapsthemostcommonformofvolitionalvoicemodulation
inhumansinvolvesmanipulatingthearticulators,includingthelips,tongueandjaw,to
producedifferentvowelsoundsinarticulatedspeech[23].Wecanalsoactively
modulatethepitchofourvoicesbyadjustingthetensionandtheeffectivelengthofthe
vocalfolds,orbyincreasingsub-glottalpressure(i.e.,airflowfromthe
lungs)[24].Pitchmodulationisimportantforintonation,prosody,andemotional
expression,andisalsoobservedinactingandsinging[22,25].
Althoughthecapacityforvoicepitchmodulationinspeechproductioniswell
documented,whetherhumansexploitthiscapacitytoadjustthenonverbaldimensions
oftheirvoicesduringsocialinteractionshasnotyetbeensystematicallyinvestigated.
Theabilitytovolitionallychangethepitchofourvoicemaybeevolutionarily
advantageous.Duringsocialandsexualcommunication,suchvocalmodulationcould
functiontohonestlycommunicateone’smotivationsandemotions,butmayalsobe
usedtofavourablymanipulatetheperceptionsandbehavioursofothers,including
potentialmates[22].Indeed,menandwomencanvolitionallylowertheirvoicepitch
wheninstructedtosoundmoremasculine[26]orphysicallylarger[27],andbothsexes
modulatetheirpitchwheninstructedtosoundconfident,dominantandintelligent[14].
Thus,notonlyarehumanscapableofvocalcontrol‘ondemand’,butalsooffine-tuning
voicemodulationstomimicrealorperceivedassociationsbetweenphysicaland
psychologicaltraitsofaspeakerandtheirvoice.
Studiesexaminingvoicemodulationinmatingcontextshave,todate,onlybeen
conductedinthelaboratoryusingwidelyvariedmethodologies,andhaveproduced
mixedresults[13,28–31].Somestudieshavefoundthatmenspeakwithalowerand
lessvariablevoicepitch[13,29]oralowerminimumvoicepitch[31],whereasothers
reportanincreaseinmen’smeanpitchandpitchvariability[28,31]whenspeaking
withahypotheticalfemalemate.Likewise,womenhavebeenshowntoeitherincrease
[30],decrease[13,14],ornotaltertheirvoicepitch[31]whenspeakingtohypothetical
malemates.Inthesestudies,datingcontextsweremocked(e.g.,participantswere
askedtoleaveavoicemessageforanunknownpersonwhosephotoorvideothey
viewed),andtheattractivenessofhypotheticaldatingpartnerswaseithernot
controlledorwaspre-ratedbyanothergroupofparticipants.
Here,werecordedthevoicesofthirtyadultmenandwomen(aged20-40)takingpart
inrealspeeddatingevents,andexaminedwithin-individualchangesintheirvoicepitch
parametersasafunctionoftheirdate’soveralldesirability(i.e.numberofsuccessful
speeddates),andimportantly,theirownpersonalmatechoicepreferenceforeach
datingpartner.Thepresentstudyisthefirsttoexaminehumanvoicemodulationina
real-worldmatechoicescenario.Withthishighdegreeofecologicalvalidityand
multiplematepreferencemeasures(individualandgroup-level),thisstudyaddresses
limitationsofpastworkthatlikelycontributedtoinconsistentfindings.
METHODS
Participants
Thirtyparticipantswererecruitedbyaprofessionalspeeddatingcompanyviaposters
andonlineadvertsannouncinglocalspeeddatingeventsforsinglemenandwomen
aged20to40.Participantswerethenassignedtooneoftwoagegroupstolimitage
differencesbetweendatingpartners,asistypicalinspeeddating.Agesrangedfrom20
to33intheyoungergroup(mean22±1.7inwomen,28.3±1.0inmen)and25to40in
theoldergroup(mean29±4.1inwomen,29.0±5.6inmen).Althoughmenwereon
average3.5yearsolderthanwomen(28.5vs24.9years),theagedifferencebetween
pairsinspeeddatesaveragedlessthanayear(0.07±6.9years)andwasnot
significantlydifferentfromzero(t213=-.137,p=.89).Beforeconfirmingtheir
participation,interestedindividualswereinformedthattheirvoiceswouldberecorded
duringtheeventforsubsequentacousticanalysisaspartofaresearchstudy.All
participantsprovidedsignedconsentbeforetakingpartinthestudy.
