Abstract
Discrete trial training is a popular teaching method for individuals with autism, but it is not easily implemented with fidelity due to its complexity. This is the first meta-analysis of single-case experimental design studies to quantify the impact of behavioral skills training on individuals’ ability to implement discrete trials with fidelity. Furthermore, this meta-analysis examines the four training methods that make up behavioral skills training—feedback, instruction, modeling, and rehearsal—to determine the “active ingredients” of behavioral skills training. A total of 46 single-case experimental design studies are included in this meta-analysis. Hierarchical linear modeling, which has the ability to analyze clustered data, is the meta-analytic technique used to estimate the effectiveness of behavioral skills training across studies. Results show that behavioral skills training has a statistically significant positive effect on discrete trial training implementation fidelity; therefore, behavior skills training is recommended for discrete trial training implementation instruction.
Keywords
Discrete trial training (DTT) or discrete trial instruction (e.g., Pollard etal., 2014) is a popular evidence-based practice, and it is frequently used when working with children with autism spectrum disorders (Majdalany etal., 2014). Defined as an intensive 1:1 teaching session that is meant to be implemented in a distraction-free environment (Pellecchia etal., 2015), DTT can be applied by mass implementing the teaching trials, interspersing trials with previously mastered skills, or distributing trials with breaks in between trials (Henrickson etal., 2015; Majdalany etal., 2014).
DTT can include various components and steps. The three essential components of DTT, known as the three-term contingency (Skinner, 1953), are the instructor presenting an instruction (i.e., the discriminative stimulus; the instructor says, “Point to the picture of a dog”), waiting for the learner to respond (i.e., the behavioral response; the child points to the picture of a dog), and the instructor providing a consequence (i.e., reinforcing stimulus; the instructor says, “Great job pointing to the picture!”). Examples of other DTT components include, but are not limited to, securing the learner’s attention before beginning the session, establishing a contingent tangible, and presenting the instruction only once. One defining component of DTT is the use of a hierarchy of prompts (e.g., from most to least intrusive) to promote errorless learning (e.g., Severtson & Carr, 2012). More recently, researchers have advocated for the use of a “progressive” version of DTT that encourages individuals to incorporate natural language and flexible prompt fading (Leaf etal., 2016). The DTT evaluation form (Fazzio etal., 2007), which is frequently cited in DTT training literature (e.g., Wightman etal., 2012), lists a total of 21 DTT components for instructors to master, but other trainers may utilize more or less components for a successful DTT session. One reason to have less DTT components, for example, would be to simplify the implementation procedure for certain individuals (e.g., parents, peers, or teaching assistants) who may have less experience using complex interventions. Readers are advised to reference Fazzio et al. (2007) to see an example of the components that can be a part of DTT.
Implementation fidelity of DTT has been directly linked to student success, highlighting the importance of implementing DTT with fidelity when working with students. For example, Jenkins et al. (2015) conducted a parametric analysis of implementation fidelity errors, and they found commission errors to be detrimental for skills acquisition. In another study, by Carroll et al. (2013), children with autism acquired target skills at a slower rate when the DTT was implemented with low fidelity. Therefore, proper training is essential, and even more so when considering the wide range of contexts in which discrete trials are implemented. DTT can be implemented in multiple different settings, such as schools, clinics, university research centers, and at home, and can be implemented by people with various skill sets, such as special education teachers, paraprofessionals, and parents.
Each context in which DTT is implemented presents different challenges and advantages. Implementing interventions in a home setting can be difficult because the parent or caregiver may be required to be home during sessions and there may be lack of oversight from staff regarding the implementation fidelity of the intervention (Leaf etal., 2018). Some challenges of implementing evidence-based practices like DTT in a clinical setting include cost, lack of parental involvement, and the need for more intensive trainings (Leaf etal., 2018). Within a classroom setting, paraprofessionals may be ill-prepared to implement evidence-based practices, such as discrete trials, because they do often do not receive extensive training (Brock & Carter, 2016). It is important that discrete trials can be implemented by different individuals and across contexts because DTT implementation fidelity has been directly linked to learner success; West et al. (2013) found that when evidence-based practices are not delivered properly, students may display limited progress on academic goals. Reed et al. (2013) found DTT to be most effective when implemented consistently and with fidelity. Thus, regardless of the context or individual who is implementing discrete trials, effective trainings are essential so that DTT can be implemented with fidelity and have the greatest possible positive effect on the learner.
