Top t-angDisordersVol.25, No. 3, pp. 207-21920()'i LippmcotrWilliams & Wilkins, Inc.Stimulabilityand TreatmentSuccessSusan Rvacbew,PhDThisarticleaddresses2questionsofimportancetothetreatmentofspeechsounddisorders:(1) When selecting treatmenttargets, is it bestto begin with themost or the least stimulable po-tential phoneme targets? (2) When treating imstimulable phonemes, which treatmentprocedureswill resultin the best outcome?A summary of the findings from3 randomizedcontrolledtrials isprovided.In these studies, outcomes were generally better whenstimulable targets were treated;however,outcomesforunstimulahletargetswereimprovedby includingphonemicperceptiontraining alongside phoneticplacementproceduresin thetreatmentprogram. The clinicianmusttake finalresponsibilityforjudging theapplicability of these re,search findings to eachindividualcase. Clinical decisions should be made after discussing the knownbenefits and ri,sks of anygiventreatment practice with the client and/or the clients family. Key v/ords: ei'ieience based practice,phonological disorder,speech perception, speech sounddisorder,speech therapy, stimulabilitySTIM U IJ V B IL ITYreflectsa child's ability-tocorrectlyimitateagivenphonemewhenprovidedwiththeinstructionto"watchatidlisten"followedbymodelsofthephoneme,usually in the contextof nonsensesyllables orsimplerealwords(foranhistoricaloverviewoftheclinicalapplicationofstimtilability-testingprocedures,seePowell&Miccio,1996).Stimuiabilitytestingisrecommendedasanessentialpartofanassessment,evenwhenthe"clockis running" andtheclinicianisforcedtomakedeparturesfromidealas-sessmentpractices(e.g., Bleile,2002; Miccio,2002).Promthe School of Communication Sciences andDisorders,Mcdill University.Montreal,Quebec,Canada.Theauthor helped develop and has a financial interestin Speech Assessment and Interactive Learning Systems,a treatment procedure that was evaluated in severaloftbe studies summarizedin this article.This article wasprepared with support fmmthe Cana-dian Language andLiteracy Research Netu^ork(wivw.cllnet.ca). Portions of this article were /nvsented as partofaseminaron"Evidence-Based Practice:TheWhy andthe How"chaired fry AmyWeiss and Rehecca McCavley,at the2004 annualconvention ofthe A merican Speech-Langtiage-Hearing Association.Corresponding author: .SusanRvachew,PhD,SchoolofCommunication Sciences and Disorders, McGill Univer-sity,1266Pine Avenue West, Montreal,Quebec,CanadaH3G IA8(e-mail: susan.rvacheu>@mcgillca).Onereasonforincludingstimulabilitytest-ing in anassessmentof a child'spbonologicalskillsisthattheresultsmayhaveclearprog-nosticindications.Improvementsinarticula-tory accuracy for an unmasteredphonemearemorelikelytooccuroveragiventimepe-riodwhenthechildis stimulable,ratherthanunstimulable,foraccurateproductionofthespeechsound in question (e.g., Miccio, Elbert,&Forrest,1999;Tyler,1996),Furthermore,childrenwhohavegenerallyhigherlevelsofstimulabilityshowbetterprogressovertimethanchildrenwhohavegenerallylowerlevelsofstimulability(eg.,Sommers,Leiss,Delp,Gerber,Fundrella,Smith,Revucky,Ellis,&Haley,1967),Tliesefindingsapplyregardlessofwhetherchildrenshowtyp-icalordelayedspeechdevelopmentandregardlessofwhethertheyarereceivingintervention.Tbereis a consensusthatstimulabilitytestrestiltsalsohaveimplicationsfortreatmentplanningin generalandfortargetselectioninparticular.Thereisconsiderablecontroversyabouttheclinicalimplicationsofstimulabil-ityoralackthereofforthedesignofanet-fectivephonologyintervention,however(foran historicaloverviewof this controversy,seePowell&Miccio,1996),Basicresearchonstimulabilitypresentsaproblemforclini-caldecisionmakingbecausetheapparent207208TOPICS IN LANGUAGEDISORDERS/JULY-SEPTEMBER 2005implicationsofthebasicresearchfindingsare contradictory: if stimulable phonemes im-proveevenwithouttreatment,thelogicalcotirseofactionmightbetoavoidthesephonemesas treatmenttargetsandfocusin-tervention on the unstimulahle phonemes; onthe other hand, if unstimulablephonemes donotimproveevenwhentheyaretreated,anequallylogicalcourseofactionmightbetoavoid themas treatmenttargets and focus in-terventiononthestimulablephonemes. Re-solvingtheissue requirestheclinicianto re-view the relevant literature while applying theprinciples of evidence-basedpractice to iden-tifythecourseof actionthatis likelytoleadto the best clinical outcome for a given client.Thepurposeof thisarticleis