The effects of autonomy support on salivary alpha-amylase : The role of individual differences

The effects of autonomy support on salivary alpha-amylase: The role of individual differences

Vanda Sieber

, Julia Schüler

, Mirko Wegner

aUniversityofZurich,Switzerland

bUniversityofKonstanz,Germany

cUniversityofBern,Switzerland

a b s t r a c t

Theempiricalevidencefortherelationshipbetweenautonomy-supportiveenvironmentsandphysio- logicalstressisinconsistent.Whereassomestudiesreportadecreaseinstressinautonomy-supportive environments,otherstudiesshowanegativeeffectofautonomyonphysiologicalstress. Asprevi- ousresearchhasnotconsideredindividualdifferenceswithinthisrelationship,thepresentresearch aimstoclosethisempiricalgapbyproposingthatanimplicitautonomydisposition,whichisdefined asa dispositionalpreference forself-determination, serves as amoderator. In anexperiment, we testedwhethertheautonomydispositionmoderatestheeffectofdifferentteachingstyles(controlling, autonomy-supportive,andneutral)ontheacutephysiologicalstressresponse(salivaryalpha-amylase) inadolescents(N=69).Thestudyrevealedthatparticipantswithahighimplicitautonomydisposition displayedlowersalivaryalpha-amylaseresponseswhenexposedtoautonomy-supportivevignettescom- paredtowhentheywereexposedtocontrollingorneutralteachingstyles.Theoppositepatternwasfound instudentswithalowimplicitautonomydisposition.Theresultsillustratethatexperimentallyinduced variationsinautonomysupportleadtodifferentphysiologicalstressresponses,dependingonindividual differencesintheimplicitautonomydisposition.

1. Introduction

Several situations in everyday life can lead to psychosocial stress,whichisknowntobereflectedinphysiologicalprocesses andcanconstituteaserioushealthrisk(DickersonandKemeny, 2004).Oneimportantaspectaffectingstressineverydaysituations isthebehaviorofpersonsinhigherhierarchicalpositions,suchas superiorsintheworkcontext(Nieetal.,2015)orteachersatschool (ReeveandTseng,2011).Previousstudieshaveconvincinglyshown thatautonomysupporthasbeneficialeffectsondifferentfacetsof well-beingsuchasvitalityandlifesatisfactionacrossdifferentcon- texts(Adieetal.,2008;Levesqueetal.,2004;Patricketal.,2000).

However,therearealsostudiesshowingthatautonomy,suchasthe possibilitytomakechoices,maydecreasepsychologicalwell-being (GrantandSchwartz,2011;Schwartz,2000;SchwartzandWard, 2004).Therearefewerstudiestestingtherelationshipbetween autonomysupportandphysiologicalstress.Theexistingstudies

∗Correspondingauthor.

E-mailaddress:sieber@psychologie.uzh.ch(V.Sieber).

onthislink(ReeveandTseng,2011;O’Donnelletal.,2015)have revealedinconsistenciesanditisnotclearwhetherautonomyis associatedwithanincreaseoradecreaseinphysiologicalstress.

Inaschoolcontext,ReeveandTseng(2011)wereabletoidentify effectsofteachers’autonomysupportonstudents’cortisollevels.

Applyingreasoningfromself-determinationtheory(DeciandRyan, 1985,2000),whichstatesthatpeoplebenefitfromautonomysup- portReeveandTseng(2011),foundthatchildrenconfrontedwith acontrollingteacherdisplayedhigherphysiologicalstressduring a learningactivitythanchildrenconfrontedwithanautonomy- supportiveteacher.Theschoolcontextisofparticularimportance forthepresentstudybecauseautonomyhasbeenpreviouslyshown topositivelyaffectareasthatarerelevantforchildren’spsycholog- icalwell-being(RyanandGrolnick,1986),motivation(Reeveetal., 2004),andperformanceinschool(BlackandDeci,2000).