Different training methods are used when teaching individuals to implement DTT. These training methods include, but are not limited to, instruction (e.g., Salem etal., 2009), feedback (e.g., McKenney & Bristol, 2015), modeling (Catania etal., 2009), and rehearsal (Arnal etal., 2007). Instruction manuals are sometimes utilized due to their flexibility, cost-effectiveness, and self-guided nature (Thomson etal., 2012), although previous research has found instruction alone to be an ineffective training method (e.g., Ward-Horner & Sturmey, 2012). Feedback, specifically performance feedback, can help to ensure that mistakes made during DTT implementation are corrected. One previously conducted meta-analysis on the effect of performance feedback on teacher treatment integrity found performance feedback to have a moderate effect on an individual’s ability to implement evidence-based practices with fidelity (Solomon etal., 2012). Modeling is a beneficial training method because it allows the individual to see the different components of DTT “in action,” as verbal or written instruction might not convey how each component should be delivered. Modeling also allows for the demonstration of different skills across different contexts (Morgan & Salzberg, 1992), which is useful since DTT can be utilized to teach a range of skills. Rehearsal is a useful training method because it allows the participant to practice more difficult elements of DTT that might not be understood through other types of interventions. For example, certain prompting procedures should be used after the DTT recipient responds incorrectly two times in a row; rehearsal allows for the trainer to engage the participant in these unique situations (Gerencser etal., 2018).
One popular training package is behavioral skills training (BST), which includes the four training methods of feedback, instruction, modeling, and rehearsal delivered together and/or sequentially. BST has been used successfully to teach and maintain accurate implementation fidelity of discrete trials (Lerman etal., 2016) and has been an effective training method for teachers, clinicians, and parents (Day-Watkins etal., 2018). Other research supports the finding of BST to be effective; Sarokoff and Sturmey (2004) found BST to be highly effective in training individuals to use DTT, and Brock and colleagues (2017) found it to be effective for teaching implementation of other educational strategies as well (e.g., reinforcement, prompting, pivotal response training). It is also an effective method for learner acquisition and promotes the generalization of teaching skills in novel situations (Fetherston & Sturmey, 2014).
Several studies have attempted to determine the “active components” of BST. Ward-Horner and Sturmey (2012) and Madzharova et al. (2012) found modeling and feedback to be the most essential components of BST, while LaBrot et al. (2018) found feedback to be the most impactful component. Solomon et al (2012) also found performance feedback to have a moderate effect on an individual’s ability to implement evidence-based practices with fidelity, and Cardinal et al. (2017) found video modeling and feedback to be effective when delivered together. However, as noted by LaBrot et al. (2018), results from the componential analysis are difficult to interpret because instruction is often delivered first, and it thus can be difficult to evaluate the differential impact of the individual components. More research is needed in this area.
Although previous research has investigated the effect of BST and the different training components of BST on evidence-based practices, including DTT implementation fidelity (e.g., Leaf etal., 2019; Shapiro & Kazemi, 2017), these previous studies are qualitative reviews and did not calculate an effect size (i.e., quantifying the effectiveness of BST and the different training components). No known meta-analyses to date have quantitatively examined the impact of BST and the individual training components of BST on individuals’ ability to implement discrete trials with fidelity. Furthermore, previous systematic reviews did not focus on single-case experimental design (SCED) studies; they included both group design studies and single-case experimental design studies. Due to the detailed information that SCEDs provide about participants and the ability for participants to serve as their own controls, it would be beneficial to conduct a meta-analysis that focuses solely on SCEDs. Previous studies also did not examine whether the effects of trainings last across time. Several studies on DTT have sought to determine whether the training effectiveness lasted during a later maintenance phase (Catania etal., 2009; Parnell etal., 2017). It would be helpful to compile these results and conduct one analysis across studies (i.e., meta-analysis) to determine whether the DTT trainings have lasting effects.
Based on the aforementioned research, the research questions for this study are as follows:
Method
The procedures of this meta-analysis were conducted in accordance with recommendations from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Moher etal., 2009). PRISMA provides standards and evidence-based procedures for researchers conducting systematic reviews and/or meta-analyses.
