Semantic and phonological codes interact in single word production

Journalof ExperimentalPsychology:Learning,Memory, andCognition1999,Vo. 25,No.2,345-361

Copyright1999by theAmericanPsychologicalAssociation,Inc.

SemanticandPhonologicalCodesInteractin SingleWordProduction

MarkusF. DamianandRandiC. MartinRiceUniversity

The relationshipbetweensemantic-syntacticandphonologicallevels in speakingwas inves-tigatedusing a picture namingprocedurewith simultaneouslypresentedvisual or auditorydistractorwords.Previousresultswith auditorydistractorshavebeenusedto supporttheinde-pendentstagemodel(e.g.,H. Schriefers,A. S.Meyer, & W. J.M. Levelt, 1990)whereasresultswith visualdistractorshave beenusedto supportan interactive view (e.g.,P. A. Starreveld &W. La Heij, 1996b).Experiment1 demonstratedthatwith auditorydistractorssemanticeffectsprecededphonologicaleffectswhereasthe reversepatternheld for visual distractors.Exper-iment 2 indicatedthat the resultsfor visual distractorsfollowed the auditory patternwhendistractorpresentationtime waslimited. Experiment3 demonstratedan interactionbetweenphonologicalandsemanticrelatednessof distractorsfor auditorypresentation,supportinganinteractive accountof lexical accessin speaking.

Researchersinterestedin speechproductionwidely agreeon theassumptionthatlexical accessin languageproductionrequiresa distinctionof at leasttwo levelsof representation:afirst level thatis concernedwith semantic-syntacticproper-ties,andasecondlevel concernedwith word form properties(i.e.,phonologicalform). In Levelt’s (1989)modelof speak-ing, for instance,preparationof an utteranceconsistsof asequenceof stageswhich is basedon a prelinguisticconcep-tualization,or message,of the plannedutterance.First, ap-propriatelexical entriesareretrieved that specifylanguage-specificsemantic(e.g.,conceptualarguments)andsyntactic(e.g.,syntacticword classandgrammaticalgender)proper-ties. Following KempenandHuijbers(1983),thetermlem-masis often usedfor theserepresentations.Subsequently,correspondingword forms areencoded.Theserepresenta-tionscontainsoundrepresentations,includingsegmentalandmetric information,andarecommonlytermedlexemes.Fi-nally, a phoneticplan is formed and executedin the artic-ulation process.Becausethe lexicon is separatedinto tworepresentationallevels (lemmaand lexemeaccess),suchamodeliscommonlynameda”two-step”accountof speaking.Althougha greatdealof disagreementexistsasto theexactcharacteristicsof thesestages,the necessityto hypothesize

MarkusF. DamianandRandiC.Martin, Departmentof Psychol-ogy, RiceUniversity.

Theresearchreportedin thisarticleservedaspartialfulfillmentof the requirementsfor the PhD degreeat Rice University for thefirst author. Preparationof this article was supportedin part byNationalInstituteof HealthgrantnumberDC 00218to Rice Uni-versity. We thankAndrew Shirey for assistancein collecting thedata.

Correspondenceconcerningthis article should be addressedto Markus F. Damian, who is now at the Max Planck In-stitute for Psycholinguistics,Wundtlaan1, PB 310, 6500 AHNijmegen, the Netherlands. Electronic mail may be sent [email protected].

two levels of lexical accessin speakingis relatively undis-puted.

Evidencefor the separationof lexical retrieval into asemantic-syntacticand a phonological componentcomesfrom varioussources. For example,when speakers are ina ”tip-of-the-tongue”state,they appearto have accessto se-mantic(Brown & McNeill, 1966)andsyntactic(Vigliocco,Antonini, & Garrett,1997)propertiesof thetargetword,butareunableto retrievetheappropriateword form or gainonlypartialphonologicalaccess.Althoughthey maybeableto re-trievesomerudimentaryphonologicalpropertiesof thetargetword, thephenomenonsuggestsa blockagebetweenlemmaandlexemelevel andthussupportsthenotionof two distinctstagesin lexical retrieval. Similar, but muchmoredramatic,problemscanbeshown in anomicpatients(e.g.,Goodglass,Kaplan,Weintraub,& Ackerman,1976). Thesepatientsof-ten producea multitudeof semanticcircumlocutions:theygeneratedescriptionsof thesemanticpropertiesof thewordto beretrieved,for examplesaying”that’sagoodeatingbird”whentrying to retrieve”turkey”. Thesecircumlocutionssug-gestnormal or near-normal retrieval of semanticinforma-tion with somedifficulties in retrieving phonologicalinfor-mation. A further sourceof evidencecomesfrom speecherrorsfrom normal speakers. For instance,Garrett (1975)proposeda distinctionbetweenword andsoundexchanges,with eachtype possessingdistinct characteristics:word ex-changesnormally take placebetweensyntacticphrasesoreven clauses,preserve their mutual word class,and fulfillsimilar grammaticalfunctions. In contrast,soundexchangeerrorsmostlyaffectadjacentwordswhichareoftenfrom dis-similar syntacticcategories,but typically shareform-relatedcharacteristics.Thesefindingsaretakento indicatethatwordexchangesresult from the selectionof the wrong lemma,whereasphonologicalerrorsrevealthemalfunctioningof thephonologicalencodingsystem. A final sourceof evidencefor thedistinctionbetweensemantic-syntacticandphonolog-ical stagesin speakingcomesfrom psycholinguisticstudieson the time courseof speechproductionin normalspeakers

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2 MARKUS F. DAMIAN AND RANDI C. MARTIN

(Levelt, Schriefers,Vorberg, Meyer, Pechmann,& Havinga,1991;Peterson& Savoy, 1998;Schriefers,Meyer, & Levelt,1990)aswell aselectrophysiologicalevidence(van Turen-nout, Hagoort,& Brown, 1997), both suggestingan earlystageof lexical-semanticactivationfollowedby a laterstageof phonologicalencoding(seeLevelt, Roelofs,& Meyer, inpress,for acomprehensivereview).

Apart from this fundamental distinction betweensemantic-syntacticandphonologicalcomponentsin lexicalretrieval, some theoriesof speechproduction have mademorespecificclaimsaboutthenatureof therepresentationalstagesand their relation to each other. ”Discrete two-step models” (Levelt, 1989; Levelt et al., 1991) assumethat speaking proceedsin serial stagesfrom lemma tolexemeretrieval. It is arguedon theoreticalgroundsthatsemanticand phonologicalrepresentationalsystemsare sofundamentallydifferent from eachother that they shouldbe conceptualizedas distinct and discrete. Within thisframework, it is assumedthat phonological encoding isrestrictedto onesinglelexical item. That is, althoughthesemodels normally assumethat a set of semantic-syntacticlexical items is activated in responseto conceptualinput,only a singleselectedtarget lemmapropagatesits activationto the phonological level (Levelt et al, 1991, p.124).Furthermore, discrete models propose that phonologicalencodinghasno impacton theearlierlexical level. In otherwords,activation proceedsexclusively in a forward fashionthrough the productionsystem,and there is no feedbackfrom the lexemeonto the lemmalevel (Levelt et al., 1991,p.125).In combination,thediscretetwo-stepview conceivesof thestagesinvolvedin lexical retrieval aslargely modularin Fodor’s (1983)senseof cognitivemodularity.

Thereareanumberof findingsin theliteraturethatappearto causeproblemsfor the discretetwo-stepview, however.Most prominently, corporaof naturallyoccurringspeecher-rors appearto containan above-chanceratio of speecher-rors that are both semanticallyand phonologicallyrelatedto the target word, or so-called”mixed errors” (e.g., Dell& Reich,1981). Also, recentneuropsychologicalevidencesuggeststhatsomeaphasicswith a high occurrenceof wordsubstitutionsproducemixed errors at above-chancelevels(Best,1996; Blanken, 1990). The discretetwo-steptheoryof speakingproposesstrict independencebetweenthe in-volvedrepresentationallevels. Accordingly, bothsemantic-syntacticandphonologicalcomponentsshouldexert an in-dependentinfluenceon the productionof errors,andmixederrorsshouldbe found at no more than chancerate. Theabove-chanceoccurrenceof this type of error appearstobe incompatiblewith discretemodelsunlessadditionalas-sumptionsare introduced. For instance,it hasbeenarguedthat the speaker internally monitorshis/herown speechbymeansof a ”lexical monitoring” system(Baars,Motley, &MacKay, 1975;Levelt, 1989)which filters out all but occa-sionalspeecherrorsbeforethey areovertly produced.Sucha systemcan accountfor the occurrenceof mixed errorsby claiming that theseerrorwordsresemblethe targetwordtwofold, namelyin bothsemanticandphonologicalrespects.Consequently, sucherrorsaremorelikely to go undetected

than words that are either semanticallyor phonologicallyrelatedto the target, resulting in a higher occurrencethanwould bepredictedby purechance.Within this hypothesis,themechanismthataccountsfor mixederrorsis not a com-ponentof thespeechproductionsystemperse,but ratheranexternalprocess.

Alternatively, however, mixederrorsmight ariseasa nat-ural consequenceof the structureof the productionsystemitself. Interactive models(Dell, 1986;Dell, Schwartz,Mar-tin, Saffran, & Gagnon,1996; Stemberger, 1985) abandonthe notion of discrete,modularstagesand insteadproposesemantic,lexical, andphonologicallevels thatareintercon-nectedin a network fashion. As a result, thesemodelsareincompatiblewith thespecificassumptionsmadeby discretemodels: First, interactive modelsgenerallyproposeparal-lel phonologicalencodingof multiple items. That is, anen-tire setof lemmanodesthathasbeenactivatedon the basisof thepreverbalmessagepropagatessomedegreeof activa-tion to theword form level. Second,mostinteractivemodelsimplementspreadingof activation from the lexemebacktothelemmalevel (but seeHumphreys,Riddock,andQuinlan,1988, for an exception). Models that implementfeedbackof activation accountfor the occurrenceof mixed errorsbyassumingthatwordssemanticallyaswell asphonologicallyrelatedto the targetword receive additionalactivation fromtheir semanticoverlapwith the target word aswell asfromtheir phonologicalresemblanceto the correctword. As aresult,”mixed” lexical unitspossessa higherselectionprob-ability than would be predictedby either type of relation-shipalone.Therefore,interactive modelsaccountfor mixedspeecherrorswithin theproductionsystemitself andwithoutproposingexternalmechanismslikealexical monitoringsys-tem. However, a crucialassumptionof thediscretetwo-stepview of speechproduction- unidirectionalityof processing-is abandoned.

