Review of the Efficacy of the Picture Exchange Communication

J Autism Dev Disord (2009) 3914711486 inside 10. 1007/s10803-009-0763-y ORIGINAL PAPER A Review of the Ef? cacy of the try Exchange talk last outs Intervention Deborah Preston ? assure Carter Published on t genius 3 June 2009 O Springer attainment+Business Media, LLC 2009 Abstract The ledger picture Exchange Communication establishment (musculus pectoralis) is a dialogue class that has become massively roled, especi each(prenominal)y with sisterren with autism. This melodic theme reports the results of a look back of the empirical literature on pectoral med eachion. A descriptive review is domiciliated of the 27 studies identi? d, which let in hit-or-missized masteryled trials (RCTs), former(a)wise host de scrapes and wizard slip studies. For 10 arrogate angiotensin-converting enzyme publication projects the constituent of nonoerlapping discip bank bill (PND) and dower surpass median (PEM) inflection were visitd. plot of ground thither be few RC Ts, on balance, lendable explore provides prelude evince that pectoral is readily learned by near thespians and provides a reputes of colloquy for individuals with microscopic or no functional linguistic conversation. real express mail entropy stir some commanding encumbranceuate on two heartycommunicative and challenging de intendours, slice effects on obstetrical deli precise maturement remain unreadable.Directions for future look into argon discussed including the formerity acquire for however well-conducted RCTs. Key lyric envisage vary conference system A Augmentative and choice confabulation A Autism Introduction Serious de? cits in chat embodiment type of the primary symptomatic criteria for autism (Ameri empennage psychiatrical Association 2000). It has been estimated that around D. Preston A M. Carter (&) Macquarie Univer stupefyy particular(a) procreation Centre, Macquarie University, Sydney, NSW 2109, Australia e-mail mark. emailp rotected edu. au unmatched-third to whiz-half of electric s removerren and adults with autism do non corroborate unctional deli rattling (Mirenda 2003). Such individuals whitethorn show yet pre-intentional communion, much(prenominal)(prenominal) as compass for a desi rose-cheeked item, or converse whitethorn demonstrate intent finished ways such as alternating eye gaze, and conventional gestures such as fountainheading (Yoder et al. 2001). Communication may overly take the form of challenging behaviors (Mirenda 1997). When legal transfer confabulation does develop it may be limited mainly to unusual or echolalic verbalizations (Paul 2005). Individuals with upright developmental disabilities early(a) than autism may excessively yield to develop wrangle and language skills (Westling and Fox 2004).In launch to help develop communication skills, various forms of increasing and alternative communication (AAC) invite been developed. These include the procedure of manual signs (e. g. , Layton 1988 Yoder and Layton 1988), voice offput communication devices (VOCAs) (reviewed by Lancioni et al. 2001), and various simulacrum-based systems (Keen et al. 2001 Sigafoos et al. 1996). The consider Exchange Communication System ( pecs) is a picturebased system developed by Bondy and frosting (1993, 1994) to help young children with autism acquire functional communication skills. pectoralis appears smart for several(prenominal) reasons.First, it avoids dif? culties inhithernt in separate systems by requiring actually few prerequisites in event the b atomic tally 18ly prerequisite is that the individual feces classly indicate (e. g. , by r apiece(prenominal)(prenominal)ing for an item) what he or she essentials, in a mode that thatt joint be shaped into exchanging a physical sign such as a picture (Bondy and ice 2002). Other skills such as eye contact, travel or verbal imitation skills, the ability to sit quietly in a chair, match -to-sample skills, picture contrariety, or the ability to fol embarrassed verbal prompts atomic fleck 18 non necessary (Bondy and icing 1994, 2002), at least(prenominal) at the earliest broadcast set. 23 1472 J Autism Dev Disord (2009) 3914711486 help, the ? rst skill taught in pectoralis is requesting. Requesting has often been puted in early instruction of individuals with developmental disabilities due to motivational circumstances (Reichle and Sigafoos 1991). In relation to pectoralis, it is argued that individuals with autism in particular atomic deem 18 less in all likelihood to be motivated by the social consequences of labeling or commenting (Bondy and freeze 1995) and more than than likely to be motivated by requesting and inst antly obtaining a speci? c, typically concrete, desired item (Bondy and freezing 1994).Third, pectoralis consistently addresses the issue of spontaneity, which has often been inform as fussatic in individuals with autism spectr um disorders (ASD) (Chiang and Carter 2008 Koegel 2000). Rather than macrocosm symbiotic on a match to establish a communicative turn, or requiring a first mate to arrest for the learner to billet to a picture plank or generate a manual sign, which could strong be missed, pectoralis speci? cally teaches the individual to fire the partner and gain their solicitude by putting a picture symbol into their hand. quaternionth, picture symbols backside be laid-backly iconic, closely resembling their referents (Ganz and Simpson 2004 Mirenda 2003). Consequently, they may be considerably recognized by the learner (Ganz and Simpson 2004) and atomic number 18 more recognizable by communicative partners than some contrasting(a)(a) systems, such as manual signs (Lancioni et al. 2007). The pectoral communications communications protocol begins with a reinforcer respectment dvirtuoso which the flight simulator determines an ordered list of reinforcers for the individual (B ondy and Frost 1998). This is fol down(p)ed by six fleshs, which ar brie? overviewed in tabularise 1. For each phase, the criterion for palmy completion is 80% or more trials successful without prompting in a 10-trial block (Charlop-Christy and J bingles 2006). The randomized reserve trial (RCT) is recognized as providing the gold government none for evaluating clinical interpositions in argonas such as medicine and education (Evidence-Based medicine Working Group 1992 What Works Clearingho design 2006) and ideally paygrades would be limited to such reason (Carter and Wheldall 2008).Such designs, however, argon comparatively r be in educationrelated argonas (Carter and Wheldall 2008) for a variety of reasons and clinicians moldiness often look to a second line of evidence to inform decision-making. Single overthrow quasi observational designs lease repeated meters of the parasitical inconstant over date with a individual(a) or keen come of actors. Although not of fering the criterion of evidence of RCTs, the lift out of these designs are considered capable of strongly arrestling major threats to cozy daring and strong conclusions about causal inference can be emaciated (Campbell and Stanley 1963 Horner et al. 005). Similarly, high look quasi-experimental collection designs, speci? cally those involving non-equivalent assemblys with pre- seek matching, are ordinaryly considered to be interpretable (Flay et al. 2004). The weakest take of evidence is provided by pre-experimental designs, such as atomic number 53 group pre-testpost-test studies, where few threats to internal validity are constraintled and causal inference cannot be inferred with any degree of con? dence (Campbell and Stanley 1963). Early paper on pectoralis were man-sizedly descriptive with limited schooling (e. . , Bondy and Frost 1993, 1994, 1995, 1998), or presented consequence info without simplicity (e. g. , Schwartz et al. 1998). In recent eld, howev er, a upshot of interpretable group studies (e. g. , Yoder and scar 2006b) and star undetermined studies (e. g. , Charlop-Christy