Source of arousal and memory for detail

25 Pages·2010·2.2 MB·English

Memory&Cognition
1999,27(l), 166-190
Source ofarousal and memory for detail
TERRYM.LIBKUMAN,PENNEYNICHOLS-WHITEHEAD,
JAMESGRIFFITH,andROSALIETHOMAS
CentralMichigan University,Mt. Pleasant,Michigan
Twoquestionsabouttherelationshipbetweenarousalandmemorywereinvestigated:First,doesthe
source ofarousal influencememory,and,second, whatimpact does arousal haveonmemoryforde
tail?InExperiment 1,physiologicalarousal (runningornotrunninginplace)wasfactoriallycombined
withemotionalarousal (viewinganeutralor anemotionalslidesequence). Recognitionmemorywas
testedforgist,centraldetail,andbackgrounddetail.Experiments2and3weresimilartoExperiment1,
withtheexceptionthatacuedrecalltask wasusedinExperiment2andphysiologicalarousalwasma
nipulatedwithstationarybikinginExperiment3.Theresultsoftheseexperimentsindicatedthatphys
iologicalarousalhadlittleimpactonmemoryandthatemotionalarousalledtoimprovementsinmem
oryforbothcentralandbackgrounddetail.Overall,theseresultssupportedthenotionsthatthesource
ofarousalisanimportantdeterminantofanevent'smemorability(Christianson, 1992a)andthatemo
tionalarousalserves toenhancethescope ofmemory(i.e.,flashbulb memory;Brown& Kulik,1977).
Weareinterestedintwo questionsconcerningthe re psychological, for example. Itis hoped that this view, if
lationship between arousal and memory. First, does it takenseriously,wouldleadtoempiricalinvestigationsex
matterhowoneisaroused-thatis,doesinducingarousal ploring in more detail the relationship betweentypes of
through different means lead to differencesin memory? arousal and their impact on memory. Systematic explo
Second, what impact does arousal have on memory for ration would be particularly important, given the lack of
centralandperipheral (background)details? anypersuasiveexplanationconcerningthe sourcesofau
Theanswertothe first questiondepends onthenature tonomicnervous systemactivation(Mandler, 1992).
ofthe arousal. The traditional view,possibly beginning Onlyafewstudies havecompareddifferentwaysofin
withYerkesandDodson's (1908)inverted-U,assumesthat ducingarousal,especiallywithin the framework ofmem
arousal isaunitaryprocesswith nonspecificor general ory research. Christianson and Mjorndal (1985) com
izableproperties. Similarly, Duffy (1962) characterized pared the memory performance ofsubjects who were
arousal as the "excitation ofthe individual as a whole" aroused throughadrenalineinjectionswiththatofsaline
(p.3).Morerecently,andconsistentwiththeunitaryview, injected controls. No differences in memory for neutral
Revelleand his colleagues (e.g., Humphreys & Revelle, pictureswerefoundbetweenthetwogroups. Christianson,
1984;Revelle& D.A.Loftus,1992)referredtothearousal Nilsson,Mjorndal,Perris,andTjellden(1986) compared
construct as the nonspecific energetic or intensity com adrenaline-injectedsubjectswhoviewed neutralpictures
ponent ofmotivation. The traditionalview,however,has with saline-injected subjects who viewed emotionally
had its critics. Neiss (1988a, 1988b) and Christianson arousingpictures.Christiansonetal.reportedthattheemo
(1992a), for example, have taken the position that the tionally arousing pictures led to decrements in memory
inverted-Uisirrefutableandthereforeshouldbe"retired." performance(i.e., amnesia).The data from these studies
Thealternativeviewistocharacterize arousalasamul led Christiansonand his colleaguesto concludethat the
tistateormultidimensional process(Neiss, 1988a,1988b). sourceofarousal isimportantindeterminingitsinfluence
Thisviewisconsistentwith the earlier classicalwork of on memory. In particular, the source ofarousal must be
Lacey(1967), inwhich hedivided arousal into thephys relevant to the to-be-remembered event before it can
iological,thecognitive,andthebehavioral.Giventhelack haveany impactonmemory.
ofsolidtheoryandthepaucity ofdata,Broadbent's(1971) Oneofthepurposesofthepresentresearchwastofur
position maybe the most tenable-thatis,as apractical therexploretheeffectsofdifferentsourcesofarousal on
matter,itmaybebettertooperationallyseparatethe var memory. In particular,two sources ofarousal were ma
ious indices ofarousal into the physiological and the nipulated: physiological arousal, induced by stationary
running or biking, and emotional arousal, induced by
slides containingscenesofasurgeonperforminganop
ThisresearchwassupportedbyaCentralMichigan University Fac eration. The present factorial design (i.e., presence or
ultyandCreativeEndeavorsgrantawardedto1.M.L.Wethankthefol absence ofphysiological arousal factorially combined
lowingindividuals for their thoughtfulcomments: Elizabeth Loftus, with presence or absence ofemotional arousal) permits
HajimeOtani,DebraPoole,DanielReisberg,andCharlesStabler.Cor
usto lookatthe interactivenature ofdifferentsources of
respondenceconcerningthispapershouldbeaddressedto1.M.Libku
man, Departmentof Psychology,Central Michigan University, Mt. arousal, somethingthat hasnotbeen examinedinthe lit
Pleasant, Michigan 48859(e-mail: [email protected]). erature.
Copyright 1999Psychonomic Society,Inc. 166
SOURCEOF AROUSAL AND MEMORY 167
The second question (i.e., what impact does arousal recent reviews ofthis literature (Christianson, 1992a;
have on memoryfor centraland peripheraldetails?)has Heuer& Reisberg, 1992) have supportedthe theory.
