Effectiveness of the Picture Exchange Communication System (PECS) on Communication and Speech for Children With Autism Spectrum Disorders: A Meta-Analysis Michelle Flippin Stephanie Reszka Linda R. Watson University of North Carolina at Chapel Hill Purpose: The Picture Exchange Communication System (PECS) is a popular communication- training program for young children with autism spectrum disorders (ASD). This meta-analysis reviews the current empirical evidence for PECS in affecting communication and speech out- comes for children with ASD. Method: A systematic review of the literature on PECS written between 1994 and June 2009 was conducted. Quality of scientific rigor was assessed and used as an inclusion criterion in computation of effect sizes. Effect sizes were aggregated sepa- rately for single-subject and group studies for communication and speech outcomes. Results: Eight single-subject experiments (18 participants) and 3 group studies (95 PECS participants, 65 in other intervention/control) were included. Results indicated that PECS is a prom- ising but not yet established evidence-based intervention for facilitating communication in children with ASD ages 1–11 years. Small to moderate gains in communication were demon- strated following training. Gains in speech were small to negative. Conclusions: This meta-analysis synthesizes gains in communication and relative lack of gains made in speech across the PECS literature for children with ASD. Concerns about maintenance and generalization are identified. Emerging evidence of potential preintervention child char- acteristics is discussed. Phase IV was identified as a possibly influential program characteristic for speech outcomes. Key Words: autism, Picture Exchange Communication System, communication intervention, speech D elayed development of language is an early and per- sistent marker of autism (Lord, Risi, & Pickles, 2004). Although estimates vary, approximately 25% of chil- dren with autism do not develop functional speech (Volkmar, Lord, Bailey, Schultz, & Klin, 2004). Thus, the need for early and effective communication training for children with autism is clear. However, given the myriad communication-training strategies available, it is difficult for clinicians to choose the most effective intervention for an individual child with autism spectrum disorders (ASD). Variability in language outcomes for children with ASD makes it difficult to predict which children will go on to develop speech and which children will require augmentative and alternative communication. In ad- dition, differential response to intervention for individual children with ASD makes it difficult for clinicians to identify the best method of communication training for any one partic- ular child. Given the heterogeneous nature of ASD, variability in treatment outcomes is likely to be a function of individual, pretreatment characteristics (Lord et al., 2005). To date, there are no clear guidelines for clinicians in determining which communication strategy is likely to be effective for an indi- vidual child with ASD. The purpose of this meta-analysis is to review the current empirical evidence for one communi- cation strategy, the Picture Exchange Communication System (PECS). PECS is a manualized program for teaching children to use an exchange-based communication system that has been a common intervention choice for nonverbal children with ASD in clinical and school settings. In this meta-analysis, the quality of the current research evidence for the PECS method is assessed. Additionally, pretreatment characteris- tics of children who responded to PECS training are identified across studies to generate a profile of a young child with ASD for whom PECS may be an appropriate and effective communication intervention, and program characteristics Research American Journal of Speech-Language Pathology • Vol. 19 • 178–195 • May 2010 • A American Speech-Language-Hearing Association 178
Transcript
Effectiveness of the Picture ExchangeCommunication System (PECS) onCommunication and Speech for Children WithAutism Spectrum Disorders: A Meta-Analysis
Michelle FlippinStephanie ReszkaLinda R. WatsonUniversity of North Carolina at Chapel Hill
Purpose: The Picture Exchange CommunicationSystem (PECS) is a popular communication-training program for young children with autismspectrum disorders (ASD). This meta-analysisreviews the current empirical evidence for PECSin affecting communication and speech out-comes for children with ASD.Method: A systematic review of the literature onPECS written between 1994 and June 2009 wasconducted. Quality of scientific rigor was assessedand used as an inclusion criterion in computation ofeffect sizes. Effect sizes were aggregated sepa-rately for single-subject and group studies forcommunication and speech outcomes.Results: Eight single-subject experiments(18 participants) and 3 group studies (95 PECSparticipants, 65 in other intervention/control) wereincluded. Results indicated that PECS is a prom-ising but not yet established evidence-based
intervention for facilitating communication inchildren with ASD ages 1–11 years. Small tomoderate gains in communication were demon-strated following training. Gains in speech weresmall to negative.Conclusions: This meta-analysis synthesizesgains in communication and relative lack of gainsmade in speech across the PECS literature forchildren with ASD. Concerns about maintenanceand generalization are identified. Emergingevidence of potential preintervention child char-acteristics is discussed. Phase IV was identifiedas a possibly influential program characteristicfor speech outcomes.
Delayed development of language is an early and per-sistent marker of autism (Lord, Risi, & Pickles, 2004).Although estimates vary, approximately 25% of chil-
dren with autism do not develop functional speech (Volkmar,Lord, Bailey, Schultz, & Klin, 2004). Thus, the need for earlyand effective communication training for children with autismis clear. However, given the myriad communication-trainingstrategies available, it is difficult for clinicians to choose themost effective intervention for an individual child with autismspectrum disorders (ASD). Variability in language outcomesfor children with ASD makes it difficult to predict whichchildren will go on to develop speech and which children willrequire augmentative and alternative communication. In ad-dition, differential response to intervention for individualchildren with ASD makes it difficult for clinicians to identifythe best method of communication training for any one partic-ular child. Given the heterogeneous nature of ASD, variability
in treatment outcomes is likely to be a function of individual,pretreatment characteristics (Lord et al., 2005). To date, thereare no clear guidelines for clinicians in determining whichcommunication strategy is likely to be effective for an indi-vidual child with ASD. The purpose of this meta-analysis isto review the current empirical evidence for one communi-cation strategy, the Picture Exchange Communication System(PECS). PECS is a manualized program for teaching childrento use an exchange-based communication system that hasbeen a common intervention choice for nonverbal childrenwith ASD in clinical and school settings. In this meta-analysis,the quality of the current research evidence for the PECSmethod is assessed. Additionally, pretreatment characteris-tics of children who responded to PECS training are identifiedacross studies to generate a profile of a young child withASD for whom PECS may be an appropriate and effectivecommunication intervention, and program characteristics
Research
American Journal of Speech-Language Pathology • Vol. 19 • 178–195 • May 2010 • A American Speech-Language-Hearing Association178
that may support the development of speech in childrenthrough the PECS program are discussed.
Brief Overview of PECSPECS is a behaviorally based pictorial communication
system designed for children with social-communicative def-icits. Using PECS, expressive communication skills are tar-geted through the training of requests and, later, comments.As Bondy and Frost (1994, p. 3) describe, “Children usingPECS are taught to approach and give a picture of a desireditem to a communicative partner in exchange for that item. Bydoing so, the child initiates a communicative act for a con-crete item within a social context.” It is important to note thatthe term PECS does not refer generally to all exchange-basedpictorial communication interventions (i.e., exchanging aphotograph or line drawing for a corresponding real item);rather, PECS is a specific, manualized intervention protocol.