et al. 2002 Tincani 2004) perk up been published. Lancioni et al. (2007) reviewed the subroutine of pectoral muscle and VOCA (voice output communication aids) for request making in individuals with developmental disabilities. In increment to studies following the pectoral muscle protocols of Frost and BondyTable 1 compendious musculus pectoralis stages Phase Teaching target I II Make requests through picture exchange Persistence in initiating communication variety among symbols Introduction of sentence structure tell question with a request Commenting Description Second person acts as a prompter from tramp learner when learner reaches for the desired item, physically prompts to exchange picture prompts faded as quickly as practicable Communicative partner moves gradually come on away picture is also gradually locomote just away number of communicative partners change magnitude Communication book is introduced lay of items requested is increase, notwithstanding except whizz picture and item is unattached at a time Initially, two pictures are presented (highly preferred and neutral or disliked) more pictures are added later, more than one preferred item is offered at a time periodic cor opposeence checks are carried out to check accuracy at discrimination Taught to mapping a sentence strip, placing an I want as well as the symbol requests can also be expanded with attri besideses such as color or size, e. g. I want red playdough Taught to answer question What do you want? Taught to respond to some other simple questions such as What do you see? gradually, more extemporary commenting is developed trine IV V VI 123 J Autism Dev Disord (2009) 3914711486 1473 (1994, 2002), they also included studies employing any conventional use of pictorial material as a way of making requests for preferred items (p. 4).Th us, studies that did not follow pecs protocols, and in which the participants pointed to a picture rather than in reality exchanging it, were included (e. g. , Dyches et al. 2002 Keen et al. 2001). In addition, no guarantee was do to quantify the info obtained from the studies to esteem all the boilers suit ef? cacy or authorization of the blast or the effect of pertinent inconsistents on outcomes. To date, no countywide review of empirical literature speci? cally examining the pectoral approach of Frost and Bondy (1994, 2002) appears to build been published. The present paper looks speci? cally at studies of pectoral muscle intercession as depict by Frost and Bondy (1994, 2002).In the absence of a substantial number of gold-standard RCT studies that would allow a conventional meta- outline, a broader approach to rating of the question was undertaken. This review is intended to testify the living empirical research on pectoralis, with speci? c consideration o f the research designs sedulous and, consequently, the strength of conclusions that can be legislaten. excluded (e. g. , Son et al. 2006). One article in which previously taught communication victimisation the pectoralis class was compared to facilitated communication (Simon et al. 1996) was excluded because thither was no PECS interpellation during the see. The select of Rosales and Rehfeldt (2007), in which the ? rst lead phases of PECS was taught prior to the experiment, was lso excluded because no info on the results of the PECS preparedness was provided. Analysis A sum-up of each paper was prepared including participants, research design, discourse and continuation of knowledge, outcomes investigated, setting, PECS version and phases implemented, and a summary of the outcomes, as well as inter-observer and adjective dependability, social validity, tutelage and oecumenicality info. Ages of participants were coded into 5, 58, 917, or over 18 old age. Four c ategories of helpless variable were identi? ed PECS exchanges (number or lot of self-governing exchanges), speech or outspokenization, social-communicative behaviors, and hateful behaviors.As the majority of studies employed single overmatch designs, they were coded for quality utilize an adaptation of the guidelines for single return research presented by Horner et al. (2005). These indicators intercommunicate several areas adequacy of participant and setting descriptions dependent variables independent variables service line experimental control/internal validity external validity and social validity. A check of 10 points were allocated to each area with the exception of external validity, which was allocated 5 points in recognition of the inherent limitations of single subject designs in this regard. Thus, studies were rated on a outmatch from 0 to 65, with high hemorrhoid indicating bulkyer quality.Details of the criteria are included in the vermiform process. T raditionally, single subject studies sire been interpreted by visual inspection of interpreted info (Reynhout and Carter 2006). More recently, attempts harbour been made to quantify results of these studies objectively, and to provide reliable selective information summaries for evaluating evidence-based discussions (Parker et al. 2007). The around comm sole(prenominal) utilise of the resulting statistical indices is the percentage of non-overlapping information (PND) (Scruggs et al. 1987). The PND is the percentage of discourse data points that are above (or below when behavior decrement is targeted) the highest (or lowest) service line data point.Scruggs and Mastropieri (1998) provided guidelines for the interpretation of PND pull ahead between 91 and 100 indicate highly strong disturbances, between 71 and 90 efficient incumbrances, between 51 and 70 questionable hitchs, and 50 or below ineffective incumbrances. Whilst PND has been criticized on a number of gro unds (e. g. , onlyison and Method Search strategy Empirical studies using PECS were identi? ed through computerized searches of A? Education, British Education Index, ERIC, Expanded academician ASAP, Linguistic and Language Behavior Abstracts, PsycINFO, PubMed and ScienceDirect, using the descriptors PECS or aspect Exchange Communication System. In addition, manual searches of the reference lists of articles identi? ed were carried out to locate further studies.Studies were included if they (1) (2) were journal articles in English from 1992 to July 2007 utilize PECS (Bondy and Frost 1994 Frost and Bondy 1994, 2002) as whole or part of an handling strategy as indicated by reference to platform documentation and description of execution of instrument presented group or individual data on the results of the intervention. (3) Articles that referred to PECS barely did not follow Frost and Bondys protocol were excluded. For example, Dooley et al. (2001) use a PECS-based schedule board (p. 58) only no actual picture exchange. In addition, articles that apply a picture exchange system save did not speci? cally stated that the PECS protocols (Bondy and Frost 1994 Frost and Bondy 1994, 2002) were employed were 123 1474 J Autism Dev Disord (2009) 3914711486 Gorman 1993 Salzberg et al. 1987 White 1987), it is heretofore the most(prenominal) widely employ statistic for quantifying data from single subject studies (e. g. Bellini and Akullian 2007 Erion 2006 Lee et al. 2007 Reynhout and Carter 2006 Xin et al. 2005). A particular mischief of PND is that if any service line data point has reached the jacket or ? oor level of the beat scale, the work out PND is 0%, even if visual inspection indicates a treatment effect (Ma 2006). Ma (2006) has suggested an alternative, the percentage of data points exceeding the median (PEM). The PEM is the percentage of treatment data points that are above (or below when behavior decrease is targeted) the median baseline da ta point. there is also evidence that PEM may correlate better with author judgments of broadcast ef? cacy than PND (Ma 2006).Nevertheless, PND is by far the most widely utilise metric for summarizing single subject studies and comparative