Caregiver-Implemented Communication Interventions for Children Identified as Having Language Impairment 0 Through 48 Months of Age: A Scoping Review

Abstract

Purpose:

Caregiver-implemented interventions are frequently used to support the early communication of young children with language impairment. Although there are numerous studies and meta-analyses supporting their use, there is a need to better understand the intervention approaches and identify potential gaps in the research base. With that premise, we conducted a scoping review to synthesize existing data with an end goal of informing future research directions.

Method:

We identified relevant studies by comprehensively searching four databases. After deduplication, we screened 5,703 studies. We required included studies (N = 59) to evaluate caregiver-implemented communication interventions and include at least one caregiver communication outcome measure. We extracted information related to the (a) study, child, and caregiver characteristics; (b) intervention components (e.g., strategies taught, delivery method and format, and dosage); and (c) caregiver and child outcome measures (e.g., type, quality, and level of evidence).

Results:

We synthesized results by age group of the child participants. There were no studies with children in the prenatal through 11-month-old age range identified in our review that yielded a caregiver language outcome measure with promising or compelling evidence. For the 12- through 23-month group, there were seven studies, which included eight communication intervention groups; for the 24- through 35-month group, there were 21 studies, which included 26 intervention groups; and for the 36- through 48-month group, there were 21 studies, which included 23 intervention groups. Across studies and age groups, there was considerable variability in the reporting of study characteristics, intervention approaches, and outcome measures.

Conclusion:

Our scoping review highlights important research gaps and inconsistencies in study reporting that should be addressed in future investigations.

Supplemental Material:

https://doi.org/10.23641/asha.20289195

Communication development is critical for later academic, social, and vocational success (Hoff, 2013; Morreale et al., 2017; Roulstone et al., 2011). However, communication impairments impact between 6 and 8 million people in the United States alone (National Institute on Deafness and Other Communication Disorders [NIDCD], 2016). To reduce this impact and promote positive outcomes for young children who demonstrate communication delays and disorders, the receipt of early intervention aimed at facilitating and strengthening communication skills is critical (e.g., Justice et al., 2009; Rescorla, 2009). Toward that end, intervention approaches that teach caregivers ¹ to implement strategies that target and enhance their everyday communication interactions with their child experiencing communication delays and disabilities are empirically supported (e.g., Heidlage et al., 2020; Roberts & Kaiser, 2011).

Rationale and Evidence Base for Caregiver-Implemented Communication Interventions

Caregiver-implemented communication interventions can support a wide range of skills central to a child's development. Communication reflects the process of sharing information and may be characterized as language-based (i.e., linguistic; e.g., use of conventional signs, words, and syntax) or social (i.e., nonlinguistic; e.g., use of gestures, vocalizations, eye gaze, and appropriate turn taking in both receptive and expressive domains). Thus, focus on caregiver-implemented communication interventions is important for several reasons. First, this approach is consistent with theoretical and empirical knowledge that communication is learned within the context of social interactions and is transactional, with important roles for the child and the caregiver, such as contingent responses from the caregiver (e.g., Dunst et al., 1989; Ford et al., 2020; Sameroff, 2009). Second, embedding intervention within children's routine interactions with their caregivers is logical, effective, and efficient given that these interactions frequently occur and children are often motivated to regularly engage with their caregivers (e.g., Heidlage et al., 2020; Schreibman et al., 2015). Third, these interventions can be further used in ways that align with the child's and caregiver's cultural, ethnic, social, and developmental assets, a necessary component of broad scale implementation within an increasingly diverse society (National Association for the Education of Young Children [NAEYC], 2020).

Meta-analyses are useful to evaluate overall effects of caregiver-implemented interventions across studies. Results of several meta-analyses and reviews provide rich support for teaching caregivers strategies to promote early development broadly (e.g., Jeong et al., 2021) as well as specific strategies to enhance the language skills of young children with delays and disabilities (e.g., Heidlage et al., 2020; Law et al., 2004; Roberts & Kaiser, 2011; Roberts et al., 2019). These meta-analyses demonstrate that caregiver-implemented interventions positively impact early child social communication and language skills, particularly expressive language, of children who are at risk or who have communication impairment (Barton & Fettig, 2013; Heidlage et al., 2020; Roberts & Kaiser, 2011; Roberts et al., 2019). Additionally, results indicate that communication outcomes do not differ when the intervention is implemented by trained parents or clinicians (Fuller & Kaiser, 2020; Law et al., 2004), and there is some indication that for children on the autism spectrum, interventions that include both parents and clinicians may be most beneficial (Hampton & Kaiser, 2016).