Incontrasttothisevidenceforthepositivestress-reducingeffect ofautonomy-supportiveenvironments,adifferentstudyillustrated thatautonomycanalsoelevatestress.Arecentlypublishedstudyby O’Donnelletal.(2015)foundthatpeopledisplayedahigherphys- iologicalstressresponse,asreflectedintheirheartratevariability, heartrate,andsalivaryalpha-amylase,whengiventheopportunity

Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-382599 Erschienen in: Psychoneuroendocrinology ; 74 (2016). - S. 173-178

https://dx.doi.org/10.1016/j.psyneuen.2016.09.003

tochoosethetimingoftheirbreaksduringawordprocessingtask inasimulatedofficeenvironment.

Evenapplyingthenecessaryamountofcautionwhencompar- ingthesestudies(differentsetting,differentsamples,anddifferent indicatorsforphysiologicalstress),theyrevealacertaininconsis- tencyabouttheeffectofautonomy-supportivesocialenvironments onphysiologicalstressresponses.Consideringthevastliterature ontheimpactofautonomy-supportivesocialenvironmentsinthe schoolcontextondifferentaspectsofwell-beingandmotivation (RyanandGrolnick,1986;Reeveetal.,2004;BlackandDeci,2000), thepresent studyexamines the effect of autonomy-supportive socialenvironmentsin aschoolcontext,more precisein physi- caleducation.Thissettingisconsideredasparticularlyimportant, aspositiveexperiencesinphysicaleducationclassesareseenas animportantaspectcontributingtoamoreactivelife-style and thereforecancontributetoahealthierlife(Haggeretal.,2003).

Moreover,thepresentresearchsuggestsanautonomydisposition asamoderatingvariable.

Theautonomydispositionisdefinedasastableconcerntoexpe- riencepsychologicalfreedomandtheendeavortofeeloneselfto betheactingagentacrossdifferentsituations(DeCharms,1968;

Schüleretal.,2014).Likeotherimplicitdispositions,whichhave beenshowntoaffectphysiologicalstressresponses(Wegneretal., 2014),theimplicitautonomydispositionisassumedtoreflectnon- consciousandaffect-basedpreferencesforcertainincentives(e.g.

feelingautonomous)(Schüleretal.,2014).Intwostudies,Schüler etal.(2014)foundthatautonomysupportwasespeciallybeneficial intermsofmotivationandwell-beingforpeoplewithamoderate tohighimplicitautonomydispositionbutnotforpeoplewithalow implicitautonomydisposition.Thisresultfullyconfirmsa“match- inghypothesis”(e.g.HoferandBusch,2011;Schüleretal.,2013;

Schüleretal.,2010;SheldonandSchüler,2011),accordingtowhich individualsbenefitiftheirpersonality(e.g.,achievementmotive, autonomydisposition)fitstheirsocialenvironment(e.g.,oppor- tunityforexperiencesofcompetenceorautonomy,respectively).

However,theexistingworkonthematchinghypothesishassofar notanalyzedtheeffectsonstress.Thepresentresearchfillsthisgap bytestingthehypothesisthattheimplicitautonomydisposition moderatestheeffectsofanautonomy-supportiveenvironmenton physiological stress.To bemore specific, we analyzedwhether experimentally-inducedautonomysupportinaschoolsportcon- textproduces differenteffects on salivaryalpha-amylase (sAA) levelsinschoolchildrenwithhighandlowautonomydispositions.

Bytesting thismoderatorhypothesis, weaimtoclarifyhow autonomy-supportive environments affect physiological stress reactionsinaschoolcontext.Wedesignedanexperimentinwhich adolescents’physiological short-termreaction toanautonomy- supportiveorautonomy-restrictivesportteacherwasexamined.

In contrast tolong-term reactionsto stress, which are reliably measuredbycortisol–thatbeingtheprincipalhormoneofthe hypothalamic–pituitary–adrenal axis (HPA) (Ali and Pruessner, 2012; Chrousos, 2009) – short-term and fast stress responses (Skoludaetal.,2015)aremorestronglyrepresentedbytheactivity ofthesympatheticnervoussystem(SNS).TheresponseoftheSNSis veryquick:itactivatespre-ganglionicsympatheticnerves,located in the locus coeruleus. This mechanism triggers the release of norepinephrineandepinephrinefromtheadrenalmedulla,which inturntriggersseveralperipheralreactions,suchasanincreasein salivaryalpha-amylase(sAA),heartrate,andbloodpressure,which canbemeasuredrelativelypromptlyaftertheonsetofthestressor (Ali and Pruessner, 2012; Chrousos, 2009; Naterand Rohleder, 2009).Inrecentresearch,sAAhasbeenshowntoreliablyreflect the short-term reaction to different stressors in experimental situations (Allwood et al., 2011; Nater et al., 2005; Nater and Rohleder,2009;vanStegerenetal.,2006;Skoludaetal.,2015).