Oneof thetoolsby meansof which thenatureof thetwostagesof lexical accessin speakingcan be experimentallyinvestigatedis the picture-word interferenceprocedure. Inthistask,participantsperformtimednamingresponsesto tar-get picturesof basicobjects. Simultaneously, they arebe-ing confrontedwith so-calleddistractorwords that are vi-sually embeddedin the object,andare instructedto ignorethesewords. In analogto Stroop’s (1935) seminalcolor-wordtask,participantsappearto processthedistractorwordsautomatically, andconsequently, wordsthataresemanticallyrelatedto the picturehave beenshown to slow namingre-sponsescomparedto unrelatedwords (e.g., Picture: AP-PLE, Word: ORANGE; e.g.,Rosinski,Golinkoff, & Kuk-ish, 1975). On theotherhand,form-relatedwordsspeedupnaminglatenciesrelativeto unrelatedwords(Picture:BELL,Word: BELT; e.g.,Posnanski& Rayner, 1977,1978;Rayner& Posnanski,1978). In contrastto most versionsof theStrooptask,targetanddistractorstimulusareseparatestim-uli in thepicture-word interferencetask.Thus,thestimulus-onsetasynchrony (SOA) betweenpictureanddistractorcanbe manipulated,which allows the investigationof the vari-ous stagesinvolved in speaking. For instance,GlaserandDungelhoff (1984)demonstrateda semanticinterferenceef-

INTERACTIVITY IN SPEAKING 3

fect that centeredaroundan SOA of 0 ms, and StarreveldandLa Heij (1996b)additionallyshowed that phonologicalfacilitationeffectscanbeobtainedwith SOAs rangingfrom-200msto +100ms.

A further modificationof this procedurehasbeenintro-ducedby Schriefers,Meyer, andLevelt (1990).Becauseor-thographicandphonologicalcharacteristicsarehighly con-foundedin mostlanguages,thereis somedoubtasto theex-actlocusandorigin of thefacilitationcausedby form-relatedvisual distractorwords in the studiesdescribedabove. Inorderto ensurethat phonologicallyrelateddistractorwordsimmediatelytappedinto phonologicaloutputrepresentationsinvolved in speaking,Schrieferset al. presenteddistractorwordsauditorily insteadof visually. Semanticinterference,but no phonologicaleffect, wasobtainedat anSOA of -150ms, whereasphonologicalfacilitation, but no semanticef-fect, wasobtainedat SOA = 0 ms andSOA = +150ms. Ina furtherexperiment,Schrieferset al. ruledout a nonverbalconceptualconflictastheorigin of semanticinterferenceandinsteadlocatedthiseffectat thelevel of lemmaretrieval (seealsoDamian,Bowers,& Katz, 1997,for further supportofthis conclusion). The resultswere interpretedasreflectingthe separateandserialcontributionsof lemmaretrieval andlexemeaccessduringthepreparationof thenamingresponse.

A close survey of the findings from the picture-wordinterferenceparadigmdemonstratesa striking discrepancybetweenvisual and auditory distractorswith regard to thepatternof semanticand phonologicaleffects. Starreveldand La Heij’s (1996b) study with visually presenteddis-tractors yielded phonologicalfacilitation effects that pre-cededand followed semanticinterferenceeffects in time.In contrast,Schrieferset al.’s study with auditory distrac-tors demonstrateda sequenceof semanticinterferencefol-lowed by phonologicalfacilitation. However, both versionsof the procedurehave been taken as supportingparticu-lar claimsor constraininghypothesesregardingspeechpro-duction. For instance,Schrieferset al. (1990) interpretedthe sequenceof semanticandphonologicaleffectsobtainedwith auditorydistractorsasin line with discretetwo-stepac-countsof speechproduction. In contrast,Starreveld andLaHeij (1996b)obtainedan interactionbetweensemanticandphonologicalfactorswith visual distractorsandconcluded,basedon Sternberg’s (1969)additive-factorsmethod,that adiscretemodelcannotbeadequate(thespecificdetailsof thisexperimentwill beprovidedlater). For obviousreasons,ei-ther conclusionis prematureaslong asthe discrepancy be-tween the effects of visual and auditory distractorsacrossmodalitieshasnot beensatisfactorily explained. However,to date,therehasbeenlittle attemptto uncover thesourceofthis disparity.

A further difficulty in interpretingthesefindings arisesfrom the fact that the effectsof visual andauditorydistrac-torshavebeeninvestigatedby differentgroupsof researchersandin differentexperiments.That is, it is not entirelyclearwhetherthe discrepantfindings reflect someyet unknownstimulusor proceduralproperty, or a genuinelyinterestingfact thata modelof speechproductionmustaccountfor. Inorderto clarify this issue,the following experimentdirectly

comparedtheeffectsof visuallyandauditorilypresenteddis-tractors.

Experiment1

Method

Participants. Thirty Rice University undergraduatestu-dentsservedasparticipantsin orderto meeta classrequire-mentfor experimentalparticipation.

Materials. Twenty-eightline drawings of commonob-jects were selectedfrom the Snodgrassand Vanderwart(1980) set. For eachpicture, a categorically relatedwordwasselectedthat servedasthe semanticallyrelateddistrac-tor. An orthographically/phonologically relatedword waschosenthatsharedaminimumof theinitial two phonemesaswell asthe initial two letterswith thepicturelabel. Finally,anunrelatedword wasselectedthatstoodin no obviousre-lationshipto the target picture. This yielded a total of 84picture-distractorcombinations(28pictures � 3 conditions).All threedistractorconditionswerematchedin termsof theaveragenumberof lettersandphonemes.

Design. The experimental design included DistractorModality (Visualvs. Auditory) asa between-subjectsfactor,aswell astwo within-subjectsfactors,namelySOA with fivelevels(-200ms,-100ms,0 ms,+100ms,and+200ms),andTarget-DistractorRelationwith threelevels (Unrelated,Se-manticallyRelated,PhonologicallyRelated).Fifteenpartic-ipantswererandomlyassignedto eachDistractorModalitycondition. Eachparticipantsaw the setof 84 picture-wordpairs at all five SOAs (-200 ms, -100 ms, 0 ms, +100 ms,and+200ms). Theorderin which participantsreceivedtheSOA blockswasbalancedaccordingto a Latin Squarede-sign. Itemswerepresentedin a pseudorandomfashionsuchthatthesamepictureneverappearedtwiceonsubsequenttri-als.

Apparatus. The picturesand distractorswere presentedfrom anApple PowerPCcomputerusingPsyScope(Cohen,MacWhinney, Flatt, & Provost, 1993). The picturesweredigitized at a sizeof approximately3 � 3 in andpresentedasblack line drawings on white background.The auditorydistractorswererecordedby afemalespeaker, digitizedwitha samplingfrequency of 20 kHz, andpresentedvia LabtecLT-100 headphones.The visual distractorswere shown inuppercaseHelvetica18-pointbold font in thecenterof eachpicture. The computerscheduledpresentationof the stim-uli andrecordeda participant’s responsetimesto thenearestmillisecondby meansof avoice-activatedrelay.

Procedure. Participantsweretestedindividually. At thebeginning of the experiment, they were familiarized withthe setof experimentalpicturesby viewing eachpictureonthecomputerscreenfor 2000mswith theappropriatenameprinted below it. A practiceblock was then administeredin which participantsperformeda namingresponseto eachof the picturespresentedin randomorder. Responsesotherthanthe expectedoneswerecorrectedby the experimenter.


Next, asecondpracticeblock wasadministeredin which thepictureswerepresentedaccompaniedby unrelateddistractorwords.Again,unexpectedresponseswerecorrected.Finally,the five experimentalblockswerecarriedout, consistingof84 namingresponseseach. Breakswereprovided betweentheexperimentalblocks.Eachtestingsessionthusconsistedof 420experimentaltrialsandlastedapproximatelyonehour.

On eachindividual trial, participantsfirst viewed a fixa-tion crosspresentedat thecenterof thescreenfor 1000ms.After a blank interval of 500 ms, the pictureappeared.Atvaryingintervalsbeforeor afterthepictureonset(dependingon theSOA block), thedistractorwasplayedover thehead-phones(in theauditorydistractorgroup)or presentedat thecenterof thepicture(in thevisualdistractorgroup).Partici-pantsperformedthenamingresponseby speakinginto a mi-crophone;thepicturedisappearedfrom thescreenassoonasthevoicekey triggered.Visually presenteddistractorwordswereterminatedsimultaneouslywith thepictureoffset. Fol-lowing eachnamingresponse,the experimenterjudgedtheresponsetobeeithercorrector incorrect(whichincludedpic-turenamesotherthantheexpectedones,repairs,stutteringormouthclicks, or malfunctioningof thevoicekey) by typinga codeinto thecomputer. Eachtrial wasfollowedby a 1500msintertrial interval.1

Results

All responsesjudgedto be incorrectby theexperimenterwereexcludedfrom the analysis.Likewise, responsetimeslonger than 2000 ms or shorter than 250 ms were elimi-nated.Finally, responsetimesdeviatingmorethanthreestan-darddeviationsfrom a participant’s conditionalmeanweredeleted.Theseproceduresresultedin theexclusionof 2.0%,0.0%,and1.4%of thedata,respectively. A total of 3.4%ofdatapointsweredeletedin thisway.

Table1 lists the meanresponselatencies,variedby Dis-tractorModality, Target-DistractorRelation,andSOA. Fig-ure1 displaysthesemanticandphonologicaleffects(Unre-latedminusRelatedcondition). With visual distractors,se-manticallyrelateddistractorsappearto causeaninterferenceeffect that peaksat an SOA of 0 ms. Critically, phonolog-ical/orthographiceffectsprecedethe semanticeffect, as in-dicatedby a substantialamountof facilitation at SOA = -200 ms and-100 ms. In contrast,auditorydistractorsyieldsemanticinterferenceeffectsrangingfrom SOA = -200 msto SOA = 0 ms, aswell asphonologicalfacilitation effectsrangingfrom SOA = - 100msto SOA = + 200ms.

A 2 (DistractorModality) � 5 (SOA) � 3 (Condition)ANOVA wasconductedon the datawith DistractorModal-ity asa between-subjectsfactor, andSOA andConditionaswithin-subjectsfactors. The effect of DistractorModalitywas insignificant in the subjectsanalysis,F1 = 1.32, andmarginally significantin theitemsanalysis,F2(1,54)= 3.74,p = .059,MSE = 109,309,indicatingthatvisualandauditorydistractorsshowed roughly comparableoverall amountsofinterference.A maineffect of SOA, F1(4,112)= 63.55,p �.001,MSE = 188,318,F2(4,216)= 435.30,p � .001,MSE= 348,568,aswell asmain effect of Condition,F1(2,56)=

Table1Experiment 1: Mean Response Latencies (in Milliseconds),varied by Distractor Type (Visual vs. Auditory), Relatedness(Unrelated vs. Semantic vs. Phonological) and Picture-WordOnset Asynchrony (SOA)

Distractor SOA (in ms)type -200 -100 0 +100 +200

VisualUnrelated 700 714 744 693 620Semantic 698 725 786 716 640Phonological 666 687 693 643 608

AuditoryUnrelated 695 706 707 637 605Semantic 723 730 734 641 606Phonological 690 683 671 591 581

80.84, p � .001, MSE = 91,225,F2(2,108) = 82.40, p �.001,MSE = 179,574,wereobtained.Furthermore,a signif-icantSOA � Conditioninteractionwasobtained,F1(8,224)= 7.93,p � .001,MSE = 3,590,F2(8,432)= 9.15,p � .001,MSE = 6,590, as well as a significant SOA � DistractorModality interaction,F1(4,112)= 6.68, p � .001, MSE =19,785,F2(4,216)= 45.33,p � .001,MSE = 36,300.Criti-cally, asignificantthree-waySOA � Condition � DistractorModality interactionwasfound,F1(8,224)= 2.80,p = .006,MSE = 1,267, F2(8,432) = 3.55, p = .001, MSE = 2,559,indicatingthat the way in which SOA andConditionmodi-fiedeachothervarieddependingonwhetherdistractorswerepresentedvisually or auditorily.