Questionnairescompletedaftertheeventconfirmedthatallparticipantsweresingle.
Thereportedamountoftimesinceapreviousrelationshiprangedfrom1to60months
anddidnotdiffersignificantlybetweenthesexes(mean19.3monthsamongwomen,
11.9monthsamongmen;t24=1.08,p=.29).Halfofthewomen,andone-quarterofthe
men,reportednotpreviouslyhavingparticipatedinaspeeddatingevent.Amongthose
whohad,participationratesrangedfrom1-2(women)and1-15(men).Meninour
samplethereforereportedgreaterexperiencewithspeeddatingthandidwomen(t26=-
2.34,p=.03,equalvariancesnotassumed).
Procedure
Weheldtwospeeddatingeventsco-organisedandco-directedbyanexperienced
speeddatinghost,heldinadedicatedroomatalocalcafé.Participantsarrived
individuallytothecaféwheretheyweregreetedbythehostandresearchers.Upon
arrival,thehostexplainedthespeeddatingprocedurestoparticipantsinsmallgroups,
andeachparticipantwasgivenanametagandbookletinwhichtomarktheirpersonal
matechoicepreferencesaftereachspeeddate(i.e.,‘yes’or‘no’).Afterproviding
informedconsent,participantswerefittedwithaportablevoicerecorderandheadset
andseatedatoneofseveraldesignatedtables.
Followingtypicalspeeddatingprocedures,eachdatingroundlasted6minutesafter
whichmenrotatedtoanadjacenttable.Duringthebriefinterludebetweendates,both
sexesindicatedtheirpreferencefortheirpreviousdateinapersonalizedbookletby
marking‘yes’or‘no’besidethatdate’sID.Thisprocesscontinueduntilallmenand
womenhaddatedoneanother.Followingthefinalround,participantsweregiven
additionaltimetoindicatetheirmatechoicepreferences.Asiscustomaryatspeed
datingevents,participantswhowere‘matched’(i.e.,whoindicatedamutualpreference
foroneanother)wereinformedbyemailwithin24hoursandgivenoneanother’s
contactinformation.Participantsalsocompletedashortquestionnaireaftertheevent,
inwhichtheyindicatedtheirage,sex,andwereaskedtoprovidedemographic
informationanddetailsregardingpreviousspeeddatingexperience.
Acousticrecordingandanalysis
Participants’voiceswererecordedthroughouttheentiredurationofthespeeddating
eventusingportableTascamDR-05recordersandlightweight(12g),discreetcardioid
condenserheadsetmicrophonesatasamplingrateof96kHzand24-bitamplitude
quantization.RecordingswerestoredontomicroSDHCmediacardsasuncompressed
WAVfilesandlatertransferredtoalaptopcomputerforeditingandanalysis.This
methodallowedustoobtainhighquality,directionalvoicerecordingsthatwould
otherwisebedifficulttoobtaininanoisyenvironmentusingastationarymicrophone.
AcousticeditingandanalysiswereperformedinPraatv.6.0.21[32].Fragmentsof
silence,acutenoise,nonverbalvocalizations(e.g.,laughter)andmulti-voicing(e.g.,the
voiceofthedatingpartner)werefirstmanuallyremovedfromaudiofiles.Recordings
werethensegmentedintomultiplepartseachcorrespondingtoagivenparticipantand
asinglespeeddate.Wefurtherspliteachsoundfileintothreeequaltimesegments
(beginning,middleandendofthedate;meansegmentduration50.6±23s),resultingin
atotalof726voiceclipsforacousticanalysis.