data are available on a go of interventions. The application of the PEM statistic is actually limited to date scarce, apt(p) its potential advantages, it was decided to calculate some(prenominal) PEM and PND value in the current review. It has also been argued that con? dence in ? ndings from analysis of single subject studies may be streng whenceed if bigeminal approaches to synthesis converge on similar conclusions (Smoot et al. 1990). PND and PEM statistics were cipher for all single subject studies with graphed data including a baseline and intervention phase. changing conditions (i. e. , PECS phase changes), were coded as part of the intervention phase.Metrics were initially careful for treatment data only and thusly for all int ervention data, including treatment, forethought and initiation phases. The PND statistic was cipher for each get using the pooled number of non-overlapping data points crossways all subjects and categories of dependent variable (PECS exchanges, speech/ utterance, social-communicative behaviors, undesirable behaviors). In addition, a PND statistic was metrical for each participant and for each category of dependent variable indoors relevant studies. Similarly, PEM statistics were cipher using the pooled number of data points exceeding, or below when discriminate, (i. e. , for undesirable behavior) the baseline median.In plates where the exact value of data points on a graph was dif? cult to determine, a retroflex of the graph was obtained from a Portable Document initialize copy of the article or a good quality digital scan. Subsequently, numeric data were extracted using the Digitizelt (Bormann 2003) computer software. Inter-Rater Reliability PND and PEM determine wer e independently metric by the ? rst and second authors for ? ve randomly selected single subject studies (50% of studies for which calculation was possible). Values were calculated for each graph that included a baseline and time-series data. Where more than one panel was shown on the selfsame(prenominal) graph (e. g. quadruple baseline, alternating treatments), a value was calculated for each panel. For each panel, dependability was calculated by dividing the overthrow percentage value by the high percentage value and multiplying by 100 (i. e. , if both(prenominal) raters concur on the percentage value, the reliability was 100%). The same ? ve studies were independently rated for quality indicators by the ? rst and second authors. Inter-rater reliability was calculated by dividing the number of agreements by the summarise of agreements and disagreements, and multiplying by 100. Inter-rater reliability for both PND and PEM was 100% for 54 panels and over 90% for the remaini ng triad panels with an general think agreement of 99. 8%.There were discrepancies in only three graphs the majority of these related to determining how many another(prenominal) data points were present in very small ? gures. Inter-rater reliability for quality indicators was 97. 5%. Results A summary of the participants, research design, inclusion of alimony or installation data, PECS phases taught, and outcomes examined is presented in Table 2. Research project The early studies (Bondy and Frost 1993, 1994, 1998 Schwartz et al. 1998) were all reports or chopine rating data without enough experimental control, as were two later studies (Liddle 2001 Webb 2000). Malandraki and Okalidou (2007) utilize a case study.Magiati and Howlin (2003), in their pilot study, used a pre-PECS treatment measure plus three measures over time, with data mainly from teacher ratings. All of these studies can be considered pre-experimental. Of the 14 single subject studies, 4 used alternating t reatments. Adkins and Axelrod (2001), chamber and Rehfeldt (2003) and Tincani (2004) compared PECS and manual signing, man Bock et al. (2005) compared PECS and VOCA (voice output communication aid). Four studies (Charlop-Christy et al. 2002 Rehfeldt and starting time 2005 Tincani et al. 2006, Study 1 Yokoyama et al. 2006) used a multiple baseline crosswise participants, while two (Frea et al. 2001 Kravits et al. 2002) used a multiple baseline crossways settings, one (Marckel et al. 006) used a multiple baseline across descriptors taught, and one ( e. e. cummings and Williams 2000) used a multiple baseline across activities. both studies ( chromatic et al. 2006 Tincani et al. 2006, Study 2) used an ABAB design, while one (Ganz and Simpson 123 Table 2 compendious of Studies Ages drug-addicted variable Research design nutriment (M) PECS or stimulus generalisation (G) Phases data I triplet I terzetto IIII IIV IIII IIII IIII IVI III go for exchange, sign Picture exchange, VOCA P icture exchange Picture exchange, speech Picture exchange, speech Speech kindly/communicative Picture exchange, sign language Speech, social, behavior (variation) Authors Participants DiagnosisAdkins and Axelrod (2001) 35 Autism Autism Autism Autism Autism 1 ill characteristics Autism 2 autism, 3 PDD 35 age Single-subject (multiple baseline) 312 age Single-subject (multiple baseline) M,G 1940 solar days Single-subject (alternating treatment) G 37 age 37 years Non-equivalent control group Non-equivalent control group G 32 months weapons platform evaluation 6 years Program evaluation 6 years adult Program evaluation 4 years Single-subject (alternating treatment) G 1 PDD 7 years Single-subject (alternating treatment) G Bock et al. (2005) 6 Bondy and Frost (1993) 74 Bondy and Frost (1994) 85 Bondy and Frost (1998) 1 J Autism Dev Disord (2009) 3914711486 Carr and Felce (2007a) Carr and Felce (2007b) 10 41 chamber and Rehfeldt (2003) 4 Charlop-Christy et al. (2002) 3Cumming s and Williams (2000) Autism Autism Autism Autism 14 ASD Autism or ASD Autism Autism 16 autism/PDD-NOS 36 years 2231 years 2034 years 45 years 10 years Case study Single-subject (multiple baseline) Single-subject (multiple probe) Program evaluation Single-subject (ABAB) Single-subject (alternating treatment) 911 years Single-subject (multiple baseline, ABAB) 512 years Single group School Program evaluation 6 years Single-subject (multiple baseline) 37 years 411 years Single-subject (changing criterion RCT G M G M G G G G G 4 years Single-subject (multiple baseline) 5 Picture exchange, other IIII IIV IVI IIII IVI IVI IVI Extension IIII IIV IIV IIII IIV Picture exchange, behavior Picture exchange, speech Picture exchange, speech, ADOS-G Picture exchange, speech, social Picture exchange Picture exchange, speech, other Picture exchange Picture exchange (improvised requests) Picture exchange, other Picture exchange, speech, other Picture exchange Picture exchange Picture exchange, sign, speech PECS, speech 1475 Frea et al. (2001) 1 Ganz and Simpson (2004) Howlin et al. (2007) 3 84 Kravits et al. (2002) 1 Liddle (2001) 21 Magiati and Howlin (2003) 34Malandraki and Okalidou (2007) 1 Marckel et al. (2006) 2 Rehfeldt and stemma (2005) 3 Schwartz et al. (1998) 31 nether regionr et al. (2006) 5 Tincani (2004) Autism 2 1 autism, 1 PDD-NOS 56 years 123 Tincani et al. (2006) 3 1476 J Autism Dev Disord (2009) 3914711486 Maintenance (M) or generalization (G) data M,G 2004) used a within subjects changing criterion design. In several studies, a changing criterion was included, re? ecting the PECS phase changes alone it was secondary to the main design (Bock et al. 2005 chamber and Rehfeldt 2003 Cummings and Williams 2000 Rehfeldt and Root 2005 rock musicr et al. 2006 Tincani 2004 Tincani et al. 2006 Yokoyama et al. 2006).Comparative group designs were employed in ? ve papers. Yoder and Stone (2006a, b) used random appointment to PECS or Responsive Education and Pre linguistic surround Teaching (RPMT) intervention groups, while Howlin et al. (2007) used random assignment of classes to immediate treatment, delayed treatment or no treatment with PECS groups. Carr and Felce (2007a, b) used a quasiexperimental group design whereby PECS intervention and