Inclusion and Exclusion Criteria
The search was limited to articles investigating the effectiveness of training(s) to teach DTT implementation fidelity. The training(s) needed to include BST or any of the four components of BST to be eligible. The DTT implementation fidelity needed to be directly observed and measured on a percentage scale (e.g., 0–100) and calculated by determining the total number of steps that were performed correctly by the participant divided by the total possible number of DTT steps. The articles selected for inclusion were limited to those that utilized an SCED. The data needed to be provided in graphical or tabular form to be included in the meta-analysis, and the independent variable needed to be systematically manipulated, as recommended by What Works Clearinghouse (WWC; 2020). Studies needed to show three demonstrations of intervention effectiveness at three different points in time (e.g., a multiple-baseline design with three participants; WWC, 2020). Studies also needed to meet WWC (2020) standards with or without reservations in regard to number of data points per phase (e.g., a reversal design with a minimum of four phases per case and a minimum of three data points in each phase). Studies that included DTT trainings paired with trainings for another teaching method were also not included to eliminate the possibility of the other trainings serving as confounding variables (e.g., Nosik & Williams, 2011). Last, studies that included duplicate data (e.g., dissertations that were later published) were excluded.
Search and Study Selection
The following scientific databases were used to select primary level articles: Education Full Text, PsycINFO, Educational Resources Information Center, and Academic Search Complete. We decided that SCED studies published between 1977 and 2019 would be eligible for inclusion. This start date is the year of the earliest article (Koegel etal., 1977) included in the systematic reviews by Leaf et al. (2019) and Thomson et al. (2009). The keywords used in the scientific databases were “discrete trial” AND “autism,” “discrete trial” AND “instructor,” “discrete trial” AND “staff,” “discrete trial” AND “paraprofessional,” or “discrete trial” AND “parent.”
Search terms were not restricted, could be present in any field (e.g., title, abstract, full text), and included gray literature such as dissertations and theses. Gray literature was included to help address issues of publication bias, as other methods commonly used to address publication bias such as funnel plots and/or robust Egger’s regression are not suitable for SCEDs (Barton etal., 2017).
Two coders independently completed the primary search process. First, they read the title and/or the abstract of all the primary search studies to determine whether the study potentially met the inclusion criteria. If the title indicated that the study was potentially related to teaching discrete trial implementation, the coders read the study abstract as well. After this screening process, any articles that were not related to teaching discrete trial implementation were eliminated. The coders then screened the full text of the remaining articles, and articles were further eliminated if they did not fit the study eligibility criteria. Next, an ancestry search was conducted using the systematic reviews by Leaf et al. (2019), Shapiro and Kazemi (2017), and Thomson et al. (2009) to determine additional studies. The title and abstract of all articles included within the systematic reviews were screened.
Total agreement among the two researchers for articles eligible for full-text review was 95%. Agreement between researchers was 100% for articles that were fully screened and met eligibility criteria. A graphical display of the selection process is displayed in Appendix A in the online supplemental materials.
The data software program WebPlot Digitizer 2.0 (Moeyaert etal., 2016; Rohatgi, 2014) was then used to retrieve raw SCED data from graphs of primary studies retained for inclusion in the meta-analysis.
Coding of Variables
A description of the different variables that were coded for each of the included articles is provided in the next section. Each variable was operationally defined so that the variables would be reliably coded by the researchers. These variables were used in inferential analyses.
Behavioral skills training. BST occurred when instruction, modeling, rehearsal, and feedback were implemented simultaneously or sequentially during the training.
Feedback. For the purpose of this study, the definition of feedback was limited to performance feedback. When a participant performed DTT and received information from an observer regarding the quality and/or accuracy of their DTT implementation, this was considered feedback. Feedback from the result of quizzes or tests (sometimes included as part of instruction) was excluded from this definition (e.g., Thiessen etal., 2009).
Instruction. This was defined as any form of information about implementing DTT that was given verbally, digitally, or in print form.
Modeling. Modeling was defined as any demonstration of DTT implementation by another person that occurred in real life or video recording (e.g., Catania etal., 2009).
Rehearsal. This was defined as structured role-play of DTT implementation that occurred with another person in the presence of a trainer. Rehearsal did not include instances where the participant independently practiced the skill or practiced the skill with an imaginary person (e.g., Thomson etal., 2012). Rehearsal could occur during data collection in the intervention phase if participants delivered DTT to a trainer role-playing a child (e.g., Higbee etal., 2016).