2. Methods

2.1. Participants

Sixty-ninestudents(34females.¹)agedbetween12and16years (M=14.16,SD=1.30)participatedintheexperimentalstudy,which tookplaceonaregularschoolday.Theparticipantswererecruited inhighschoolsintheGerman-speakingpartofSwitzerlandandthe samplewasprimarilyCaucasian(N=63;SwissAfrican:N=3,Swiss Hispanics:N=3).Participationwasonavoluntarybasis.Partici- pantsandtheirparentssignedaninformedconsentformpriorto participation.Thepresentstudywasapprovedbytheethicscom- mitteeoftheFacultyofHumanSciencesattheUniversityofBern, SwitzerlandandisinaccordancewiththeDeclarationofHelsinki.

2.2. Designandprocedure

Theexperimentwasconductedinaregularschoolsetting.Sixty participantsweretested in theafternoonand nine participants weretestedinthemorning.Theparticipantsfirstcompletedthe PictureStoryExerciseinordertoassesstheirimplicitautonomy disposition.Afterwards,participantsgavethefirstsalivasample,so astodeterminetheirbaselinesAA.Inordertoobtainunbiasedsam- ples,theparticipantsrinsedtheirmouthswithwaterandwerenot allowedtotalkwhilethesalivasamplesweretaken.Additionally, theywerenotallowedtoconsumenicotineorcaffeine,eatordrink foratleastonehourbeforethesalivasampling.Afterthesaliva samplehadbeentaken,theyreadthegeneralinstructionsforthe experimentalmanipulationandwererandomlyassignedtoeither anautonomy-supportive(AS,n=27),anautonomy-restrictive(AR, n=22),oracontrolgroup(CG,n=20).Inbothexperimentalgroups (ASandAR),participantswereaskedtoprojecttheirthoughtsinto asetofsevenscenariosinwhichtheyhadtointeractwitheither anautonomy-supportiveoracontrollingsportsteacher(forasim- ilarprocedureseeSchüleretal.,2014).Participantswereaskedto vividlyimaginethescenarios,visualizethem,andfocusontheir thoughtsandemotions.Thescenarioswereformulatedfollowing theitemsfromtheHealthClimateQuestionnaire(Williamsetal., 1996)whichwereadaptedtothesportcontext(e.g.,“Ifeelthat my coachprovidesmewithchoices and options”).Tofacilitate thesubject’simagination,theitemswereembeddedintoatypi- calsceneofaphysicaleducationlessoninschool.IntheASgroup, participantsreadscenarioslike:“Yourphysicaleducationteacher explainsthattherearedifferentwaystocarryoutanexerciseand letsyouchoosethewayyouwanttodoit.”Peopleintheautonomy- restrictivegroupreceivedasimilarscenario,wherethebehavior oftheteacherwaschangedintoautonomy-restrictivebehavior, anexamplebeing:“Yoursportsteachertakesadecisionwithout givingarationaleanddeterminesthewayyouhavetocarryout theexercise.”Meanwhilethecontrolgroupwasinstructedtoread thedescriptionofasporthall.Afterthe10-minvignetteexercise, theparticipantswereaskedtogivea secondsAAsample. After samplecollection,theparticipantsansweredquestionsconcerning medicalissues,medication(includingcontraceptives),substance abuse(e.g.smoking,cannabisconsumption),caffeineconsumption, aswellassleepinghabits.²Afterthecompletionofthequestion- naire,theparticipantsweredebriefedaboutthestudy’saims,and writteninformationwasprovidedincludingcontactdetailsofthe responsiblepersonsofthestudy.

1Noneofthefemaleparticipantswereonbirthcontrol.

2Thesurveycontainedothervariablesthatwerecollectedtoanswerresearch questionsnotrelatedtothepresentone.