In the PECS program, a child’s expressive communicationabilities are shaped via the use of reinforcement, delay, andgeneralization across trainers and settings. PECS trainingconsists of six phases (see Table 1). In Phase I: The PhysicalExchange, two trainers physically prompt the child to exchangea single picture for a preferred item, without distractor pic-tures. In Phase II: Expanding Spontaneity, a communicationbook is introduced, and increased distance is placed betweenthe child and communicative partner. The child is requiredto get a picture symbol from his or her communication bookand travel to the communicative partner to request an item.Placement of picture symbols is varied in the book, and gen-eralization is targeted across a variety of trainers and contexts.In Phase III: Picture Discrimination, the child discriminatesbetween two picture symbols (first between a highly desiredand a nondesired item and then between two desired items). InPhase IV: Sentence Structure, the child makes a request bybuilding and exchanging a two-picture-sequence sentencestrip with an “I want” symbol plus the picture symbol for thepreferred item. In Phase IV, after the child has requested bygiving the sentence strip, the communication partner providesthe verbal model “I wantI” and uses a time delay beforelabeling the requested item and handing the sentence strip andrequested item back to the child. In Phase V: Responding to“What Do You Want?” the communicative partner introducesthe verbal prompt “What do you want?” As Phase V interven-tion continues, a time delay is inserted between the verbalprompt and an additional gestural prompt toward the “I want”picture symbol. Eventually, the child begins answering thequestion before his or her communicative partner uses thegestural prompt. Finally, in Phase VI: Responsive and Spon-taneous Commenting, comments are trained via the exchangeof a sentence strip in response to the communicative partner’squestions (i.e., “What do you see?” and “What do you have?”contrasted with the request cue “What do you want?”).
Ease of implementation for both children and interven-tionists is one of the features that helped PECS to become awidely popular social-communication-training system for chil-dren with ASD. For example, children do not need to masterprerequisite skills (e.g., eye contact, gestures, and verbal imi-tation) prior to beginning PECS training. Rather, children withrelatively limited skills begin exchanging picture symbols to
request preferred items immediately upon starting the firstphase of PECS. Also, because PECS is a behavioral approachthat shapes communication via the use of reinforcers, it ismotivating for children. Finally, there is little initial trainingrequired for trainers to implement PECS (i.e., usually a 2-dayworkshop).
Limitations of PECS include the restricted range of com-municative functions targeted in the approach. The communi-cative repertoire trained in PECS consists primarily of requests(Phases I–V). A response form that the PECS developerslabel “comments” is trained in the final phase (Phase VI).However, comments as defined in the program are not true,self-initiated comments. Rather, the comments are responsesto adult prompts, learned via shaping and rewards. PECSdoes not include steps in the program to specifically guide thechild to initiate with picture communication symbols to shareinterests with others (i.e., the type of communicative actsgenerally considered as “commenting”). In addition, othercommunicative functions that develop early among typicallydeveloping children, such as protests and refusals, are not
TABLE 1. Six phases of Picture Exchange CommunicationSystem (PECS) training.
Phase Description
I Training begins on a single picture of highly desired item.Student picks up picture of desired item and releases intocommunicative partner ’s hand in exchange for desireditem. Communicative partner gives the item to the childwhile naming the item (e.g., “car ”). Two adults (i.e., thecommunicative partner and a physical prompter) are usedduring this phase.
II A communication book is introduced, and increased distanceis placed between the child and communicative partner.Child is required to get picture from her communicationbook and travel to communicative partner to request item.To increase spontaneity and persistence, placement ofpicture symbol is varied in the book. Also, generalizationacross a variety of trainers, contexts, and reinforcers isintroduced at this phase.
III Child is required to discriminate between two picturesymbols (highly desired vs. nondesired item to graduallymultiple desired items). Correspondence checks aredone to ensure that child is truly requesting preferreditem.
IV Child uses a sentence starter (“I want”) to make a request bybuilding and exchanging a 2-picture-sequence sentencestrip with “I want” symbol plus picture symbol for preferreditem. Communicative partner provides verbal model “IwantI” and pauses before labeling the requested itemand handing sentence strip and requested item back tochild. Communicative partner differentially reinforcesany vocal attempt.
V Communicative partner introduces the verbal prompt “Whatdo you want?” Over time, a delay is inserted betweenthe verbal prompt and an additional gesture prompttoward the “I want ” picture symbol. The child beginsanswering the question before her communicativepartner uses the gestural prompt.
VI Comments are trained as child exchanges sentence stripsto respond to partner ’s communicative questions (i.e.,“What do you see? ” “What do you want?” “What doyou have?”).
Note. From PECS Training Manual (Frost & Bondy, 2002). Adaptedwith permission.
Flippin et al.: Effectiveness of PECS 179
directly targeted in PECS. For example, although PECS trainsdiscrimination between preferred and nonpreferred items, thestandard PECS protocol does not provide a built-in method fordirectly indicating that an item is notwanted. Finally, as PECS isan aided communication technique, preparation of picturesymbols can be labor intensive for clinicians, and the need tocarry a communication book with limited vocabulary choicescan be restrictive for children using the PECS approach.
In the 14 years since its inception, PECS has been widelyadopted in special education settings for children with ASD.Descriptive reports have suggested that the PECS methodleads to increased functional communication in a relativelyshort time period and, sometimes, speech development inchildren with ASD. For example, in a retrospective report onlongitudinal data for children with autismwhowere 5 years ofage and younger, Bondy and Frost (1994) documented thatmore than half of the 66 participating children were able touse speech without pictures to communicate within a year ofstarting PECS. Similar gains in the use of PECS symbols tocommunicate and in the development of spontaneous speechhave been documented across other case studies and quasi-experimental reports (e.g.,Magiati &Howlin, 2003; Schwartz,Garfinkle, & Bauer, 1998; Webb, 2000). Further, these in-creases in communication and speech were documented tooccur over a relatively short time period, within 6 to 14monthsof starting PECS (Schwartz et al., 1998; Webb, 2000). Al-though these reports offer anecdotal support for the effec-tiveness of PECS, the quality of evidence is limited dueto lack of experimental control. Empirical studies on theacquisition and impact of PECS strengthen the quality ofevidence related to the effectiveness of PECS and haveadded to the evidence base for this approach.
Previous Reviews of PECSSeveral recent reviews have employed varying scopes and
methodologies to examine the efficacy of PECS for commu-nication and/or speech outcomes for children and adults withvarious disabilities. For instance, Lancioni and colleagues(2007) reviewed the literature on the effectiveness of pictorialexchange communication interventions (including PECS)and voice output communication aids in promoting requestingamong childrenwith developmental disabilities. In that review,the authors concluded that 170 out of 173 children who par-ticipated in studies of PECS or other pictorial exchange com-munication interventions showed improvement in their abilityto make requests. The independent variables in that review,however, were not limited to PECS, and participant inclusioncriteria were not specific to autism.