All of the aforementioned variables were dummy coded: 0 if the variable was not present and 1 if the variable was present.
Implementation fidelity. This was defined as the percentage of DTT steps implemented correctly. For example, if there were 10 DTT components identified in the study, and the participant completed eight of the 10 components correctly, the participant scores 80% implementation fidelity for that session.
Maintenance session: Maintenance was coded for each individual observation. Maintenance phases were any sessions that took place at least 1 day after the training had ended. If a maintenance phase occurred, it was recorded in number of days after the last intervention phase.
Six other variables were also coded for this study, including the participant’s experience implementing DTT, the number of discrete trial steps included for measuring the dependent variable implementation fidelity, and if the participant practiced with a child or a confederate (adult acting as a child). The definitions of these other variables can be found in Appendix B in the online supplemental materials.
Interobserver Agreement
Interobserver agreement (IOA) was calculated for a subset of studies (30%). For this subset, each of the variables was double coded by the first author of this study and another doctoral student with past experience implementing DTT. The agreement among coders was divided by the total number of agreements plus disagreements. This was calculated for each individual variable. The total IOA for variables coded across observations, participants, and studies was 100%. A detailed version of the IOA for each individual variable is available upon request.
Risk of Bias
Risk of bias for individual studies was evaluated by the first author of this study. The domains that were evaluated for each study can be found in Appendix C in the online supplemental materials, and they are adapted from the risk of bias tool for single-case design studies (Reichow etal., 2018). This quality appraisal tool was chosen for use as it was based upon the Cochrane Risk of Bias tool, with additional SCED-specific considerations (Reichow etal., 2018). This tool is also more comprehensive than other tools available for use, such as the Single-Case Analysis and Review Framework (SCARF; Ledford etal., 2016). Using the nine domains and definitions of low, high, and unclear risk of bias provided by Reichow et al. (2018), each study was evaluated and rated as having either a low, high, or unclear risk of bias. The same second coder who conducted IOA also evaluated the risk of bias for each study, and the inter-rater reliability was 100%.
Analysis
Hierarchical linear modeling (HLM) is a meta-analytic method that can be used for the quantitative integration of primary level effect sizes. HLM has several benefits that make it a desirable analysis technique for single-case design meta-analyses. HLM is able to analyze clustered data, or observations within participants and participants within studies (Van den Noortgate & Onghena, 2003). The effect sizes are allowed to vary across participants and studies. The HLM method allows investigating the effectiveness of an intervention for multiple participants and studies using one analytic model.
Analysis Models
DTT implementation fidelity score (DTTIAijk) is the dependent variable and represents the outcome score on measurement occasion i for participant j being part of study k. The variable “Moderator” represents the moderating variable (BST or one of the individual training components). Phaseijk is a dummy-coded independent variable. This variable indicates whether observation i nested within participant j belonging to study k is part of the baseline (i.e., Phaseijk = 0) or treatment phase (i.e., Phaseijk = 1). Timecijk was centered around the last training session of the treatment phase, that is, the last observation during the intervention phase was coded as 0, with previous observations coded in descending order and any following observations in ascending order. This was necessary to evaluate the effectiveness of BST and the individual training sessions at the end of the training (i.e., during the last observation data point during the training phase). The analysis model is introduced in Equation 1.
Level 1:
In this equation, β0jk indicates the baseline level for participant j nested within study k, and β1jk indicates the difference between the baseline level and the last data point of the intervention phase for participant j nested within study k. β2jk indicates whether the intervention effect differs across the different levels of the moderator variable. β3jk indicates the slope during the treatment phase for participant j within study k. β4jk indicates the change in slope between the treatment phase and maintenance phase for participant j within study k. In this equation, ∅ refers to the lag 1 autocorrelation, while eijk refers to the residuals, which are assumed to be identical and normally distributed. Autocorrelation is when observation points close to each other are more similar than observations that are further apart (Shadish & Sullivan, 2011). Lag 1 autocorrelation was added to the model because accounting for autocorrelation can help increase the control of type I error rate control, as well as improve the model’s statistical power (Heyvaert etal., 2017)
Four different models were specified using Equation 1. Model 1 included the moderator BST, Model 2 included the moderator modeling, and Model 3 included the moderator rehearsal. Due to the large number of studies that included instruction in either the baseline or intervention phase (n = 44, 96%), instruction was unable to be isolated as a variable to determine the impact of this training component. Furthermore, too few studies included feedback as a training component separate from BST (n = 5, 11%), and so this training component could not be isolated and included in a separate analysis model. Equation 1 was also used without any moderators to find the overall effect across all training types, and this is referred to as Model 4. These four models used the same data set, so Bonferroni correction was used to control type I error rates (∝ = .05/4 = .0125).