Need for More Information About Caregiver-Implemented Communication Interventions

Across meta-analyses and reviews focused on caregiver-implemented communication interventions, there is great variability in populations represented in the studies included (e.g., age and disability), the specific interventions evaluated, and the caregiver and child outcome measures. For example, the Roberts and Kaiser (2011) meta-analysis included 18 experimental studies published between 1988 and 2010 with parent-implemented interventions targeting child communication (excluding dialogic reading) for children between 18 and 60 months of age with any type of language impairment. Studies had to include at least one type of child language measure. The Barton and Fettig (2013) review included 24 studies with experimental designs published between 1972 and 2012 in nine selected peer-reviewed journals. Their inclusion criteria specified a focus on a parent-implemented intervention for children with disabilities 8 years of age or younger, with child outcomes that could include language, play, or a reduction in challenging behaviors. Hampton and Kaiser (2016) included 26 studies published between 1980 and 2014 with children on the autism spectrum under the age of 8 years. Studies were required to include spoken language outcome measures. Roberts et al. (2019) included 76 studies published between 1988 and 2019 with children under the age 6 years for whom parents served as the primary interventionist with parent and/or child outcome measures. Studies were excluded if the comparison group received treatment. The Heidlage et al. (2020) meta-analysis included 25 randomized control trials (RCTs) of parent-implemented interventions published between 1992 and 2015 for children 0–8 years of age. Child language outcomes were based on parent reports, standardized direct assessments, and observations.

Because a typical goal of a meta-analysis is to address a specific clinical question for a particular population and necessitate rigorous study designs, they can be narrow in scope (Gurevitch et al., 2018). In contrast, the goal of a scoping review is to better understand the nature and extent of a research base to help motivate a more rigorous review, such as a systematic review (Grant & Booth, 2009). Systematic reviews typically aim to determine what is known in a particular area and provide recommendations for future research (Grant & Booth, 2009). Given that there is a strong clinical research base supporting the use of caregiver-implemented communication interventions for young children with communication delays and disabilities (i.e., meta-analyses described above), it is now important to identify any gaps in this base. Addressing these gaps is critical to ensure that the research base is robust and applicable to as many populations as possible. A scoping review is thus a logical next step for the field to summarize critical components of caregiver-implemented communication interventions, such as populations represented, features of the intervention (e.g., intervention provider, language, location, dosage, strategies, and context), and outcomes targeted.

Purpose and Research Questions

The purpose of the current scoping review was to better understand the extent, range, and nature of research focused on caregiver-implemented communication interventions. We aimed to identify research gaps in the existing literature to motivate further, empirically driven research on caregiver-implemented communication interventions to expand the evidence base (Arksey & O'Malley, 2005). At the time that we preregistered our scoping review (May 2019), there were no other known studies that shared our review objectives. Since that time, the Bridging the Word Gap Research Network (BWGRN; Carta et al., 2014) has published a series of reviews (see the works of Greenwood et al., 2020; Haring Biel et al., 2020; Larson et al., 2020; Mahoney et al., 2020; Walker et al., 2020) with some overlap in scope with this study.

There are, however, several distinct differences between the studies. First, the BWGRN literature base included studies with children birth to 5 years of age, and preschool- and kindergarten-aged; whereas, we limited our review to only include studies of children 0 through 48 months of age who have not yet received formal schooling. We did this with recognition that caregiver-implemented communication intervention approaches are likely to differ considerably for infants, toddlers, and preschoolers compared with older children who are entering more formal education prekindergarten and kindergarten programs and likely to have different communication and language goals. Second, related to this focus, the BWGRN literature base included studies for which caregivers and/or classroom teachers were taught to implement interventions; we limited our studies to only those for which primary caregivers were taught the interventions. None of the BWGRN reviews have focused exclusively on early language interventions implemented by primary caregivers of children with language impairment. As such, although the breadth of our scoping review was wide, we limited our study questions in the current review to

1. What populations have been represented in research focused on caregiver-implemented communication interventions for children with language impairment in terms of child and caregiver characteristics?

2. How have intervention components of caregiver-implemented communication interventions been represented in the research? The components of interest included the (a) person delivering the intervention, (b) language used to deliver the intervention, (c) location, (d) intervention dosage, (e) delivery format (e.g., group and one-on-one) and method (e.g., in-person and telehealth), (f) instructional methods, (g) strategies taught to caregivers, and (h) targeted contexts (e.g., play routines).

3. What caregiver and child outcome measures have been used to evaluate caregiver-implemented communication interventions for children with communication impairment?