In order to follow up on these results, two furtherANOVAs wereconductedin which the datawereanalyzedfor eachDistractorModality condition separately. For vi-sualdistractors,a main effect of SOA, F1(4,56)= 24.17,p

� .001,MSE = 84,358,F2(4,108)= 203.43,p � .001,MSE= 155,239,a main effect of Condition,F1(2,28)= 55.92,p

� .001, MSE = 55,381,F2(2,54) = 50.72,p � .001, MSE= 112,585,anda SOA � Condition interaction,F1(8,112)= 7.14, p � .001, MSE = 3,252, F2(8,216) = 7.89, p �.001, MSE = 6,237,wereobtained. Simple testscorrectedwith Dunnett’sprocedurewereconductedthatcomparedtheUnrelatedto the Phonologicaland the Semanticconditionwithin eachSOA group. Thesetestsindicateda significantdifferencebetweentheUnrelatedandthePhonologicalcon-

1 This procedurewassimilar to Starreveld andLa Heij’s (1996,Exp. 1) andSchriefers,Meyer, andLevelt’s (1990,Exp. 2) studiesin thatSOAs werepresentedin a blockedfashion,with experimen-tal conditionsrandomizedwithin eachblock. In thepresentexper-iment,picturesremainedon thescreenuntil a responsewasmade,whichprovidesboththeparticipantandtheexperimenterwith feed-backover the functioningof thevoicekey. In contrast,Schriefers,Meyer, andLevelt andStarreveld and La Heij presentedpicturesfor a fixed periodof time (400 ms und 357 ms respectively). Wedid not expectthis deviation to have a major impacton theresults,given that Levelt et al. (1991)estimatedboth lemmaandlexemeaccessto occurwithin thefirst 400msafterpictureonset.


dition for SOAs rangingfrom -200 ms to +100ms, aswellasasignificantdifferencebetweentheUnrelatedandtheSe-manticcondition for SOA = 0 ms and+100 ms. All othercomparisonswerenot signficant.

For auditorydistractors,a maineffect of SOA, F1(4,108)= 50.80,p � .001,MSE = 229,629,F2(4,108)= 273.90,p �.001,MSE = 229,629,a main effect of Condition,F1(2,54)= 29.06,p � .001, MSE = 69,684,F2(2,54) = 32.58,p �.001, MSE = 69,684,and a SOA � Condition interaction,F1(8,216)= 3.57,p � .001,MSE = 2,913,F2(8,216)= 4.48,p � .001,MSE = 2,913,wereobtained.Dunnetttestsindi-cateda significantdifferencebetweentheUnrelatedandthePhonologicalcondition for SOAs rangingfrom -100 ms to+200ms,aswell asa significantdifferencebetweentheUn-relatedandthe Semanticcondition for SOAs rangingfrom-200msto 0 ms.

Discussion

Theresultsreplicatedthediscrepancy betweentheeffectsof auditoryandvisual distractorspreviously reportedin theliterature. With visualdistractors,semanticinterferenceap-pearedin a time window rangingfrom SOA = 0 msto SOA= +200ms,whereasthephonological/graphemicfacilitationeffect spanneda rangeof SOAs from -200ms to + 100ms.Thesefindingsarequitesimilar to thosefrom StarreveldandLa Heij’s(1996b)study. In contrast,auditorilypresenteddis-tractorscauseda semanticinterferenceeffect at the earlierSOAs (-200ms, -100ms,and0 ms)anda phonologicalfa-cilitation effect at laterSOAs (-100ms,0 ms,+100ms,and+200 ms). Sucha patternroughly resemblesthe sequenceof semanticandphonologicaleffectsobtainedin Schrieferset al.’s (1991)original study. Note,however, thattheir studyshowedasharpdistinctionbetweenSOAs revealingsemanticandthoserevealingphonologicaleffects,whereasthepresentexperimentdemonstratedaconsiderabledegreeof overlapatintermediateSOAs, andexclusively semanticor phonologi-cal effectsonly at moreperipheralSOAs.2

Of course,SOAs arenot directly comparableacrossdis-tractor modalities. Visually presentedwords are probablyprocessedin parallelandcanbeassumedto gainquiterapidaccessto their semanticcodes.In contrast,whena word isauditorily presented,acertaintime spanwill berequiredun-til the recognitionpoint is reachedandsemanticeffectscanarise. In the picture-word interferenceprocedure,a longerprocessingdurationof the distractorword translatesinto alarger negative SOA at which an effect can be obtained,andaccordinglyauditory distractorsshouldshow semanticeffects at earlier SOAs than visual ones. Roughly, this isthe patternthat was found: auditorily presenteddistractorsshowedsemanticinterferenceatSOA = -200ms,SOA = -100ms,andSOA = 0 ms,whereasvisually presenteddistractorsshowedsimilar effectsat SOA = 0 ms,SOA = +100ms,andSOA = +200ms. Whenphonologicalfacilitationeffectsareanalyzednot in termsof their absoluteSOAs, but relative tothe onsetand offset of the correspondingsemanticeffects,thediscrepancy regardingdistractormodalitybecomesevenmoreapparent:with auditorydistractors,theonsetof seman-

Figure 1. Experiment1: Effectsof semanticallyandphonologi-cally relateddistractors(unrelatedminusrelatedcondition)variedby distractormodality(visualvs. auditory)andstimulus-onsetayn-chrony (SOA: -200ms,-100ms,0 ms,+100ms,+200ms).

tic interferenceprecededthe onsetof phonologicalfacilita-tion by two SOA steps,whereaswith visual distractors,theonsetof semanticinterferencefollowedtheonsetof phono-logical facilitationby two SOA steps.

The questionariseswhat possiblecausesunderliesucha discrepancy. Two possibleexplanatationshave beensug-gestedin theliterature.Accordingto thefirst possibilitydis-cussedbyDell andO’Seaghdha(1991)andStarreveldandLaHeij (1996b),theapparentsequenceof semanticandphono-logical effectsobtainedwith auditorily presenteddistractorsis anartifactresultingfrom theextensionof auditorystimuli

2 Other experimentsconductedin our laboratoryhave showncomparableresultsin that with auditorydistractors,semanticandphonologicaleffectsalwaysappearto overlapat SOAs near0 ms.It is not clearat presentwhetherhigher items and/orparticipantsvariability in our experimentcould accountfor the differencetoSchrieferset al. (1990)’s original findings.However, we donot be-lieve thatsuchanoverlapshouldbeinterpretedasevidenceagainstthediscretetwo-stepview favoredby theseauthors.


over time. EarlierSOAs allow full processingof thedistrac-tor word by the time of lexical accessto the target name,whereasat later SOAs, only the initial segmentsof the dis-tractorwordhavebeenprocessedat thattime. Consequently,semanticinterferencecan ariseonly at earlier SOAs sincesuchaneffectrequiresaccessto thelexical identityof thedis-tractor. In contrast,phonologicallyrelateddistractorwordsyield a facilitation effect only at later SOAs becausehereonly the initial segmentsof the wordshave beenprocessedwhich are congruentwith the target. At earlier SOAs, theincongruenceof thedistractorwith thetargetnameis clearlydetectable,andphonologicalfacilitationarisingfrom partialform overlap is counteractedby the recognitionof this in-congruence.Thepredictionderivedfrom theseassumptionsis a patternof earlysemanticinterference,followedby laterphonologicalfacilitation, just aswasobtainedby Schriefersetal. andtheaboveexperiment.However, thispatternresultsfrom the temporalextensionof auditorily presentedwordsandshouldnotbetakenasevidencefor thediscretetwo-stepnotionof lexical retrieval in speechproduction.In fact,com-patiblewith this claim, visually presenteddistractorswhicharenosequentiallyprocesseddonotshow thesequenceof se-manticandphonologicaleffectstypical of theauditorycon-dition.

Contradicting this hypothesis, Meyer and Schriefers(1991) demonstratedphonologicalfacilitation not only fordistractorwordsthat wereword-initially related(like in thepresentstudy),but alsofor distractorsthatwereend-relatedto the target name. This finding implies that the sequentialcharacterof auditoryword recognitionis irrelevantin regardto thefacilitationeffect,andconsequently, theclaim thatthepatternof semanticandphonologicaleffects in this task isjust an artifact resultingfrom the temporalextensionof au-ditory stimuli is notvalid. In contrast,MeyerandSchriefers’findings lend further supportto the assumptionthat suchasequencereflectsthe respective contributionsof lemmaandlexemeprocessingin speechproduction.

A secondpossibility in accountingfor the differenceintheeffectsof visualandauditorydistractorsis thatprocess-ing of distractorwordsdiffers fundamentallyacrosspresen-tation modality. The arisingof early phonologicalfacilita-tion effectswith visually presenteddistractorsmight be at-tributableto processesof input processingof the distractorword, as, for instance,suggestedby Roelofs, Meyer, andLevelt (1996): Theactivationof form-relatedlexical neigh-bors- eitherin thevisualwordform lexiconor thephonolog-ical input store- could facilitatelemmaretrieval time of thepicturenamewhile leaving its phonologicalencodingrela-tively unaffected.Sucha claim receivessupportfrom a pic-ture naming study by Lupker (1982) which indicatedthatboth visual and phonologicalsimilarity significantly con-tribute to the net facilitation effect obtainedfrom visuallypresenteddistractors. Furthersupportcomesfrom a num-ber of studiesdemonstratingform-relatedpriming effectswith visually presentedprime and target words (Grainger& Segui, 1992; Lukatela& Turvey, 1990; Meyer, Schvan-eveld,& Ruddy, 1974;Segui & Grainger, 1990). Moreover,competitoreffectsarisingduringtheprocessingof singletar-

Figure 2. Processingof targetpicturesanddistractorswith fixed(A) or unlimited(B) presentationduration.

getwordshave beendemonstratedin a varietyof tasks(An-drews,1989,1992;Coltheart,Davelaar, Jonassen,& Besner,1977; Forster& Shen,1996; Grainger, 1990; Grainger&Jacobs,1996; Grainger& Segui, 1990; Johnson& Pugh,1994; Sears,Hino, & Lupker, 1995; Snodgrass& Mintzer,1993). Consequently, it is possiblethat at leastpart of thephonologicalfacilitation effect obtainedwith visually pre-senteddistractorsin picturenamingmight beattributabletovisualeffectsduringinputprocessing.