toexaminetbeempiricalevidencerelatingtotreatmentofunstimulable and stimulable phonemes.THEORIESABOUTTHENATUREOFSTIMULABIUTYTraditionally,stimulabilit>'wasviewedasevidenceofthestructuralandfunctionalin-tegrityoftbechild'sspeechmechanism. Amorerecenttheorypositsthattheabilityto imitate a speech sound reflectsunderlyingphonologicalknowledge aboutthe pboneme(Powell & Miccio, 1996), Phonological knowl-edgeincludesanunderstandingofthelin-guisticfeaturestbatforma givenpboneme.thecontrastiverelationshipsbetweenthephonemeandotberphonemes,andthepbonotacticenvironmentsinwbicba givenpbonememayoccur.Underlyingphonolog-icalknowledgeis,inturn,seenastheba-sistorgeneralizationofarticulatoryaccu-racybothwithinandacrossphonemesandphoneme classes. Tliis theoretical perspectiveis linkedtotbesuggestionthatunstimulablephonemes should be the focus of interventionbecauseteachingtbesesoundsprovidesanopportunitytointroducenewphonologicalknowledgethatwillreorganizethechild'sphonologicalsystemandresultinenhancedgeneralizationof learning fromtreatedto un-treated phonemes.Lof (1996) examined the correlates of stim-ulabilityinanefforttoilluminatetherela-tionship between stimulability and phonolog-icalknowledge.Thirtychildren'sunderlyingphonologicalknowledgeforeachofseveralcommonlymisarticulatedphonemeswas de-terminedbyassessingphonemicperceptionusingaprocedurerecommendedbyLocke(1980).Specificallythechildwasaskedtojudgethecorrectnessoftargetwordspro-ducedby an adult,eitbercorrectlyorwith asimulatederror(i.e.,iftbechildhascorrectphonemicperceptionforthe/I/phoneme,[lif] shouldbe perceivedas a correctproduc-tionoftbeword"leafbut[wil]shouldbejudged to be incorrect), Lof found that all pos-siblecombinationsofphonemicperceptionperformanceandstimulabilityoccurred.Forexample,tbesamechildmightperceive/k/and be stimulable for tbis pboneme, perceive/r/andnotbestimulableforthisphoneme,misperceive/I/andbestimulablefortbisphoneme,andmisperceive/s/butnotbestimulable for this pboneme. Rvachew, Rafaat,and Martin (1999) replicated this finding withtwoadditionalsamplesofcbildren,usingasimilar testprocedure exceptthatrecordingsof authenticrather thansimulatederror pro-ductions were used for tbe phonemic percep-tion task. These data, summarizedin Table 1,demonstratethatunderlyingknowledgeof aphonological contrast and stimulability are in-dependentconstructs.Lof (1996) found that stimulability was pos-itively associatedwith greater visibility of thetarget sound, older age of the child, higher so-cioeconomicstatus of the family,and greateroverallspeech-imitationabilitiesofthechildasreportedbytheparent,Lofspeculatedthatstimulabilitymay also reflectchild focus(Kwiatkowski & Shriberg, 1993), meaning tbepropensityofthechildtoattendtothe rele-vant aspects of the model combined with thechild'smotivationtochangehisorberpro-duction accuracy.Theseresearcb findings suggestthatstim-ulabilityandphonemicperceptionareinde-pendentabilitiesthatareeachrequiredforphoneme acquisition as illustrated in Figure 1.StimulabilityandTreatmentSuccess209Table1.Relationship betweenphonemic perceptionand stimulability across three studies and53 children*StudyLf(1996)Rvachew ctRvachew etTotalalal(1999),(1999),StudyStudy12Perceiveandstimulable6101026Notperceiveandnotstimulable103215Perceivebut notstimulable91616Notperceivebutstimulable57820*The values represeni numbers of phoneme,s Lorresponding to each combination of perceptual abiliw and stimulability.The totals sum to greater thantbenumber of subjectsbecause multiplephonemes were testt-d persubject.The totalnumber of phonemes assessed, summed across the 53 children, was 77.Stimulabilityreflectsthestructuralandfunc-tionalintegrityof thespeechmechanism,thechildsaccesstovisual,tactile,andkines-thetic informationabout the requiredarticula-tory gestures,imitationskills, and childfocus.Phonemicperceptionarisesfromthestruc-turalandfunctionalintegrityofthechildsauditoryandspeechperceptionmechanisms,thechild'saccesstoappropriatespeechin-put,andthecognitive-linguisticskillsre-quiredforprocessingandlearningfromthatinput.TheframeworkillustratedinFigure1 alsoreflectsthefindingthatstimulabilitydoesnotbyitselfleaddirectlyandinevitablytophonemeacquisition, even whenthe child re-ceivestherapyforremediationofthespeechsound errors (Miccio etal.,1999; Tyler,1996).Rvachewetal.