Table1

Summaryofhierarchicalregressionanalysisforvariablespredictingpost-testsAA,with95%biascorrectedandacceleratedconfidenceintervalsreportedinparentheses.

Confidenceintervalsandstandarderrorsbasedon1000bootstrapsamples.

Variable Model1 Model2 Model3

B SEB p B SEB p B SEB p

Timeatsampling 0.367 0.195 0.061 0.374 0.206 0.066 0.433 0.217 0.047

BaselinesAA 2.851 0.240 0.001 2.864 0.264 0.004 2.835 0.261 0.001

ExperimentalGroup

AR-dummy −0.184 0.642 0.770 −0.010 0.651 0.989

CG-dummy −0.255 0.575 0.673 −0.395 0.553 0.493

Autonomydisposition(Aut) 0.045 0.219 0.840 −0.522 0.342 0.138

Experimentalgroup×Aut

AR-dummy×Aut 1.372 0.684 0.046

CG-dummy×Aut 0.956 0.444 0.037

Note:AR:autonomyrestrictiongroup,AS:autonomysupportgroup,CG:controlgroup,AR-dummy(AS:0,AR:1,CG:0),CG-dummy(AS:0,AR:0,CG:1).

Fig.1.Effectofexperimentalmanipulation(AS=autonomysupport,AR=autonomyrestriction,CG=controlgroup)×implicitautonomydispositioninteractiononsquare roottransformedsAA(salivaryalpha-amylase).

2.3. Materials

2.3.1. Implicitautonomydisposition

TheimplicitautonomydispositionwasassessedusingthePic- tureStoryExercise(PSE,SchultheissandPang,2007;Murray,1943).

Inthepresentstudy,participantswereaskedtowriteimaginative storiesaboutfourstandardpictures(stimulusmaterial:womenin alaboratory,ship’scaptain,trapezeartists,andboxer).Thepartici- pantswereinstructedtolookatthepicturefor15sandthenwrite astoryaboutthepictureforfourminutes.Weanalyzedthestories usingscoringcategoriesfromDeCharmsandPlimpton(1992);for asimilarprocedureseeSchüleretal.,2014).Autonomywascoded whenoneofthefollowingcategorieswasmentionedinthesto- ries:(a)self-determinedgoalsetting,(b)instrumentalactivitiesto reachthegoal,(c)realityperception,(d)personalresponsibility, (e)self-confidence,and(f)personal causation.Twoexperienced raterscodedthestories.Theirinter-raterreliability(ICC)was0.94.

Scoringdisagreementswerediscussedandresolvedinadditional sessions.Autonomyscoresrangedfrom0to15(M=6.36,SD=3.79).

Forsubsequentanalyses,thescoreswerecorrectedforwordcount (rangefrom82to333words),astheywerecorrelated(asrecom- mendedbySchultheissandPang,2007).Followingtheguidelines givenbySchultheissandPang(2007),weusedregressionanalysis toresidualizetheimplicitmotivescoresforwordcountandused theresidualscoresintheanalysesreportedbelow.

2.3.2. Salivaryalpha-amylase

Salivaryalpha-amylase(U/ml)wasassessedbylettingpartic- ipantspassivelydrool10mlofsalivaintosamplingtubesusing SaliCaps^® (IBLInternational,Hamburg,Germany). SaliCapshave beenpreviouslyusedsuccessfullytoassesssAAindifferentstud- ies(forthisprocedure,seealsoSchoofsandWolf,2009;Sumter etal.,2010).Aftercollection,thesampleswerestoredat−20^◦C untilanalysis(seeRohlederetal.,2004;Strahler,2012).Achemi- luminescenceimmunoassayprocedure(IBL,Hamburg,Germany) wasappliedtoassess sAAlevelsin thesamples.Theintra-and inter-assaycoefficientsfortherawsAAscoreswerebelow3%.As theraw sAAmeasuresweresubstantially skewedfor thebase- line (skew=1.18, SE=0.29) as well as for the post-test scores (skew=0.90,SE=0.29),asquareroottransformationwascarried out(transformedskewbaseline=0.38,SE=0.29,transformedskew post-test=0.28,SE=0.29),inordertoobtainanormaldistribution (forthis procedure, seealso Grangeret al.,2007).Additionally, thescoreswerez-transformedinordertoconductthemoderation analysis.