control groups were chosen by geographical location, and included both within subjects and between group measures. Pre-test equivalence of the groups was established. Participants Picture exchange, speech PECS Phases IVI IVI G IVI G Single-subject (multiple baseline)) IIV Picture exchange, speech Dependent variable Speech genial In total, in that respect were 456 participants in the 27 studies of these, 394 (86%) received PECS intervention and 62 (14%) were in non- or alternative-intervention groups. Of the total, 377 (83%) were described as having ASD. Ages of participants floatd from 20 months to 40 years and there were 198 males (43%) and 38 (8%) females with the gender of 220 (48%) of particip ants unstated. Where the same or a subgroup of participants were account in multiple studies (Carr and Felce 2007a, b Yoder and Stone 2006a, b), they were counted only once. The group experimental (Howlin et al. 007 Yoder and Stone 2006a, b) or quasi-experimental (Carr and Felce 2007a, b) studies involve a total of 161 participants (35% of the total sample) 98 in PECS intervention groups and 92 in control or other treatment groups. The Delayed manipulation Group in the Howlin et al. (2007) study was used as both control and intervention at diametrical times. All these children were described as having autism or PDD-NOS and belittled or no speech. They ranged in age from 20 months to 11 years at study commencement. These studies all provided information on the initial abilities of the participants based on alike(p) tests. The single subject studies involved a total of 42 participants (9% of the total sample) and all provided information on diagnosing, age and gender. hardly a m inority provided information on the diagnostic instrument or protocol used to identify ASD (Ganz and Simpson 2004 Marckel et al. 2006 Yokoyama et al. 2006), described the degree of autism or provided standardized assessment data or a description of general ability for all participants (Chambers and Rehfeldt 2003 Frea et al. 2001 Kravits et al. 2002 Rehfeldt and Root 2005 Stoner et al. 2006 Research design Program evaluation 5570 months RCT 2154 months Autism/PDD 36 Yoder and Stone (2006a) 2053 months Autism/PDD Yoder and Stone (2006b) 36 RCT Diagnosis Participants 6 Table 2 Summary of Studies 123 Yokoyama et al. (2006) Authors Webb (2000) 3 Autism 5 ASD 57 years Ages J Autism Dev Disord (2009) 3914711486 1477 Yokoyama et al. 2006).Most researchers did document initial communication skills, either using standardized test results or a description of functional skills, although some descriptions were negligible. Participants were well-nigh entirely described as non-verbal or having l ittle or no functional speech, or in some cases no functional communication. The participants in the Marckel et al. (2006) study were able to use PECS independently to amaze requests at the start of the research. Participants in three studies were explicitly identi? ed by researchers as having challenging behavior (Adkins and Axelrod 2001 CharlopChristy et al. 2002 Frea et al. 2001). Interobserver and Procedural Reliability Interobserver reliability was inform for 20 of the 27 papers reviewed. Papers in which interobserver reliability was not report included ? e to begin with course of study evaluations (Bondy and Frost 1993, 1994, 1998 Liddle 2001 Webb 2000) and one single subject study (Adkins and Axelrod 2001). Reliability ranged from 80. 3 to 100% calculated on between 10 and 100% of data. trinity studies (Howlin et al. 2007 Kravits et al. 2002 Malandraki and Okalidou 2007) estimated reliability on less than a peripheral standard of 20% of total sessions. In contrast, pro cedural reliability was reported for only 7 of the 27 studies (Bock et al. 2005 Cummings and Williams 2000 Marckel et al. 2006 Tincani 2004 Tincani et al. 2006 Yoder and Stone 2006a, b) and discussed but not formally calculated in one other (Stoner et al. 2006). Where reported, procedural reliability ranged from 96 to 100%.In two papers (Yoder and Stone 2006a, b) less than 20% of sessions were used for the estimate. Social Validity Formal measures of social validity were reported in only four papers (Magiati and Howlin 2003 Marckel et al. 2006 Tincani 2004 Yoder and Stone 2006a). Settings Fourteen studies were conducted in a picky school, special preschool or special class style setting. Remaining studies were conducted in a variety of settings including an integrated preschool, regular classroom, homes, clinics, day treatment facilities, and combinations of these settings. Ef? cacy and Effectiveness of PECS Of the total group of 394 individuals who received PECS intervention, only one child was reported as being nsuccessful at k straightaway at least phase I (Liddle 2001), and one adult had dif? culty with the motor and cognitive demands of the teaching and failed to do past phase I (Mike, Stoner et al. 2006). Carl, from Tincanis (2004) study, was more successful with manual signs than PECS, but, the great majority successfully mastered at least some phases of PECS. Outcome data will now be considered further, initially focusing on pre-experimental designs, then single subject designs, quasi-experimental group designs and ? nally RCTs. This will be followed by a more particulared consideration of bread and butter and generalization. Pre-Experimental Studies several(prenominal) studies used pre-experimental designs.Bondy and Frost (1993) reported data on the implementation of PECS and put increase communicative initiations and use of pictures. Bondy and Frost (1994, 1998), Schwartz et al. (1998), Webb (2000), and Liddle (2001) also presented data on PEC S implementation and reported increases in spoken language following PECS training. Schwartz et al. install that children were able to acquire communication with PECS training and there was evidence of generalization across pragmatic function. These studies, however, lacked capable experimental control, and especially disposed(p) the young age of the children involved in at least four studies, it is unknown how communication would have developed without the intervention.In their pilot study, Magiati and Howlin (2003) used a pre-treatment measure and three teacher ratings over time. They ready signi? formalism increases in PECS level (d = 2. 91),1 frequency of spontaneous use (d = 1. 75), and number of symbols used (d = 3. 01) over the 6 months following teacher training in PECS and its subsequent introduction. These are very large effect sizes by educational standards. They also rig small but still statistically signi? slope increases in the number of signs (d = 0. 31), word s (d = 0. 32) and phrases (d = 0. 30) used, and in the overall level of spontaneous communication (d = 0. 83). Outcomes were, however, measured mainly through teacher rating scales.The results must be handle with caution as they are likely to have been in? uenced by expectations and the research design was very weak. 1 For pre-test post-test designs, effect sizes were calculated by subtracting the pretest mean from the post-test mean and dividing by the pooled standard deviation. For studies involving a resemblance group, effect sizes were calculated by subtracting the mean of the control or alternate treatment group from the mean of the PECS intervention group and dividing by the pooled standard deviation. 123 1478 J Autism Dev Disord (2009) 3914711486 Single Subject Studies PND and PEM statistics were calculated for the 10 single subject studies that provided baseline and intervention data.Initially, calculations were conducted on treatment data just and then on all interventio n data, including treatment, maintenance and generalization. When compared, the overall mean differences in favor of the treatment but data were very small, only 0. 4% in the case of PND and 0. 