The participant-specific parameters in Equation 1 were allowed to vary between participants, as it is unrealistic to assume that all participants and all studies would have the same parameter estimates. In the Level 2 equation introduced next, the case-specific population parameters from Equation 1 are allowed to vary around a study-specific parameter.
Level 2:
In Equation 2, θ00k indicates the mean baseline level across participants in study k. θ10k indicates the difference between the baseline level and the last data point of the intervention phase across participants in study k. θ20k indicates the effect of the moderator on the intervention effectiveness. θ30k indicates the mean trend during the intervention phase across participants in study k. Furthermore, u0jk, u1jk, u2jk, and u3jk indicate how participant j from study k deviates from the study-specific baseline level, intervention effect, moderator effect, and time trend, respectively, during the intervention. The deviations are assumed to be multivariate normally distributed.
The study-specific parameters were allowed to vary between studies (see Equation 3).
Level 3:
In Equation 3, ϕ000 indicates the mean baseline level across participants and across studies. ϕ100 indicates the difference between the baseline level and the last data point of the intervention phase across participants and across studies. ϕ200 indicates the effect of the moderator on the intervention effectiveness across participants and studies, and ϕ300 indicates the trend in the intervention phase across participants and studies. v0jk, v1jk, v2jk, and v3jk indicate the deviation of study k from the mean baseline level, treatment level, moderator effect, and intervention trend, respectively. The deviations are assumed to be multivariate normally distributed. Meta-analysts are mainly interested in the coefficient estimates across studies, and so this is what is reported in the Results section, as answers to the research questions.
Study-specific effect sizes were also calculated. The effect sizes reflect the changes in level (change between baseline level and last observation of the intervention phase). This gives an idea about the variability in study-specific intervention effects. All the analyses were performed using the statistical software program RStudio (RStudio Team, 2015).
Results
Study Selection
The database search resulted in the identification of 3,394 articles, with 3,332 articles remaining after removing duplicates. After screening the title and abstracts of the latter, 86 articles remained eligible for full-text screening. After screening the full text of the 86 remaining articles, we eliminated articles if they did not fit the study eligibility criteria. After the full-text screening of the articles yielded from the database search, the ancestry search yielded a total of 92 additional articles, and two remained after duplicates were removed. By the end of the full-text screening of articles from the database search and the ancestry search, 43 articles remained eligible for inclusion. Finally, because some articles included more than one study, a total of 46 studies were included in the meta-analysis. A flowchart detailing the study selection procedure can be seen in Appendix A in the online supplemental materials.
Descriptive Statistics
The number of participants across all 46 studies was 224. A total of 130 (58%) participants received BST as their training. Detailed information regarding the variables and specific primary-level study characteristics can be found in Appendix D in the online supplemental materials, including the number of participants and participant type, the training(s) they received, and the criteria used within the study to determine if mastery of DTT implementation was reached. Table 1 demonstrates the combination of trainings found across studies and participants. A total of 51 participants (23%) participated in a maintenance phase. The maintenance phase occurred anywhere between 4 and 224 days after the last intervention session.
Training Combinations Across Single-Case Experimental Design Studies and Participants.