Weusedabatch-processingscripttomeasurefiveparametersoffundamental
frequency:mean(F0mean),range(F0minandF0max),variabilityandcontour,
includingstandarddeviation(F0sd)andthecoefficientofvariation(F0CV;givenbyF0
sd/F0mean[33]).AllF0parametersweremeasuredusingPraat’sautocorrelation
algorithmwithasearchrangeof60-600Hzandatimestepof0.01s.Spuriousoctave
jumpsweremanuallycorrected(see[34]).Perceptually,F0mean,minandmax
representtheaverage,lowerandupperrangesofaspeaker’svoicepitch,respectively,
withrelativelylowervaluessounding‘deeper’.Incontrast,F0sdrepresentsthe
absolutedegreeofvoicepitchvariabilityaroundthemeanacrossanutterance,andF0
CVadjuststhisvariationtothemagnitudeofF0therebycontrollingforthenonlinear
perceptionofvoicepitch.Thus,F0CVmorereliablyrepresentstheperceptualsalience
ofthisF0variability.
Preferencescores
Wecomputedthreetypesofpreferencescoreforeachparticipant.Desirabilityscores
representhow‘desired’theparticipantwasbyothers,andwerecomputedbydividing
thenumberofdateswhomarkedtheparticipantas‘yes’bythetotalnumberofdates,
givingtheproportionofdatingpartnerswhoindicatedapreferencefortheparticipant.
Choosinessscoresrepresenthow‘choosy’theparticipantwas,andwerecomputedby
dividingthenumberofdateswhomtheparticipantmarkedas‘yes’bythetotalnumber
ofdates.Finally,matchscoresindicatethenumberoftwo-waypreferences,thatis,the
numberofdatesonwhichbothparticipantsindicatedamutualpreferenceforone
another.
StatisticalAnalysis
Weusedlinearmixedmodels(LMMs)withmaximum-likelihoodestimationtotestfor
within-individualvariationinF0parameters(voicepitchmodulation).Weranseparate
modelsforeachsexduetonon-independenceinfemaleandmaledata(pairinginspeed
dating),andbecausevocalparametersandpreferencesdifferbetweenthesexes.
WeexaminedF0modulationasafunctionofthepersonalmatechoicepreferencesof
bothdatingpartners(i.e.,indicatingoneanotherasa‘yes’or‘no’),thespeaker’soverall
choosinessscore,andthedate’soveralldesirabilityscore.Preferencevariableswere
includedasfixedfactors(chosedate,theparticipantmarkedthatrespectivedateasa
‘yes’;chosenbydate,thedatemarkedtheparticipantasa‘yes’)orfixedcovariates
(choosinessscoreofspeaker;desirabilityscoreofdate).Participantidentitywasincluded
asarandomsubjectvariableinallmodels,andtheagedifferencebetweeneachman
andwomanoneachspeeddatewasincludedasarandomcovariate.Weadditionally
includedtimesegmentasafixedfactortoexaminewhethervoicechangesweremore
likelytooccuratthebeginning,middleorendofadate.Thesefactorswerefirst
examinedinafullyfactorialmodel.Therewerenomainorinteractioneffectsof
choosinessscoreofspeakeronvocalparametersforeithersex,thereforethisvariable
wasexcludedfromthefinalmodels.Timesegment,althoughnotsignificant,was
retainedinfinalmodelstoavoidpseudo-replication;itsinclusiondidnotaffectthe
patternofresults.Thefinalmodelcanbedescribedwiththeequation:
𝑦"# = 𝑏& + 𝑢&# +𝑏*𝑋"# +𝑏,𝑋"# + 𝑏-𝑋"# + 𝑏.𝑋"# + 𝑏/𝑋"# + 𝑢/# 𝑋"# + 𝜖"#
Note:b1–chosedate;b2–chosenbydate;b3–timesegment;b4–date’soveralldesirability;b5–agedifference
betweeneachmanandwomanoneachspeeddate;u0j–acomponenttotheinterceptmeasuringvariabilityin
intercepts;u5j–acomponenttotheslopeoftheoverallmodelthatmeasuresthevariabilityinslopes
Followingthis,weexaminedsignificantmaineffectsofcategoricalvariablesintheLMM
usingpairwisetestswithŠidákcorrectionformultiplecomparisons,andexamined
significantmaineffectsof,orinteractionswith,continuousvariables(i.e.,date’s
desirability)usinglinearregressiontoillustratethedirectionandstrengthofthese
relationships.Forinteractionsbetweencontinuouscovariatesandfixedfactors,we
averagedvocalparameterswithineachrelevantfixedcategory(e.g.,chosedate,didnot
choosedate,)andplottedseparatelinesofbestfitforeachfixedfactor.