8% for PEM. It was considered that the inclusion of all intervention data provided the best indicator of the ef? cacy of the overall mail boat and these data were used for the remaining analysis. Results are provided in Table 3. Calculations were not possible for the four additional single subject studies (Adkins and Axelrod 2001 Cummings and Williams 2000 Ganz and Simpson 2004 Rehfeldt and Root 2005). These studies either lacked baseline data (e. g. alternating treatment design without baseline) or lacked baseline data that corresponded rulely to that stack away in intervention. The overall mean PND was 78. 5% (range 50 100), placing the PECS intervention in the effective range (Scruggs and Mastropieri 1998). The overall mean PEM was 89. 1% (range 72. 3100). lumber indicator score are also presented in Table 3, and ranged from 30. 6 to 55. 7 out of a possible 65 points. Correlation between musical note Indicator scores for each study and their associated study PND was not signi? slang term (rs = -0. 05, p = 0. 87). For PEM there was a trend toward weaker studies producing higher effect sizes but this did not reach signi? cance (rs = -0. 44, p = 0. 19).MannWhitney U tests or KruskalWallis one-way ANOVAs were used to compare PND and PEM values across participant and study characteristics and these data are presented in Tables 4 and 5. No signi? cant difference in PND was rear for age, gender, setting, inclusion of maintenance or generalization data, or research design. A signi? cant difference was tack for PND scores for outcome variables, with studies addressing picture exchange only having a higher mean PND than those that included other dependent variables (i. e. , speech, social, behavioural, with or without picture exchange). A signi? cant difference was also set in motion between PND values for participant diagnosis.Post hoc comparison showed that PND for children identi? ed with autism (i. e. , autistic disorder) were signi? cantly start out than for the other two groups, but these groups were not signi? cantly several(predicate) from each other. No signi? cant difference was arrange between PEM values for any of the study or participant characteristics although participant diagnosis approached signi? cance (p = . 06). Four of the single subject studies included data speci? cally relating to speech development from which PND and PEM values could be calculated (Charlop-Christy et al. 2002 Tincani 2004 Tincani et al. 2006 Yokoyama et al. 2006). The mean calculated PND was 49. % (range 19. 5 100) and PEM 54. 2% (range 25. 0100). These values are in the non-effective or at best very mildly effective range but with wide variation. Charlop-Christy et al. (2004) give increases in speech during PECS training. Tincani (2004) examined independent word vocalizations during PECS and sign language training. The addition of a Table 3 Single subject studies PND and PEM results study quality results Study PND PEM Study quality (Maximum 65) Picture Speech Social Behavior general Picture Speech Social Behavior overall exchange exchange Adkins and Axelrod (2001) Bock et al. (2005) Chambers and Rehfeldt (2003) Charlop-Christy et al. 2002) Cummings and Williams (2000) Frea et al. (2001) Ganz and Simpson (2004) Kravits et al. (2002) Marckel et al. (2006) Rehfeldt and Root (2005) Stoner et al. (2006) Tincani (2004) Tincani et al. (2006) Yokoyama et al. (2006) Mean SD 92. 1 100. 0 100. 0 87. 7 97. 3 77. 5 90. 6 98. 6 68. 7 90. 0 10. 9 59. 8 100. 0 20. 0 19. 5 49. 8 38. 4 86. 8 86. 8 n/a 26. 0 0 13. 0 18. 4 92. 1 100. 0 55. 6 50. 0 87. 7 97. 3 77. 5 95. 3 70. 5 58. 6 78. 5 18. 8 92. 1 100. 0 100. 0 87. 7 100. 0 90. 1 90. 6 98. 6 89. 9 94. 3 5. 2 65. 7 100. 0 25. 0 26 . 0 54. 2 36. 0 95. 95. 6 n/a 85. 0 100. 0 92. 5 10. 6 90. 1 95. 3 72. 3 76. 7 89. 1 10. 6 92. 1 100. 0 76. 3 100. 0 87. 7 100. 0 30. 6 55. 7 43. 8 52. 4 32. 9 42. 4 35. 3 50. 4 49. 6 43. 8 50. 3 48. 2 45. 7 50. 3 45. 1 7. 6 123 J Autism Dev Disord (2009) 3914711486 Table 4 Means, standard deviations and MannWhitney U test results for PND and PEM scores of study and participant characteristics Variable N PND M (SD) step indicators C50 50 PECS only Includes other Yes No 5 74. 3 (16. 6) 5 82. 6 (21. 7) 5 90. 9 (8. 9) 5 66. 0 (18. 0) 3. 0 0. 94 84. 6 (7. 5) 93. 5 (12. 0) 3. 0 1. 98* 94. 0 (5. 7) 84. 1 (12. 6) 7. 0 1. 14 5. 0 1. 6 U z PEM M (SD) U z Research design Multiple baseline Alternating treatments ABAB Age Under 5 58 2. 0 1. 56 76. 5 (0. 3) 92. 2 (9. 4) 4. 0 1. 04 87. 9 (11. 2) 93. 9 (8. 7) 6. 0 1. 27 89. 9 (12. 2) 11. 0 0. 21 88. 5 (10. 5) 88. 5 (12. 5) 52. 0 0. 46 92. 5 (11. 2) 6. 0 0. 52 2. 0 1. 56 917 18? Diagnosis Autism PDD-NOS/autistic charact eristics Other Setting Special school/ preschool Clinic Integrated preschool Home Combination 10 1 1 9 8 90. 1 (12. 5) 3. 87 79. 3 (n/a) 50. 0 (n/a) 74. 3 (30. 4) 82. 3 (21. 8) 2 57. 1 (2. 1) 8 83. 8 (17. 0) 9 8 3 9 13 85. 0 (17. 0) 2. 58 73. 1 (31. 2) 72. 2 (21. 4) 87. 9 (18. 5) 69. 8 (25. 9) 7. 68* 93. 8 (7. 3) 84. 4 (11. 4) 75. 4 (18. 8) 93. 5 (11. 1) 6 3 1 70. 0 (19. 0) 3. 82 95. 8 (4. 0) 77. 5 (n/a) 479 Table 5 descriptive statistics and KruskalWallis One-Way ANOVA results of PND and PEM scores of study and participant characteristics Variable N PND M (SD) H PEM M (SD) H 85. 5 (12. 3) 1. 62 95. 8 (4. 0) 90. 1 (n/a) 6. 74 Outcome variables Maintenance data included Generalization data included Yes 8 80. 9 (17. 8) No Yes No Gender Male pistillate 2 68. 9 (26. 7) 4 88. 8 (12. 4) 6 71. 6 (20. 0) Procedural reliability data 83. 7 (13. 2) 5. 59 100. 0 (0) 92. 8 (9. 8) 90. 4 (11. 8) 2. 29 79. 3 (n/a) 100. 0 (n/a) 87. 8 (13. 1) 89. 2 (13. 4) 2 100. 0 (0) 14 89. 2 (15. 2) 25 78. 9 (23. 9) 40. 5 1. 12 5 92. 5 (11. 2) note * Indicates signi? cant result at 0. 05 level for two-tailed test reinforcer delay in phase IIIb resulted in increase in word vocalizations. Tincani et al. 2006) examined word vocalizations and vocal approximations during PECS training, and found a decrease during phases I-III forwards dramatic increases in phase IV. In a second experiment, looking at phase IV only, a higher percentage of word vocalizations was found with the reinforcement delay procedure than without. Yokoyama et al. (2006) examined frequency and intelligibility of vocalization during PECS training in phases I-IV these authors also found an increase with the time delay procedure. Several other studies provided data on speech development, which was not fitting for calculation of PND or PEM values. Kravits et al. (2002) found an increase in frequency of intelligible speech but not in range of spoken vocabulary.Ganz and Simpson (2004) found that words per trial change magnitude noticeably during phase IV or phases III and IV of PECS training, in particular, simultaneously with delayed word precedenting. Charlop-Christy et al. (2002) provided the only appropriate data for calculation of PND and PEM values for social outcomes. From this very small amount of data, the PND of 86. 8% and PEM of 95. 6% suggest an effective or highly effective intervention. Variables that increased in this study were eye contact, joint watchfulness, cooperative play, and frequency of initiations and requests including but not limited to PECS requests. Initiations and requests Note * Indicates signi? cant result at 0. 05 level for two-tailed test ncreased the most, and joint attention also increased in all three children. It has been suggested that a direct positive alliance exists between joint attention and communication in children with autism, with improvement in one potentially stimulating an increase in the other (CharlopChristy et al. 2002). Kravits and colleagues (2002 ) reported some increase in term of social interaction with peers although these data were not equal for calculation of PND or PEM as only the mean level in each phase was presented. PND and PEM scores were calculated for data from only two studies for behavioral variables (CharlopChristy et al. 2002 Frea et al. 2001). The mean PND was 13. 