Thereareat leasttwo problematicaspectswith regardtothis hypthesis. First, it is an openquestionwhethersuchproposedneighborhoodeffects are powerful enoughto in-fluencetargetretrieval in thepicture-word interferencetask,given that the distractorwords are only incidentally pro-cessed.Likewise,sucheffectsarequite transientin interac-tive modelsof visual word recognition(e.g.,McClelland&Rumelhart,1981). Therefore,co-activation of lexical com-petitorsin thepicture-wordinterferencetaskmighthaveonlya negligible impact on target retrieval in the current task.Second,if this hypothesisis to explain the differenceinthe patternof semanticandphonologicaleffectsacrossdis-tractor modalities,it follows that no suchco-activation ef-fectsshouldoccurduring auditoryword recognition. Con-tradicting this claim, auditory lexical co-activation effectshave beendemonstratedin a numberof studiesinvestigat-ing form-relatedpriming (Goldinger, Luce,& Pisoni,1989;Goldinger, Luce,Pisoni,& Marcario,1992;Radeau,Morais,& Dewier, 1989; Slowiaczek& Pisoni, 1986; Slowiaczek,Nusbaum,& Pisoni,1987).Althoughinvestigationsof lexi-cal co-activationeffectsof singleauditorily presentedwordsarequitescarce(but seeMarslen-Wilson,1990),sucheffectsarealsopredictedby currentmodelsof auditoryspeechpro-cessing(e.g.,Marslen-Wilson& Tyler, 1980;McClelland&Elman,1986).In summary, theempiricalfindingsto datedonot supporttheclaim thatvisualandauditoryword recogni-tion differ fundamentallyfrom eachotherwith regardto theco-activationof competingitems.

We favor yet another, much simplerexplanationfor thediscrepancy betweenvisually and auditorily presenteddis-


tractors. In the picture-word interferencetask, the asyn-chrony interval betweenpicture and word is manipulatedwith theintentionof tappinginto thevariousrepresentationalstagesinvolvedin speechpreparation.For this manipulationto achieve its aim, it mustbe assumedthatdistractorwordshave a roughly fixed accesstime (seePanelA of Figure2)and,dependingon their onsetrelative to the picture,eitherinterferewith semanticretrieval of thetargetword (atearlierSOAs) or facilitatephonologicalencoding(at later SOAs).Theassumptionof afixedandlimited accesstime seemsap-propriatefor auditorily presenteddistractorswhich have afixedextensionovertimeandthusterminate”naturally” withtheir offset. Althoughonemight assumethat thephonolog-ical andsemanticrepresentationsremainactivatedfor sometime period following the endof the word, the durationofthis activation might be expectedto be relatively brief forunattendedwords.

In contrast,visually presenteddistractorsdo not have afixedduration,andasa consequence,the interval for whichthey arepresentedis arbitrary. In Experiment1, visuallypre-senteddistractors- togetherwith the picture- remainedonthe screenuntil the participanttriggeredthe voice key. Inparticular, visualdistractorsin theSOA = -200msandSOA= -100msconditionsappearedon thescreenbeforethepic-turewaspresented,but thenremainedon throughoutpresen-tation of the picture. In Starreveld and La Heij’s (1996b)study, both picturesand distractorwords remainedon thescreenfor 375 ms after pictureonset. Accordingto Leveltet al.’s (1991)estimates,both lemmaandlexemeactivationroughly take placewithin thefirst 400msof namingprepa-ration. This implies that in Experiment1 aswell asStarrev-eldandLa Heij’s study, distractorwordswerepresenton thescreenwhile bothtargetlemmasandlexemeswereaccessed,independentof the SOA of their onset(seePanelB of Fig-ure 2). Both experimentsrevealedphonologicalfacilitationeffectsat earlySOAs, which crucially distinguishedthepat-tern from the one obtainedwith auditory distractorwords.We hypothesizethat such”early” form-relatedeffectsarisebecause,dueto their unlimited presentationduration,thesedistractorsneverthelesstapinto a ”late” stageof speechpro-duction(i.e., lexemeactivation).That is, we assumethat thevisualdistractorsunintentionallyactivatetheir lexical repre-sentationswhile they remainon thescreen.3

An experimental test of this hypothesis is relativelystraightforward. Theonly proceduraldetail thatneedsto bealteredis the presentationdurationof the distractorwords.A completematchbetweenauditoryandvisualdistractorsinthis regardis of coursenot possible:Semanticaccessin au-ditory word recognitioncritically dependson when”lexicaluniqueness”is achieved, whereasvisually presentedwordsprobably gain relatively faster accessto semanticcodes.However, theissueat questionis whethervisually presenteddistractors,if their presentationdurationis limited, yield apatternof effectscomparableto theoneobtainedwith audi-tory distractors.The following experimentusedthe stimulifromExperiment1andcleareddistractorsfromthescreenaf-terapresetinterval, eventhoughthetargetpicturesremainedon thescreenuntil a responsewasmade.

Experiment2

Method

Participants. TwentyRiceUniversityundergraduatestu-dentsservedasparticipantsin orderto meeta classrequire-mentfor experimentalparticipation.

Materials. Theemployedstimuli wereidenticalto thoseusedin Experiment1.

Design and Procedure. Only distractorsin the visualmodality were used. The conditionswere the sameas inExperiment1. Thus,theexperimentaldesignincludedSOAwith five levels(-200ms,-100ms,0 ms,+100ms,and+200ms) andTarget-DistractorRelationwith threelevels (Unre-lated,SemanticallyRelated,andPhonologicallyRelated)aswithin-subjectsfactors.

The procedurewasidentical to the oneemployed in Ex-periment1,with oneexception.Within eachtrial, thedistrac-tor wordwasdisplayedfor only 200msandthenreplacedbyastringof ”X” lettersthatservedasamaskandstayedonthescreenfor 500ms. All othertemporalparametersremainedidenticalto Experiment1. In particular, thepictureremainedon thescreenuntil thevoicekey triggered.

Results

As in Experiment1, all responsesjudgedto be incorrectby the experimenter, responsetimesshorterthan250ms orlongerthan2000ms,andresponsetimesdeviatingmorethanthreestandarddeviationsfrom aparticipant’sandcondition’smeanwereexcluded. Theseproceduresresultedin the ex-clusionof 3.0%,0.6%,and1.4%of thedata,respectively. Atotalof 5.0%of datapointsweredeletedin thisway.

Table2 andFigure3 displaythe results. Substantialse-mantic interferenceeffectscanbe found for SOAs rangingfrom -100 ms to +100 ms. In contrast,facilitation effectsfrom form-relateddistractorsappearto set in at SOA = 0ms andstretchinto the positive SOAs. Critically, no form-relatedeffectsarefoundat SOA = -200ms,andtheeffectatSOA = -100msis verysmall.

An ANOVA conductedon the datashowed a significantmain effect of SOA, F1(4,76) = 7.40, p � .001, MSE =36,233,F2(4,108)= 46.36,p � .001,MSE = 50,479,a maineffect of Condition, F1(2,38) = 39.81, p � .001, MSE =64,240,F2(2,54) = 48.48,p � .001, MSE = 94,386,andasignificantSOA � Conditioninteraction,F1(8,152)= 10.57,p � .001,MSE = 10,277,F2(8,216)= 20.13,p � .001,MSE= 14,872.

DunnetttestswereconductedthatcomparedtheUnrelatedto thePhonologicalandtheSemanticconditionwithin eachSOA group. The Unrelatedconditiondifferedsignificantlyfrom thePhonologicalconditionat SOAs rangingfrom 0 ms

3 Thanksgo to GaryDell, ZenziGriffin andtheothermembersof thelanguageresearchgroupat theUniversityof Illinois for sug-gestingthisalternative interpretationto us.


Table2Experiment 2: Mean Response Latencies (in Milliseconds),varied by Relatedness (Unrelated vs. Semantic vs. Phono-logical) and Picture-Word Onset Asynchrony (SOA)

Distractor SOA (in ms)type -200 -100 0 +100 +200

Unrelated 714 710 738 741 689Semantic 731 735 782 774 673Phonological 715 704 695 671 660

to +200ms,andfrom theSemanticconditionat SOAs rang-ing from -100 ms to +200ms. All othercomparisonswerenot significant.

Of further interest is a comparisonbetweenthe resultsfrom this experimentand the findings from Experiment1.First, the effectsof manipulatingthe visual distractordura-tion was assessedby comparingthe presentresultsto thecondition from Experiment1 with visually presented,tem-porally unlimiteddistractors.An ANOVA conductedon thecombineddatafrom bothexperimentsrevealeda significantthree-way interactionbetweenExperiment,SOA, andCon-dition, F1(8,264)= 2.75,p = .006,MSE = 2,070,F2(8,432)= 4.96,p � .001,MSE = 2,790. Furthertestscomparedthesize of a distractoreffect (Unrelatedminus Relatedcondi-tion) ata particularSOA level betweenthetwo experiments.Thesetestsshowed significantlygreaterphonologicalfacil-iation for the group with unlimited distractorpresentation(Exp. 1) thanfor the groupwith masked distractorpresen-tation(Exp. 2) at SOA = -200msandSOA = -100ms. Thisfinding underscoresour assertionthat presentationdurationof visually presenteddistractorshasa crucial impacton thepresenceor absenceof ”early” phonologicalfacilitationandthusdeterminestherelativesequenceof semanticandphono-logical effects. A further significantcomparisonconcernedthe semanticeffect at SOA = +200 ms, at which the groupwith unlimited presentationduration(Exp. 1) still showedsubstantialinterference,while the groupwith limited dura-tion (Exp. 2) showeda nonsignificantfacilitatoryeffect.

Second,thepresentresultswerecomparedto theauditorydistractorcondition in Experiment1. An overall ANOVAagain showed a significant Experiment � SOA � Condi-tion interaction,F1(8,264)= 2.95, p = .004, MSE = 2,211,F2(8,432)= 5.42, p � .001, MSE = 3,762. A comparisonof the effects (Unrelatedminus Relatedcondition) at eachSOA levelbetweenthetwo experimentalgroupsyieldedonlyonesignificantdifference:at SOA = +100 ms, the seman-tic interferenceeffect wassignificantlylargerin thevisuallymaskedthanin theauditorygroup. We take the fact thatnoother comparisonyielded significantresultsas supportforour claim that visually and auditorily presenteddistractorsyield largely comparableeffectswhenpresentationdurationis takeninto account.