3. Results

3.1. Preliminaryanalysesanddescriptivestatistics

In preliminary analyses we found that the three exper- imental groups did not differ regarding their baseline sAA

scores(AS:M=100.07,SD=75.84;AR:M=96.09,SD=53.41;CG:

M=145.91;SD=99.30),F(2,68)=2.695,p=0.08.Correlationalanal- ysesrevealedthatsAAwasnotassociatedwiththeparticipants’age, r=−0.03,p=0.79.Additionally,nosignificantdifferencesinbase- linesAAlevelswerefoundbetweenpeopleassessedinthemorning andintheafternoon,t(9)=−0.83,p=0.43,aswellasforgender,t (66)=1.08,p=0.27³.Butthetimeofsamplingwasassociatedwith thedependentmeasureofsAA,r=0.29,p=0.02,andistherefore includedinfurtheranalysesasacontrolvariable.

3.2. Moderationanalysis

Inordertotestthemoderatingeffectoftheimplicitautonomy dispositiononsAAresponsesinthethreeexperimentalgroups,a hierarchicalregressionanalysiswasconductedinthreesteps(see Table1).In thefirstmodel, wecontrolled forthebaseline sAA scores,aswellasforthetimeoftesting(z-transformed).Thesecond modelincludedtheexperimentalmanipulation(AS,AR,CG)and themoderator(implicitautonomydisposition).Inthethirdmodel, theinteractionbetweentheimplicitmotiveandtheexperimen- talconditionswasadded.Inordertotesttheinteractionbetween thethreeexperimentalgroups(AS,AR,CG)andautonomydispo- sition,thetwodummyvariablesAR-dummy(coded1forAR,0for ASand0forCG)andCG-dummy(coded0forAS,0forARund1 forCG)werecreated.Theinteractionterms(Model3)weresig- nificantforAR-dummy×autonomydisposition,b=1.37,se_b=0.68, p=0.046,95%BCaCI[0.230,2.962]andforCG-dummy×autonomy disposition,b=0.96,se_b=0.44,p=0.037,95%BCaCI[0.100,1.897].⁴ Thenatureofthisinteractionis depictedinFig.1; peoplewith a high implicit autonomy disposition display the highest sAA scoreswhentheyareexposed toanautonomy-restrictivephys- icaleducationteacher,compared withan autonomy-supportive physicaleducationteacher.In thecontrolgroup, peoplewitha highimplicitautonomydispositiondisplayhighersAAscoresthan thoseintheautonomy-supportivegroup.Incontrast,peoplewith alowimplicit autonomydispositionhadlowersAAlevelsinan autonomy-restrictivesetting,aswellasinthecontrolgroup,but highersAAlevelsintheautonomysupportivegroup.

4. Discussion

Past research examining physiological stress responses to experimentalvariationsin autonomyhasproducedinconsistent results,somefindingpositive andothers negativerelationships.

Thepresentstudyproposesanindividualdifferentiatingvariable, theimplicitautonomydisposition,asanimportantmoderatorof theeffect of autonomysupportonsalivary alpha-amylase.The resultsof the regression analysis illustrate that experimentally inducedvariations in autonomysupport provided by theenvi- ronment(autonomy-supportivevs.autonomy-restrictivebehavior ofaphysicaleducationteachervs.neutraldescriptionofagym) leadtodifferentphysiologicalstressresponsesasreflectedbysAA,

3 Additionallygenderwasnotfoundtobeamoderatoroftheinteractioneffectin themainanalysis,AR-dummy×autonomydisposition×gender,b=1.81,se_b=1.43, p=0.79,95%[−2.069,2.710];CG-dummy×autonomydisposition×gender,b=0.32, seb=1.92,p=0.22,95%[−1.142,4.761].

4 Theinspectionoftotalwordcountindicatesthatfourparticipantswrotestories whichwereshorterthan30words,whichrecurrentlyisconsideredasathreshold forcodingmotiveimagery(c.f.WalkerandAtkinson,1958;HoferandBusch,2011).