alsoledtoanumberofalternativeviews.Themore recent This theoretical account has beenusedto explainthe
view suggeststhat memory for both centraland periph weapon focus effect that has been reported in the eye
eral informationshouldimprovewith arousal. Flashbulb witnessliterature.The weaponfocus effect isassumedto
memories(Brown&Kulik, 1977;Conway, 1995)areas occur, for example,whensomeoneisan eyewitnesstoa
sumedtocontainrelativelypermanentandcompletepho robbery or shooting. Presumably,the eyewitnesswill be
tographic detail ofan emotional event. Brown and Ku able to describe the weapon in greatdetail but will pos
lik's flashbulb mechanismparallels Livingston's (1967) sess little ifany memory about the perpetratoror other
neurophysiological nowprinttheory: Ifan eventis suf aspects ofthe event (Cutler, Penrod, & Martins, 1987;
ficiently arousing and is highly consequential to the in Kramer, Buckhout,&Eugenio, 1990;E.F.Loftus, 1979;
dividual, anowprintcommandis given. The brainthen E.F.Loftus,G.R.Loftus,& Messo, 1987;Maass& Kohn
permanently records all available information (i.e., all ken, 1989). However,there are studiesthat havefailed to
sensory input and cognitions immediately priorto and providesupportfortheweapon focus theory(see Steblay,
during the event), leadingtoavivid, detailed, and accu 1992,forameta-analysisofthesedata). Inaddition,many
rateaccountoftheemotionaleventaswellasofthedetails ofthese studiesaredifficulttocompareandinterpretbe
surrounding the emotional event. In addition to Brown cause ofdifferences in methods and to-be-remembered
and Kulik, evidence favoring this view includesBohan material as well as differing definitions ofcentral and
non's (1988),Christianson's(1989),andHeuerandReis peripheral information (Christianson, 1992b; Heuer &
berg's (1990) research. Finally, and most recently, the Reisberg, 1992).
basic assumptions and empirical findings ofthis view The variability in the definitions ofcentral and pe
have been incorporated into a causal model, using a ripheral informationisparticularlytroublesome,because
structural equations approach (Conway et al., 1994). it might be related to the different conclusions across
However,despitethedevelopmentofsophisticatedmod studies. Heuer and Reisberg (1992), for example, have
eling procedures, as well as the inherent interest in the suggestedthatmemoryfordetailisdependentonthe re
flashbulb notion, there is considerable debate concern tention interval: Shortdelays are assumedto lead to in
ing the natureofthe phenomenon. Forexample,towhat feriormemoryfordetail,whereas longdelaysareassumed
extentcan flashbulbmemoriesbeexplainedonthe basis to lead to superior memory for detail. Christianson
ofordinarymemorymechanisms(Cohen,McCloskey,& (1992a)hasinterpretedthisliteratureasindicatingthatre
Wible, 1988, 1990; McCloskey, Wible, & Cohen, 1988; searcherswho havefocusedoncentraldetail orgisthave
Pillemer, 1990; Schmidt & Bohannon, 1988)? In addi concluded that emotional arousal improves memory,
tion, the evidence supporting this position is largely whereasresearcherswho have focusedonperipheralde
anecdotal, leading to questions concerning the veracity tailhaveconcludedthat emotionalarousalimpairsmem
ofthe reported memories (McCloskey et al., 1988). ory. Obviously, these interpretations are dependent on
Studiesthat have comparedindividual accounts oftrau what constitutescentralandperipheraldetail. Heuerand
maticevents havereportednumerouscontradictionsand Reisberg (1992) suggested that we do not know which
discrepancies (e.g., McCloskey et aI., 1988). Further partitionofcentralandperipheralisthe correctone and,
more, Weaver (1993) concludedthat individuals simply therefore, itmaybebest totreatthecategorizationofthe
havemoreconfidenceconcerningtheirmemoryfortrau to-be-remembered material as an empirical matter. In
matic events, rather than there being any differences in otherwords, investigationsinwhich centraland periph
theirmemoriesper se.Finally,theexperimentalevidence eral detail are definedand treateddifferentlymay be of
supportingthepositionthatarousalleadstoimprovement some value inclarifyingthe issue. Ourtreatmentofthis
in both central and peripheral information is scarce. In issue isbasedon the Heuerand Reisberg(1990)and the
fact, wewereable tofindonlyone sourcethat supported Burke, Heuer, andReisberg(1992)studies.Intheformer
this view (Heuer& Reisberg, 1990), and this studycar study, centralandperipheraldetailswere definedas"el
ries with it interpretative problemsconcerningthe defi ements central to the story ... and details peripheral to
nition ofwhat constitutescentraland backgrounddetail. thestory"(p.497),respectively.Usingrecognitionandre
This issue will be discussed in more detail later in this callmeasures,theirresultsindicatedthat, when subjects
paper. were aroused, memory performance increased for both
The more popular alternative position (Easterbrook, centralandperipheraldetail. Inthe latterstudy,recogni
1959)assumesthat higharousalnarrowsthe focus ofat tion test items were categorizedinto four types ofto-be
tention, which, in turn, allows the organism to focus on remembered information: Items previously categorized
only the more salientcues. This hypothesis leads to the ascentraldetailweresubdividedintogistandbasic-level
prediction that the central details ofan event should be visual information, and items previouslycategorizedas
well remembered, whereas the peripheral detailsshould peripheral detailwere subdividedinto centraldetailand
not.The earlierdata supportingthis viewwere inconclu backgrounddetail.Althoughtheresults ofthisstudywere
sive (Eysenck, 1976, 1977). However, authors ofmore complicated,thedatabasicallyindicatedthat, whensub-
168 LIBKUMAN, NICHOLS-WHITEHEAD, GRIFFITH, AND THOMAS
jects werearoused, memoryforcentral detail improved, weremostevident,particularlyforcentralandperipheral
whereasmemory forbackgrounddetail declined. details, intheimmediatetesting condition,wedidnotbe
In the present series ofthree experiments, we have lievethatitwasnecessarytoincludeadelayedtestingcon
replicated much ofthe methodology ofthe Heuer and dition.
Reisberg (1990) and Burke et al. (1992) experiments.
However,becausewewerenotabletoempiricallyseparate Method
basic-levelvisualinformationfromgist,thesecategories Subjects.EightyundergraduatestudentsfromCentralMichigan
werecombinedintoone.Forthepurposeofclarity,wewill University were recruitedfrom introductorypsychologyclasses.