Risk of Bias
Risk of bias results can be found in Appendix C in the online supplemental materials. The studies included in this meta-analysis were mixed in terms of the category sequence generation. The majority of studies (n = 23, 53%) had unclear risk of bias for this category; many studies utilized a multiple-baseline design with staggered start points but did not specify how these start points were determined. Concerning the category of participant selection, clear inclusion criteria were used for 10 (23%) studies, indicating low risk of bias. There was an unclear risk of bias for the category of participant selection for 24 (56%) studies and high risk of bias for nine (21%) studies. In regard to blinding participants and personnel, only one study (Serna etal., 2016) explicitly stated that the participants were blind to the hypothesis during both the baseline and intervention phases, indicating a low risk of bias. For the category concerning procedural fidelity, 17 studies (40%) had a low risk of bias, and 24 studies (56%) had a high risk of bias, as they did not report procedural fidelity. As for the category of blinding outcome assessors, only two studies explicitly stated that the raters were naïve to the study hypothesis. Twenty-four studies (56%) had high risk of bias for this category for reasons such as the first author also recorded the data (e.g., Fazzio etal., 2009). For the category selective outcome reporting, most studies had a low risk of bias (n = 35, 81%), as they did not have missing data. For dependent variable reliability, all studies except one (O’Guin, 2010) had a low risk of bias. For the category data sampling, 15 studies (35%) had a low risk of bias, while 28 studies (65%) had an unclear risk of bias. Other possible risks of bias are reported in Appendix C.
Inferential Statistics
The effect size of the 46 individual studies can be seen in the forest plot in Appendix E in the online supplemental materials, which was created with the package metaphor (Viechtbauer, 2010) in RStudio (RStudio Team, 2015). This forest plot shows the intervention effect for each study along with a 95% confidence interval. The magnitude of the intervention effect varies between studies, and so HLM can offer more insights into the results as this analytical technique is able to separate within-case, between-case, and between-study variance.
The baseline level was consistent across all models and was estimated to be 40.61%, γ̂000 = 40.61, t(3400) = 16.76, p < .0125. This indicates that before the intervention phase, participants were implementing DTT with 40.61% accuracy, which is considered to be low (see Appendix D in the online supplemental materials for mastery criteria). The mean change in DTT implementation fidelity between the baseline phase and the intervention phase at the last point of the intervention was estimated to be 49.97%, γ̂100 = 49.97, t(3693) = 18.25, p < .0125. This was evaluated using Model 4, and it indicates that at the end of the trainings, the average participant was able to implement DTT with 90.58% accuracy. Previous studies (e.g., Gerencser etal., 2018; Nosik etal., 2013) used a criterion of 90% DTT implementation accuracy as a threshold for mastery of implementing DTT (see Appendix D in the online supplemental materials). Therefore, it can be concluded that overall, individuals can be trained to implement DTT with fidelity. An overall positive trend was detected during the intervention phase, γ̂200 = 1.33, t(3693) = 5.26, p < .001, indicating that with each additional observation, participants’ DTT implementation accuracy increased by 1.33.
RQ1
Model 1 was used to determine whether BST is more effective than trainings that utilize BST components (i.e., studies with only one, two, or three BST components). Results showed that the moderation effect of BST was 12.69%, γ̂200 = 12.69, t(3692) = 10.69, p < .0125. Participants who received BST had an average estimated DTT implementation score of 96.06%, demonstrating that participants who received BST were statistically significantly more likely to have a higher DTT implementation score than those who did not receive BST (i.e., received only one, two, or three training components).
RQ2
Models 2 and 3 were used to determine whether modeling and rehearsal are effective training components. For Model 2 (modeling as the moderator), the moderation effect of modeling was 1.35%, γ̂200 = 1.35, t(3692) = 0.91, p =.36. Participants who received modeling had an average DTT implementation score of 90.59%. This was not statistically significant, meaning that there is no difference in DTT implementation average for those who did and did not receive modeling as an intervention. For Model 3 (rehearsal as the moderator), the moderation effect of rehearsal was −1.79%, γ̂200 = −1.79, t(3692) = −0.99, p =.32. Those who had rehearsal during the training implemented DTT with an average of 88.28% fidelity.
Participants who rehearsed during the training phase were not statistically significantly more likely to have a higher DTT implementation fidelity score than those who did not engage in rehearsal.
RQ3
Model 1 was used to determine whether the effects of training last across time. The change in rate between the slope of the intervention phase and the slope of the maintenance phase was −4.39, γ̂200 = −4.39, t(3399) = −2.86, p < .025. This indicates that there was a statistically significant difference between the intervention phase and maintenance slope. Participants had a slight decline in implementation fidelity after the intervention was finished.