Sexdifferences,effectsofparticipantage,oreffectsoftheagedifferencebetween
datingpairsonchoosiness,desirabilityandmatchscoresoronpersonalmatechoice
preferencesweretestedusingone-wayanalysesofvarianceorlinearregression.All
testsweretwo-tailedatanalphalevelof.05.
RESULTS
Desirability,choosiness,andmatches
Wefoundthatwomenwereonaveragesignificantlychoosierthanmen(F1,29=6.74,
p=.01):whilewomenindicatedapreferencefor30%(range0-67%)oftheirdates,men
indicatedapreferencefor51%(range13-88%).Inturn,women’sdesirabilityscores
weresignificantlyhigherthanmen’s(F1,29=6.72,p=.01),averaging52%inwomen
(range0-91%)comparedto28%inmen(range0-67%).Bothpartnersindicateda
mutualpersonalpreferenceforoneanotheron14%ofdates;individualsuccessrates
formatchesrangedfrom0%(nomatch)to33%(women)and38%(men),anddidnot
differsignificantlybetweenthesexes(F1,29=0.61,p=.81).Desirabilityandchoosiness
scorescorrelatednegativelyinbothsexes,howeverthisrelationshiponlyreached
statisticalsignificanceamongwomen(r=-.60,p=.03;men:r=-.24,p=.35),
indicatingthatwomenwhoweremoredesirablewerealsochoosier.
Participantagedidnotsignificantlypredictdesirabilityscores(men:F1,16=1.7,p=.21;
women:F1,11=3.8,p=.08),choosinessscores(men:F1,16=.05,p=.82;women:F1,11=4.4,
p=.06),ormatchscores(men:F1,16=.38,p=.55;women:F1,11=.004,p=.95)ineithersex,
thougholderwomenshowednonsignificanttrendstowardlowerdesirabilityscores,
andhigherchoosinessscores,comparedtoyoungerwomen.
Voicepitchmodulation
Linearmixedmodels(LMMs)testedforwithin-individualchangesinvoicepitch
parametersacrossspeeddates(seeStatisticalAnalysis).Table1reportssignificant
effectsofmodelsconductedseparatelyforeachsex.
Table1.Within-individualF0modulation.LinearMixedModelsexaminingrelationships
amongspeeddatingpreferences,date’soveralldesirability,andwithin-individualmodulation
ofvoicepitchparametersinwomen’sandmen’svoices,controllingfortheagedifference
betweendatingpartners.Onlysignificant(p<.05)effectsarereportedhere,forfullmodel
outputsandestimatedmarginalmeansseeTablesS1andS2.Modelsyntaxisprovidedin
supplementalmaterials.SeealsoFigure1.
Voice
parameterModelsource df1,df2 F p
Women
F0mean Intercept 1,321 9411.2 <.001
Chosedate 1,321 18.7 <.001
Date’sdesirability 1,321 19.1 <.001
Chosedate*Date’sdesirability 1,321 9.8 .002
F0min Intercept 1,321 595.2 <.001
Chosenbydate 1,321 4.6 .034
F0max Intercept 1,321 6237.0 <.001
Chosedate 1,321 4.0 .047
F0sd Intercept 1,321 1571.9 <.001
Chosedate 1,321 16.4 <.001
Date’sdesirability 1,321 14.8 <.001
Chosedate*Date’sdesirability 1,321 6.9 .009
F0CV Intercept 1,321 2013.1 <.001
Chosedate 1,321 7.0 .009
Date’sdesirability 1,321 5.5 .02
Chosedate*Chosenbydate*
Date’sdesirability
1,321 3.9 .048
Men
F0mean Intercept 1,321 1089.6 <.001Chosedate
1,321 4.6 .033
Chosedate*Chosenbydate*
Date’sdesirability
1,321 4.4 .036
F0min Intercept 1,321 633.0 <.001
Date’sdesirability 1,321 6.6 .01F0max Intercept 1,321 340.2 <.001F0sd Intercept 1,321 173.2 <.001F0CV Intercept 1,321 257.9 <.001
Womenmodulatedtheiraveragevoicepitch(F0mean),maximumvoicepitch(F0
max),andpitchvariability(F0sdandCV)asafunctionoftheirpersonalmatechoice
preferencesacrossspeeddates(Fig1a).PairwisetestswithŠidákcorrectionshowed
that,overall,womenspokewithasignificantlyhigherF0mean(p<.001,df=321,95%
CIfordifference=6.5to19.3)F0max(p=.01,df=321,95%CI=4.2to36.5),andF0
variability(F0sd,p<.001,df=321,95%CI=4.0to11.5;F0CV,p=.006,df=321,95%
CI=.005to.029)towardmentheychoseaspotentialmates(markedas“yes”)than
towardmentheydidnotchoose(markedas“no”).Theaveragemagnitudeofwomen’s
meanvoicepitchmodulation(13Hz)exceedsperceptualdiscriminationthresholdsby
almostthree-fold[9].