Thesubjects wererandomly assignedtothefourtreatmentcondi
callthiscombinedcategorygistthroughoutthepaper. In
tions,withtherestrictionthateachconditioncontainanequalnum
Experiment1,weexaminedtheroleofphysiologicaland
berofwomenandmen.
emotionalarousal onmemoryfordetail. Thepurposeof MaterialsandApparatus.Thestimuliconsistedoftwosetsof
thesecondexperimentwastoextendthegeneralityofthe 12slidesthatweredevelopedbyHeuerandReisberg(1990).1Each
findings fromour first experiment(where arecognition slidewasaccompaniedbyatapednarrativethatwasalsodeveloped
measurewasused)byusingacuedrecallmeasureofmem byHeuerandReisberg(1990)andrevisedbyus.AKodakCarousel
850slideprojectorwasusedtoprojecttheslidesontoascreenata
ory.Finally,thethird experimentexaminedthepossibil
size ofapproximately 18 X 24in.and aheight ofapproximately
itythatdeclining arousal levels(inExperiments 1and2,
3\12ft.Thesubjectswereseatedapproximately6ftfromthescreen.
arousalwasinduced throughstationaryrunningpriorto
AWollensak3Mtape recorderwasused topresent thetaped sen
encodingbutwasnotmaintainedduringtheencodingin tences.Thetaperecording incorporated atonetosignalautomatic
terval)mayberesponsiblefortheeffectsinExperiments1 advancementoftheslideprojector.
and2.Inthethirdexperiment,physiologicalarousalwas Theslidesdepictedtwoversionsofastoryaboutamotheranda
maintained bystationarybikingduring encoding. sonvisiting thefather atwork.Inone(neutral) version, thefather
isamechanicandfixes acar.Intheother (emotional)version,the
Overall,thedesign forthethreeexperimentsinvolved
fatherisasurgeon andperforms anoperation. Theslidepresenta
sourceofarousal(physiologicalandemotional)andtype
tionhadthreephases,withtheemotionalmanipulationtakingplace
ofinformation (central detail, background detail, and inPhase2.InPhase I,Slides1-3andthecorrespondingtapednar
gist). In these three experiments, the predictions were rativeswereidentical forbothstories,showingthemotherandson
similar. Ifthe multiple state model proposed by Chris ontheirwaytovisitthefatheratwork.Slide4showedthefather's
tiansoniscorrect, physiologicalarousal shouldnot have workplace-agarage inthe neutral version and ahospital inthe
emotionalversion. The second phase containedthe four critical
anyimpactonanymeasureofmemory(i.e.,central,back
slides(5-8),whichdifferedforthetwoconditions.Intheemotional
ground, orgist), whereasemotionalarousal shouldlead
condition,thesonwatchesthefatherperformanoperationonapa
to enhanced memory. Furthermore, ifthe Easterbrook tient.Fortheneutralcondition,thesonwatchesthefatherrepairthe
(1959) hypothesis and the conclusions ofChristianson engine ofan automobile. The differing slides were matchedas
(1992a)andHeuerandReisberg (1992)arecorrect,emo closelyaspossible forcontentandvisualform. Thenarrativesen
tional arousal should lead to memory enhancement for tencesforeachslidewerematchedascloselyaspossibleforstruc
tureand length. InPhase 3(thefinal phase), Slides 9-12andthe
central but not for background detail (i.e., the weapon
correspondingnarrativeswerethesameforbothconditions, show
focus effect; E. F. Loftus, 1979). On the other hand, if
ingthemotherleavingthefather'sworkplace,makingaphonecall,
flashbulbtheory (Brown&Kulik, 1977)iscorrect,emo
andhailing acab. Phase delineations were made for purposes of
tional arousal should lead to memory enhancement for analysesonlyandwerenotapparenttothesubjects.
centralandbackgrounddetail.Nopredictionsweremade IntheBurkeetal.(1992)andHeuerandReisberg (1990) stud
for gist, although it could be argued that memory im ies, the slides were also subdivided into three phases. However,
provementshouldoccurforthismaterialaswell. theseauthors includedthefirst threeslidesinPhase Iandthenext
five slides in Phase 2, with the remainingfour slides being in
Iftheunitary view ofarousal iscorrect,memoryper
Phase3.Itispossible, therefore, thatanydifferences inresultsbe
formanceforphysiologicalandemotional arousal should
tweentheBurkeetal.andHeuerandReisberg (1990) studiesand
mimic thepredictions for emotional arousal inthe mul ourstudiesmaybeafunction oftheplacementofSlide4.Onthe
tistatemodel-thatis,onlymaineffectsshouldoccurfor basis ofour view,whether Slide 4(for both the hospital andthe
bothtypes ofarousal. In other words, the effects should garageslidesequences)isplacedinPhase IorPhase2isdependent
beadditive,not multiplicative. ontheperceivedreactivity andemotionality ofSlide4inthehos
pitalslidesequence. Iftheperceivedreactivityandemotionality of
thisslideissimilartothosefortheslidesinPhase I,Slide4should
EXPERIMENT1
beplaced inPhase I. Iftheresponses are similar tothose forthe
slidesinPhase2,itshouldbeplacedinPhase2.IntheBurkeetal.
The main purpose ofExperiment 1was to determine andHeuer and Reisberg (1990) studies, aswell as inthe present
theinfluence ofphysiological and emotional arousal on studies,ratingscaledataonreactivityandemotionalityoftheslide
recognition memory for the central and background, or presentationdid not address this issue, because the ratings were
peripheral,aspects ofanevent.Although this study repli basedontheentireslidesequence.