Runningtheregressionwithoutthoseparticipantsdoesnotchangetheinteraction pattern(AR-dummy×autonomydisposition,b=1.35,se_b=0.69,p=0.045,95%BCa CI[0.185,2.886]).However,theanalysisforthecomparisonbetweenthecontrol groupandtheautonomysupportivegroupwasweaker,anddidnotreachsignifi- cance,CG-dummy×autonomydisposition,b=0.78,seb=0.47,p=0.09,95%BCaCI [−0.134,1.703].

dependingonindividualdifferencesintheimplicitautonomydis- position.

Taking a closer look at the interaction pattern (see Fig. 1) showsthatpeoplewithahighimplicitautonomydispositionin theautonomy-restrictivegroupdisplayhigher sAAscores,indi- catinghigherlevelsofstress,comparedwithpeoplewithahigh implicitautonomydispositionintheautonomy-supportivegroup andthoseinthecontrolgroup.Forpeoplewithalowimplicitauton- omydisposition,theinteractionpatternisreversed:peoplewith alowimplicitautonomydispositionintheautonomy-supportive groupdisplaythehighestsAAscorescomparedwiththeothertwo experimentalgroups(controlgroupandautonomyrestriction).

Thisresultisinlinewiththeexistingempiricalevidencefrom thematchinghypothesisproposedbySchüleretal.(2013,2014), which states thatpeoplediffer in howtheyreact toautonomy supportprovidedbytheenvironmentdependingontheirimplicit autonomydisposition.Thisstudycontributestothesefindingsby showing that a fit betweendisposition and environment leads todecreasedsalivaryalpha-amylaselevelswhereas amismatch betweenthesevariables leadstoincreasedlevels.Thus, forthe firsttime,aphysiologicalstressresponsehasbeenshowntobe dependentonthedisposition–environmentinteraction.

Thisfindingisofhightheoreticalrelevance,asitprovidesan insightintohowautonomyaffectsphysiologicalstress.Moreover, itcanbeseenasafirststeptoexplainingwhydifferentstudiescame todivergingconclusionsconcerningtheimpactofautonomyon physiologicalstress(O’Donnelletal.,2015;ReeveandTseng,2011).

Additionally,ourresultshaveahighpracticalrelevance,asthey suggestthattheimplicitautonomydisposition–asamoderatorof thelinkbetweenautonomysupportandphysiologicalstress–is animportantfactortoconsiderwhendesigninghealth-promoting schoolenvironments.

5. Limitationsandfurtherdirections

Whereasthepresentstudyfocusedonashort-termphysiologi- calstressreaction,futureresearchisstronglyencouragedtoassess whetheramismatchbetweentheimplicitautonomydisposition andlong-lastingautonomysupportfromtheenvironmentcanlead tochronicstress,whichcanbemeasuredwithlong-termstress indicators,suchascortisol.Inordertoanalyzelong-termstress reactions,thoroughlycontrolledfieldexperimentsareneeded,in whichforexampleateacher’soracoach’sautonomy-supportive behavior isaltered over a longerinterventionperiod of several weeks.Additionally, future researchmight want toadd further short-termstressindicatorsoftheANS,suchasheartrate,heartrate variability,orskinconductance,inordertoconfirmourfindings withsAA.Moreover,ifapplicable,futureresearchshouldstandard- ize timeof sampling,which would beofadditionalimportance whenanalyzingcortisolknowntobesensitivetodiurnalvariations (DickersonandKemeny,2004).

Oneofthestrengthsofthepresentstudyisthatitexamines sAAresponsesinayoungsampleagedbetween12and16years, addingtothescarceresearchbaseinthisagegroup.However,pre- viousresearchcomparingsAAresponsesindifferentagegroups suggestedthatchildrenandolderadultsshowattenuatedresponse patterns(Strahleretal.,2010).Studiesalsosuggestedthatdiffer- encesinpubertalstatusmightbeassociatedwithsAAresponses tosocialevaluativepsychologicalstressorssuchastheLeidenPub- licSpeakingTask(seevandenBosetal.,2014)orpeerrejection (Stroudetal.,2009).Evenifthetaskinthepresentstudydidnot directlyinvolvesocialevaluation,itwouldbeinterestingforfuture researchtoincludeanobjectivemeasureofpubertalstatusinaddi- tiontotheassessmentofparticipants’age.Thiscouldbedoneby aself-reportquestionnairesuchasthepubertaldevelopmentscale

(Petersenetal.,1988)orifapplicable,throughaphysicalexami- nationbyatrainedclinicianwhichisconsideredbestpracticeby manyresearchers(seevandenBosetal.,2014).