0% while the mean PEM was 92. %, but, interrogative sentence of graphed data showed treatment effects, indicating that decreased problem behaviors occurred in conjunction with increased communication skills through PECS training. Two studies compared sign language to PECS interventions (Chambers and Rehfeldt 2003 Tincani 2004) and one compared a VOCA to PECS (Bock et al. 2005). For each of these studies PND and PEM were equal, and a higher value was found for PECS than for the alternative intervention. For Tincani (2004) calculated values were 95. 3% for PECS and 92. 3% for sign, for Chambers and 123 1480 J Autism Dev Disord (2009) 3914711486 R ehfeldt (2003) values were 100% for PECS, and 65. 7% for sign, and for Bock et al. 2005) values were 92. 1% for PECS and 79. 7% for VOCA. Quasi-Experimental Group Studies Carr and Felce (2007b) found signi? cant improvement in several aspects of communicative interaction between children and stave following 15 h of PECS training (Phases I-III). Signi? cant increases were found for total child-toadult initiations, linguistic initiations, the percentage of adult response, the percentage of child response, and signi? cant decrease in adult-to-child interactions with no opportunity for child response. These differences were found in comparison to both a pre-intervention measure over time and to a non-intervention and non-equivalent control group.Examining a subset of this group, who used at least one word during observations, Carr and Felce (2007a) reported that over 6 weeks training in PECS phases I-III, 3 of the 24 children in the PECS group increased their spoken words. A further 2 w ho did not speak at pretesting did so at post-testing, while there was a marginal increase in speech for one child in the control group. RCTs besides three RCT studies were located. Yoder and Stone (2006a) conducted an experimental study of 36 children with autism, aged 2154 months, who were randomly assigned to PECS or RPMT intervention groups. They found that the PECS group showed a signi? cantly great increase in frequency of speech (d = 0. 3) and in number of divers(prenominal) words used (d = 0. 50) afterward 6 months of intervention, but by 6 months post-intervention the difference was no longer evident. Interestingly, they also found differing effects according to pretreatment characteristics children who were low in initial object exploration bene? ted more from the RPMT intervention, while those who were higher bene? ted more from PECS, these effects being evident 6 months post-intervention. Overall, there was a signi? cant increase in non-imitative spoken acts over 1 y ear. The actual increases were from a mean of 0. 25 nonimitative spoken acts in a 15-min session to a mean of 5. 5, and from a mean of 0. 7 different non-imitative words to a mean of 3. Given the young age of the children, the fact that their initial verbal mental age averaged 11. 9 months (range 719 months), just at the stage when verbal language is likely to develop naturally, it seems instead possible that this increase could be attributed to maturation. In a second article, Yoder and Stone (2006b) examined the effect of the interventions on the three major types of intentional communication used prior to speech development, (i. e. initiating joint attention, requesting, and turn-taking). They found that, overall all three communicative functions increased signi? cantly, but RPMT increased turn-taking more than PECS.Children who were higher in initiating joint attention before treatment had greater increases in both initiating joint attention and requesting following RPMT interv ention, while those who were initially lower in initiating joint attention had greater increases following PECS intervention. Howlin et al. (2007) conducted a group RCT of 84 children with autism, examining the effect of teacher training and consultancy in PECS. It should be stressed that this study examined the effectiveness of a consultancy model to deliver PECS, rather than the ef? cacy of PECS per se. Thus, the study was celebrated in that it appears to be the only research to examine effectiveness (i. e. , outcomes under clinical rather than optimal conditions). Howlin et al. ound that rates of communicative initiations and PECS usage were signi? cantly increased immediately following intervention, but that these effects were not keep once the intervention ceased. They found no signi? cant increase in frequency of speech. Howlin et al. also examined ADOS-G (Lord et al. 2000) terra firma scores for communication and reciprocal social interaction. They found no increase in mos t ADOS-G ratings, with the exception of a decrease in the malignity score for the Reciprocal Social Interaction domain at the 10 month followup. Unfortunately, no data was provided on the ? delity of implementation of the PECS program, or hence on the ? delity of the teacher training.Maintenance and Generalization Only ? ve studies provided data on maintenance. Two of the RCT studies included long-term follow-up. Yoder and Stone (2006a) found that differences in speech variables were not maintained 6 months post-intervention, while Howlin et al. (2007) found that for the 26 children assessed at a 10-month follow-up, the increased rate of communicative initiations and PECS usage found immediately post-intervention was not maintained. Two single subject studies and one case study measured maintenance of skills 610 months postintervention (Charlop-Christy et al. 2002 Malandraki and Okalidou 2007 Yokoyama et al. 2006). Charlop-Christy et al. ound that speech and socio-communicative be haviors had been maintained or continued to increase for one participant followed up 10 months post-training. Yokoyama et al. found maintenance of PECS skills both in the training room and at home, 68 months after training for the three participants in their study. Malandraki and Okalidou in their study of one child found maintenance of skills 6 months after the main intervention. While the difference was not signi? cant and the number of studies was low, for the single 123 J Autism Dev Disord (2009) 3914711486 1481 subject studies both PND and PEM were lower for studies that included maintenance data (Table 4).Fifteen of the 27 studies included some data on generalization of PECS skills. The great majority of these were positive, with skills generalizing to different settings, people and stimuli. For some studies, generalization was an integral part of the way data were collected (CharlopChristy et al. 2002 Yoder and Stone 2006a, b). For others, generalization to untrained situatio ns was speci? cally probed (e. g. , participants in Stoner et al. s (2006) study generalized their skills to use in fast sustenance restaurants). Several studies demonstrated generalization to the classroom teacher or to home. In a small number of instances, generalization was unimpressive or absent.For example, in the Adkins and Axelrod (2001) study, tests for generalization simply required the child to mand for an object without immediately prior prompted trials. Carl, from Tincanis (2004) study, failed to generalize PECS skills to classroom teachers, preferring to use sign language. Discussion The PECS program was originally knowing to provide a regularity of communication for children with autism, particularly those who do not use functional speech. PECS appears to be a normal intervention (Howlin et al. 2007) but, unfortunately, popularity of a haltn treatment does not necessarily re? ect actual ef? cacy (Green et al. 2006 Reynhout and Carter 2006). Only three RCTs have be en reported to date. The studies of Yoder and Stone (2006a, b) compared PECS to RMPT.PECS was superior for some children but the study was designed to compare two treatments and, consequently, did not include a control arm. Thus, no conclusions can be drawn about the relative superiority of either intervention to a non-treatment control. Howlin et al. (2007) provided