Inordertodeterminetheperceivedreactivityandemotionalityof
cates,inpart, theexperimentsofBurkeetal.(1992),itis
eachslide,datawerecollectedon36introductorypsychology stu
important tonote that the Burke etal. studydid include
dents.Thesestudentswererandomlyassignedtothehospitalorthe
a delayed testing condition, whereas our study did not. garageslidesequence.Eachslidewasshownfor10sec.Duringthis
Because the effects ofinterest in the Burke et al. study interval,thesubjects wereinstructed toviewtheslideandratethe
SOURCE OFAROUSAL ANDMEMORY 169
emotionalityand theirresponses, using the same rating scale in ontojudgethe items onthe revised memorytest. Unlimitedtime
strument(describedinthe following paragraph) that was used to was allowed forthejudgestoview the slides, read the narratives,
evaluate the entire slide sequence in the present experiments. andmaketheirevaluations.Contentvaliditywasquantifiedbyusing
Analyses ofthese data indicatedthatonly Slides 5~8inthehospi a4-point rating scale toassess the relevance ofeach test item for
talpresentationelicitedagreement,indicatingthattheseslideswere eachcategoryofinformation. Ratings werethendichotomizedinto
emotionallyarousingand that the subject's response to them was twocategoriesofrelevance-weakorstrong. Onlyitemsjudgedto
emotional.Slide4wasthereforeplacedinPhase Iforallanalyses bestronglyrelevantbya75%orgreaterconsensusamongthejudges
reportedinthispaper. Wouldtheresults ofourstudiesbeanydif were retained for the final version ofthe test. All the other items
ferent ifSlide 4wasplacedinPhase 2?The results when Slide 4 wererevised andjudgedagain oromittedentirely.Overall, there
wasinPhase Iwerecomparedwiththeresults whenSlide4wasin vised version ofthefour-alternativeforced-choice recognitiontest
Phase 2forall ofthe memorymeasures inallofour studies. The contained87questions intheemotionalversionand90questions in
outcomes ofthese analyses indicatedthat the results were essen the neutral version. Items were distributedas evenly aspossible,
tiallythesame, regardlessoftheplacementofSlide 4. with8to10itemspercategory,perphase.Fifty-threepercentofthe
APolarFavorheart rate monitorwasused totrackthesubject's itemshadacontentvalidity of1.00,and47%oftheitemshadaco
heartratesthroughouttheslidepresentation,toassessarousal. The efficientof.75.Thetesthadanoverallcontentvalidity coefficient
monitorwasstrappedaroundthesubject'sbody at the levelofthe of.88.QuestionspertainingtoSlides 1-3 and9-12wereidentical
solarplexus. A9-pointLikertscale (anchoredon one end with forboth emotionalandneutral conditions.Questionspertainingto
stronglydisagree[ascalevalueof-4]andtheotherendwithstrongly Slides 4-8were matchedascloselyaspossible forthe twocondi
agree [ascale value of+4])wasused toratetheemotionalityand tions.Thequestionstestedmemoryforthreecategoriesofinforma
thesubject'sreactionstotheentireslidesequence. Aquestionnaire tion:gist,centraldetail,andbackgrounddetail.Anexampleofagist
thatcontainedquestions(unrelatedtothecontentoftheslidesand questionwas"motherandsonare..."Thefouralternativeswere:en
narrative) abouthowlongthesubjectstendedtothinkaboutevents teringabuilding,passingaplayground,buyingcigarettes,andwalk
beforeandaftertheyoccurredactedasafiller tasktemporallysep ingdownthesidewalk. Thecorrect answerwasthelastalternative.
arating theslidepresentationandtherecognitiontest. Anexampleofacentraldetailquestion was"whatisthecolorofthe
Contentvalidity ofthe recognitiontest. Acontentvalidity door?" The four alternativeswere: blue, brown, green, and black.
studywasconductedontherecognitiontestusedintheBurkeetal. Thecorrectanswerwasthefirstalternative.Anexampleofaback
(1992)study.ThistestwasoriginallydevelopedbyHeuerandReis grounddetailquestionwas:"oneoftheobjectsthatspilledoutofthe
berg (1990) and then modifiedbyBurke etal.Four graduatestu carwas..."Thefouralternativeswere:abriefcase,anairlinebag,
dentswhowerenotpartofthestudyweretrainedasjudgesandthen asparetire,andatoolbox.Thecorrectanswerwasthesecondalter
askedtocategorizethe questionsaccordingtothedefinitionspro native.Thequestionspertainingtothethreecategoriesweredistrib
vided byBurke et al. There wasvery little consensus(an overall uted asevenlyaspossible across the test. The questions werepre
contentvaliditycoefficientof.35)among thejudgesastothecor sentedin the same sequence for all the subjects, because some
rectcategoriesforthequestions.Disagreementoccurredlargelyin questions presupposedanswerstoprevious questions.
separatinggistfrombasic-levelvisualinformationandcentralfrom Design. Thedesignwasa2 X 2 X 3 X 3factorial,withphysio
backgrounddetail. Test items were revised, whereverpossible,to logicalarousal(arousalandnonarousal)andstorytype(emotionaland
removeambiguitiesand tomakesurethat options agreedwiththe neutral)asbetween-subjects variablesandphase (1-3)andcategory
informationintheslidesandthenarrativesforboththearousal and ofinformation(gist,centraldetail,andbackgrounddetail)aswithin
theneutralconditions.Thenarrativesweusedwerethesameasthe subjectsvariables.Eachcategoryofinformationwasanalyzedsepa
narrativeslistedintheappendix(p.506)oftheHeuerandReisberg rately,using percent correct recognition asthe dependent measure.
(1990) paper, with the exception ofSlides 9, 11, and 12.In the Procedure. The subjectswere tested individually. The experi
HeuerandReisberg(1990) paper,Slide9narrativesfortheneutral mentergreetedandseatedeachsubjectandthenreadtheinstructions
and arousal conditionswere "motherleaves the garage being late aloud. Theexperimenterinformed the subjects thatthepurposeof
forherjob"and"motherleavesthehospitalupsetbywhatshesaw," thestudywastoinvestigate theeffects ofvisual stimulionphysio
respectively. In Slide 11,the neutral and arousal narratives were logical arousal. The instructions also indicatedthat the subjects
"motherapologizesforherdelaytoherboss"and"motherasksher mightberequiredtoruninplaceandthenaskedthemtosignacon
boss to get the day off," respectively. In Slide 12,the neutral and sentformstatingthattheyknewofnomedicalorotherreasonwhy
arousal narratives were "she tries to hail acab downtown at the theyshouldnotparticipate.Approximately5minafterthesubjects
number3busstop" and"shetriestohailacabhome atthenumber wereseated,theexperimentertookabaselinemeasureofheartrate.