(1999)showedthatimprove-mentsinspeechsoundaccuracyforagivenstructural and functional integrity ofthe auditoryand speechperceptionmechanismsAppropriateinput(many and variedexemplarsof contrastingphonemecategories).Cognitive-linguisticprocessingabilitiesPhonemicperceptionPhonemeacquisitionStructural and functional integrity of'the speech mechanism.Appropriateinput(visual, tactile, andkinaestheticinformationabout therequired articulatory gestures).Imitation skills.Focus and motivation.StimulabilityFigure1. An illustrationoftheproposedrelationshipsamongphonemicperception,stimulability,andphoneme acquisition.210TOPICSIN LANGUAGE DisoRDERsyJiiLY-SEPTEMBER 2005phoneme were most likely to occur when thechilddemonstratedstimulabilityandphone-mic perception prior to the onset of a 12-weekphonologyintervention (improvements wereobserved for 64% of phonemes that were per-ceivedandstimulableand0% ofphonemesthat were not perceived and not stimulable).A theoryoftheprocessbywhichphone-mic perceptionand stimulabilitymightinter-acttoproducephonemeacquisitionisin-stantiatedinaneuralnetworkmodelcalledDirections inauditoryspace toVelocities inArticulatorspace (DIVA; Guenther.1995).Acentralfeatureof thismodelis thatthegoalofarticulationis assumedtobetheachieve-mentof a particular acoustic-phoneticprod-uct(as opposedto a specificconstellation ofarticulatorygestures). Thelearneruses audi-toryfeedbacktoidentifydeviations fromthedesiredacoustic-phonetietargetspaceandthenadaptsthe articulatory gestures tobothachieveandmaintaitiarticulatoryaccuracy,evenasthevocaltractisundergoingdevel-opmentalchangesinsizeandshape(Callan,Kent,Guenther,& Vorperian,2000). For ex-ample,the /JV phonemeis characterizednotbyaspecificpeakfrequencyofnoiseen-ergy, but rather by a range of frequenciesthatarelowrelativetothosepeakfrequenciesthatcharacterizethe /s/ phoneme. Feedbackoftheacoustic-phoneticproductofspeechmovementsallowsthechildtolearnto pro-duce the varying constellations of articulatorygestures that will result in this phoneme in dif-ferentphonetic contexts (e.g., greater tongueretractionisrequiredinthecontextofun-rounded than rounded vowels).Figure1 alsosuggestssomeinterventionproceduresthat may beeffective.Theemer-genceofphonemicperceptionandstimula-biiity eachrequire certaininputs to the childthatarefullyunderthecontroloftheclini-cian.Manyempiricalinvestigationshavere-vealedthetypeofinputthatisrequiredfortheinductionofcategoricalperceptionofphonemes(Guenther,Husain,Cohen,&Shinn-Cunningham,1999;Maye,Werker,&Gerken,2002;Rvachew,1994).Specifically,the learner must hear a broadly vaiying distri-butionof exemplars of contrastingphonemecategories.Forexample,whenteachingthechild to perceive the contrast between /s/ and/J/, it is bestto presenta large number of ex-emplarsofwordscontaining/s/andwordscontaining/J/,ideallyproducedbydifferenttalkers. Most of the words that the child hearsshouldrepresenttheprototypicalexemplarsofthetwosoundcategories(i.e.,lowerfre-quency fricative noise for /J/ and much higherfrequency fricative noise of/s/). However, it isalso importantto presentsome exemplars ofthese phonemesthat are less than ideal, eventhose approaching the category boundary be-tweenthe two sounds.Theinputsrequiredforachievingstimula-bilityshouldprovideinformationabouttheappropriatepositioningofthearticulatorsandhelpthechildfocusattentionontac-tile andkinesthetic feedbackassociated withtheproductionoftheappropriatearticula-torygestures.Modelling,shaping,andpho-neticplacementtechniquesare suggestedinSecord(1981)andhavebeenshowntobeusefulforremediatingspeechsounderrors(Powell,Elbert,Miccio,Strike-Roussos,&Brasseur,1998).EVALUATING THEEVTOENCEAlthoughmanytreatmentefficacystudiesthatarerelevanttothetopicofstimula-bilityhavebeenpublished,mostofthesehaveemployedexperimental(e.g.,multiplebaseline)ornonexperimental(e.g.,multipleprobe) single-subject designs and thus are notparticularlywellsuitedtothetworesearchquestionsconsideredhere(Gierut,Elbert, &Dinnsen, 1987; Gierut, Morrisette, Hughes, &Rowlands,2001; Powell,Elbert,& Dinnsen,1991;Tyler& Figurski,1994). A fullreviewandcritiqueofalltherelevanttreatmentef-ficacy studiesis beyondthescopeof tbis ar-ticle. However, a fewstudies involving a ran-domizedcontrolled design will bediscussed.A randomizedcontrolledtrialis essentialforstudying thistopicbecauseitis theonly de-signthatcanhelpdifferentiatematurationfrom generalization and treatment effects(forStimulabiiityandTreatment Success211furtherdiscussionofresearchdesignissues,see