In amore narrowly focused synthesis of 13 studies of PECS,Tien (2008) reached similar conclusions that PECS appears tobe an effective intervention for improving functional commu-nication skills for participants with ASD. In a broad review ofall of the empirical articles published on the PECS approach,Sulzer-Azaroff, Hoffman, Horton, Bondy, and Frost (2009)synthesized data from 34 peer-reviewed studies to concludethat PECS is an effective means of training functional com-munication for individuals with impaired or no speech. Thatreview was not limited to specific participant ages, diagnoses,or outcome variables. While these reviews provide important
syntheses of the evidence for PECS, they do not provide as-sessments of the quality of the studies included, or quantita-tive analyses of results.
In contrast, Schlosser and Wendt (2008) employed bothquality assessment and quantitative analyses in their system-atic review of the effects of augmentative and alternativecommunication intervention on communication and speechproduction for childrenwith autism. Although the independentvariables examined in that review were not limited to PECS,articles that met criteria for review included seven studies (sixsingle-subject experiments and one group design) in whichPECSwas the independent variable. The authors proposed thatPECS was highly effective for teaching requesting to childrenwith autism. In contrast, the authors reported mixed resultsfor speech outcomes, with two studies yielding percentage ofnonoverlapping data (PND) considered highly effective forpromoting speech, one study ineffective, and one studymixed(highly effective for one participant and ineffective for another);however, effect sizes (ESs) were not aggregated. Further-more, since the publication of that review, several additionalgroup and single-subject experiments have been publishedthat add to the evidence base for the PECS approach. Mostrecently, Preston and Carter (2009), in their examination ofthe efficacy of PECS in 10 single-subject and three group de-signs, reached similar conclusions to Schlosser and Wendt(2008) that PECS is effective in providing a means of commu-nication for individuals with little or no speech but that thedata are not as clear for speech outcomes following PECStraining. Assessment of quality and calculation of ESs werecompleted for individual studies in that review; however, par-ticipant criteria were not limited to children with a diagnosisof autism, and independent variables were not limited tostandard PECS protocol. Rather, the review included studieswith participants ranging in age from early childhood to adult-hood, studies of participants with comorbid diagnoses (e.g.,autism and attention deficit /hyperactivity disorder [ADHD],blindness, and deafness), and studies that involved modifi-cations of the PECS approach. Thus, despite the contributionsof these systematic reviews of literature, to date no meta-analysis has examined the effectiveness of the standard PECSprotocol on communication and speech outcome variablesfor children with ASD.
Research Questions and MethodThe evidence base for PECS includes both single-subject
designs and group research. To thoroughly evaluate the evi-dence for this intervention, both types of studies must beconsidered in the meta-analysis. Calculation and aggregationof ESs for meta-analysis is well established for group designsand is becoming increasingly accepted practice in single-subject experiments (Schlosser & Sigafoos, 2008). Althoughthere is not a standard metric, the calculation of ESs in single-subject designs allows for the comparison of treatment out-comes within and between individuals as well as comparisonof the relative strength of treatments (Beeson & Robey, 2006).In the autism literature, specifically, meta-analysis of single-subject studies has contributed to the evidence base for severalpopular interventions, including social skills training (Bellini,
180 American Journal of Speech-Language Pathology • Vol. 19 • 178–195 • May 2010
Peters, Benner, & Hopf, 2007; Schneider, Goldstein, &Parker, 2008), video modeling (Bellini & Akullian, 2007),and self-management (Suk-Hyang, Simpson, & Shogren,2007). Although there is not a way to aggregate ESs acrosssingle-subject and group designs, including single-subjectresearch in a meta-analysis allows for a more comprehensiveunderstanding of the effect of an intervention (Kavale, Mathur,Forness, Quinn, & Rutherford, 2000). In fact, several studieshave employed meta-analytic techniques for both single-subject and group designs to determine the effectiveness ofinterventions for children with externalizing behaviors anddisruptive behavior disorders (Maughan, Christiansen, Jenson,Olympia, & Clark, 2005), ADHD (Fabiano et al., 2009), andautism (Schlosser & Wendt, 2008). Given the volume ofsingle-subject publications, the current meta-analysis includesboth single-subject and group studies of the PECS approach.This meta-analysis provides an evaluation of the quality ofempirical evidence, using appropriate quality indicators forsingle-subject or group designs. In addition, ESs are aggre-gated within each type of design to examine the effectivenessof PECS for both speech and communicative outcomes spe-cifically for young children with ASD. This study addressedtwo research questions:
1. What are the effects of PECS on communication outcomesfor children with ASD?
2. What are the effects of PECS on speech outcomes forchildren with ASD?
Search StrategyStudies were identified for inclusion in this meta-analysis
through a three-step process. First, searches were conductedto identify conceptual and empirical articles related to PECSpublished between 1994 and June 2009 that included at leastone child participant (18 years or younger) with ASD, inthe following databases: PsycInfo, ERIC, Academic SearchPremier, and Cumulative Index to Nursing and Allied HealthLiterature (CINAHL). Table 2 describes the search terms andyields. Search terms used were Picture Exchange Communi-cation System, autism, PECS, and Bondy and Frost. Reversesearches were then conducted to identify articles that cited theseminal article on PECS (Bondy & Frost, 1994). Second, re-sults were cross-referenced with articles listed on the researchpage of the official PECS Web site (www.pecs.com/research.htm). Finally, reference lists were examined from three rele-vant literature reviews (Preston & Carter, 2009; Schlosser &Wendt, 2008; Sulzer-Azaroff et al., 2009) to identify additionalstudies that were not captured through previous searches. Thesystematic search returned 54 articles. Of the 54 articles iden-tified, only empirical studies (single-subject experiments or
TABLE 2. Search strategies across general-purpose databases.
PsycInfo (DE “Picture Exchange Communication System”) 48(DE “Picture Exchange Communication System” AND DE “autism”) 45 added AND “autism”(DE “Picture Exchange Communication System” OR DE “PECS”) 154 added OR “PECS”(DE “Picture Exchange Communication System” OR DE “PECS”
AND DE “autism”)51 added AND “autism”
(DE “PECS”) 150(DE “PECS” AND DE “autism”) 45 added AND “autism”(Reverse search for articles citing Bondy & Frost, 1994) 98
Academic SearchPremier
(DE “Picture Exchange Communication System”) 36(DE “Picture Exchange Communication System” AND DE “autism”) 24(DE “Picture Exchange Communication System” OR DE “PECS”) 3,295 added OR “PECS”(DE “Picture Exchange Communication System” OR DE “PECS”
AND DE “autism”)71 added AND “autism”
(DE “PECS”) 3,141 added AND “autism”(DE “PECS” AND DE “autism”) 28 added AND “autism”(Reverse search for articles citing Bondy & Frost, 1994) 32
ERIC (DE “Picture Exchange Communication System”) 33(DE “Picture Exchange Communication System” AND DE “autism”) 24 added AND “autism”(DE “Picture Exchange Communication System” OR DE “PECS”) 82 added OR “PECS”(DE “Picture Exchange Communication System” OR DE “PECS”
AND DE “autism”)81 added AND “autism”
(DE “PECS”) 76(DE “PECS” AND DE “autism”) 23 added AND “autism”
CINAHL (DE “Picture Exchange Communication System”) 52(DE “Picture Exchange Communication System” AND DE “autism”) 48 added AND “autism”(DE “Picture Exchange Communication System” OR DE “PECS”) 192 added OR “PECS”(DE “Picture Exchange Communication System” OR DE “PECS”
AND DE “autism”)56 added AND “autism”
(DE “PECS”) 188(DE “PECS” AND DE “autism”) 49 added AND “autism”(Reverse search for articles citing Bondy & Frost, 1994) 13
Note. DE = descriptor; ERIC= Education Resources Information Center; CINAHL= Cumulative Index to Nursing and Allied Health Literature.