3busstop,"respectively.Theneutralandarousalnarrativesweused After abriefdemonstrationbytheexperimenter,thesubjectsin
for Slides 9, 11,and 12were identicalto their neutral narratives, thephysiologicalarousal conditionwere asked torun inplace for
with theexceptionthat, inSlide 9,theword hospitalreplacedthe Imin.TrouveandLibkuman(1992)reportedthatthisprocedurein
wordgarageinourarousal condition. creases heartratebyabout 60%andthatittakes about6-8minfor
Sometestitemscouldnotbealteredsatisfactorilyandwereelim heart ratetoreturntobaseline.Thetimeofincreasedphysiological
inated entirely. New items were added to equalizethe number of arousal is,therefore,wellwithin theboundariesofthetimeittakes
itemsacross conditions,categories,andphases. Thetargetnumber to view the slides(about84sec). The subjects inthe nonphysio
was 10items per category, per phases, for both storyconditions. logicalarousal conditionwererequiredtositfor Imin.Thephysi
The category ofbasic-level visual information was combined ological arousal subjectswereagain seated, andasecondmeasure
withgist,becausejudgescould notconsistentlyseparatethe items ofheart ratewastaken.Asecondbaselinemeasureofheart ratefor
for these categories. In addition, the main interestofthe present thenonphysiologicalarousalsubjectswastaken 1minafterthefirst
studywasthecontrastbetweencentral andbackgrounddetail, and, measure. Theslidepresentationthenbeganimmediatelyandlasted
therefore, theseparationofbasic-levelvisual informationandgist approximately84sec.Eachslidewasshownfor6sec,witha I-sec
wasunnecessary. interval betweenslides. Eachtaped narrativebegan approximately
Initially,thejudgesweretrainedwithashortslidestory withac Y2 sec after the corresponding slide appearedand lasted approxi
companyingnarratives, aswellasindividual slides thatwereunre mately4sec. Heart ratesweremonitoredthroughoutthepresenta
lated.Acompanionsampletestwasusedtoprovideeachjudgewith tion,with individualmeasurestaken approximately2,4,and6sec
realisticpractice. Thejudgesweregivenwritten definitionsandin after each slide began. After viewingthe slides, thesubjectswere
structionsandimmediatefeedback onthesampletest,beforegoing giventheemotionalityscales andafillertaskthattook 10-15min
170 LIBKUMAN, NICHOLS-WHITEHEAD, GRIFFITH, AND THOMAS
tocomplete. Therecognitiontestwasthenadministered.Afterthe Memorymeasures. Figure 1depictsthe three mem
testwascompleted,thesubjectsweregivenawrittendebriefingand ory measures for physiological arousal across phases.
thanked fortheirparticipation. Figure2depictsthethreememorymeasures foremotional
arousal across phases. The95%confidenceintervalsare
Results plottedaroundthemeans. Theconfidenceintervalswere
Cell means and standard errors for all ofthe depen calculated using the pooled estimate of the within
dentmeasures forthethree experimentsarepresentedin conditionvariance(G.R.Loftus&Masson, 1994)foreach
tabular form inthe Appendix. phase.Eachphaseincludedthebetween-subjectsvariables
Heart rate data. Initial baseline heart rates ranged ofphysiological and emotional arousal. When viewing
from51to110beatsperminute(bpm).A2(physiological both figures, it is clear that memory performance was
arousal) X 2 (story) analysis ofvariance (ANOVA) re bestforgist,worstforbackgrounddetail,andintermediate
vealed no significant effects. Mean heart rates ranged forcentral detail. Inaddition, memoryperformanceim
from76to79bpm.Forthesecondbaselinemeasurement, provedacrossphases forgistbutnotforcentral detailand
takenafterphysiologicalarousal wasmanipulated, heart backgrounddetail.
rateswere significantlyhigher for the subjects who ran Figure 1indicates that physiological arousal did not
inplace(M=139bpm) than forthesubjectswhodidnot influenceanyofthememory measures.In contrast,Fig
run in place [M= 80 bpm; F(1,76) = 249.87, MSe = ure 2indicatesthat emotionalarousal did influencetwo
276.74,p < .0001]. ofthe memory measures. The first panel indicates that
Heartrateswererecordedthreetimesduringeachslide, gistwasnotinfluencedbyemotionalarousal. Thesecond
approximatelyevery2sec.Thesecondmeasure(takenap panel indicatesthat central detail memory was superior
proximately4secafterslideonset)foreachslidewasused for the hospital story, relative to the garage story, for
tocalculatemeangroupheartratesforeachphase. A2 X Phases 1and2.Thesefindings replicate,inpart, thoseof
2 X 3(physiological arousal X story X phase) ANOVA Burke et al. (1992), who also found that subjects who
revealed significant effects for physiological arousal viewedthe emotionalstory performedbetterinPhase 2,
[F(1,76) = 11.92, MS = 981.01, P < .0009], phase wherethearousalmanipulationtookplace.Thethirdpanel
e
[F(2,152)= 174.45, MS = 20.05, P < .0001], and the indicates that background detail memory was superior
e
physiological arousal X phase interaction [F(2,152) = forthegarage story, relative tothe hospitalstory,during
97.5l,p< .0001].Theinteractionindicatedthatthemean Phase 1.Most notable, however, is the superior perfor
heartratesforthesubjects whoraninplace startedmuch mance for the subjectswho viewed the hospital story in
higherandthendropped,relativetothesubjectswhodidnot Phase 2.
run inplace.No significanteffectswere found for story.
Thesecond measureofheart rate wasused becauseit Discussion
wouldallowsometime(4sec)fortheeffectsoftheslides Anexaminationoftheseresults revealstwointeresting
onheartratetomaterialize. However,inordertoreplicate findings. First, no effects were found for physiological
themethod used byBurkeetal.(1992), the lowest heart arousal. Second, although emotional arousal had little
rate measure for each slide was also used to calculate impact ongist, itenhancedmemoryforbothcentral and
meanheartrates forthenonphysiologicallyarousedsub background detail. It is important to note that memory
jects. Unfortunately, these measures were not recorded performance for gist improved across the phases for all
forthefirst 9subjects,soonlydatafromthe last 31sub groups, probablybecauseofthedevelopmentofthestory
jects in the nonphysiological arousal conditions were lineacrossphasesofthe slide presentation(i.e., theear
availableforanalysis. The 2(story) X 12(slides)mixed lieraspects ofthe story provideaframeworkforthelater
effects ANOVArevealed only a significant main effect aspects, which are betterencodedand remembered).
forslides [F(11,319)= 12.38, MS = 10.92,P< .0001]. It shouldalsobenotedthatthecentralandbackground
e
Ingeneral, mean heartrates declinedfrom Slide 1(M= detail memory performance ofthe subjects in Phase 1
43.93) through Slide 3(M= 80.10) and then essentially wasdifferentfortheemotionalstory,relativetotheneutral
remained stable for theremainingnine slides. story.Becausethe emotionalmanipulationtook place in
Rating scales. Analyses ofthe emotionality rating Phase 2,the story effects in Phase 1were not expected.