However,thesemaineffectswerequalifiedbyinteractionsbetweenwomen’spersonal
matechoicepreferencesandmen’soveralldesirabilityscores.AsillustratedinFigure
1b,womenraisedtheF0meanandabsolutevariability(F0sd)oftheirvoicesondates
withmentheypersonallypreferred,butonlytowardmenwithdesirabilityscores
below0.50(i.e.,menchosenbyfewerthanhalfoftheirdatingpartners),forwhom
womenraisedtheirpitchbymorethan20Hzonaverage.Incontrast,women
marginallyloweredthesepitchparameterstowardmentheypreferredandwhose
desirabilityscoreswereamongthehighest.Ondateswithmentheypreferred,14%
and12%ofthemodulationinwomen’sF0meanandF0sdwasexplainedbytheman’s
desirabilityscore,respectively,whereasthedesirabilityofnon-preferredmendidnot
predictwomen’svoicepitchmodulation(Fig1b).Whilewomenspokewithaless
monotonevoice(higherF0CV)towardmentheypreferred,themagnitudeofthisvoice
changealsodecreasedasmen’soveralldesirabilityincreased,andwasabsentondates
inwhichneitherthewomannorthemanshowedapersonalpreferenceforone
another.
Variationinwomen’sminimumpitchwasnotqualifiedbythedate’soveralldesirability
norwomen’sownpreferences,butratherwaspredictedsolelybymen’spreferences.
WomenspokewithalowerF0minondatesinwhichtheirdatingpartnerchosethem,
loweringtheirF0minbyanaverageof15.8Hzcomparedtodatesonwhichtheywere
notchosen(p=.007,df=321.95%CI=-27.3to-4.3;Fig1a).
Menalsomodulatedtheirvoicesacrossspeeddates.AlthoughtheLMMindicatedthat
menspokewithalowerF0meantowardwomentheychose(markedas“yes”)than
towardthosetheydidnotchoose(Table1),pairwisetestsshowedthatthismaineffect
didnotreachsignificancefollowingŠidákcorrection(p=.26,df=321,95%CIfor
difference=-11.0to-2.9;Fig1c).Indeed,likewomen,thiseffectwasqualifiedbya
significantinteraction,indicatingthatmenloweredtheirF0meanmoretowardwomen
withlowthanhighdesirabilityscores,andonlyondateswithwomentheychoseas
potentialmates,particularlyifthosewomenchosetheminreturn(Fig1d).Indeed,men
loweredtheirF0meanbymorethan20Hz,orapproximatelyfourtimesthejust-
noticeabledifference,toward‘matched’womenwhosedesirabilityscoreswereamong
thelowest.Likefemaleparticipants,thedesirabilityofnon-preferredwomendidnot
predictmen’smeanvoicepitchmodulation(Fig1d).Linearregressionfurthershowed
thatmenloweredtheirF0minwhenspeakingtowomenwithrelativelyhigheroverall
desirabilityscores,regardlessofpersonalpreference(Fig1c).