group design) published in English in a peer-reviewed journalwere considered for inclusion in this synthesis. The remaining30 studies were reviewed for inclusion criteria by at least twoof the authors. Interrater reliability for inclusion of studieswas 93.3%. In the rare instances of disagreement, the decision toinclude or exclude an article was reached by consensus. Studiesincluded in this meta-analysis met the following criteria:
Participants. This meta-analysis included children youngerthan 18 with a diagnosis of autism, ASD, or pervasive devel-opmental disorder-not otherwise specified (PDD-NOS).Five studies on the use of PECS with adults (Chambers &Rehfeldt, 2003; Rehfeldt & Root, 2005; Rosales &Rehfeldt,2007; Stoner et al., 2006; Ziomek & Rehfeldt, 2008) werenot included. In addition, five studies of participants diag-nosed with neurological or developmental disorders otherthan autism (Bock, Stoner, Beck, Hanley, & Prochnow, 2005;Kern, Gallagher, Staosta, Hickman, & George, 2006) or withboth autism and a comorbid physical or neurological diag-nosis such as ADHD (Adkins & Axelrod, 2002), blindness(Lund & Troha, 2008), and deafness (Malandraki & Okalidou,2007) were not included.
PECS implementation. The independent variable in thismeta-analysis was one or more of the six manualized PECSphases. Five studies with independent variables that werecomponents or modifications of the manualized PECS meth-odology (Cummings & Williams, 2000; Dooley, Wilczenski,& Torem, 2001; Ganz, Cook, Corbin-Newsome, Bourgeois,& Flores, 2005; Ganz, Sigafoos, Simpson, & Cook, 2008;Yokoyama, Naoi, & Yamamoto, 2006) were not included.For the alternating treatment single-subject study conductedby Angermeier and colleagues (Angermeier, Schlosser, Luiselli,Harrington, & Carter, 2008), which compared the effec-tiveness of PECS in two conditions (PECS with Picture Com-munication Symbols and PECS using Blissymbols), only datafrom PECS trials using Picture Communication Symbols(as recommended in the PECS manual) were included. Forthe study by Tincani, Crozier, and Alazetta (2006), data wereincluded for Study I, which used the standard PECS protocol.
Outcome variables. The dependent variables for the meta-analysis were (a) communicative behaviors (e.g., requestsand initiations) and (b) speech or vocalization. Two studieswith outcomes that were nonlanguage behaviors—that is,aggressive behavior (Frea, Arnold, & Vittimberga, 2001) andproblem solving (Marckel, Neef, & Ferreri, 2006)—were notincluded in this meta-analysis. Finally, one study of PECSin which symbols were modified with braille for use with avisually impaired therapist was excluded because the grapheddata of communication outcomes in that study were providedfor the therapist and not the child participants (Charlop,Malmberg, & Berquist, 2008).
Articles selected for review. A total of 11 studies (eightsingle-subject experiments and three group designs) metcriteria for inclusion. For the purpose of this meta-analysis,findings from articles that analyzed data from the same par-ticipants (i.e., Carr & Felce, 2007a, 2007b; Yoder & Stone,2006a, 2006b) were collapsed into a single study.
Data extraction and decisions. Data extracted from pub-lished studies of PECS included participant diagnoses andages, experimental design, outcome variables, phases ofPECS trained, and reported results. For group studies, ESs
were extracted if reported; if not, reported statistics fromwhichESs could be calculated were extracted. For single-subjectstudies, data points on communication and speech outcomevariables were extracted from plotted graphs to calculate ESs.In the study by Angermeier and colleagues (2008), in whichbaseline data were reported separately for each of thetrained PECS phases, ESs calculated for communicativeoutcomes were averaged across the trained phases of PECSfor each participant. For the study by Charlop-Christy,Carpenter, Le, LeBlanc, and Kellet (2002), which employeda multiple-baseline-across-settings design, ES was averagedacross the two contexts (academic and play sessions) inwhich speech outcomes were measured. Finally, to satisfythe independence assumption of meta-analysis, for fourstudies in which multiple outcome variables were reportedfor speech (Charlop-Christy et al., 2002; Ganz, Simpson, &Corbin-Newsome, 2008; Yoder & Stone, 2006a, 2006b)and communication (Howlin, Gordon, Pasco, Wade, &Charman, 2007), variables were averaged so that only oneES per construct (i.e., speech or communication) was includedfor each study in calculation of the composite ES (Hedges& Olkin, 1985). Included outcome variables and summariesof the data for group and single-subject designs included arepresented in Tables 3–6.
Quality of EvidenceThe quality of evidence for the PECS approach was evalu-
ated via the use of rating scales adapted from guidelines byHorner et al. (2005) and Wolf (1978) for single-subject de-signs (see Appendix A) and by Gersten et al. (2005) for groupdesigns (see Appendix B). Quality indicator items were as-signed a rating of adequate, partially adequate, or inadequate/unknown and a score of 2, 1, or 0 points, respectively. Eacharticle was independently coded for quality assessment bythe first two authors. Interrater reliability was calculated viapoint-to-point agreement on the 11 included articles andranged from 84.2% to 100%. Composite scores were talliedas a percentage of points assigned out of total possible pointsfor each article. Scores at 90% and above were consideredto be strong quality of evidence. Scores ranging from 75% to90% were considered to be adequate quality of evidence, andscores of 74% and below were considered to be inadequatequality of evidence.
Overall, the quality of evidence for PECS was consideredto be adequate (see Tables 3–6). Quality assessment ratingsof group studies ranged from strong to inadequate levels ofevidence (one study of strong quality and two of inadequatequality) for the effectiveness of PECS on communicative andspeech abilities of children with autism. For group designs,the quality of evidence for PECS would be strengthened byimproved measurement and reporting of treatment fidelity.For example, in two of the three group studies in this meta-analysis, treatment fidelity was not reported.Withoutmeasuresof treatment fidelity, it is difficult to know whether PECS wasdelivered in the appropriate manner and dosage; thus, it isdifficult to demonstrate a functional relationship between theintervention and the communication and speech outcomes.