scale data, using 2 X 2 (physiological arousal X story) Oneexplanationfortheseeffects isthat Slide 4isdiffer
ANOVAs,revealed asignificantstory effect forboththe ent inthe two conditions. Slide 4 inthe emotional story
emotionality ofthe slide presentation [F(1,76) = 51.72, includesthe front ofahospitalbuildingthat occupiesal
MS =3.31, P < .0001] and the subjects' responses most the entire frame ofthe slide. Otherthan cars inthe
e
[F(1,76)=48.34, MS =2.85, P< .0001]. The subjects street, the only otherdetails are items such as windows
e
who viewed the hospital story rated the story and their andlightpoles. Intheneutral story, Slide 4depictsagas
responses asbeing more emotionalthan didthe subjects station, with adarkbuildinginthebackgroundandacar,
whoviewedthegaragestory(Ms= 5.6and5.0vs.2.7and asmall building, and apole inthe foreground. The con
2.4,respectively, when the signonthe 9-pointscale was trastbetweenthetwoslides,interms ofcontentandcom
ignored). No other effectswere significant. position, isquite clearandcouldleadtoperformancedif-
SOURCEOFAROUSAL AND MEMORY 171
QlntraIDeIaII
1m
1CIl
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...... ItlE11Jd118 1lO
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III p;;; 4=' III
70
70
~ III JIII
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10 10
0 0
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8ackgolIldDetail
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70
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Phase
Figure1.Experiment1:Memoryforgist,centraldetail,andbackgrounddetailasafunctionofphaseandphysi
ologicalarousal.
ferencesbetweenthe twostories.There isanother possi with findings reported by Heuer and Reisberg (1990)
ble explanation for the memory differences in Slide 4. and Burke et a1.
However,because this effect is also evident in Experi The most important finding ofExperiment 1wasthe
ments 2and 3, discussionofthis issue will be reserved improvementinmemoryforbackgrounddetailwhenthe
for the General Discussion section. FinalIy,in contrast subjectswereexposedtotheemotional arousalcondition
to the Heuer and Reisberg (1990) and the Burke et al. (i.e.,thehospital story). Thisfindingwascontrary tothe
(1992)studies, inwhichheartratesdeclinedforsubjects Burkeetal.(1992)results,inwhichtheyfoundthatmem
who viewed the emotional story (i.e., the orienting re ory for background detail was superior for the garage
sponse), we found that heart rates declined for the sub story.WepartialIy replicatedtheBurkeeta1. experiment
jects in both the emotional and the neutral conditions. inorderto determinewhether wecouldobtain thesame
Although wewere notabletosupport thenotion thatthe resultsasBurkeetal.inourlaboratory.Resultsthatmimic
hospital version had aphysiological impact on the sub those ofBurke eta1. would lendcredibilitytothenotion
jects, it is clear from the rating scale data that the sub thatthedifferencesinthetwoexperimentswereduetothe
jectswhoviewedthehospital versionperceivedthiscon construction ofthe dependent measure and not to some
ditionasbeingmoreemotional thandidthesubjects who other extraneous source. The essenceofthis replication
viewed the garage version. This finding is consistent wasto use the recognition measure that Burke etal. de-
172 LIBKUMAN, NICHOLS-WHITEHEAD, GRIFFITH, ANDTHOMAS
Figure2.Experiment1:Memoryforgist,centraldetail,andbackgrounddetailasafunctionofphaseandemotional
arousal.
velopedandusedinbothoftheirexperiments. Basically, There was considerable similarity between the Burke
the subjects were tested with the four categories (gist, etal.results and ours. Ofparticularimportancewerethe
basic-levelvisualinformation,centraldetail,background resultsforcentralandbackgrounddetail. Inbothstudies,
detail)thatwereconstructedbyBurkeetal. the major finding was that, during emotional arousal,
Exceptforsomeminordifferences,weessentiallyrepli there was a memory advantage for central detail and a
catedtheBurkeetal.(1992)methodologywith40under memorydisadvantageforbackgrounddetail. Theresults
graduate students who were randomly assigned to the were also the same for gist and basic-level visual infor
twostoryconditions. Theminordifferences includedthe mation, inthatboth studiesreportedimprovementacross
instrument and the location used to measure heart rate phasesforgistandadeclineacrossphases forbasic-level
(Burkeetal.usedaCICspeedometerwiththeearlobe as visualinformation.Themajordiscrepancyoccurredwith
thesource;weusedaPolarFavormonitorthatwasplaced theheartratedata.Wewerenotabletofind evidencesup
aroundthesubject'sbodyatthelevelofthesolarplexus), portingtheorientingreactionthatBurkeetal.found.The
achinresttostabilizeheadmovements(Burkeetal.used heart rate measure may be responsible for these differ
one, wedid not), and the method ofadministering the ences. Heuerand Reisberg (1990) and Burke etal. used
memorytest(Burke etal.usedacomputer, wedid not). an earlobe photocell to measure opacity ofblood flow,
SOURCEOF AROUSALAND MEMORY 173
whereasweusedchestelectrodestomeasureelectricalac beplacedineachcondition.Checkingsubjectfiles indicatedthat I
tivityofthe heart. Measurementsusingthe earlobepho subjecthadservedinExperiment I.Herdatawerediscarded, leav
tocell canbeinfluencedbybodymovementsandbybright ing19subjects inthephysiologicalarousal,neutralstorycondition.
MaterialsandApparatus.The stimuli (slides andnarratives),
orchanginglights,whereastheEKGsignalisverystrong
emotionalrating scalesquestionnaire,andapparatus (slideprojec
in the chest area and less susceptible to interference
torand heart ratemonitor)werethe sameasthose usedinExperi
s
(Heart Rate MonitorBuyer Guide, 1992). In addition, ment I.Thesubjectswerealsotestedinthesameenvironment,with
Legerand Thivierge (1988), in a study that experimen thestimuli andapparatus beingarrangedinthesamemanner.
tally compareda varietyofheart rate monitors with the Contentvalidityofthe cued recalltest. The questions from
more conventional ECG, reported high correlationsbe therecognitiontestusedinExperimentIwereconvertedtocuedre
callquestions. Forexample,intherecognitiontest,thequestionwas
tween chest monitor readings and ECG readings and
asked,"Whatisthecolorofthedoor?" The fouralternatives were
poor correlations between earlobe readings and ECG
blue,brown,green,andblack.Thecuedrecallquestionwasphrased
readings. The authors concluded that chest monitors "Thecolorofthedooris__."Thecorrectanswerwasblue.The'
were stable and valid, whereas earlobe measures have procedureforestablishingcontent validity wassimilar tothepro
problemswithstabilityandvalidity. Althoughwedidnot cedureoutlinedinExperiment I.Theoverallcontentvaliditycoef
find the orienting response, it is important to note that ficient was89.57. Fifty-eightpercentoftheitemshadacoefficient
of1.00,and42%hadacoefficientof.75.Finally,therewereafew
the ratingscale data in the replicationindicatedthatthe
items,particularlybackgrounddetail, forwhichthepossibilityex
subjects in the emotional story condition perceived the
istedformultiplecorrectanswers.Inordertoremedythisproblem,
storyasbeingmorearousingthandid the subjectsinthe
3individuals (thesecondandthirdauthorsofthispaperandagrad
neutralstorycondition. uatestudentfamiliarwiththestudy)viewedeachslideandlistedall
thepossibleanswersthatcouldbecorrectforeachcuedrecallques
EXPERIMENT2 tion.These answerswerescored ascorrectforthosesubjects who
respondedwiththese answers.