Figure 3. Experiment2: Effectsof semanticallyandphonologi-cally relateddistractors(unrelatedminusrelatedcondition)variedby stimulus-onsetasynchrony (SOA; 200ms,-100ms,0 ms,+100ms,+200ms).

Discussion

Similar to Experiment1, thesemanticinterferenceeffectis mostpronouncedat SOA = 0 ms andpresentto a lesserextent at the neighboringSOAs. In contrast,phonologicalfacilitation is now foundexclusively at thelaterSOAs rang-ing from 0 msto +200ms,whereas,in Experiment1,suchaneffectwasfoundat SOAs rangingfrom -200msto +100ms.In otherwords,Experiment2 yieldedasequenceof semanticinterference,followed by phonologicalfacilitation. Suchapatternbearsahighresemblanceto thepatternobtainedwithauditorydistractors,but differssubstantiallyfromtheoneob-tainedwith theunlimitedvisualdistractorsin Experiment1.We concludethat it is neitherthe”identity priming” nor the”input priming” hypothesisdetailedabove thataccountsforthediscrepancy in thepatternobtainedwith visualandaudi-tory distractors.Rather, anoverlookedproceduraldetail- thepresentationdurationof thedistractor- causedthedifferencein how semanticandphonologicaleffectstemporallyrelateto eachother. Whenthepresentationdurationof thedistrac-tor waslimited, a similar pattern- semanticinterferencefol-lowedby phonologicalfacilitation- wasobtainedwith visualandauditorydistractors.

This finding implies that we can now invest reasonabletrust in Schrieferset al.’s suggestionthatthesequenceof se-manticandphonologicaleffectsobtainedin theirexperimentreflectsthe underlyingstagesof lexical accessin speaking.The fact that even visually presenteddistractorsdisplayedsucha patterndemonstratesthat the temporalextensionofauditorily presentedwords cannotbe the causefor the se-quenceof effectsfoundwith auditorydistractors.Thus,po-tential differencesin how visually andauditorily presenteddistractorwordsareprocessedis irrelevantwith regardto thepicture-word interferenceprocedure.In this way, our find-ingsarein agreementwith Meyer andSchriefers’(1991)re-sultsdemonstratingthat not only word-initially related,butalso end-relatedphonologicaldistractorscan facilitate re-


sponses.Boththeirsandourfindingsunderscoretheassump-tion that the sequenceof semanticandphonologicaleffectsconstitutesa basicfactaboutlexical accessin speakingthatmodelsof languageproductionhave to accountfor.

Theimplicationsin regardto the”input priming” hypoth-esisforwardedby Roelofsetal. arelessclear. Notethattheseauthorstailored their argumentas a rebuttal to StarreveldandLa Heij’sconclusions,but did notexplicitly outlinetheirclaimsin regardto the differencebetweenvisually andau-ditorily presenteddistractors.At thevery least,our findingssuggestthatlexical co-activationduringvisualwordprocess-ing cannotbetheonly differencebetweenthevisualandau-ditory patterns. Suchco-activation effects shouldbe mostpronouncedat earlystagesof word processing,which corre-spondto a lateSOA in thepicture-word interferenceproce-dure. However, the differencebetweenvisual andauditorydistractorsconsistedin the presenceor absenceof phono-logical effectsprecedingthe onsetof semanticeffects,andthisdifferencewaseliminatedwhenpresentationdurationofvisualdistractorswaslimited. This finding would appeartoimply thatsuchcohorteffectsareirrelevantfor thephonolog-ical facilitationto arise.We concludethatwith auditorydis-tractors,phonologicalfacilitation effectsmost likely reflecttheexclusiveeffectsof thedistractoronword form encodingfor production.

Let us now turn to a more detaileddiscussionof Star-reveld and La Heij’s (1995, 1996b) study. This researchwasbasedon a numberof experimentsreportedby RaynerandSpringer(1986)in which pictureswerepairedwith su-perimposeddistractorwords that representeda wide rangeof conditions. Critically, both graphemicsimilarity andse-manticcategory membershipbetweenpicture label andvi-suallypresenteddistractorword wereindependentlyvaried.Thecentralfinding consistedof theobservationthatseman-tic and form-relatedeffects yielded a non-additive effectin the picture-word interferenceprocedure:preservingthegraphemiccharacteristicsof thepicturelabelreducedthecat-egory interferenceeffect beyondtheextentpredictedwithinanadditive model. Thefact that thetwo factorsappearedtomodify eachotherwas taken to suggestthat both semanticinterferenceandgraphemicfacilitation interactat a centralstageof cognitiveprocessing:semanticallyrelateditemsareassumedto conflict due to their conceptualoverlap whilegraphemicallysimilar items show facilitation due to inputprocessesfeedinginto the conceptualsystem(althoughal-ternative possibilitieswerealso discussed).Starreveld andLa Heij (1995)pointedout a numberof weaknessesin thisstudy: in Experiment1 and2, conditionswerepresentedinablockedfashion,whichmightpotentiallyhavegivenrisetoanticipationeffects. In Experiment1B, the conditionswererandomlyintermixed,but here,thesemanticinterferenceef-fect by itself did not reachstatisticalsignificance. Finally,whenorthographicsimilarity wasdefinedasfirst-lettersim-ilarity, the resultswere ratherinconsistent. Starreveld andLa Heij factorially crossedsemanticsimilarity, definedascategory membership,andgraphemicsimilarity, definedasan overlapin the initial consonant-vowel combination,andpresentedthe experimentalconditionsin a randomlymixed

fashion. The resultsreplicatedthe interactionbetweenthetwo factorsearlierdemonstratedby RaynerandSpringer. Ina furtherstudy, StarreveldandLa Heij (1996b)demonstratedsuchaninteractionbetweensemanticandorthographicsimi-larity notonly for asituationin whichpicturesanddistractorsaredisplayedsimultaneously, but for a wide rangeof SOAs.Basedon Sternberg’s (1969)additive-factorsmethod,Star-reveldandLa Heij interpretedtheobtainedstatisticalinterac-tion betweensemanticandorthographicfactorsasindicatingoneof two possibilities:eithertheprocessof lemmaretrievaldoesnot exist or is irrelevant in speechproduction,or if itexists,lemmaretrieval mustreceive feedbackfrom thewordform level. Theformeraccount,favoredby theauthors,wastermedthe”nameretrieval” account.StarreveldandLa Heijconcludedthat, in orderto explain their findings,a separatelexical-semanticstageis not necessary;all that is requiredis a word form level separatefrom the conceptualsystem.Retrieval of thecorrectlexical item, in this model,is a one-stepprocessresidingat theword form level thatis subjecttosemanticinterference(for instancevia spreadof activationinthesemanticsystem,see,e.g.,Roelofs,1992a,1992b,for apossiblemechanism)aswell asorthographic/phonologicalfacilitation (resultingfrom the priming of word form infor-mation). As both the experimentalfactorsof semanticandphonologicalrelatednesspresumablyaffect a single repre-sentationallevel, suchan accountwould indeedpredict theobtainedinteractionbetweenthetwo factors.

However, Schrieferset al.’s results,as well as the find-ingsfrom Experiment2, establisha sequentialpatternof se-manticandphonologicalprocessingasa basiccharacteristicof speechproduction.Thesuggestedtwo separatestagesoflexical accessaredifficult to reconcilewith Starreveld andLa Heij’s ”nameretrieval” account,whichassumesthatbothsemanticandform-relatedfactorsaffect a singlerepresenta-tional level. In contrast,a two-stepaccountof speakingiscompatiblewith sucha sequence.Of course,this prelimi-nary conclusiondoesnot speakto the questionof whethersucha two-stepaccountmustnecessarilybeconceivedof asmodularor ”discrete”. Indeed,Harley (1993)demonstratedthataninteractivemodelis ableto producearoughsequenceof earlysemanticandlatephonologicalactivation.Althoughthecomputationaldetailsof this modelareopenfor debate,his reportindicatesthat thesequentialpatternshouldnot beinterpretedasnecessarilyruling out non-modularaccounts.Consequently, the presentfindingsshouldbe interpretedascorroboratinga two-stepaccountof speechproduction,irre-spective of whethermodularor interactive versionsare fa-vored.

This opensthepossibility that the logic of Starreveld andLa Heij’s experimentcould be employed in order to testthe assumptionsmadeby the ”discrete” two-stepmodelofspeaking.Auditorily presentedor limited visual distractorsyield a sequenceof semanticandphonologicaleffects. As-sumingthat this patternreflectsthe respective contributionsof lemma and lexemerepresentations,the additive-factorsmethodcould testwhetherthesetwo stagesareadditive orinteract.In thisregard,thediscretetwo-stepmodelof speechproductionallows straightforwardpredictions:the presence


of semanticinterferencein theabsenceof a phonologicalef-fect at a negativeSOA would betakenasindicatingthat thespeechproductionprocessisatthelemmaretrievalstage,andphonologicalpropertiesof the distractorword are entirelyirrelevant at this point. Consequently, semanticallyrelateddistractorsthat arealsophonologicallyrelatedshouldyieldthesamesemanticinterferenceeffectassemanticallyrelated,phonologicallyunrelateddistractors.Thereversepredictionwould be madefor positive SOAs: the presenceof phono-logical facilitation in the absenceof semanticinterferencepresumablyreflectsthecompletionof semantic-syntacticre-trieval and the accessof word form information. As a re-sult,distractorsbothsemanticallyandphonologicallyrelatedshouldyield facilitationeffectscomparableto thoseobtainedfrom phonologicallyrelated,semanticallyunrelatedwords.In otherwords,thediscretetwo-stepmodelclearlypredictsadditivity of therespectiveeffectsof semanticandphonolog-ical similarity.

If insteadan interactionbetweenthe two factorsis ob-tained,sucha finding would clearly poseproblemsfor thebasicassumptionsof the two-stepmodel. If additive-factorlogic holds,theneithera) thetwo factorsaffect thesamerep-resentationallevel, or b) thereis someinteractivity betweenthe two levels. Given that Experiments1 and2 suggesttheserialityof representationalstages,possibilitya) canbedis-counted. Thus, an interactive relationshipwould argue infavor of non-modularaccountsof speechproduction.

In orderto investigatethis issue,thefollowing experimentemployedananalogof Starreveld andLa Heij’s (1996b)ex-perimentby factorially crossingsemanticandphonologicalrelatednesswhile usingauditorydistractors.

Experiment3

Method

Participants. Forty-two Rice University undergraduatestudentsserved as participantsin order to meeta classre-quirementfor experimentalparticipation.