Quality assessment ratings of the single-subject experi-ments ranged from strong to adequate (three studies of strong
182 American Journal of Speech-Language Pathology • Vol. 19 • 178–195 • May 2010
184 American Journal of Speech-Language Pathology • Vol. 19 • 178–195 • May 2010
TABLE6.
Summaryofsp
eech
outcomes
andqualityratin
gsforgroupdes
igns.
Referen
ceParticipan
tsAge
s(yea
rs;m
onths)
Des
ign
PECS
phas
esTreatmen
tfid
elity
(Y/N)
Dep
ende
ntva
riables
Res
ults
repo
rted
Qua
lityratin
g(%
scores
)ES
G/M
How
linet
al.(20
07)
26im
med
iate,
3;9–
8;9
RCT
NR
NFrequ
ency
ofsp
eech
Nosign
ifica
ntch
ange
infreq
uenc
yof
words
I(45
)0.05
M28
delaye
d,5;2–
9;5
29co
ntrol
5;1–
10;0
Yod
er&Stone
(200
6a,2
006b
)17
PECS,
3;0–
7;0
RCT
I–VI
YNon
imita
tive
words
;no
nimita
tive
spok
enac
ts
Ove
rall,
PECSmore
effectivethan
RPMT
infacilitatingwords
andsp
oken
acts;
PECSes
pecially
effectiveforch
ildren
with
low
JAan
dhigh
object
exploration;
adva
ntag
esforPECS
grou
pat
Tim
e1no
tmaintaine
dat
Tim
e2
S(100
)0.57
M19
RPMT
Flippin et al.: Effectiveness of PECS 185
quality and five of adequate quality). Quality of the single-subject experiments would be strengthened by inclusion ofmeasures of maintenance, generalization, and social validity.Follow-up measures to assess maintenance and generaliza-tion were reported in only 50% of the single-subject studies,and social validity was measured in only two of the eightsingle-subject designs. Failure to measure maintenance, gen-eralization, and social validity in the PECS single-subjectliterature is consistent with other single-subject investigationsin the autism literature. For example, Odom and colleagues(2003) reported that only 35% of single-subject interventionexperiments with individuals with ASD measured mainte-nance and only 41% reported generalization measures. Know-ing whether speech and communication gains made during thePECS program are maintained after stopping PECS interven-tion is important for clinicians in deciding on a communication-training approach for children with autism.
Analysis ProceduresFor group designs, ESs for posttest group differences were
reported as given or calculated from published data. For onestudy that reported results using the nonparametric Mann–Whitney U statistic (Carr & Felce, 2007a, 2007b), an equiv-alent of Cohen’s d was calculated as outlined by Rosnowand Rosenthal (2008). The dequivalent metric represents the“value of d analogous to the result for an exactly normallydistributed outcome with N/2 units in each group” (Rosnow& Rosenthal, 2008, p. 382). For another study (Howlin et al.,2007), Cohen’s d was calculated from the published oddsratios as outlined by Chinn (2000). Standard interpretationof Cohen’s d (Cohen, 1988) was used to consider the strengthof evidence for group design studies (i.e., <0.2 = trivial;0.2–0.5 = small; 0.5–0.8 = moderate; >0.8 = strong).
For single-subject experiments, two methods of calculatingES were used, as there is not currently an established metricfor ES in single-subject experiments (Beretvas&Chung, 2008).In the first analysis, data from published graphs were enteredand analyzed using the software program ITSACORR (Crosbie,1993). ITSACORR conducts an analysis of the single-subjectdata by fitting least-squares trend lines to baseline and treat-ment phases while controlling for autocorrelation and shortdata sets (Maughan et al., 2005). ITSACORR was chosenover other methods of ES calculation (e.g., standardized dif-ference approach) because of the validity of this approachfor graphs with zero slope in the baseline phase (Huitema,2004) and undefined standard deviations (i.e., less than twodata points in baseline or all baseline data points equal to zero;Beeson & Robey, 2006; Kratochwill, Stoiber, & Gutkin,2000). ITSACORR provides an F statistic as well as tests ofchange in intercept and change in slope. The y-interceptt statistic given by ITSACORR and the number of data pointsper phase were used to calculate ESs as Glass’s delta, asoutlined by Maughan et al. (2005).
In addition to the ITSACORR method of data analysis forsingle-subject designs, the studies were also analyzed usingthe PND method, in which the highest data point in baselinephase was identified and the percentage of data points duringintervention exceeding this level was calculated (Scruggs,Mastropieri, & Castro, 1987). PND could not be calculated
for three studies that used alternating treatment (Angermeieret al., 2008; Beck, Stoner, Bock, & Parton, 2008) or changingcriterion designs (Ganz & Simpson, 2004) without a base-line phase. Interpretation of PND scores as outlined byScruggsand colleagues (Scruggs, Mastropieri, Cook, & Escobar, 1986)is as follows: <50% = unreliable treatment; 50%–70% =questionable effectiveness; 70%–90% = fairly effective;>90% = highly effective.
After individual ESs were calculated, composite ESs forthe speech and communication outcome variables were com-puted independently for single-subject and group designs.For single-subject multiple-baseline designs across partici-pants, ESs are reported as the mean ES for all participants. Asstudy quality is a focus of this meta-analysis, a threshold ofat least adequate quality was set for inclusion of a study inthe computation of aggregate ESs (Pettiti, 2000). All eight ofthe single-subject experiments met criteria of at least adequatequality. For group designs, however, only one of the threegroup experiments met quality criteria. Thus, for the groupstudies, individual ESs are described here, and aggregate ESswere not calculated.
Synthesized ResultsFindings were synthesized to evaluate the effectiveness of
the PECS approach on communication and speech outcomesfor children with autism. Results are reported separately forsingle-subject studies and group designs, as ESs from single-subject experiments tend to be inflated when compared withthose of group designs (Swanson & Sachse-Lee, 2000), andthere is nomethod to combine ESs from different experimentaldesigns (Kavale et al., 2000).
Communication OutcomesCommunication outcomes examined in the PECS litera-
ture include the frequency of PECS exchanges, requests(Angermeier et al., 2008; Beck et al., 2008; Ganz & Simpson,2004; Ganz, Simpson, & Corbin-Newsome, 2008; Howlinet al., 2007; Kravits, Kamps, Kemmerer, & Potucek, 2002;Tincani, 2004; Tincani et al., 2006), and initiations (Carr &Felce, 2007a, 2007b; Howlin et al., 2007). Increases in com-munication outcomes following PECS training were demon-strated across both single-subject and group studies. Overall,for the single-subject experiments, the mean weighted ESwas 0.51. The confidence interval did not include zero, 95%CI[0.04, 0.67]; therefore, the assumption can be made thatPECS treatment had a significant impact on communicationoutcomes. Themean PND of 84.3%, 95%CI [68.4%, 100.1%],indicates that PECS is a “fairly effective” treatment for im-proving communication for young children with autism. How-ever, evidence of the maintenance and generalization ofcommunication gains made through PECS intervention islimited in the single-subject literature. In fact, maintenanceof communication gains was measured in only one of theseven single-subject studies that examined communicationoutcomes. In that study, Angermeier and colleagues (2008)reported that all three participants maintained mastery levelof communicative exchanges at the Phase II level of PECSimmediately after completing Phase II training. Furthermore,
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generalization of communication gains achieved throughPECS was measured in only three single-subject studies.Beck et al. (2008) measured generalization across settingsfor two of the four participants in their study comparing theeffectiveness of PECS and VOCA. Probes conducted in thechildren’s homes demonstrated limited generalization ofcommunication gains made through PECS 1 week afterschool-based training. One participant used PECS to requestonly once during the sessions, while the other participantdemonstrated only three requests using PECS (vs. 17 re-quests when using a voice output device).