Design and Procedure. The design was a2 (physiological
The majorpurposeofExperiment2was to determine
arousal) X 2(storytype) X 3(phase) X 3(categoryofinformation)
the influence ofphysiological and emotional arousalon
factorial, with the first twoasbetween-subjectsvariables andthe
cuedrecallforcentralandbackgrounddetailofanevent. lasttwoaswithin-subjectsvariables. Eachcategoryofinformation
The majordifferencebetweenExperiments 1and2con wasanalyzedseparately,usingpercentcorrectcuedrecallasthede
cerns the nature ofthe memory task. In Experiment 1, pendentmeasure. The emotionalityrating scale and heart rates
memorywas measuredwitharecognitiontask, whereas measures wereusedtoassessemotionalandphysiologicalarousaL
The subjectswere tested, using the procedureoutlined inExperi
inExperiment2,memorywas measuredwitha cuedre
ment I.
call task. Themajorquestion,ofcourse,concernsthe ex
tentto which the findings reported in Experiment I are
Results
repeatable for a cuedrecall task. In otherwords, do the
Heart rate data. Initial baseline heart rates ranged
findings from Experiment 1have any generality?
from 54 to 115 bpm. The 2 (physiological arousal) X 2
Cuedrecall was chosen becausethe numberand dis
(story) ANOVA revealedamaineffectofstory [F(1,75)
tribution oftest items across categories ofinformation =4.60, MS = 164.16,p < .04], indicatingthatthe sub
(gist, centraldetail,andbackgrounddetail)andphasesin e
jectswho laterviewedthe hospitalstory(M=84.72)ini
the recognitiontaskcouldbeessentiallymaintainedina
tiallyexhibitedhigherheartrates than the subjectswho
cuedrecall task, thusallowingformorevalidcomparisons
laterviewedthegaragestory(M=78.51).An analysisof
between the two tasks. Although there is considerable
the second baseline measure indicatedthat heart rates
discussioninthe cognitiveliteratureconcerningthe role were higher[F(1,75)=462.48,MS = 177.84,p< .0001]
offamiliarity and retrieval processes in recognitionand e
for the subjects who ran in place (M= 142.20) than for
recalltasks (seeWilhite&Payne, 1992,forabriefreview),
the subjects who did not run in place (M= 78.65). No
we know ofno a priori reason for assuming that these
othersignificanteffects were noted. Itis clearfrom the
tasks willbedifferentiallysensitivetomemoryforcentral
heartrateanalysisthatinitialheartratesare confounded
and background detail. However, in a study concerned
withstoryconditions.Itispossiblethatthe subjectswith
withmemoryfortraumaticevents,ChristiansonandE.F.
higherinitialheartratesare moresensitivetothecontent
Loftus (1987)usedarecall tasktoassess thematicmemory
ofthe stories than are the subjects with the lower initial
and arecognitiontasktoassessdetails.Theseauthorsre
heart rates, which, in turn, could account for any re
portedthatmemory for the thematiceventwas superior
portedmemorydifferences in the stories. Althoughthis
and memory for detail was inferior, relative to aneutral
confound was not found for the second baseline heart
condition.Thesedata suggestthat,inourcuedrecallstudy,
rates (note that the means were 80.30 and 77.00 for the
memoryforgistshouldbe superiorforthehospitalstory,
subjects who were not physiologically aroused [i.e., the
relative to the garagestory.
subjectswhodidnotruninplace] andwhoviewedthehos
pital story orthe garage story, respectively), it is still
Method
possiblethatthememorydataarecontaminated.There
Subjects.EightyundergraduatestudentsfromCentralMichigan
fore, all subsequentanalysesconcerningthe ratingscales
University were recruitedfrom introductory psychology classes.
The subjects wererandomly assigned tothe fourtreatmentcondi and memory measures wereconductedwithan analysis
tions,withtherestrictionthatanequalnumberofmalesandfemales ofcovariance (ANCOVA), with initial heart rate as the
174 LIBKUMAN,NICHOLS-WHITEHEAD,GRIFFITH, AND THOMAS
covariate. Although ANCOVAs will be reported here, indicatedthat the subjects responded more emotionally
ANOVAswere also conductedonthese measures. Only to the hospital story than to the garage story. These ef
two differences were noted. First, inthe ANOVAanaly fectsweremoderatedbytheinteraction,whichindicated
ses,maineffects ofphasewerefoundforgistandcentral that, when the subjects were both physiologically and
detail (but not backgrounddetail), indicatingthatmem emotionallyaroused,theirperceivedemotionalreactions
ory performance improved across phases. In the AN (M= 6.00) were greater, as compared with the remain
COVAanalyses, a main effect ofphase was found for ingthree treatmentcombinations(the meansforthehos
background detail (again, memory performance im pital nonarousal, garage arousal, and garagenonarousal
provedacrossphases)but not forgist and centraldetail. groupswere4.20,2.26,and2.55,respectively). Thisfind
Second, inthe ANOVAanalysis ofbackgrounddetail, a ingisconsistentwith theinteractionconcerningtheper
main effect for physiological arousal was found (mem ceived emotionalityofthe slide presentation.
ory performance was better for the subjects who ran in Memorymeasures. Figure 3depicts the three mem
place, relativeto the subjectswho did not run in place). ory measures for physiological arousal across phases.