InadditiontocontrollingforagedifferenceinLMMs,weranadditionalanalysesof
variancethatconfirmedthattheagedifferencebetweensexesineachspeeddatingpair
didnotsignificantlypredictthematechoicesofeithersexineitheragegroup(younger
women:F1,76=0.02,p=.90,olderwomen:F1,29=1.18,p=.29;youngermen:F1,76=3.74,
p=.06,oldermen:F1,29=0.51,p=.48).Moreover,ourLMMshowednosignificanteffect
oftimesegmentonvoicepitchmodulation(TableS1),indicatingthatpitchmodulation
emergedearlyinthespeeddateandpersistedatasimilarmagnitudethroughout.
Figure1.Women’sandmen’sF0modulationacrossspeeddates.Panels(a)and(c)showmaineffectsofpersonalmatechoicepreferencesonvoicepitchmodulation,whereaspanels(b)and(d)showinteractionsbetweenpersonalpreferencesanddate’soveralldesirability.ColumnsinbargraphsrepresentestimatedmarginalmeansfromLMMs(seeTables1andS2),whereerrorbarsrepresentstandarderrorsofthemeans.Markersinscatterplotsrepresentindividualspeeddates;markersfordistinctcategoriesareminimallyoffsetalongthex-axistoavoidoverplottingandtoimprovevisualisation.Asterisks’indicatestatisticalsignificanceofpairwisecomparisonsfollowingŠidákcorrection,where***p<.001,**p<.01,*p<.05,andnsp>.05.Correlationcoefficients(r)aregivenbesideeachlinearregressionline.Seeembeddedlegendforadditionaldetails.
Relationshipsbetweenvoicepitchanddesirabilityorchoosiness
Inadditiontoexaminingwithin-individualfluctuationsinvoicepitch(thatis,how
participantsmodulatedtheirvoicesfromdate-to-date),wetestedwhetherbetween-
individualdifferencesinpitchpredicteddesirabilityandchoosinessscores.Average
pitchparameterswerecomputedforeachparticipantbyaveragingF0parameters
acrossalldates,within-individuals,andregressedagainsttheiroveralldesirabilityand
choosinessscores.
Wefoundthatwomen’sF0minexplained43.7%to55%ofthevarianceintheir
desirabilityscores(r=-.66,p=.014,n=13),indicatingthatwomenwithlowerpitch
minimaweremoredesiredbymen.Thestrengthofthisrelationshipincreasedafter
controllingforwomen’schoosinessscores(rp=-.74,p=.006,df=10).Although
relationshipsbetweenwomen’sdesirabilityandtheirF0mean(rp=-.45)andF0CV(rp
=.37)weremoderateinstrength,noothervoicepitchparameterexplaineda
significantamountofvarianceinthedesirabilityorchoosinessscoresofeithersex
(TableS3).
DISCUSSION
Theresultsofthisstudysupportthehypothesisthatwomenandmenmodulatetheir
voicesinreal-lifematechoicecontextsbasedonpersonalmatechoicepreferences,and
thematequalityofapotentialpartner.Womenspokeinahigher-pitchedandless
monotonevoiceonspeeddateswithmentheychoseaspotentialmates,howeveronly
ifthosemenalsohadarelativelyloweroveralldesirabilityscore(i.e.,werepreferred
byfewerthan50%ofotherwomen).Menloweredtheirmeanpitchondateswith
womentheypersonallypreferred,butheretoo,themagnitudeofmen’svoicepitch
modulationdecreasedastheirdates’overalldesirabilityincreased.
Previousstudiesexaminingvoicemodulationinmockdatingcontextshaveproduced
conflictingresults[13,28–31],possiblybecausedatingpartnerswerehypothetical,and
theirdesirabilitywasbasedsolelyonpre-ratedattractivenessofphotosorvideos
ratherthanonparticipants’personalpreferences.Here,weshowthatpersonalmate
choicepreferencescandeviatefrom,interactorevenconflictwithgroup-based
desirabilityscores.Indeed,althoughwomengenerallyspokewithahigherpitch(inline
with[30]),andmenwithalowerpitch(inlinewith[13,31]),towarddatingpartners
theymarkedas‘yes’,thiswasdrivenlargelybydatingpartnerswithlowerdesirability
scores,towardwhombothsexesalteredtheirvoicepitchbymorethan20Hz(1.5
semitonesinwomen,2.7inmen)onaverage.Infact,womenspokewithalowervoice
pitchtowardmenwhowerebothhighlydesiredbyotherwomenandwhomthey
personallypreferred.Thisfindingsupportsatleasttwootherstudies[13,14]that
reportthatwomenlower,ratherthanraise,theirvoicepitchinamatingcontext,and
thushighlightstheneedtoconsiderbothgroup-levelandindividualmatepreferences
infuturework.