Althoughthevignettemethodhasseveralstrengths,suchas minimizing theeffects of physical activityonthe physiological measuresAA(seeforexampleNaterandRohleder,2009),future researchmightalsotesttherelationshipexaminedhereinareal- lifesetting,inordertostrengthenthegeneralizabilityoftheresults.

Additionally,futurestudiesemployingvignettescouldimprovethe methodologicalprocedurebyforexampletestingwhetherindivid- ualsdifferintheirabilitiestoimaginethescenarios,andwhether thisinfluencesthereportedresults.Onelimitationofthepresent studyisthatwedidnotmeasurehowmuchautonomysupportthe participantsexperienced.Thiswasduetothefact,thatweuseda questionnairewhichisusuallyusedtomeasureautonomysupport (Williamsetal.,1996)todesignthevignettes.Employingsucha manipulationcheckwasconsideredasredundantinformation.In ordertoavoidadministeringredundantinformationtothepartic- ipants,futureresearchmightforexampleuseavisualanalogscale withanchorwordsrelatedtoautonomysupport(e.g.,“Icouldact completelyself-determined”versus“Ifeltcontrolled”)inorderto provideamanipulationcheck.

Futureresearchmayalsofocusondifferentsettings,suchas workenvironments, health settings,and other educationalset- tings (universities). More research is also needed to examine the differential effect of established leadership styles, such as transformational leadership,which is known to foster thesat- isfaction of basic psychological needs and support a person’s self-determination(Kovjanicetal.,2012).

Additionally, future research might focus on mechanisms underlying the negative effect of autonomy supportive envi- ronments forpeoplewitha low implicit autonomydisposition.

Followingtherationaleofpreviousresearch,studiescouldassess whether the heightened stress response in people with a low implicit disposition is due to more difficulties in goal striving in domains that target thespecific disposition they are low in (seeSchultheissandKöllner,2014).Autonomy supportiveenvi- ronments therefore might act as a stressor for people with a low implicit autonomydisposition, and might lead toeffortful goal-pursuitandlowmotive-drivenhedonicresponse.Moreover, autonomysupportiveenvironmentscouldalsoactasdisincentive (Schultheiss,2008)forotherimplicitmotives(suchasaffiliationor achievement)forpeoplewithalowautonomydisposition.Asacon- sequence,thedisincentivecouldactasstressortotheirdominant implicitmotive(SchultheissandKöllner,2014).

Conflictsofinterest

Theauthorshavenoconflictsofinterestanddeclarenonfinan- cialinterests.Allauthorsdiscloseanyactualorpotentialconflict ofinterestincludinganyfinancial,personalorotherrelationships withotherpeopleororganizationsthatcouldinappropriatelyinflu- ence,orbeperceivedtoinfluence,theirwork.

Contributors

Allauthorswereinvolvedintheconceptionanddesignofthe study.Theacquisitionandanalysisofthedatawasmainlycon- ductedbyVS.VSwrotethefirstdraftofthemanuscript. JSand MWmadesubstantialcontributionstothefirstdraft,byrevising itcritically.Allauthorscontributedandhaveapprovedthefinal manuscript.

Roleofthefundingsource

ThisworkwassupportedbyfundsfromtheFederalOfficeof Sports in Switzerland (Grant NR 37-203). Saliva sampling was fundedbyresearchfundingoftheUniversityofBern,Switzerland (31-375).Bothfundingsourceshad nofurtherrole inthestudy design;collection,analysis,andinterpretationofdata;inwriting thereport;orinthedecisiontosubmitthepaperforpublication.

Acknowledgements

VandaSieberis supportedbytheFederal Officefor Sportin Switzerland(BundesamtfürSport).Additionallywewouldliketo thankManuelaEngelandSamanthaGerberfortheirsupportindata collection.

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