Inthe ANCOVAanalysis, nomain effect for physiolog Figure4depictsthethreememory measures foremotional
ical arousal was found. arousal acrossphases.The 95%confidenceintervalsare
AsinExperiment I, the second ofthe three measures plotted around the means, using the same approach as
ofheart rate for each slide was used to calculate mean that used in Experiment 1.It isclearfrom viewing both
group heart rates. Heartrates declinedacrossthephases figures thatmemoryperformancewasbestforgist,worst
[F(2,150) = 229.95, MSe = 22.08, p < .0001], and the forbackgrounddetail,andintermediateforcentraldetail.
physiological arousal X phase interaction [F(2,150) = Itisalso evidentthat gist improvedacross phases. Both
139.95,P < .0001] indicatedthat the heart rates ofthe ofthese observationsare consistentwith the findings in
subjectswhoraninplacestartedmuchhigheranddropped Experiment I.
muchfasterthandidthose ofthesubjectswhodidnotrun Figure 3indicatesthat physiologicalarousalhadlittle
inplace. impact on memory. Only in the third panel did physio
Finally,for the subjectswho didnot run in place, the logicalarousalhaveanyimpact, and this effect indicated
lowestheartrate measureforeach slide was used to cal that exercise improved memory for background detail
culate mean heart rates. This was the measure used by during Phase 1.Incontrast, Figure 4indicatesthatemo
Burke et al. (1992), which led to the finding that heart tional arousal produced numerous effects on memory.
rates declined during the hospital story, relative to the The gist panel indicates that memory performance was
garagestory.The2(story) X12(slides)ANOVArevealed superiorforthegaragestory,relativetothehospital story,
onlyaneffectofslides[F(11,418)=15.94, MS =9.81, for Phases 2 and 3. More important, however, are the
e
P< .000I], which indicatedthatheartrates declinedfor findings for central and background detail. The central
bothgroupsacrossslides,withthegreatestdecline occur detail panel indicatesthat memoryperformancewassu
ringduring the first three slides. periorfor the hospitalstory,relative to the garage story,
Rating scales. The 2 (physiological arousal) X 2 during Phase 2. The background detail panel also indi
(story) ANCOVA ofthe rating scale data for the emo cates that memory was superior for the hospital story,
tionalityoftheslidepresentationrevealedsignificantef relative to the garage story,during Phase 2. In addition,
fects forstory [F(1,74)=48.07, MS =3.16,p < .0001] however,thebackgrounddetailpanelindicatesthatmem
e
and for the physiological arousal X story interaction orywassuperiorforthe garage story, relativetothehos
[F(I,74) = 8.12, p < .006]. The main effect indicated pital story, during Phase 3. Finally, it should be noted
thatthehospitalstory(M= 5.48)wasperceivedasbeing thatbackgrounddetailmemoryperformancewassimilar
more emotionalthan the garage story (M=2.68). How inthetwostoryconditionsduringPhase 1.Thisfinding is
ever,thiseffectwas moderatedbythe interaction,which contrarytothatinExperiment 1,wherethe garage story
indicated that, for those subjects who were physiologi wassuperiorto the hospital story duringPhase 1.
cally aroused, the difference betweenthe hospital story
condition (M=6.30) andthegaragestory condition(M= Discussion
2.37) was greater than for those subjects who were not ThepurposeofExperiment2wastodeterminewhether
physiologicallyaroused(hospital andgaragestorymeans the findings obtainedin Experiment I, using arecogni
were4.65 and 3.00, respectively). tion task, could be confirmed in Experiment 2, using a
The 2 (physiological arousal) X 2 (story) ANCOVA cued recall task.
ofthe subjects' responses to the slide presentation re InExperiment 1,nogroup differenceswere found for
vealed significant effects for physiological arousal the initial baseline heart rate data, whereas in Experi
[F(I,74) = 5.02, MSe= 2.55,p < .03], story [F(1,74)= ment 2, the subjects who would later view the hospital
55.70,p< .0001], and thephysiologicalarousal X story story had higher heart rates than did the subjects who
interaction [F(l,74) = 8.44, P < .005]. The physiologi would later viewthegarage story.Theseeffects werenot
cal arousal effect indicated that the physiologically found forthe secondbaselinemeasure. Acomparisonof
aroused subjects responded more emotionally than did the initial and secondbaselineheartrate means isinfor
thenonphysiologicallyarousedsubjects. The story effect mative. Forthe subjectswhowould laterruninplace,the
SOURCEOFAROUSAL AND MEMORY 175
QnraIDalail
1lXl 1lXl
......eea. ......lGe.dIe
IlO -o-1Geea. IlO -0-e.dIe
III ~ III
70 70
Q
j III I III
Sl Sl i= -=::::t
J j =t==--
«l «l
:Jl :Jl
2D 2D
10 10
0 0
2 3 2 3
F't8e F't8e
BackgroundDetail
100
80
IIll
70
J:
J
40
:Jl
2D
10
OL---.-------..--------r--
2 3
Phase
Figure3.Experiment2:Memoryforgist,centraldetail,andbackgrounddetailasafunctionofphaseandphysi
ological arousal.
initialbaselinemeans forthehospital andgarage stories whodidnot. Furthermore, heartratedeclinedatthesame
were85.75and77.54,respectively.Afterrunning inplace rate across phases for both story conditions. This latter
(i.e., the second baseline measure), the means for the findingdidnotsupport theBurke etal.(1992) datacon
hospital andgarage stories forthese same subjectswere cerninganorientingresponse.
142.45 and 143.95, respectively. For the subjects who There were somenotable differences between Exper
would not later run in place, the initial baseline means iments Iand 2concerningthe emotionalityrating scale
forthehospital andgarage storieswere83.75and79.55, data. In Experiment I, only story effects were found,
respectively.Thesecondbaselinemeasures forthesetwo whereas inExperiment2,there was, inaddition to story
groups were 80.30 and 77.00, respectively. Although effects, aphysiologicalarousal X story interaction. The
theseheartratedifferencesarenotsubstantial,ANCOVAs interaction indicated that the ratings were most pro
were used in all subsequent rating scale and memory nounced for those subjects who ran inplace andviewed
datatoruleoutthepossibilitythatinitialheartrateswere the hospital story. Although we do not havea plausible
influencingthesemeasures. Theheartratedata recorded explanationforthesediscrepancies, itisimportanttore
duringtheslidepresentationwassimilarforExperimentsI memberthat, inbothexperiments,thehospital storywas
and 2. Inboth cases, heart rate declined at a faster rate ratedasbeingmoreemotional thanwastheneutralstory.
forthesubjects whoran inplace, relative tothe subjects Itisalsointerestingtonote,aswillbediscussedlater,that