the only effectiveness study conducted. They found signi? cant effects on communicative initiations but this was not maintained once the intervention ceased. Thus, further inquiry of approaches to the delivery of PECS in clinical settings is needed. Con? dence in the Howlin et al. study is somewhat emasculated by the lack of any data on treatment ? delity, which is a critical feature in study quality (Gersten et al. 2005).The nature and quantity of data arising from RCTs at this point in time is insuf? cient to draw ? rm conclusions regarding the PECS interventions. Thus, probably the highest priority for research in this area is the conduct of further RCTs examining both ef? cacy and effectiveness in applied settings. In the absence of an adequate body of RCTs, clinicians still need to make certain decisions regarding interventions and may need to look to the second line of evidence. Evidence supporting the PECS intervention was provided by the well-designed quasi-experimental studies of Carr and Felce (2007a, b), which incorporated a non-equivalent control group with demonstration of pre-test equivalence between groups.Arguably, the bulk of interpretable data on PECS comes from single subject studies. For the relevant studies, the overall, mean PND (78. 5%) and PEM (89. 1%) ? gures support the preliminary conclusion that PECS may be an effective intervention, at least when implemented under research conditions. There was a signi? cant difference between the PND results for studies that only looked at picture exchange outcome variables and those that included other collateral variables, such as speech, social, or challenging behavior. This indicates that, unsurprisingly, PECS training appears to be most effective in providing a successful means of communication through picture exchange.Nevertheless, it should be acknowledged that the number of studies remains relatively low and single subject designs have several limitations, including low external validity. While these studies contribute to our knowledge and give us a preliminary indication of the ef? cacy of PECS, they are not a substitute for well-conducted large scale RCTs. A substantial number of the extant studies were preexperimental in nature, particularly the early research. As such, they are not able to provide convincing demonstrations of experimental control. Hence, these studies offer no interpretable evidence on the ef? cacy of PECS. The effect of PECS training on speech development remains un terminate.Research into various forms of AAC suggests they may have the potential to enhance speech development (C ress and Marvin 2003 Millar et al. 2006 Romski and Sevcik 2005) although results have sometimes been inconsistent (Carter 1999 Millar et al. 2006). Several of the studies reviewed in this paper reported increases in speech following PECS training, but others, including Howlin et al. (2007), reported little or no effect. Where speech increased, this has often occurred concurrently with phase III or IV of PECS, and in particular when a time delay was introduced. A related question, for which there is as yet no empirical evidence, is whether PECS training affects comprehension.Brady (2000) found increased comprehension skills with the use of VOCAs and it would be worth investigating whether PECS would have a similar effect. In comparison with other AAC systems, better overall results were obtained with PECS in the studies reviewed here (Adkins and Axelrod 2001 Bock et al. 2005 Chambers and Rehfeldt 2003 Tincani 2004). Nevertheless, there was disagreement in the results depending on in itial imitation skills and, possibly, participant preference. It has been argued that individuals with ASD may bene? t from visually cued instruction (Quill 1997) and further inquiry of this issue would seem apologiseed. In addition, existing 123 1482 J Autism Dev Disord (2009) 3914711486 application of PECS appears to have been only when limited to graphic symbols.There are distinct advantages to the use of three-dimensional actual symbols, including decreased cognitive lading and high iconicity (Rowland and Schweigert 1989, 1990 Turnell and Carter 1994). The exploration of the use of PECS with tangible symbols, especially with individuals who are low functioning, would seem warranted. Only 5 of the 27 studies provided data on maintenance of PECS skills or other dependent variables. It is good of note that maintenance was problematic in both RCTs (Howlin et al. 2007 Yoder and Stone 2006a) that examined the issue. Overall, available evidence is mixed but there is certainly suf? cient doubt to indicate that maintenance should be formally and systematically monitored in the clinical application of PECS programs.Fifteen studies provided data on generalization of skills, the vast majority of these found that generalization did occur, but what was described as generalization varied greatly. There were several methodological limitations and issues in the research examined that warrant comment. In general, participant descriptions were poor, making it dif? cult to assess whether the intervention is best suited to individuals with particular characteristics. While nearly all studies provided a diagnosis, few speci? ed the diagnostic protocol or criteria. Further, when participants were diagnosed with ASD, few researches act to quantify the degree of autism.Noting the range of behaviors and symptom mischievousness possible within individuals presenting with autistic disorder, and even greater variation in the broader autism spectrum, this would seem to be relev ant, if not critical, information. Few researchers provided standardized assessment data or a detailed functional description of general ability, but probably re? ecting the aim of the intervention, most did provide some description of initial communication skills. While the number of studies was clearly insuf? cient to reach ? rm conclusions, PND data suggest that individuals with PDD-NOS or showing autistic traits made more progress with PECS than those with autistic disorder.It is unclear whether this is because the PECS protocol is better suited to them, or because they would do better with any treatment. Without further clear and consistent quanti? cation of the degree of autistic symptomatology, it is impossible to evaluate further this variable in relation to the ef? cacy of the PECS intervention. In addition, there was insuf? cient data on quick functioning to enable analysis of any relationship to PND or PEM. It is recommended that, in future studies, standardized psychome tric data, standardized functional assessment of adaptative behavior, and clear information on initial communicative abilities should be provided.In addition, where a diagnosis of autism is provided the level of autistic symptomatology should be quanti? ed. Procedural reliability data were very limited, with data only gaining the conventional minimum standard in 5 of the 27 studies. Because of the absence of this data, it is not possible to determine in many cases whether what was being implemented was in fact the PECS program as designed. PECS is a mingled and multi-component intervention making the veri? cation of treatment integrity even more critical. The absence of such information in research studies is somewhat dif? cult to understand given that the PECS manual (Frost and Bondy 2002) gives explicit and speci? criteria for assessing the integrity of training during each phase. Nevertheless, research on PECS is not alone in this regard and lack of procedural reliability data has been reported as a problem in other recent intervention reviews in the area of autism (e. g. , Bellini and Akullian 2007 Reynhout and Carter 2006). The calculated PND (88. 8%) and PEM (89. 