Rvachew & Nowak, 2001).STIMULABILITYANDTARGETSELECTIONSTRATEGYRvachewandNowak(2001)investigatedthe relative effectivenessof two distinct targetselectionstrategiesontreatmentoutcomes,using a randomizedcontrolleddesign.Forty-eight 4-year-(3ld children witb moderate or se-verespeechsounddisordersreceiveda pre-treatmentassessment (Al), a (>week block oftreatment targeting two consonantphonemes(bUx:k1), a second assessment(A2), another6-weekblockoftreatmenttargetingtwoad-ditionalconsonantphonemes(block2), andaposttreatmentasse.ssment(A3),All assess-ments were conducted by a speech-langtiagepathologist who was blind to the childsgroupassignmentandtreatmenttargets.Thetreat-mentapproachduringeachblockwastra-ditional,withphoneticplacement,shaping,andmodellingtechniquesusedtoestablishstimulabilityatthesyllablelevel.Oncestim-ulabilityinsyllableswasachieved,thechildwasprovidedwithopportunitiesforartic-ulationpracticeinimitatedwords,sponta-neouswords,imitatedpatternedsentences,spontaneouspatternedsentences,imitatedsentences,andspontaneoussentences.Allchildrenbeganthetreatmentprogramatthestimulationphaseandprogressedfromonetreatmentsteptothenextuponachieving80% correctresponding.Thephonemesthatweretargeteddur-ingthetwotreatmentblocksdependedonwhetherthechildwasassignedatrandomtoreceivetreatmentforthemoststimula-ble, early developingsounds(ME group)ortheleast stimulable,late developing sounds(LL group). At each of the three assessments,thechildwas askedtoimitateall itemsfromthe ProductivePhonologicalKnowledge Pro-file (Gierutetal.,1987), whichprovides19opportunities to producemost of the Englishconsonants. The child's responses were usedto rankthe child's unmasteredphonemes ac-ct)txlingtotypeofProductivePhonologicalKnowledge. Gierutetal. describedsixtypesofproductivephonologicalknowledgethatreflecttheconsistencywithwhichthechildarticulates a givenphonemeacross word po-sitions. Potential treatment targets were thosephonemesthatwereattype4(masteredinatleastonebutnotallthreewordposi-tions),type5 (inconsistentlycorrectbutnotmasteredinanywordposition),ortype6(never correct). Rvachew and Nowak consid-ered type 6 pbonemes in their study to be un-stimulable because the child failed to producethe phoneme correctly even after15 opportu-nities to imitate it in simple words. These po-tential treatmenttargetswere furtherrankedwithineachtypeofProductivePhonologicalKnowledgeaccordingtothe90thpercentileageofacquisition,accordingtoSmit,Hand,Freilinger,Bernthal,andBird (1990). In eachtreatmentblock, children assignedto the MEgroup received treatmentfor the two soundsthatweremoststimulable andearliest devel-oping,withtheprovisothatthetwosoundsnotsharethesamemannerclass(e.g.,/k/and /f/would be selected as treatment targetsratherthan/k/and/g/).ChildrenassignedtotheLL groupreceivedtreatmentforthetwo sounds that were least stimulable and lat-est developing, again with the constraintthatthetwosoundsnotsharethesamemannerclass(e.g.,/r/and/ s/wouldbeselectedastreatmenttargets rather than / s/ and /J/), ThecriteriaforchoosingtargetsforchildrenintheLL conditioneffectivelyensuredthatthisgroup would receive treatmentfor unstimula-ble sounds, at least during the first treatmentblock.Themostfrequentlytargetedsoundsduringthefirsttreatmentblockforthe MEgroup were /k/and /f/.Themostfrequentlytargeted consonants during the first treatmentblock for the LL group were / s/ and /r/,Figtire 2 shows mean group response accu-racy for three sets of consonants from the Pro-ductivePhonologicalKnowledgeProfileforthethreeassessments,withtheME group'sperfonnanceshown in the leftpanel (2a) andtheLL group'sperformanceshownintheright panel (2h). The three sets of consonantsillustrated in Figure 2a are the most stimulable212a.14cQ.10(ATOPICSINLANGUAGEDISORDERS>(JULY-SEPTEMBER2005b.TreatmentprovidedTreatmentnotprovidedBlock1 targetBlock2 targetNevertreatedAl A2AssessmentA3140)1^VIcoTreatmentprovidedTreatmentnotprovidedNevertreatedBlock2 targetBlock1 targetAl A2AssessmentA3Figure2.MeanntimberofcorrectresponsesforcertainconsonantsontheProductivePhonologicalKnowledgeProfile,administeredatthreeassessmentpoints:priortotreatment(Al),afterthefirsttreat-mentblock(A2), andafterthesecondtreatmentblock{A3). Tliepanelontheleft(a)showstheresultsforchildrenintheME group,andthepanelontheri^ht(b)showstheresultsforthechildreninthe LLgroup. (BasedondatafromRvachew& Nowak,2001).phonemes (treated in the first block), the sec-ondmoststimulablephonemes(treatedinthesecondblock),andtheleaststimulablephonemes(nevertreatedintheME group).ThethreesetsofconsonantsillustratedinFigure2b aretheleaststimulablephonemes(treatedinthefirstblock),thesecondleaststimulablephonemes(treatedinthesecondblock),andthemoststimulabiephonemes(never treated in the LL group).Expressingthechangeinscores fromoneassessmenttothenextintheformofmeanresidualizedgainscoresallows fora numberofdifferentcomparisonsofrelativerateofchange,aftertakingintoaccountthechild'spretreatmentlevelofproductiveaccuracyforthesephonemes(specifically,aresidual-ized gain score is the differencebetweenthechild s actualposttreatmentprobescore andthescorethatwouldbepredictedfromthechild spretreatmentprobescore,asdeter-mined by a regression equation derivedfromthepretreatmentandposttreatmentprobescores for all 48 children).First,therateofchangeduringblockswhenthephonemesweretreatedwas com-paredwiththerateof changeobserveddur-ingblockswhenthephonemeswerenottreated.Theseanalyseswereconductedsep-arately withineach group and cotifirmedthedifferencesinrateofchangethatareread-ily observablein Figure 2. For theMEgroup,therateofchangefortbemoststimulablephonemes was higher during the block wbenthesepbonemesweretreated,thanduringtheblockwhenthesephonemeswerenottreated;0.44versus0.05:K95) =2.60, p=.011;seesolidlinesversusdashedlinesforblocks1and 2 targets in Figure 2a. For the LLgroup, the rate of changefortheleast stimu-lablephonemes was higher during the blockwhen these phonemes were treated, than dur-ingtheblockwhenthesephonemeswerenottreated; 0.08 versus-0.56; /(95) =4.58,StimulabilityandTreatment Success213p=,000; seesolidlinesversusdashedlinesfor blocks 1and 2 targets in Figure 2b, In otherwords, gains were greater forblock1targetsduring block1thanduringblock2. whereasgains weregreater forblock2 targets duringblock 2 than during block1, This was true forboth groups.Ihesecondanalysisconsideredrateofchangefortreatedphonemesacrossthe MEand LL groups. The rate of change in produc-tion accuracyfrom A1 to A3 for treated stim-ulable phonemes was greater than the rate ofchangefortreatedtinstimtilablephonemes;0,25versus-0.51;K9i)=3-78, p=.000;highestline in Figure 2a versus lowest line inFigure 2b,Tbetbirdanalysisconsideredtherelativerate of change for stimulable pbonemes acrossthe ME and LL groups. From Al to A3, tbe rateof change shown by the ME group for treatedstimulablephonemeswasnotsignificantlygreater thanthe rate of change sbownby theLL group for untreated stimulable phonemes;0,25 verstis 0,21; rt:94) =0.22,/? =,829; high-estlineinFigure2aversusbigbestlineinFigure 2b.Thefinalanalysisconsideredtherateofchange for unstimulable phonemes across theME andtheLL groups.FromAltoA3, therate of change shown by the ME group for un-treated unstimulablepbonemeswas actuallysignificantlygreaterthantherateofchangeshownbytbeLLgroupfortreated unstimu-lablephonemes;0,05versus-0,51;?(94)=2,97, p=,000; lowestlineinFigure2a ver-suslowestlineonFigure2b,Overall,treat-mentprogresswasverypoorforunstimu-lablepbonemesbuttreatingthestimulablephonemes first appeared to facilitate improve-mentsforunstimulablephonemesinthe MEgroup.Othermoreglobalmeasuresofcbangeinthisstudy,includingPercentageofConso-nantsCorrect,didnotrevealanysignificantdifferencesinoutcomesbetweentbetwogroups of participants. Therefore, it is nol sur-prisingtbattbemostappropriateinteqire-tationoftbesefindingsisamatterofcon-tinuingdebate(Morrisette&Gierut,2003:Rvaehew &Nowak, 2003), However, there isno doubt that, in this study, whichinvolved atraditional treatment approach, children weremostlikely tomaster tbetargetedconsonantwben it was stimulable (fiirther studies are re-quiredtodeterminewhetherthissameout-comewouldbe acbievedin the contextof aphonologicalinterventioninvolvingminimalpairs procedures).ParentsandcliniciansweremostsatisfiedwiththeoutcomeoftheME targetselectionstrategy. Targeting stimuiable sounds first didnotpreventtbechildrenfrommakingspon-taneousimprovementstowardcorrectpro-ductionof other more difficultphonemes; infact,tbeME groupshowedgreaterprogressforuntreatedunstimulablepbonemesthandidtheLLgroupfortreatedunstimulablephonemes.Absolutelynoimprovementwasobservedfor45% of treatedunstimulable tar-gets. For these reasons, Rvacbew and Nowak(2001) concluded that the most prudent