Discussion
This meta-analysis attempts to address gaps in previous research regarding training methods’ effectiveness for teaching participants how to use DTT. This is the first meta-analysis to the authors’ knowledge that analyzed DTT training methods only while also estimating effect sizes and taking hierarchical structured data complexity into account by using an HLM technique. The aim of this study was to see if BST, which was previously demonstrated as an effective training for DTT (e.g., Sarokoff & Sturmey, 2004) would prove to be effective, as well as any of the four training components of BST (i.e., feedback, instruction, modeling, and rehearsal).
Through HLM analysis, it was affirmed that individuals can be trained to implement DTT with fidelity. Individuals implemented DTT with low levels of accuracy (40.61%) before receiving a training. Participants could likely implement DTT with low levels of accuracy since 61% of participants received instruction during baseline. After receiving a training, individuals were able to implement DTT with over 90% accuracy. As all studies had a criteria of at least 80% implementation fidelity as indicating mastery (59% of studies included in this meta-analysis set mastery at 90% or above), it can be concluded that, on average, individuals who undergo training are able to effectively implement DTT afterward. The statistically significant time trend (γ̂200 = 1.33) likely reflects the impact of the different training types that were implemented during or between the observations in the intervention phase. For example, feedback was sometimes delivered between observations (e.g., Higbee etal., 2016); this may explain the finding that implementation fidelity increases with more observations.
When feedback, instruction, modeling, and rehearsal are implemented together (BST), they are statistically significantly effective. BST is demonstrated to be largely effective, as participants who received BST implemented DTT with 96.06% fidelity, on average. This finding is in line with findings from Brock et al. (2017), Sarokoff and Sturmey (2004), Lerman et al. (2016), and others who have demonstrated that BST is an effective training method for teaching practices. The results from this meta-analysis serve as supporting evidence that training methods that utilize BST are effective and recommended for use. Furthermore, most participants in the study (69%) had no prior experience implementing discrete trials before the training, demonstrating that BST is effective even for those with no previous experience.
The variables of modeling and rehearsal were analyzed separately to determine whether either of these training components was more effective than others. It is possible that this meta-analysis did not find modeling or rehearsal to be a statistically significantly impactful training component because these training methods were not often implemented with other methods that are historically known to work well together (e.g., feedback with modeling; Madzharova etal., 2012; Ward-Horner & Sturmey, 2012). When modeling was utilized as a training, it was used alone or with only one other training component 40% of the time, and only delivered together with feedback in one study. Similarly, rehearsal was implemented exclusively with instruction 55% of the time it was utilized; it is possible that for rehearsal to be demonstrated as an effective component, it needs to be delivered with a different training method besides instruction, like feedback.
Results demonstrate that after completing the training, DTT implementation skills drop slightly with time (−4.74). However, when accounting for outliers (n = 14), there does not appear to be a difference in DTT implementation fidelity during maintenance phases (e.g., 30 days later). Outliers were calculated by determining the interquartile range, multiplying the interquartile range by 1.5, and then adding this obtained number to the third quartile, while subtracting this number from the first quartile. Any number greater or less than this respective number was marked as an outlier. These results indicate that providing DTT implementers with summary guidelines or instructional checklists could help counter a potential drop in DTT ability with time.
The risk of bias results have implications regarding the quality of single-case design research. For example, only 17 of the 46 studies reported procedural fidelity of 80% or higher across at least 20% of the DTT sessions. Similarly, many of the studies (n = 24) included scorers who were not naïve to the study hypotheses. These results show areas that are in need of improvement within the general field of single-case design. Researchers who conduct single-case design studies are encouraged to reference the risk of bias domains as outlined by Reichow et al. (2018) so that they can conduct high-quality studies with low risk of bias across the different domains. Some of the Reichow et al. (2018) definitions are open to interpretation (e.g., the definition for data sampling bias). “Adequate number of data points” was interpreted to mean five data points, as the WWC (2020) document stated that five data points are needed to meet the standards without reservation. If instead three data points per phase are considered adequate, the number of studies with low risk of bias for data sampling increases from 17 (40%) to 45 (98%) studies. Researchers who use these risk of bias domains are encouraged to make clear their interpretations of ambiguous definitions (see note at bottom of Appendix C in the online supplemental materials for more details).