Alargebodyofresearchindicatesthatmenwithrelativelylow-pitchedvoicesare
preferredbywomenasmatesandhavehighmatevalue[5,7].Thus,theobservation
thatmenloweredtheirvoicepitchinresponsetowomentheypreferred,particularlyif
thosewomenalsopreferredthem,suggeststhatvoicemodulationinmenmayfunction
toincreasetheirreproductivesuccess.Incontrast,ourresultscontradicttheprediction
thatwomenubiquitouslyfeminizetheirvoicestowardpreferredpotentialmates,as
thiswasnotthecaseondateswithhighlydesirablemen.Moreover,inoursampleof
speeddaters,womenspokewithlowerpitchminimatowardmenwhopreferredthem,
andwhencomparingacrosswomen,menpreferredwomenwhospokewithalower
minimumpitch,suchthatwomen’sminimumpitchexplainedupto55%ofthevariance
inhowdesiredtheywerebymen.
Thisapparentconflictbetweenthefunctionalrelevanceofhighversuslowvoicepitch
inwomenmayberesolvedbyconsideringthatindexicalcuestostaticspeakertraits
(e.g.,age,sex)mayfunctiondifferentlythanmoredynamic,socialorsexualcues.Thus,
whilearelativelyhighvoicepitchinwomencansignalyouth,femininityand
reproductivefecundity[7],bydynamicallyloweringhervoicepitchawomanmightbe
signallingsexualinterestandintimacytoaman[13–15].Alternatively,or
simultaneously,shemightlowerherpitchtocommunicatesocialdominanceora
confidentandmaturepersona,aspeoplewithlow-pitchedvoicesareoftenattributed
traitssuchascompetence,trustworthinessandleadership[5,17].Indeed,recent
studiessuggestthatyoungwomenareincreasinglyusingaverylowpitchregister,
resultinginvocalfryora‘creaky’quality,inprofessionalworkcontexts[35,36].
Dynamicvoicemodulationmaybeespeciallyfunctionalwhenmultiplemodalitiesare
availabletothereceiver,astheywereinourstudyandtypicallyareinsocial
interactions.Inamatingcontext,forinstance,amanmaygaugeawoman’sage,
femininity,andfecundityfromvisualandolfactorycues[37],whilesimultaneously
interpretingsocialandsexualinformationfromthedynamicpropertiesofthewoman’s
voice.Whileitispossiblethatawoman’sagemayinfluencethedirectionanddegreeto
whichshemodulateshervoicepitchtowardpotentialmates,ourresultsshowedno
effectofage,oragedifferencesbetweendatingpartners,onvoicemodulation.Agealso
didnotpredictchoosiness,desirabilityorsuccessfuldatingmatches,thoughitmustbe
notedthatthesebetween-subjectcomparisonswereunderpowered.
Inlinewithevolutionarymodelsthatimplicatewomenasthe‘choosier’sex[38],both
choosinessanddesirabilityscoreswerehigheramongwomenthanmen,withwomen
showingapersonalpreferenceforonlyone-thirdoftheirdates(comparedtoone-half
inmen).Womenalsomodulatedmorevocalparametersinresponsetopreferred
datingpartnersthandidmen,includingtheirmaximumpitch,andmostnotably,
variabilityintheirpitch,whichisknowntocommunicatemasculinityandphysical
formidabilityamongmen[6].Thissexdifferencecouldbetiedtoabilityoreffort.