strat-egyformostchildrenistotargetstimulablephonemesfirst.Ontheotherhand,10% ofdiildrenintheLLgroupactuallymasteredatreated unstimulable target sound, Stimulabil-ityshouldneverbetheonlyvariableunderconsiderationwhen selecting tbe most appro-priate pbonemes to remediate.EFFECTIVETREATMENTOFUNSTIMUIABLEPHONEMESThere are many cases whenit is necessaryto target a phoneme for wbicb tbe child is un-stimulable,Tbephonemethathasthemostimpactonintelligibilit>- may beunstimulabiefor example. If an entire class of phonemes ismissingfromthechild'srepertoire,youwillbe forcedto introduce one or more membersof thisclass evenif thechildis unstimulableforalloftherelevantphonemes.Therefore,itisimportanttoidentifytreatmentproce-duresthatwillresultinbetteroutcomesforunstimulablepbonemesthanthoseobservedby Rvacbew et al. (1999) and by Rvacbew andNowak (2001). To follow is a summary of two.studiessbowingthatphonemicperception214TOPICS IN LANGUAGEDISORDERS/JULY-SEPTEMBER 2005interventioncanfacilitatetheacquisitionofstimulabilityandeventualmasteryoftargetsounds.The frameworkshownin Figure1suggeststhatacquisitionof a given phonemerequiresaccuratephonemicperceptionofthetar-geted phonemecontrastand stimulabilityforthe target phone. Rvachew (1994) conducteda randomized control trial to test this hypoth-esis. In this study, six once-weeklytreatmentsessionswereprovidedto27preschoolerswithspeechsounddisorders,allofwhomwerecompletelyunstimulablefor/J/.Eachtreatmentsessionforallchildrenconsistedof10minofphonemicperceptiontrainingimplementedinacomputer-gameformat,followedby20minofarticulationtherapydirectedatthe/J/phoneme.Thetreatmentapproach during the articulation therapy partof the sessions was traditional, withphoneticplacement, shaping and modelling techniquesusedtoestablish.stimulabilityattheisola-tionandsyllablelevels.Ifstimulahilitywasachieved,thetreatmentprogramprogressedinstepsfromimitatedwordsthnnighprogressively longer units of speech. All childrenbeganthetreatmentprogramatthestimula-tion phase and progressed from one treatmentstep to thenextuponachieving 90% correctresponding.Thephonemicperceptiontrain-ing procedurewas alsothesame forall chil-dren: the child was asked to listen to recordedwordsandidentifythosewordsthatweregoodexemplarsofaparticulartarget.Thestimuli that the children listened to dependedonthechild sgroupassignment,howeverThe experimentalgrouplistenedto a varietyofexemplarsoftheword"shoe"recordedfromadults and children, with half the wordsbeing correctexemplars and the other half ofthe words representing commonmisarticula-tionsofthisword (e.g., [tu], [SU],[^U]). Whenthe 'i:hild accurately identifieda word as being"shoe"or "not shoe," interesting cartoon char-actersappearedonthecomputerscreentoreinforce the children for correctresponding.Thisstudyinvolvedtwocontrolgroups.Thefirstcontrolgrouplistenedtorepeatedpresentationsof a singleprototypicalrecord-ingoftheword"shoe"andasingleprototypicalrecordingoftheword"moo" andrespondedas describedabove fortheexper-imentalgroup.Thiscontrolgroupwasin-cluded to confirmthe importance of present-ingchildrenwithavarietyofexemplarsofthetargetphoneme,as opposedtopresent-ing only perfector prototypical exemplars ofthe target sound.Thesecondcontrolgrouplistenedtothewords"cat"and"Pete"producedcorrectlybya singleadulttalker.Thesechildrenwereexpectedtoidentifycorrectversionsoftheword"cat."Theclinicianwho conductedthearticulationtherapywasblindtothechild'sgroup assignment. This control condition wasnot expectedto impact the children's speechperception skills. Rather, it provided a controlfor other aspects of the phonemicperceptiontrainingprocedure(e.g.,extratherapytimeandindividualattention,theopportunitytoplay a funcomputer game).Outcome assessments were also conductedby a blind observerOn average, the childrenintheexperimentalgroupachievedstimula-bilitj'andthenlearnedtoproducethe/J/phonemeatthelevelof spontaneous words.In contrast, only one child in the second con-trolgroupachievedstimulabilityattheiso-latedsoundlevel. Theremainingchildreninthisgroupexperiencednogainevenafter6weeksoftherapy.Theperformanceofthegroupthatheard"shoe" andmoo" wasin-termediatebetweentheexperimentalgroupand the second control group. Percent correctrespondingona spontaneousobjectnamingprobe also confirmedthat the phonemic per-ception training procedure facilitated the chil-dren s acquisitionofthisdifficultphoneme.Furthermore,presentingthechildrenwith