Materials. Eighteenline drawings of common objectswereselectedfrom theSnodgrassandVanderwart (1980)setwhichhadasemanticcoordinatethatalsosharedaminimumof the initial two phonemeswith the picture name(hence-forth S&Pdistractors).In thefollowing,semantically(S)andphonologically(P)relateddistractorswereselectedthatwerematchedin termsof theirsemanticandphonologicaloverlapto the S&P distractors.As suggested,but not implementedby Starreveld andLa Heij (1996b),it is importantto matchdistractorwordsin the S&P conditionto thosein the S andthe P conditionon an individual item basisratherthan justby averagingscoresfor eachcondition. This is importantinregardto an itemsanalysis,which will otherwiseshow de-viant results.Again, phonologicalsimilarity wasdefinedasanoverlapof thetwo initial phonemesasa minimal require-ment. In addition,a phonologicaloverlapscorewascalcu-latedthatmatchedP andS&P distractorwordsin regardtotheir phonologicalsimilarity to thepicturelabel. 4 For eachindividual picture label, the phonologicaloverlapscoresof

the correspondingP andS&P distractorsdeviatedno morethan10%from eachother. Likewise,it wasensuredthat theunrelated(U) distractorswereasphonologicallyunrelatedtothe picture label as the S distractors. In regard to concep-tual overlap,semanticrelatednessratingswerecollectedforthestimuli. Thirty participantswerepresentedwith pairsofwordsandinstructedto rateconceptualsimilarity on a scalefrom 1 (very unrelated)to 5 (very related). The ratedpairsconsistedof theeighteenpicturelabelspairedwith theS&Pdistractorwords as well as eachpicture label pairedwiththreedifferentpotentialS distractors,plus the picture labelpairswith the P andthe U distractors,presentedin randomorder. Fromtheseratings,theoneSdistractorwordwascho-senfor eachindividualpicturewhoseratingscorewasclosestto thecorrespondingS&P score.Again,noneof theindivid-ual scoresfor the S&P and the S condition deviatedmorethan10% from eachother. Also, it wasensuredthat P andU distractorsweresemanticallyunrelatedto comparablede-grees.This selectionprocedureensuredthatbothphonolog-ical andsemanticsimilarity werematchedon an individualitem basis.This experimentalsoemployeda Controlcondi-tion in which no distractorword wasdisplayed.

Design. TheexperimentaldesignincludedSOA (-150ms,0 ms,and+150ms),SemanticRelatedness(Relatedvs. Un-related),andPhonologicalRelatedness(Relatedvs. Unre-lated)aswithin-subjectsfactors.Eachsetof 90picture-wordpairswasdisplayedthreetimesatdifferentSOAs. Theorderin which participantsreceivedtheSOA blockswasbalancedaccordingto a Latin Squaresdesign. Itemswerepresentedin a pseudorandomfashionsuchthat thesamepictureneverappearedtwice on subsequenttrials.

Procedure. Thegeneralprocedurewassimilar to theoneemployed in Experiment1 and2. However, in accordancewith Schrieferset al.’s (1990)Experiment2, only threeSOAblocks(-150ms,0 ms,+150ms)wereadministered.Again,eachparticipantwasfamiliarizedwith thepicturesbeforetheexperimentbegan. Subsequently, two practiceblocksof 18trialseach,onewithoutandonewith auditorilypresentedun-relateddistractors,wereconducted.Finally, thethreeexper-imentalblocksof 90 trials eachwereadministered,resultingin atotalof 270experimentaltrialsfor eachparticipant.Eachtestingsessionlastedapproximatelyhalf anhour.

Results

Responsesjudgedto beincorrectby theexperimenter, re-sponsetimesshorterthan250msor longerthan2000ms,andresponsetimesdeviatingmorethanthreestandarddeviationsfrom a participant’s andcondition’s meanwereeliminated.

4 Adaptedfrom Leschand Pollatsek’s (1993) visual similarityestimate,this phonologicalsimilarity measureconsistsof an indexrangingfrom 0 to 1, calculatedastheaverageof a) the fractionofsharedphonemesbetweentwo words(e.g.,rabbit andrat) in andoutof position(e.g., � ræb� t/ and � ræt/= 3/4= 0.75),andb) thefrac-tion of sharedphonemesthatoccurin thesamepositionwithin thewords(e.g., � ræb� t/ and � ræt/= 2/4 = 0.5). Thus,thephonologicalsimilarity measurefor rabbit andrat is (0.75+ 0.5) / 2 = 0.625.


Table3Experiment 3: Mean Response Latencies (in Milliseconds),varied by Relatedness (Control vs. Unrelated vs. Semanticvs. Phonological vs. Semantic & Phonological) and Picture-Word Onset Asynchrony (SOA)

SOA (in ms)Relatedness -150 0 +150

Control 630 643 635Unrelated 670 702 691Semantic 702 733 697Phonological 665 683 646Semantic& Phonological 679 676 654

Theseproceduresresultedin the exclusionof 2.3%, 0.2%,and1.2%of the data,respectively. A total of 3.7%of datapointsweredeletedin thisway.

Table3 displaysthemeanresponsetimes,variedby SOAandpicture-distractorrelation. Figure4 displaystheseman-tic, phonologicaland semanticas well as phonologicalef-fects (Unrelatedminus Relatedcondition). Parallel to thehalf of Experiment1 thatemployedauditorydistractors,anearlystageof semanticinterferencein theabsenceof phono-logical effects is followed by a late stageof exclusivelyphonologicalfacilitation,with aninterveningstagein whichbotheffectsareobtained.Semanticallyaswell asphonolog-ically relateddistractorshave aneffect thatappearsroughlyadditiveonly atthelatestSOA, butclearlynotsoattheearliertwo SOAs.

A 3 (SOA) � 5 (Typeof Relatedness)ANOVA wascon-ductedon the datawith both factorsaswithin-subjectsfac-tors. A maineffect of SOA, F1(2,82)= 6.61,p = .002,MSE= 30,305,F2(2,34)= 26.46,p � .001,MSE = 13,584,aswellasmaineffect of Typeof Relatedness,F1(4,164)= 54.75,p

� .001, MSE = 95,787,F2(4,68) = 20.22,p � .001, MSE= 42,301,wasobtained.Furthermore,a significantSOA �Type of Relatednessinteractionwasobtained,F1(8,328)=5.67,p � .001,MSE = 5,120,F2(8,136)= 4.85,p � .001,MSE = 2,145.

Dueto thefactthatthefactorsSemanticandPhonologicalRelatednesswerefactoriallycrossed,anadditional3 (SOA)� 2 (SemanticRelatedness)� 2 (PhonologicalRelatedness)ANOVA wasperformedin which theresponsedatafrom theControl condition were omitted and all three factorsweretreatedaswithin-subjectsvariables.Table?? shows the re-sultsfrom thisanalysis.Critically, aSOA � SemanticRelat-edness� PhonologicalRelatednessinteractionwasobtainedthat wassignificantin both subjectsanditemsanalyses,aswell asa SemanticRelatedness� PhonologicalRelatednessinteractionthat wassignificantin the subjectsanalysisandmarginally significantin theitemsanalysis.

Thesignificantthree-way interactiondescribedabove in-dicatesthat the extent to which semanticandphonologicalrelatednessmodify eachothers’effectsvariesaccordingtoSOA. Consequently, theeffectsof SemanticandPhonologi-cal Relatednesswereinvestigatedat eachlevel of the factor

Figure 4. Experiment3: Effectsof semanticallyrelated,phono-logically related,andsemanticallyandphonologicallyrelateddis-tractors (unrelatedminus related condition) varied by stimulus-onsetasynchrony (-150ms,0 ms,+150ms).

SOA separately. For SOA = -150 ms, this analysisshoweda main effect of SemanticRelatedness,F1(1,41)= 27,92,p

� .001, MSE = 20,783,F2(1,17) = 19,25,p � .001, MSE= 10,012,and a main effect of PhonologicalRelatedness,F1(1,41) = 11.95,p = .001, MSE = 8,208,that approachedsignificancein theitemsanalysis,F2(1,17)= 3,47,p = .080,MSE = 4,534. Furthermore,the Semantic � PhonologicalRelatednessinteractionwassignificantin the subjectsanal-ysis, F1(1,41) = 6.60, p = .014, MSE = 4,059,but not sig-nificant in the items analysis,F2 = 2.41. Newman-Keulspairwise comparisonsindicatedthat the SemanticallyRe-lated condition differed significantly from all other condi-tions. In contrast,thePhonologicallyRelated,theUnrelated,and the Semantically& PhonologicallyRelatedConditiondid notdiffer from eachother, but differedsignificantlyfromtheSemanticallyRelatedCondition.DespitethefactthattheSemantic � PhonologicalRelatednessinteractionreportedabovewasnotsignificantin theitemsanalysis,thesamepat-tern of resultsheld when the Newman-Keuls comparisonswereperformedon itemsinsteadof subjects.

For SOA = 0 ms,theanalysisshowedamaineffectof Se-manticRelatednessin thesubjectsanalysis,F1(1,41)= 5.03,p = .030,MSE = 5,406,thatwasnot significantin the itemsanalysis,F2 = 1.90.Furthermore,amaineffectof Phonolog-ical Relatednesswasobtained,F1(1,41)= 35,13,p � .001,MSE = 60,611,F2(1,17)= 11.22,p = .004,MSE = 27,549,as well as a significantSemantic � PhonologicalRelated-nessinteraction,F1(1,41)= 10,63,p = .002,MSE = 16,301,F2(1,17) = 8,29, p = .014, MSE = 7,565. Newman-KeulstestsshowedthattheUnrelatedandtheSemanticallyRelatedconditiondifferedfrom all otherconditions.In contrast,thePhonologicallyRelatedandthe Semantically& Phonologi-cally Relatedcondition did not differ from eachother, butdifferedfrom all otherconditions.

Finally, for SOA = +150 ms, a main effect of SemanticRelatednesswas found in the subjectsanalysis,F1(1,41) =5,46, p = .024, MSE = 2,437, that was marginally signifi-cantin theitemsanalysis,F2(1,17)= 3,33,p = .086,MSE =996.Furthermore,amaineffectof PhonologicalRelatedness


wasobtained,F1(1,41) = 93.66,p � .001, MSE = 81,196,F2(1,17)= 23.95,p � .001,MSE = 36,309.In contrast,theSemantic � PhonologicalRelatednessinteractionwas notsignificantin eithersubjectsor itemsanalysis,F1 = 0.02,F2= 0.02.Newman-KeulstestsindicatedthatthePhonologicalandtheSemantically& PhonologicallyRelatedconditiondidnot significantlydiffer from eachother. Finally, the Unre-latedand the SemanticallyRelatedconditiondid not differfrom eachother.