In contrast, Tincani (2004) measured generalization acrosstrainers in an alternating treatment design. In that study, PECSwas more effective than sign language in promoting com-munication for one child; this child demonstrated pictureexchanges at levels similar to those achieved in training (93%on average) during generalization sessions conducted witha new communication partner. Similar results were reportedby Tincani and colleagues (2006), in that both participantsproduced levels of independent mands during four generaliza-tion probes with a new communication partner (i.e., the child’steacher) that were similar to those achieved during Phase IVtraining. All generalization probes were higher than levels ofcommunication achieved during baseline phase.
For the group designs, the mean weighted ES could notbe aggregated, as ES was not calculable for communicationoutcomes for the PECS intervention in one of the three groupstudies (Yoder & Stone, 2006a, 2006b) examining commu-nication outcomes, and the two group studies reporting cal-culable ES data did not meet quality inclusion criteria. Withregard to maintenance of communicative gains, concerns wereraised by one group study. Howlin and colleagues (2007)reported that the increases in rate of initiations and PECS us-age that made up immediate treatment effects were not main-tained over time, and upon follow-up, ESs were negligible,0.04, 95% CI [–0.61, 0.1], and 0.24, 95% CI [–0.42, 0.92],respectively. Maintenance of communication gains for thePECS intervention group was not reported in the study byCarr and Felce (2007a, 2007b) and not calculable from pre-sented data for Yoder and Stone (2006a, 2006b). In addition,generalization of communicative gains was not reported forany of the three group studies of PECS. Thus, overall, small tomoderate effects were demonstrated for the short-term efficacyof PECS in improving communicative outcomes for youngchildren with autism across the single-subject experimentsand group studies of PECS. Evidence for maintenance andgeneralization of communicative gains achieved throughPECS training, however, is limited and mixed.
Speech OutcomesAlthough the developers of the program describe PECS as
an augmentative communication system and are careful notto claim that PECS improves speech for children with ASD,speech is a frequently measured outcome variable in thePECS literature. Clinicians and parents alike desire informa-tion regarding the effectiveness of PECS in influencing speechoutcomes for young children with autism. Speech outcomeswere measured broadly across the PECS studies and includedthe general measures of spontaneous speech (Charlop-Christy
et al., 2002; Howlin et al., 2007) as well as more specificmeasures of the frequency of nonimitative spoken acts andwords (Yoder & Stone, 2006a, 2006b), word vocalizations(Tincani, 2004), word approximations (Ganz, Simpson, &Corbin-Newsome, 2008), vocal approximations (Tincaniet al., 2006), and average number of words spoken per trial(Ganz & Simpson, 2004). In the five single-subject experi-ments examining speech, outcomes varied widely acrossthe 12 participating children (ES ranged from –1.45 to 1.37).It is interesting to note that several single-subject studiesreported overall gains in speech based on visual inspectionand interpretation of the data. However, as a group, the meanweighted ES for speech outcome variables across single-subject studies was negligible (0.17), and the CI includedzero, 95%CI [–0.01, 0.36]. ThemeanPNDwas 44.7%, [1.8%,87.6%], indicating questionable effectiveness of the PECSapproach for increasing speech for young children with autismacross the single-subject literature.
Furthermore, maintenance of speech gains was measuredin only one of the five single-subject studies examining speechoutcomes. Charlop-Christy and colleagues (2002) reported1-year follow-up data for one participant who demonstratedmaintenance of speech gains made through PECS at levelssimilar to those achieved during PECS training.
Finally, generalization of speech gains made through PECSwas alsomeasured in only one of the five single-subject studiesexamining speech outcomes. Tincani and colleagues (2006)reported that for one participant who made gains in speechthrough PECS, four generalization probes implemented by thechild’s teacher demonstrated levels of vocalization similar tothose achieved in training. However, only two of the fourgeneralization probes were above the child’s baseline levelsof vocalization prior to starting PECS training.
Results of speech outcomes following PECS training werealso variable across the group experiments. In a follow-upanalysis of their study, Carr and Felce (2007b) noted that fiveof 17 children in PECS group showed increases in speech;however, ESs for speech outcomes in this study were notcalculable from the published data. Children in the Howlinet al. (2007) study achieved a negligible ES for speech (0.05).In contrast, moderate effects for speech outcome variables(i.e., frequency of nonimitative spoken acts, ES = 0.63, andnumber of different nonimitative words, ES = 0.50) werereported by Yoder and Stone (2006a, 2006b) at posttest intheir randomized controlled trial comparing PECS withResponsive Education and Prelinguistic Milieu Teaching(RPMT). In that study, PECS was found overall to be themore effective treatment for increasing number of non-imitative spoken communication acts, t(34) = 2.30, p = .03,and the number of different nonimitative words used, t(34) =2.10, p = .04. However, posttest advantages in speech real-ized by the PECS group were not maintained at follow-up6 months after intervention. In fact, ES for all speech out-comemeasures at 6 months after intervention was negligible(ES = 0). Thus, the variable effects in speech outcomes follow-ing PECS illustrate that the program is not equally effectivein improving speech outcomes for all children with autism.Variability in response to PECS may be due to preinterven-tion characteristics of individual children. Available evidencerelated to this possibility is examined in the following section.
Given the heterogeneous nature of the population of chil-dren with ASD, it is important for both clinical interventionand research to determine which characteristics make indi-vidual children more likely to benefit from PECS, as well asto identify which components of the PECS program are mosteffective. Therefore, in addition to determining the overalleffectiveness of the PECS communication approach, furtheranalysiswas conducted across group studies and single-subjectexperiments to identify modifying variables and preinter-vention characteristics of children who responded to PECStraining. For group studies, examination of variables thatmoderate the effectiveness of PECS provides a strong statis-tical tool which allows us to identify particular child char-acteristics that have a measurable and direct influence onspeech and communication outcomes. For single-subjectexperiments, examination of preintervention participant char-acteristics allows us to describe which children gained themost from PECS, at the level of individual participant, al-though a direct relationship between preintervention charac-teristics and speech and language outcomes is not identifiable.Three child characteristics emerged as potential pretreatmentidentifiers of a child with autism who is likely to respond toPECS intervention: (a) limited joint attention, (b) relativelystronger object exploration, and (c) limited motor imitation.