Womenhavebeenshowntomoreeffectivelymodulatetheirvocalattractiveness‘on
demand’thanmen[14].Alternatively,forwomen,datesmarkedas‘yes’werelikelyto
includemenwhomwomenweremaximallyattractedtoandmayhavethusexerted
maximalvocalefforttoward,whereasmen’slongerlistofpotentialmateslikely
includedmarginallypreferredpartnerstowardwhommenmighthavedisplayedless
vocaleffort.
Studyingvoicemodulationinreal-lifedatingoffershighecologicalvalidity,yetthelack
ofexperimentalmanipulationdoesnotallowforcausalinferencesregardingtheroleof
variousvocalparameters,ordifferentmodalities,onmatechoicepreferences.Thismay
beinvestigatedinfutureworkusingresynthesizedspeechasuni-modalandwithin
multi-modalstimuli.Givenourresults,experimentsarenowalsoclearlyneededto
gaugetheroleofownversusgroup-levelmatepreferencesonvoicemodulation.Our
smallsamplesize,whileadequateforcapturingdynamicwithin-individualmodulation
acrossspeeddates,limitstheextenttowhichinferencescanbemadeaboutbetween-
individualdifferencesinvocalparametersandbehaviour.Individualdifferencefactors,
suchastheinfluenceofpastdatingexperience,shouldthusbeinvestigatedin
replicationstudiesutilizinglargersamples.Finally,futurestudiesmayexaminethe
influenceofstress(e.g.,duetoafirstdateortherealizationofbeingaudio-recorded)
andotheremotionsonvoicemodulationinadatingcontext.
Althoughthereissomerecentevidenceforbehavioralandcontextualflexibilityinthe
vocalizationsofothermammalsandgreatapes[22],thecapacityforvolitionalvocal
controlinhumansisunprecedentedinitscomplexityandthus,initspotentialbreadth
offunctionality.Indeed,thisstudyshowsthat,whileintegraltohumanspeech
production,voicemodulationalsoaffectsthenonverbaldimensionsofvocal
communicationduringmatechoice.Thecapacityforwomenandmentodynamically
altertheirvoicepitchthereforehasthepotentialtoaffectreproductivesuccess,but
beyondthis,mayfunctiontomanipulatetheperceptionsandbehavioursofothersina
widerangeofsocial,economicandpoliticalcontexts[22].
Funding
ThisworkwassupportedbytheEuropeanCommissionthroughaMarieSkłodowska-
CurieindividualfellowshiptoK.P.(H2020-MSCA-IF-2014-655859).
Authors’contributions
K.P.andD.R.designedtheinvestigation.K.P.,M.G.andA.O.collectedthedata.J.P
preparedaudiofilesandquestionnairedataforanalysis.K.Pperformedacoustic
analysis.K.P.,andD.R.performedstatisticalanalyses.K.P.wrotethemanuscriptand
createdthefigures.Themanuscriptwasreviewed,editedandapprovedbyallauthors,
whoagreetobeaccountableforthework.
Competinginterests
Theauthorsreportnocompetinginterests.
Ethics
ThestudywasreviewedandapprovedbytheSciencesandTechnologyCross-Schools
ResearchEthicsCommittee(C-REC)oftheUniversityofSussex(ER-REBY-3,ER-KP292-
3/4).
Dataavailability
Thedatasetsupportingthisarticlewillbeuploadedtofigshare.
FIGURELEGEND
Figure1.Women’sandmen’sF0modulationacrossspeeddates.Panels(a)and(c)
showmaineffectsofpersonalmatechoicepreferencesonvoicepitchmodulation,
whereaspanels(b)and(d)showinteractionsbetweenpersonalpreferencesanddate’s
overalldesirability.Columnsinbargraphsrepresentestimatedmarginalmeansfrom
LMMs(seeTables1andS2),whereerrorbarsrepresentstandarderrorsofthemeans.
Markersinscatterplotsrepresentindividualspeeddates;markersfordistinct
categoriesareminimallyoffsetalongthex-axistoavoidoverplottingandtoimprove
visualisation.Asterisks’indicatestatisticalsignificanceofpairwisecomparisons
followingŠidákcorrection,where***p<.001,**p<.01,*p<.05,andnsp>.05.Correlation
coefficients(r)aregivenbesideeachlinearregressionline.Seeembeddedlegendfor
additionaldetails.
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