9%) ? gures for studies that did meet the standard for reporting procedural reliability, are at the high end of the effective intervention range (Ma 2006 Scruggs and Mastropieri 1998), suggesting that monitoring of procedural integrity should be a backbone feature in research as well as clinical applications of PECS. A signi? ant component of the present review was the application of PND and PEM metrics to the relevant data. PND and PEM values were in most cases very similar, with lower unevenness for PEM (see Table 4). An exception was found for data relating to behavioral variables (CharlopChristy et al. 2002 Frea et al. 2001), where high baseline variability and ? oor effects occurred, often causing the calculated PND for moved(p) graphs to be low, while the PEM was high. For example, v isual inspection of the graphed data in Frea et al. (2001) shows a clear treatment effect of the PECS intervention on disruptive behavior. Nevertheless, the calculated PND for these data was 0%, while the PEM was 100%.The version between the clear treatment effect seen in the graphed data and the PND value indicates that PEM may be a more appropriate metric for challenging behavior, where variability is likely to be high. Further, the advantages of using multiple methods of work out effect sizes for single subject research are highlighted. As previously noted, PECS is a complex multi-component intervention program. Consequently, the question arises as to which of the components are most critical to its ef? cacy. For example, reinforcer assessment is formally and systematically incorporated into PECS and this may well be a salient factor in program ef? cacy. The use of picture exchange with a partner (rather than touching or pointing to a symbol) is a key distinguishing feature of PECS, but it is unclear whether exchange per se is essential to ef? cacy.The issue of developing spontaneity is addressed in an unusually systematic way in the PECS program (Chiang and Carter 2008) but extant research 123 J Autism Dev Disord (2009) 3914711486 1483 provides only limited information on the circumstances under which communication occurs. Thus, there would appear to be considerable scope for examination of how speci? c components contribute to the overall ef? cacy of PECS. In addition, there has been only limited comparison of PECS to alternative interventions and this stands as a priority for future research. Several limitations of the current review must be acknowledged. many another(prenominal) of the earlier studies were descriptive and clear experimental control was not established.While later studies were of higher quality, only a limited number of RCTs have been conducted and much of the available interpretable data comes from second line of evidence single subj ect studies. Analysis of PND and PEM was only possible for a subset of the relevant single subject studies examined and analysis of speci? c study and participant characteristics were based on low numbers. In addition, very few studies provided adequate procedural reliability data so the finale to which PECS was appropriately implemented often remained unknown. consequence On balance, the studies reviewed provide preliminary evidence that PECS may be ef? cacious for children and adults with ASD and other developmental disabilities, who have little or no speech. Primary bene? s appear to be evident in communication by picture exchange. Identi? cation of the core aspects of the program that are important to its success, the individuals to whom it is best suited, and its relationship to other interventions remain to be substantively investigated. PECS stands as a promising intervention with some empirical support but many questions remain. The conduct of further RCTs into the ef? cac y and effectiveness of PECS stands as a high research priority. Appendix See Table 6. Table 6 Quality criteria for single subject research adapted from Horner et al. (2005) area Indicator Description of participants Participants are described with suf? ient detail to allow others to select individuals with similar characteristics and settings (e. g. , age, gender, stultification, diagnosis). One point awarded for each of the following (maximum of 5) 1. Statement of diagnosis such as autism, ASD, Asperger syndrome, intellectual disability (with or without indicating diagnostic source), age and gender 2. Diagnostic instrument speci? ed (e. g. , WISC, AAMR diagnostic criteria, DSM-IV criteria, ADOS). Must provide if ASD or 0 awarded 3. If ASD, degree of autism speci? ed either with reference to symptoms (DSM-IV) or instrument like CARS. If not ASD, award point 4. Standardized assessment data (e. g. IQ, developmental scale, adaptive behavior) OR detailed functional description of gene ral ability. Disability range (e. g. , moderate) pleasing for intellectual disability 5. Communication skills documented by means of standardized test results OR description of functional skills The process for selecting participants is described with replicable clearcutness. MUST describe the process used to select participants, not just describe the participants or their needs. This would generally include the criteria the participants must meet (e. g. , 35 years, less than 5 spoken words, diagnosis of autistic disorder) and or the process of selecting participants (e. g. , the ? rst 5 children on the waiting list).Essentially, authors must explicitly state HOW/why participants were selected Critical features of the physical setting are described with suf? cient precision to allow replication Dependent variables All dependent variables are described with operational precision Each dependent variable is measured with a procedure that generates a quanti? able index The measurement process is described with replicable precision Dependent variables are measured repeatedly over time data are collected on the reliability or inter-observer agreement (IOA) associated with each dependent variable, and IOA levels meet minimal standards (i. e. , IOA = 80% Kappa = 0. 60).Must be on minimum of 20% of sessions to be acceptable Independent variables Independent variable is described with replicable precision Independent variable is systematically manipulated and under the control of the experimenter Overt measurement of the ? delity of implementation for the independent variable. MUST be measured on a minimum of 20% of sessions to be acceptable 123 1484 Table 6 continued Area baseline Indicator J Autism Dev Disord (2009) 3914711486 A baseline phase provides repeated measurement of a dependent variable and establishes a pattern of responding that can be used to predict the pattern of future achievement if introduction or manipulation of the independent variable did not occur. Should include a minimum of 3 stable data points.High variability is acceptable if intervention effects are unambiguous The procedural characteristics of the baseline conditions should be described operationally Experimental control/internal The design provides at least three demonstrations of experimental effect at different points in time. Effects of validity alternating treatments may be added, as main comparison is not with baseline. AB designs may not be added as they do not demonstrate intervention at different times when comparing to baseline The design controls for earthy threats to internal validity (e. g. , permits elimination of rival hypotheses). pleasurable designs include multiple baseline, ABAB and alternating treatment with counterbalancing.Unacceptable designs include AB, ABA, and changing criterion External validity Social validity Experimental effects are replicated across participants, settings, or materials to establish external validity. At least thre e participants, settings or materials must be unvarnished The dependent variable is socially important death penalty of the independent variable is practical and cost effective (must be measured) Social validity is enhanced by implementation of the independent variable over across-the-board time periods, by typical intervention agents, in typical ph