Joint AttentionJoint attention refers to three-point, systematic sharing
of attention between (a) an individual, (b) an object or event,and (c) another individual (Tomasello, 1995). Evidence fromone group design study suggests that PECS may be a moreeffective communication intervention than RPMT for chil-dren with initially low rates of joint attention. In Yoder andStone’s study (2006a, 2006b), exploratory analysis of pre-treatment variables revealed that initial rates of joint atten-tion were a strong predictor of whether a child made greatercommunication (i.e., requesting) gains from either PECS orRPMT. Initiating joint attention was operationally definedas an “intentional communication act about an object thatattempts to get the adults to comment, laugh, smile, show at-tention, or give a label” (Yoder & Stone, 2006b, p. 430). Forchildren who began an intervention with initially lower fre-quencies of joint attention (i.e., one instance or less of initiat-ing joint attention across two assessment procedures), PECSwas the more successful approach in targeting communica-tion outcomes. Joint attention also emerged as a potentiallyinfluential preintervention characteristic in a single-subjectexperiment by Charlop-Christy and colleagues (2002), whichdocumented that the largest overall gains in both speechand communication were made by the youngest participant,who began the study with no spontaneous speech, and rela-tively weaker social communicative behaviors (i.e., joint at-tention, eye contact, and toy play). Thus, joint attention maybe one child characteristic to be explored as a moderatingvariable of main effects in group designs and as a preinterven-tion characteristic to describe for participants in single-subjectexperiments.
Object ExplorationA second potential preintervention variable that may mod-
erate the effects of PECS on speech outcomes is object ex-ploration. Differential response to treatment based on a child’sinitial levels of object exploration was documented by YoderandStone (2006a, 2006b). In their study,Yoder andStone definedobject exploration as the number of different toys a childtouched during a play assessment. For children with initiallyhigher levels of object exploration (+1 SD above the groupmean), PECS was shown to be a more effective treatment thanRPMT in increasing the frequency of nonimitative speech atposttest. Initial levels of object exploration were also shown tobe important inmaintaining gains in speechmade throughPECS.In fact, only children with high object exploration maintainedspeech gains at the 6-month follow-up, relative to the alternatetreatment group. Thus, object exploration may be a variablethat moderates speech outcomes achieved by children withautism through the use of PECS, but this finding has not yetbeen replicated across studies or by independent researchers.
ImitationImitation is a third potential preintervention characteristic
that may influence both speech and communication outcomesfor children participating in PECS intervention. Motor imitationwas examined as a preintervention characteristic that influencedthe acquisition and effectiveness of PECS in a single-subjectstudy comparing the effectiveness of sign language and PECSon the training of requests. In that study, Tincani (2004) ex-amined the pretreatment ability of two participants to imitate27 hand, arm, and finger movements, similar to those requiredto communicate via sign language. As was predicted by theauthor, sign language was more effective than PECS in facil-itating independent requests for a participant with relativelyhigher motor imitative ability. In contrast, PECS was the moreeffective treatment for improving communication for a partic-ipant with relatively lower motor imitative ability. With re-gard to speech outcomes, however, sign language was themore effective intervention for both participants, regardlessof initial levels of motor imitation.
Verbal imitation has also emerged as a potentially influ-ential preintervention child characteristic. Charlop-Christyand colleagues (2002) described the three participants in theirstudy, who each made gains in both communication andspeech through PECS, as having some ability to verbally imi-tate before beginning PECS training. The authors postulatethat participants’ baseline level of verbal imitation may haveaccounted for the ability to produce spontaneous speech dur-ing and after training. Assessment measures of preinterven-tion verbal imitationwere not described, however. It is importantto emphasize that results from these two single-subject ex-periments may not generalize to the overall population ofchildren with ASD. Nevertheless, motor and verbal imitationmay be a variable of interest in future studies of the effec-tiveness of PECS on communication and speech outcomesfor children with autism. In fact, given that early imitationskills have been shown to be a strong predictor of later speechdevelopment in children with autism (Charman et al., 2003;Toth, Munson, Meltzoff, & Dawson, 2006), it is interesting
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that imitation has not been more frequently examined as apretreatment characteristic across the autism communicationintervention literature.
Thus, the current evidence base for the effects of modera-tors and preintervention characteristics is limited, but themeasurement and analysis of preintervention variables in futurestudies would be invaluable in informing clinical decisionsabout the selection of effective communication interventionsfor individual children with ASD. For future group designs,examination of the potential moderating impact of preinter-vention variables such as joint attention, object exploration,and motor/verbal imitation on the effects of PECS on commu-nicative and speech outcomes is warranted. In future single-subject experiments, although statistical examination ofmoderators is not possible given the constraints of the re-search design, reporting preintervention assessment resultsfor these and other participant characteristics would allow forsystematic replication of studies and provide pilot data forlarger group studies to help identify the profile of a child withASD who is likely to make communication and/or speechgains through PECS.
Program Characteristics: Phase IV Interventionand Speech Outcomes
Another interesting and potentially clinically useful find-ing of this analysis is the impact of training PECS Phase IVon spontaneous speech for those children who went on todevelop speech through PECS. In their seminal report, Bondyand Frost (1994) documented that although speech develop-ment was not a specific aim of their approach, vocalizationsgenerally developed in the later phases of PECS training(IV to VI). Phase IVof PECS is unique in that it introducesboth verbal modeling and time delay strategies. In Phase IV,the trainer models the phrase “I wantI” and briefly pausesbefore handing the requested object to the child. Evidencefrom several single-subject studies lends empirical supportto Bondy and Frost’s (1994) initial reports of increased speechduring later PECS phases (Charlop-Christy et al., 2002; Ganz& Simpson, 2004; Tincani, 2004).
Because single-subject experiments document the partic-ipants’ changes in speech across each phase of PECS, it waspossible to compare the magnitude of gains in speech betweenPhases III and IV for those single-subject experiments thatreported speech outcomes through Phase IVof PECS (Ganz &Simpson, 2004; Ganz, Simpson, & Corbin-Newsome, 2008;Tincani, 2004). This analysis resulted in a composite ES forspeech outcomes across Phase IVof the single-subject studiesof 0.73. This lends support to evidence that for children whogo on to develop speech, Phase IV is important. In contrast,for those same children, communication gains betweenPhases III and IV were found to be negative (ES = –0.37).Large ESs for speech development and negative effects forcommunication outcomes between Phases III and IV suggestthat as these children become increasingly more verbal, speechbegins to replace the picture-based exchanges of PECS.Thus, it serves to highlight that Phase IVmay be particularlyimportant for development of speech.