avarietyofgoodqualityandlesserquality ex-emplars of the target word producedby mul-tiplechildandadulttalkerswasparticularlyeffeetive.Subsequently,a commercialversionofthephonemicperceptiontrainingprogramthatwas administeredtotheexperimentalgroupinRvachew(1994)wasdevelopedandex-pandedtocover additionalphonemesintheStimulahilityandTreatment Success215wordinitial and word final positions (SpeechAssessmentandInteractiveLearningSystem[SAII^];AVAAZ Innovations,Inc.,1994). Arecentmndomizedcontrolledtrialdemon-strated that this program enhanced sound pro-duction learning by children receiving phono-logicalinterventions(Rvachew,Nowak,&Cloutier,2004). In thisstudy,34 pre-school-age childrenwith moderate or severe speechsounddisorderswererandomlyassignedtoan experimentaltreatmentprogramor a con-trolprogramthatwasofferedasasupple-ment to their regular speech therapy sessions.Eachchildreceived16once-weeklyspeechtherapysessionsinwhichthechild'sclini-cianselectedtreatmenttargetsandprovidedthe interventions thatshefelt were appropri-ate.Aftereachofthesesessions,thechildreceivedanadditional10-mininterventionthatwas administeredhya studentresearchassistant.Thechildrenassignedtotheex-perimentalconditionreceivedthe SAILSpro-gram targeting eight consonants. The childrenassignedtothecontrolconditionlistenedtocomputerizedbooks.Again,treating clini-cianswereblindtothechild s groupassign-ment as was the speech-language pathologistwhoconductedtheoutcomeassessments.Theposttreatmentassessmentrevealedthattheexperimentalgroupdemonstratedsignif-icantly greater articulation accuracyin single-wordnamingandinconversationthandidthecontrolgroup.Furthermore,afollow-upassessment1yearlater,whenthechildrenwere approaching the end of kindergarten, re-vealedthat50% ofexperimentalgroupchil-drenhadachievedage-appropriatearticula-tion skills whereas only19% of controlgroupchildrenhadachievedarticulationskills thatwould be consideredtj'pical.One of the outcome measures was Percent-age of Consonants Correct in conversation forspecific phonemes that were not mastered bythe children prior to treatment, calculated be-foreandaftertreatment.Ihechildrenwhoreceived the SAILSprogrammade greater im-provements in articulation accuracy for thesephonemesthanchildrenwhowereassignedtothecontrolcondition.This benefittotheSAILS groupwasobservedfor11ofthe13difficultsoundsthatweremonitoredinthisstudy (see Figure 1of Rvachew et al., 2004).AlthoughthestudybyRvachewetal.(2004) was nt)t directly concernedwith stim-ulability, details of the pretreatmentand post-treatmentconversationsamplessuggestedthatthiscombinationof articulationtherapyandphonemicperceptiontrainingenhancedoutcomesforunstimulablephonemes.Figure 3 shows the change in percentcorrectarticulationofcertainconsonantsfromthepretreatmenttotheposttreatmentassess-ment,asdescribedabove.However,inthiscase, the changes in articulation accuracy areshownasafunctionofpretreatmentinven-torystatus.In otherwords, the figure showschange in articulation accuracy separately forphonemesthatwerepresentinthechild'sinventor}' prior to treatment(and thus clearlystimulable)andforphonemesthatwerenever producedin the child s inventory priorto treatment (and thus not likely to have beenstimulable). Figure3a showsthatchildren intheSAILS groupmadea27%improvementin/J/accuracyregardlessofwhetherthisphoneme was presentin the child's pretreat-mentconversationalsample.Childreninthecontrolgroupwhowerestimulablefor/J/made more than twice the gain in productionaccuracyforthisphonemethandidcontrolgroupchildrenwhoneverproducedthissoundpriortotreatment.Theresultsfor/e/andA/indicatedthatchangefromnocorrectproductionstoatleastsomecorrectproductionsoccurredonlyforchildrenwhoreceived the SAILS intervention.CONCLUSIONSl\voquestionswereaskedabouttbetreatmentofstimulableandunstimulabiephonemetargets:(1)Whenselectingtreat-ment targets, is it best to begin with the mostortheleaststimulablepotentialphonemetargets?(2)Whentreatingunstimulablephonemes,whichtreatmentproceduresareassociatedwiththehighestprobabilityof216TOPICS IN LANGUAGEDISORDERS/JULY-SEPTEMBER2005a.504540353015105027271/// in inventory|D Ijlnot in inventory12^^M5SAILS Control50454035?30n025120I15105038^ ^ ^ 114IQl in inventoryD IQl not in inventory12^ ^ ^ 10SAILS Control50454035o?3020151025Ai/in inventoryn/j/notin inventorySAILS ControlFigure3.Frf treatmenttoposttreatmentimprovementsinpercentcorrectproductionofcertainconso-nantstorchildrenwhoreceivedtheSAILSphonemicperceptiontrainingprogramversuschildrenwhowereassignedtothecontn>lgroup,asafunctionofpretreatmentinventorystati:s.