Discussion

If oneignorestheresultsfrom theSemantically& Phono-logically Relatedcondition, the findings from this experi-mentonceagainreplicatedSchriefersetal.’s (1990)findingsin that an early stageof exclusively semanticeffects con-trastedwith a laterstageof exclusively phonologicaleffects.In accordancewith thefindingsfrom Experiment1, theinter-mediateSOA yieldedbothsemanticinterferenceandphono-logical facilitation. Distractorwordsthatweresemanticallyaswell asphonologicallyrelatedto thepicturenameshowedanattenuatedsemanticinterferenceeffectat theearliestSOA(-150ms), in which the predictionfrom additivity for theseitemswasunderestimated20 msat SOA = -150ms. At theintermediateSOA (0 ms), the semanticinterferenceeffectfor theseitems was entirely eliminated. Only at the latestSOA did semanticandphonologicaleffectsroughly addupfor thesemanticallyaswell asphonologicallyrelateddistrac-tor words.

The fact that semanticinterferencewassubstantiallyre-ducedin the simultaneouspresenceof a form relationshipreplicatesboth Raynerand Springer’s (1986) and Starrev-eld andLa Heij’s (1995,1996b)findingsobtainedwith vi-sually presenteddistractorwords. Thesefindingsappeartocontradictthe predictionsmadefrom the discretetwo-stepmodel of speaking. Sucha model hypothesizescompleteindependenceof lemmaand lexemestagesand as a resultwouldpredictanadditiverelationshipamongthetwo experi-mentalfactorsof semanticandphonologicalrelatedness.Be-fore this conclusionis accepted,thevalidity of theadditive-factorsmethodshouldbe assessedin moredetail. Accord-ing to Pachella(1974),theadditive-factorsmethodis basedon thepremisethat thereactiontime interval is filled with asequenceof stagesthatprovide variousinformationaltrans-formations. Thesecognitive stagesare assumedto be en-tirely modularsuch that the manipulationof experimentalfactorssolelyaffectsthedurationof processingtakingplaceon a particular cognitive stage,but not its content. Datafrom an experimentemploying the additive-factorsmethodcan be informative in two ways. First, undera ”function-ally basedapproachto theorizing” (p.57), the presenceofa statisticaladditivity amonga pair of experimentalfactorscanserve asan operationaldevice to infer the existenceofcorrespondingprocessingstages.Second,therearepsycho-logical issuesin whichtherealreadyexistssomeindependentandexternaljustificationfor assumingtheexistenceof two ormoreindependentstages.In suchacase,theadditive-factorsframework cantestspecificassumptionsaboutthecharacter

of thesestages:additivity betweenthe relevant experimen-tal factorswould indicatethat the correspondingstagesin-deedadhereto a modulardefinition. In contrast,an interac-tion would show that the processingstagesarenot modularwith respectto eachother. Notethatthis useof theadditive-factorsmethoddoesnot excludethepossibilitythattwo fac-torsmight affect a singlestageadditively or that they affectdifferentstageswhile interacting.However, in this casethedefinitionof whatmakesa ”stage”would beundermined.Inthis sense,theadditive-factorsmethodprovidesa methodoftestingspecificclaimsaboutthe definition andcharacterofparticularprocessingstages.

It is this lattersenseof interpretationthatis relevantto thequestionof modularity vs. interactivity in speaking. Theexistenceof separatesemanticand phonologicalrepresen-tational stagesin speechproductionis an undisputedissuein the literature; indeed,Caramazza(1997,p.329)recentlycalledit ”... ascloseto a universallysharedpositionasany-thing is in cognitive science”.Thetemporalsequenceof se-manticinterferenceandphonologicalfacilitation,onceagainreplicatedin thepresentexperiment,furthersupportstheas-sertionthatlexical accessin speechproductioninvolvestwoseparablerepresentationalstages.Accordingly, theadditive-factorsmethodcanbeusedto testthemodularityassumptionof thediscretetwo-stepmodel.

To reiterate, the two-step model assumesthat lexical-semanticselectionconvergeson a single candidatewhichsubsequentlyundergoesphonologicalencodingatthelexemelevel. Specifically, only onelexical-semanticitemundergoesphonologicalencoding,and lexemeretrieval has no influ-enceon theprecedingstageof lexical-semanticselection.Itis clearthat this characterizationof lexical accessin speak-ing adheresverycloselyto themodularnatureof acognitivestagesuggestedby theadditive-factorsmethod.However, iftheseassumptionsof thetwo-stepmodelhold,it ishardtoseehow suchanaccountcouldexplaintheinteractionobtainedinExperiment3. As Roelofsetal. (1996,p.247)correctlynote,thefindingof aninteractionamongtwo experimentalfactorsdoesnot excludethepossibility that thesetwo factorsaffectseparaterepresentationalstages.However, this casewouldunderminethedefinitionof a cognitivestageasprovidedbytheadditive-factorsmethod,namelyits modularsense.

In the following, we will discusswhether models ofspeechproductionthatabandontheassumptionof strictinde-pendencebetweentheinvolvedrepresentationalstagesmightbeableto provideaplausibleaccountof theobtainedpattern.To this aim, we will look morecloselyat Roelofs’ (1992a,1992b)discretemodelof speechproductionand thencon-sideramodificationof this modelthatprovidesit with inter-activecharacteristics.

Figure5 givesa schemaof Roelofs’ model. Within thisframework, it is assumedthat distractorwordsgain simul-taneousaccessto their correspondinglemmaentries(routea) aswell astheir lexemes(routeb). An unrelateddistrac-tor word will competewith thetarget lemma,andsincelex-ical accessat the lemmalevel involvesa selectionprobabil-ity function,this competitionwill resultin a prolongedsim-ulatedselectiontime comparedto a condition in which no


Table4Experiment 3: Analysis of Variance with Picture-Word Stimulus Onset Asynchrony (SOA), Semantic Relatedness, and Phono-logical Relatedness

Participants Items

Source df1 df2 F1 MSE df2 F2 MSESOA 2 82 7.90** 31,751 34 23.86** 13,131SemanticRelatedness(SR) 1 41 39.10** 23,772 17 12.53** 10,417PhonologicalRelatedness(PR) 1 41 79.10** 128,853 17 13.62** 59.888SOA � SR 2 82 2.93† 2,427 34 2.48† 1,315SOA � PR 2 82 12.83** 10,581 34 9.64** 4,252SR � PR 1 41 10.58** 11,756 17 3.19† 6,640SOA � SR � PR 2 82 5.10** 4,308 34 3.87* 1,728†p� .10. *p � .05.**p � .01.

distractorwords are presented. In order to simulatea se-manticrelationshipbetweenadistractoranda target,it is as-sumedthatconceptualsimilarity will causespreadingactiva-tion betweenthetwo correspondingconcepts.As a result,atrade-off of activationat thelemmalevel will arise.For rea-sonsdetailedin Roelofs(1992a,1992b),this mutual trade-off will benefitthedistractormorethanit benefitsthetargetlemma,andconsequently, lemmaretrieval of the targetwillbeslowedevenmorethanin theunrelatedcondition.In con-trast, phonologicallyrelateddistractorswill activate form-relatedlexemerepresentationssuchasthetargetlexeme,andconsequently, lexemeencodingwill be accelerated.In thisway, the modelprovidesa plausibleaccountof the generalinterferencecausedby the presenceof a distractorword, aswell asthemorespecificeffectsof semanticinterferenceandphonologicalfacilitation obtainedin the picture-word inter-ferenceeffect. In orderto accountfor thesequentialpatternof theseeffect, themodelwould haveto assumethatdistrac-tor activationtransmittedto thelexemelevel decaysquickly.As aconsequence,distractorwordsthatarepresentedbeforethe onsetof the picture(i.e., earlierSOAs) would show noeffecton thestageof phonologicalencodingof thetargetbe-causetheir activation hadalreadydied out by the time thisstagewasreached.Note that this model is a discretetwo-stepmodelin thatactivationis assumedto proceedunidirec-tionally from the lemmato the lexemelevel. The mecha-nismsoutlinedabove thataccountfor semanticinterferenceandphonologicalfacilitationwouldpredictanadditiveeffectof thesetwo factors,asthecontributingrepresentationallev-elsareentirelyindependentof eachother.

Interactivemodelsof speechproduction(e.g.,Dell, 1986,Stemberger, 1985)differ from suchan accountin that theypermit feedbackfrom thelexemeto thelemmalevel. In thisway, phonologicalactivationcanto somedegreeexertanin-fluenceon theearliersemantic-syntacticlevel. As describedin the introduction, such a feedbacklink might provide aplausibleexplanationof why so-called”mixed” speecher-rors(i.e., errorsthataresemanticallyandphonologicallyre-latedto thetargetword)occurmorefrequentlythanwouldbeexpectedby chance.In orderto modify Roelofs’framework,

it couldbeassumedthatthelink betweenthestagesof lemmaandlexemeis bidirectional.In thisway, distractorwordscantransmitactivation to the lemmalevel (via routea in Figure4), to thelexemelevel (via routeb) andbackfrom thelexemeto thelemmalevel (via feedbackbetweenthelevels).

Suchafeedbackconnectionhasnoobviousconsequencesfor semanticallyrelateddistractorwords:themechanismac-countingfor semanticinterferenceoutlinedabove doesnotinvolvethelexemelevel, andasaresult,themutualtrade-offbetweentargetanddistractorlemmaactivationshouldnotbeaffected.However, thefeedbacklink hasaneffect on form-relateddistractorwords. A phonologicallyrelateddistrac-tor would be assumedto gain accessto its correspondinglexemelevel representationsandconsequentlyprime form-relatedunits,suchasthe target lexeme. If activation is per-mitted to flow backwardsthroughthesystem,thenit canbeassumedthat not only the target lexeme,but alsoits corre-spondinglemmaunit receivessomepriming. Note that thehypothesizedfeedbackconnectioncannotbe very strongasotherwiseform-relatedpriming effect would bepredictedtoappearat earlier SOAs, which is only the caseto a smallextent.

Now considerthespecialcaseof asemanticallyaswell asphonologicallyrelateddistractorword. The mechanismde-scribedabovepredictsthatsuchwords- via their phonologi-cal relationshipwith thetarget- activatethetargetlexemeaswell asto someextentthetargetlemmavia feedback.At thesametime,conceptualoverlapwith thetargetwordprolongsselectiontime for the target lemma. However, becausethecorrectlemmanodehasalreadyreceived somepriming viafeedbackfrom the lexemelevel, semanticoverlapnow haslesstime to exert its influenceon lemmaretrieval. In otherwords,thesemanticinterferencecausedby semanticallyandphonologicallyrelateddistractorswill beattenuatedthroughthe priming via the feedbacklink. In this way, both a se-manticanda phonologicalrelationshipcould affect lemmaretrieval time. A non-additive relationshipbetweenthe twofactorswould be predictedif units at the lemmalevel pos-sessa nonlinearactivation function; this type of nonlinearactivation dynamicsis implementedin practicallyall exist-


Figure 5. Discretetwo-stepmodelof speaking.From ”Interac-tion BetweenSemanticandOrthographicFactorsin ConceptuallyDriven Naming: Commenton Starreveld andLa Heij (1995),” byA. Roelofs,A. S.Meyer, andW. J.M. Levelt, 1996,Journal of Ex-perimental Psychology: Learning, Memory, and Cognition, 22, p.247. Copyright 1996by theAmericanPsychologicalAssociation.Reprintedwith permissionof theauthors.

ing modelsof speechproduction.In this case,theeffectsofthetwo factorswouldnotbeexpectedto addup,andaninter-actionwould arise,just aswasdemonstratedin Experiment3. More specifically, semanticinterferencewould be atten-uatedby a simultaneouslypresentphonologicalrelationshipbetweendistractorandtarget.