However, questions remain as to whether speech gainsrealized in Phase IV were due to the introduction of verbal
models, the use of time delay, or some combination of strat-egies that may contribute to an increase in speech productionduring PECS Phase IV. Alternatively, it may be that thosechildrenwho reach the criterion of 80%mastery in Phases I–IIIare the same children who are likely to go on to developspeech. There is some support in the PECS literature for theimpact of time delay on increased speech production (Charlop-Christy et al., 2002; Tincani, 2004; Tincani et al., 2006). Forexample, after the introduction of a 4-s delay of reinforcement,one child in Tincani’s study (2004) increased percentage ofword vocalizations from a low of 30.1% during PECS Phase IIItraining to an average of 90%. Tincani and colleagues (2006)further documented the effectiveness of using a 3–5-s delayin an alternating treatment design, with one participant whodemonstrated greater use of speech during those phases thatemployed a delay versus baseline phases. Thus, there is somelimited evidence that the verbal modeling, time delay, or somecombination introduced during Phase IVof PECS may playa role in the acquisition of spontaneous speech for those chil-dren who go on to develop speech through the PECS program,but few studies have addressed these questions, limiting theevidence available. Further research to determine whether in-cluding verbal models and time delay strategies earlier in thePECS program results in an earlier speech gains would haveimportant clinical implications.
Summary, Limitations, and Future DirectionsThis meta-analysis synthesized findings from both group
and single-subject experiments to evaluate the quality of theresearch evidence and the effectiveness of the PECS approachon speech and communicative abilities for children with au-tism.With one group design of strong quality and seven single-subject experiments of at least adequate quality documentinggains in communication following PECS training, the bodyof evidence for the PECS approach demonstrates that PECS isa promising, although not yet established, evidence-basedpractice for promoting communication in children with au-tism. In contrast, the evidence for gains in speech achievedthrough PECS is not as strong. Fewer studies have examinedspeech outcomes (one group study of strong quality and foursingle-subject studies of at least adequate quality), and ESshave varied widely across studies. Given the nine controlled,empirical studies of at least adequate quality that were iden-tified in this meta-analysis, PECS is relatively well-researchedas compared with other popular communication interven-tions for children with autism. Considering that there are onlynine such studies, however, our results on the effectiveness ofthe PECS approach should be viewed with caution.
Overall, the data do provide evidence that PECS has smallto moderate effects in improving communication skills forchildren with autism. In addition, PECS may improve speechability for some children with autism relative to speech priorto intervention or gains made as a function of other interven-tion approaches, but further research is needed related to speechdevelopment as an outcome of PECS intervention. The find-ing of a negligible aggregated ES for speech outcomes acrossthe single-subject experiments and small to negative ESs forgroup studies is an important outcome of this meta-analysisand demonstrates the value of using synthesized results to
Flippin et al.: Effectiveness of PECS 189
uncover trends in the composite data that are not readily appar-ent by visual inspection and narrative review. These resultsalso provide information on some preintervention child char-acteristics and program characteristics that may be influenc-ing speech and communicative outcomes for children withautism undergoing PECS training, but studies addressingthese questions are currently few in number.
Despite the overall adequate quality of evidence for theeffectiveness of the PECS approach and the potentially clin-ically useful identification of child and intervention charac-teristics for examining which children are most likely to havefavorable speech and/or communication outcomes throughPECS, several concerns and questions remain. One impor-tant concern is the lack of measurement and reporting oftreatment fidelity for two of the three group studies of PECSand four of the eight single-subject experiments. Withoutclear documentation of how PECS was implemented, includ-ing descriptions of personnel training and measurement ofadherence to the manualized PECS protocol, the functionalrelationship between the intervention and communicationand speech outcomes at both posttest and during generaliza-tion is unclear. In addition, there is insufficient evidence todetermine whether PECS results in generalization and long-term maintenance of communication and speech gains forchildren with ASD. Two group studies raised concerns re-garding the maintenance of communication and speech gainsmade through PECS, and only a few single-subject studiesreported maintenance or generalization measures. Clinically,this is a concern, as it is important for interventionists to knowwhether gains made in PECS can be maintained without con-tinued support, across varying contexts. Furthermore, giventhat there is only one published group design comparingPECS with a specific alternative treatment, it is still unknownwhether the PECS approach results in better communicationand speech outcomes than other available autism interven-tions. Thus, several concerns and questions remain about theoverall effectiveness of PECS for communication and speechoutcomes for children with ASD.
Questions also remain regarding the influence of modera-tors on the effectiveness of PECS and the identification ofpretreatment characteristics of childrenwho aremore likely torespond to PECS. Given the small number of studies providingthe relevant pretreatment data on participants, the evidenceis inconclusive regarding which of the currently identifiedfactors (i.e., joint attention, motor and verbal imitation, andobject exploration) contribute the most to the relative effec-tiveness of PECS on speech and communication outcomes.In addition, the three preintervention characteristics describedin this synthesis likely do not exhaust the possible initial charac-teristics of children with ASD influencing response to PECS.
Finally, Phase IVof PECS and two strategies introducedin that phase (i.e., verbal modeling and time delay) werediscussed as possible influences on speech acquisition forthose children who went on to develop speech through PECStraining. It is still unclear, however, as to whether the doc-umented increases in spontaneous speech in Phase IV arerelated to the introduction of verbal modeling, time delay, orsome combination, or whether those children who are able toachieve success in Phases I–III are simply more likely to goon to develop speech. Also unclear is whether introducing
verbal modeling and time delay components earlier in theprogram than Phase IV would result in earlier gains in sponta-neous speech or whether it is necessary to master Phases I–IIIas a foundation to developing speech in those children whodo go on to develop speech.
In summary, the overall effectiveness of the PECS approachfor communication outcomeswith children withASD is prom-ising although not yet established. Evidence for the effec-tiveness of the approach on speech outcomes is not as strong.PECS may be more beneficial for promoting speech in chil-dren with a specific developmental profile (i.e., low jointattention, low motor imitation, and high object exploration)than some alternative approaches, at least as a short-termeffect. Further empirical research is now needed to directlyexamine the generalizablity of speech and communicationgains following PECS and to examine and identify childcharacteristics that may account for the variance in outcomes.Based on this meta-analysis, we recommend that researchersinclude measures of treatment fidelity, maintenance, and gen-eralization in future studies of PECS. We also support theneed for additional studies examining the effectiveness ofPECS on speech and communication outcomes for childrenwith ASD as compared to other interventions. In addition, theevidence base for PECS will be enhanced if researchers ex-amine the potential influence of moderators and preinter-vention characteristics described in this synthesis (i.e., jointattention, object exploration, and motor and verbal imitation)and other relevant pretreatment variables. Implementing theserecommendations will strengthen the evidence base of thisapproach and aid clinicians in making informed treatment de-cisions for individual children with ASD.
AcknowledgmentThe authors thank Necdet Karasu for his advice on calculating
effect sizes in single-subject research.
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Received March 19, 2009Revision received June 30, 2009Accepted January 25, 2010DOI: 10.1044/1058-0360(2010/09-0022)