(BasedondatafromRvachewetaL, 2(M)4).StimulabilityandTreatmentSuccess217achievingaccuratearticulationofthenewphoncmt?Withregardtothefirstquestion,anindoniizedcontrolledtrialledtothecon-clusionthattreatmentofthemoststimulahlepotentialtargetsis likelytoresultinagreaterrateofchangeforthetreatedphonemethanistreatmentoftheleaststimulablepotentialtargets. The results of this studyalsosuggestedthata targetselectionstrategythatbeginswiththemoststimulableandearliestdevelopingphonemeswillfacilitatethespontaneousemergenceofunstimulablephonemes.However,thesefindingsreflectonlyasinglestudy.Greaterconfidenceintheseconclusionscouldcomefromreplica-tions and extensions of this study in additionalrandomizedcontrolledtrials.Studiesthatex-amineothercombinationsoftargetselectioncriteriawouldbevaluable.Itispossiblethatthemosteffectivetargets,intermsofpromotingsystemwidechange,mightbethosephonemesthatarestimulablebutrarelyproducedcorrectly(inotherwords,phonemesrepresentingType5ProductivePhonologicalKnowledge).Otherpossibleidealtargetsmightbeunstimulablebutearlydevelopingphonemesorstimulablelatede-velopingpbonemes.Thesehypotheseshavenotyetbeeninvestigatedexperimentally.Withregardto thesecondquestion,a num-berofstudieshavesbownthatacombina-tionotphonemicperceptionandstimtila-bilitytrainingenhanceschildren'sresponsetotreatmentClamieson&Rvachew,1992;Rvacbew,1989,1994;Rvachewetal,,1999,2004),Thisenhancementofsoundproduc-tionlearningisatleastasdramaticforun-stimulablepbonemesasitisforstimulablephonemes.TheDIVAmodel(Callanetal,.2000)suggeststhattbisenhancementoc-cursbecausetbeSAILSphonemicpercep-tiontrainingprocedureprovidesthechildwithastableacoustic-phonetictargetforthephonemebeinglearned.Thisunderlyingacoustic-phonetictargetallowsthechildtodiscoverthe mappingbetweentbephoneme,theappropriatearticulatorygestures,andtheacoustic-phoneticoutcomeof thosearticula-torygestures.Thisspecifichypothesisabouttbemecha-nismbywhichtheSAILS programenhancessoundproductionlearninghasnotbeenex-perimentallyconfirmed,however.Otherex-planationsarepossible.Thetreatmenteffectmaybeduetoamoregeneralizedprocesswherebythe childlearns toattendmore care-fullytospeechinput.Alternatively,tbepri-marylessonthattbechildlearnsmaybetomakejudgmentsabouttbeaccuracyofhisorberownspeech.Treatmentapproacliesthatrequirethechildtoself-monitormaybemoreeffectivethantraditionalclinician-monitoring procedures,regardless of whetherthe SAILS programis a componentof tbether-apy. Furthermore, these studies of tbeefficacyoftheSAILS programinvolvedeitheratradi-tional behaviorist approach or a cycles phono-logicalprocessapproachtotreatment(e,g,,Hodson&Paden,1983).TbeefficacyoftheSAILS phonemicperceptiontrainingprogramhasnotbeenevaluatedincombinationwitba morelitiguisticapproachinvolvingminimalpairs procedures (eg,,Dean fit Howell,1986),Neither has the SAILS treatmentprogrambeenevaluatedin relationto tbe multiplephonemeprogramdesignedbyMicciotofacilitateacquisitionofstimulability(Miccio,2005;Miccio&Elbert,1996),Furtberstudiesre-gardingtheefficacyofphonemicperceptiontraining to facilitatetheacquisitionofunstim-ulablepbonemesarerequired.Itmaybefrustratingtocliniciansthatre-searchersalwaysconcltidetbatmorere-searchisrequired,"Thisinevitableconclu-sion does not meanthat tbe available researchcannotsupportclinicaldecisionmaking. Ran-domizedcontrolledtrialsdoprovidegoodinformationabouttbelikelyoutcomeofagiventreatmentpracticetbragivenpopula-tionofclients.Tbespeech-languagepathol-ogistmustmakeajudgmentabouttheex-tenttowhichtheresearchfindingsapplytoaspecificchildinaspecificclinicalcontext.The clinicianshould also engage tbe child andthefamilyinadiscussionaboutthepoten-tialbenefitsandrisksassociatedwiththeap-plicationofagivenclinicalpractice.There-searchreviewedheresuggeststhatthereis218TOPICSINLANGUAGEDISORDERS/^ULY-SEPTEMBER2005averystrongtiskofachievingnogainaftersixormoreweeksoftherapywhenunstim-ulabletargetsaretreatedusingabehavioristapproach.However,there may bemanysitua-tions in which the potential benefitsoutweightheknownrisk.Thechoiceoftreatmentap-proachfor a given child is ultimatelyup to theclinician.REFERENCESAVAAZ Innovations,Inc. (1994). 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