Note that the proposedmechanismis contingenton thepresenceof at leastsomedegreeof phonologicalfacilitationperseatearlySOAs, asthehypothesizedtransmissionof ac-tivationbackfrom thelexemeontothe lemmalevel predictsa detectableinfluenceof form relatednessby itself. Indeed,at anSOA of -150ms, facilitationobtainedfrom phonolog-ically relateddistractorswasnumericallyweakandstatisti-cally notsignificant,andcorrespondingly, theinteractionbe-tweenthe two experimentalfactorswas not very powerful(significantin theparticipants,but not in theitemsanalysis).In contrast,an SOA of 0 ms yieldeda robust phonologicalfacilitationeffectof 19 ms.As aresult,thefeedbackmecha-nismwasableto effectively eliminatetheinterferenceeffectcreatedby thesemanticoverlapbetweendistractorandtargetwhena simultaneousphonologicalrelationshipwaspresent.At anSOA of +150ms,semanticinterferencepersehadallbut disappeared,andasa result, the feedbackof activationceasedto show aninfluenceonresponsetimes.Here,seman-tically aswell asphonologicallyrelateddistractorsyield ef-fectscomparableto thoseobtainedfrom form-relateditems.

A problematicaspectof such an accountmight derivefrom the fact that semanticallyand phonologicallyrelateddistractorsalways yielded an effect comparableto the oneobtainedfrom phonologicallyrelateddistractors. In other

words,the semanticinterferenceeffect for thesedistractorswasstatistically(but not numerically)eliminatedat SOA =-150 ms, andentirely disappearedat SOA = 0 ms. At thispoint, it is lessthanobviouswhethera feedbackmechanismas the one hypothesizedabove can accountfor the findingthataphonologicalrelationshipbetweendistractorandtargetnot only reduces,but ”overrides”a simultaneouslypresentsemanticrelationship. Only an actual computationalim-plementationwithin an interactive activation framework ofspeechproductionwouldshow whetherthis typeof architec-turecouldyield suchaneffect.

A very similar proposalhasbeenforwardedin a recentstudyby CuttingandFerreira(1997).Thisstudymadeuseofthe fact thathomophonesby definitionhave dissimilarcon-ceptualcharacteristicsandlemmas,but identicalwordforms.Participantsnamedpicturesof homophones(e.g.,a ”ball” asa toy) while confrontedwith distractorwordsthat werese-mantically relatedto the alternative meaningof the picturename(e.g., ”dance”, which is relatedto ”ball” asa festiveevent). The authorsdemonstratedthat suchdistractorssig-nificantly spedup naminglatenciesat an SOA of -150 ms.Becausein this conditiondistractorandtargetareconceptu-ally unrelated,the obtainedeffect mustbe mediatedvia thefactthatbothmeaningsof ”ball” haveidenticalphonologicalrepresentations.Similar to our accountof theinteractionbe-tweensemanticandphonologicalrelatednessoutlinedabove,the authorshypothesizeda feedbacklink from the lexemelevel to the lemmalevel. In this way, thedistractor”dance”couldactivatea semanticallyrelatedlemmalike ”ball” asafestive eventwhich in turn would undergo phonologicalen-coding. If feedbackfrom the lexemeto the lemmalevel isassumed,thenlemmaretrieval for ”ball” asa toy would beaccelerated.Hence,distractorssemanticallyrelatedto theoppositemeaningof a homophonicpicturecouldreducethetimerequiredto accessthecorrectlexical entryof thehomo-phonicpicture.

This accountfacesa similar problemas our hypothesisoutlinedabove: thecritical effect appearsto involve phono-logical codes,yet phonologicallyrelateddistractorsusuallydo not show a substantialeffect on naminglatenciesat thisSOA. Cutting andFerreiraarguedthat this wasthe caseasphonologicaldistractorsmerelysharea few segmentswiththetargetnameandthereforedonotprovidethetargetlemmawith much activation throughthe feedbackconnection. Incontrast,homophonespossessidenticalword forms, andasa result, the activation transmittedvia the feedbacklink isstrongenoughto reducelemmaretrieval time. Whetherthisis a plausibleaccountremainsto be seen,but it is impor-tant to note that their hypothesisis essentiallyidentical toourown.

GeneralDiscussion

Thequestionof how semanticandphonologicalrepresen-tationsrelateto eachotherhasbeena long-standingissueinresearchon speechproduction.Oneof themeansby whichthis issuehasbeenexperimentallyinvestigatedis thepicture-word interferenceparadigm. We believe that Experiments


1 and 2 provide an explanationfor a striking discrepancybetweenthe patternof semanticand phonologicaleffectscausedby either visually or auditorily presenteddistractorwords.Whenvisualdistractorsaremademoresimilar to au-ditory onesin that their displaytime is fixed,both versionsyield a patternof early semanticinterference,followed bylater phonologicalfacilitation. Thesefindingspoint out theimportanceof sucha sequenceasa centralfactaboutlexicalaccessin speechproduction.

In thelight of thesefindings,anissueraisedby StarreveldandLa Heij (1995,1996b)wasreevaluated.Starreveld andLa Heij obtainedaninteractionbetweensemanticandortho-graphicrelatednessin a picture-word interferenceparadigmwhen distractor words were presentedvisually, and con-cludedthatsemanticandorthographiceffectseitherresideininteractingrepresentationalstages,or - the versionfavoredby the authors- that both effectsariseat the level of wordform retrieval. Basedon thesefindings,theauthorsrejectedthediscretetwo-stepmodelof lexical retrieval in speechpro-duction.We considerthis rejectionpremature,giventhattheprocedureemployedby Starreveld andLa Heij doesnot tapinto thetemporalsequenceof lemmaretrievalandlexemeac-cessbecauseof theextendeddurationof visualdistractors.Incontrast,theauditoryversionof thepicture-word procedureyields a sequenceof semanticandphonologicaleffectsthatcorrespondsto thebasicsequenceassumedin lexical access.Consequently, our Experiment3 essentiallyreplicatedtheirexperimentwith auditorily presenteddistractorwords.

The results from this experimentdemonstrateda clearnon-additive influenceof theexperimentalfactorsof seman-tic and phonologicalrelatednesson responsetimes. Thisfinding is in accordancewith the results from speecher-ror researchcited in the introduction(i.e., theoccurrenceof”mixederrors”at a rateabovechance)andsuggeststhatoneof thecritical assumptionsof thediscretetwo-stepmodelofspeaking- the claim that activation proceedsunidirection-ally from semanticto phonologicalrepresentations- mighthaveto beabandoned.Theinteractionbetweensemanticandphonologicalrelatednessis mosteasilyexplainedby assum-ing thatbothfactorsmodify eachothervia feedbackfrom thephonologicalontothesemantic-syntacticlevel.

The above explanation locates the origin of the non-additive effect within the systemof speechproductionperse. Sucha hypothesisstandsin markedcontrastto accountsof ”mixed” errors in speecherror corporaby meansof aproduction-external”monitoringsystem”(Baarsetal.,1975;Levelt, 1989). Whereasthe ”monitoring” hypothesiscon-stitutesa plausibleaccountwith regardto speecherrors,weareunableto seehow it wouldaccountfor our findingsfromthe picture-word interferenceprocedure.After all, herethespeaker producesthecorrectword in theoverwhelmingma-jority of cases,and the monitor would be assumedto ac-ceptall theseresponses.Underthesecircumstances,we be-lieve that our finding provides evidencefor a production-internal mechanismthroughwhich the factorsof semanticandphonologicalrelatednessmodify eachother. Thesefind-ings shouldnot be understood,however, as contestingtheexistenceof monitoringsystemsin general.Thereis anintu-

itive plausibility to the notion thatspeakersdo indeedmon-itor their own output,aswell assomeindependentexperi-mentalevidence(e.g.,Baarsetal.,1975;Motley, Camden,&Baars,1982;Levelt, 1983).However, it is unclearhow sucha monitoringsystemcouldaccountfor thepresentfindings.

In conclusion,we believe that Starreveld and La Heij(1995, 1996b)raisedrelevant issues,but useda procedurethat doesnot provide clear answers. In contrast,our ownstudyuseda procedurethat,by employing auditorydistrac-tors,reflectedtherespectivecontributionsof lemmaandlex-emestagesof lexical access.In accordancewith StarreveldandLa Heij’s findings,an interactionbetweensemanticandphonologicalrelatednesswasobtained.Suchafindingmightbebestexplainedby abandoningthenotionof discrete,mod-ularstagesin speechproductionandallowing for someextentof interactive feedbackbetweentherepresentationallevels.

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AppendixA

Stimuli Usedin Experiments1 and2

Semantically PhonologicallyPicture related related Unrelatedname distractor distractor distractorapple peach apparel nickelbanana plum band deerbed couch bend dukebell gong belt fatebook journal boom hordebowl cup bone sandcamel giraffe camera tidedog fox doll rankdress shirt dread toolduck swan duct towerfoot knee fool unclehand elbow hash lousehorse zebra horn germmouse skunk mount hunchmushroom carrot muscle jewelonion radish onset mistpear orange pedal organpig cow pin bulkring brooch ridge locksaw axe salt maskseal whale seed threatsheep goat shield acidsock glove sorrow mailsun mars sulk puppysweater blouse sweep needletable desk tail guttertomato pepper tornado barontruck bus trunk scout


AppendixB

Stimuli Usedin Experiment3

SemanticallyandSemantically Phonologically phonologically

Picture related related related Unrelatedname distractor distractor distractor distractorapple peach apathy apricot couchbasket crib ban bag thirstbee spider beacon beetle flagbread donut brick bran nailcamel pig cash calf bucketcarrot spinach cast cabbage eveningduck raven dub dove brasselephant moose elm elk stripefly moth flu flea rakelamp candle landing lantern packagepeanut almond piano pecan dressrabbit beaver raft rat coffeesnake eel snack snail firespoon ladle sparkle spatula cablesquirrel mole skate skunk chaintrain Bus trophy trolley foxtruck jeep trap tractor celerytrumpet horn traffic trombone corner

Semantic and phonological codes interact in single word production

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