Limitations and Future Implications
This meta-analysis presents several limitations as well as implications for the direction of future research. Although HLM was determined to be the best approach for this data set due to the research questions and nesting characteristics, HLM has potential limitations, for example, distributional assumptions (e.g., assumption of homogeneous residuals). Nevertheless, future research is encouraged to use HLM as an analytical technique for meta-analyses due to its ability to consider the nesting of data (i.e., observations within cases and cases within studies). This is an important feature of HLM, since ignoring the natural hierarchy of data can lead to an underestimate of the standard error and an increase in Type I errors.
Several variables are important for consideration when determining the effectiveness of an intervention that could not be isolated and statistically analyzed. For example, the location of the training may impact the effectiveness of the training; most of the trainings were conducted at school (46%), university (28%), or private facility (14%). Due to the challenges that can occur when teaching at home (e.g., lack of oversight, issues related to generalization of skills Leaf etal., 2018]), more research is needed to determine if BST is effective for teaching DTT in a home environment. Relatedly, only 13% of participants in the study were parents; future research is needed to determine the effectiveness of BST to effectively teach parents, who may have less experience implementing evidence-based practices with fidelity. The variable “instruction” could not be analyzed in isolation due to its high prevalence in the studies (n = 44, 96%). Furthermore, instruction was frequently used by participants during the baseline phase (n = 126, 56%). Studies that had instruction during baseline were included because eliminating these studies would mean eliminating many studies from the analyses (n = 28, 61%). However, future research should examine the effectiveness of instruction alone and determine the extent to which this impacts DTT. This meta-analysis was also unable to isolate the variable feedback due to the small percentage of studies including this as a training component separate from BST (n = 5, 11%). It is, therefore, difficult to know the impact of these training methods in isolation on DTT implementation fidelity, and researchers in the future should continue to conduct research to determine the impact of these methods.
This meta-analysis did not look at student outcomes, as this information was not consistently provided in the primary studies. Although past research has demonstrated that student ability is correlated with DTT implementation fidelity (Carroll etal., 2013), it would be helpful for future research to examine the relationship between best practices and student outcomes.
Conclusion
As DTT is a frequently utilized training method for individuals with autism spectrum disorders, it is important to evaluate whether people are indeed being successfully trained to use these methods with fidelity. The purpose of this meta-analysis was to offer more insight into what makes an effective training for DTT. It supports previous research demonstrating the success of BST as a training method. An innovative and highly recommended technique, HLM, was utilized as it considers natural hierarchical data. As researchers continue to examine best practices in the future, more will be known about how to create the best trainings for different people and scenarios.
Supplemental Material
sj-docx-2-foa-10.1177_10883576221081076 – Supplemental material for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis
Supplemental material, sj-docx-2-foa-10.1177_10883576221081076 for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis by Joelle Fingerhut and Mariola Moeyaert in Focus on Autism and Other Developmental Disabilities
Supplemental Material
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Supplemental material, sj-pdf-3-foa-10.1177_10883576221081076 for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis by Joelle Fingerhut and Mariola Moeyaert in Focus on Autism and Other Developmental Disabilities
Supplemental Material
sj-pdf-4-foa-10.1177_10883576221081076 – Supplemental material for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis
Supplemental material, sj-pdf-4-foa-10.1177_10883576221081076 for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis by Joelle Fingerhut and Mariola Moeyaert in Focus on Autism and Other Developmental Disabilities
Supplemental Material
sj-pdf-5-foa-10.1177_10883576221081076 – Supplemental material for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis
Supplemental material, sj-pdf-5-foa-10.1177_10883576221081076 for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis by Joelle Fingerhut and Mariola Moeyaert in Focus on Autism and Other Developmental Disabilities
Supplemental Material
sj-tif-1-foa-10.1177_10883576221081076 – Supplemental material for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis
Supplemental material, sj-tif-1-foa-10.1177_10883576221081076 for Training Individuals to Implement Discrete Trials with Fidelity: A Meta-Analysis by Joelle Fingerhut and Mariola Moeyaert in Focus on Autism and Other Developmental Disabilities
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
This research was supported by the Institute of Education Sciences, U.S. Department of Education, through grant R305D190022. The content is solely the responsibility of the author and does not necessarily represent the official views of the Institute of Education Sciences, or the U.S. Department of Education.
Supplemental Material
Supplemental material is available on the Focus on Autism and Other Developmental Disabilities webpage with the online version of the article.
References
Supplementary Material
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