Method

Protocol and Registration

Our method is primarily based on the scoping review framework laid out by Arksey and O'Malley (2005), incorporating some recommendations of Levac et al. (2010), and reported in accordance with PRISMA-ScR (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews; Tricco et al., 2018). Supplemental Material S1 includes the PRISMA-ScR Checklist. Our protocol was drafted using the Preferred Reporting Items for Systematic reviews and Meta-Analyses Protocols (PRISMA-P) and registered prospectively with the Open Science Framework (OSF) on May 23, 2019. The protocol (https://osf.io/sbx6k) and affiliated project are available without embargo and discoverable within OSF Registries. In preparation for this review, we searched for existing registered protocols on similar topics in the Campbell Collaboration, Cochrane Collaboration, and Prospero registries.

Eligibility Criteria

We included studies in peer-reviewed journal articles (published or in press), which evaluated interventions targeting caregivers with the aim of improving child communication development. Caregiver was defined as parents or other family primary caregivers, as well as foster parents, but not professional service providers such as therapists, teachers, or day care providers. To be included in the current review, the study population must have included caregivers of children identified as having a language or communication impairment 0 through 48 months of age. This cutoff age was selected to help focus the review on caregiver-implemented communication interventions delivered prior to formal school opportunities (e.g., kindergarten) and which target communication skills relevant to a more restricted age range. Because the immediate goal of caregiver-implemented interventions is to modify caregiver behaviors, to be included in the review, the study must have included at least one caregiver communication outcome measure. We did not restrict by date or location of the study; however, results needed to be reported in English. Although, as part of a larger project, we included case studies, single-case designed studies, group quasi-experimental, or experimental designed studies, the current review was limited to group studies to allow for more consistent data synthesis and reliable interpretation. We also limited the present review to studies that included at least one group receiving a caregiver-implemented communication intervention who were identified as children with language impairment (e.g., developmental language disorder) or a condition closely associated with language or communication impairment (e.g., autism ² and Down syndrome). Our inclusion/exclusion criteria are detailed in Table 1.

Table 1.

Study inclusion and exclusion criteria related to the publication, child, and caregiver.

Criteria	Inclusion criteria description	Exclusion criteria description
Study a
Type	Peer reviewed; published or in press	Gray literature
Language	Conducted in any language; reported in English	Studies not reported in English
Design	Group experimental and/or quasi-experimental designs	SCED, case studies, reviews, meta-analyses
Child
Age	Children with a mean age or estimated mean < 48 months for which the age was reported/obtainable for all children	Children aged 48 months and older or unable to determine mean age or age range
Language or communication status	Children identified as having a language or communication impairment (e.g., DLD) or condition closely associated with language or communication impairment (autism, DS)	Typically developing children or children identified at risk for language of communication impairment (e.g., DHH, sibling of a child with autism)
Caregiver
Target group designation	Intervention target group was individuals who were primary caregivers (e.g., parent, foster parent, and relatives) of child participants, with no restriction on age If a parent education component was included in addition to a nonprimary caregiver group, the study was included	Intervention target group was nonprimary caregiver (e.g., teachers, childcare provider, service providers, and researchers) No caregiver training component
Communicative behavior as focus of intervention and measurement	Study targeted and included measurement of at least one caregiver verbal or nonverbal communicative behavior (e.g., words per minute, responsiveness, and diversity of words) Data came from self-report, behavior coding, SALT, LENA, etc.	No measure of caregiver communicative behavior Exclusion criteria added after beginning to read abstracts: Drugs as intervention Crying as sole reason for intervention

Note.  SCED = single-case experimental design; DLD = developmental language disorder; DS = Down syndrome; DHH = Deaf and hard of hearing; SALT = Systematic Analysis of Language Transcripts; LENA = Language ENvironment Analysis.

^a We had no restriction on publication date or study setting.

Information Sources

We used our inclusion criteria to develop customized search strategies in four databases selected for their coverage of relevant literature. Medline (Ovid), APA PsycInfo (Ovid), and Linguistics & Language Behavior Abstracts (ProQuest) offer complementary disciplinary scope, while including Scopus helped to ensure inclusion of studies, which might otherwise be missed. The searches were designed and conducted by social science librarians with assistance from health science librarian colleagues. The full, reproducible strategy for each database is available in Supplemental Material S2. We conducted the initial searches in May 2019 and then updated the searches in August 2020 and November 2021. The searches in the four databases produced 9,716 results. After we removed duplicates, 5,703 studies remained.

Selection of Sources of Evidence

We imported returned studies into Covidence (Covidence, Veritas Health Innovation, Melbourne, Australia; covidence.org), a software tool for facilitating synthesizing reviews and automatically deduplicating records. Prior to the title and abstract screening and full-text screening, the screeners were calibrated by screening the same 15 publications independently and then discussing disagreements. During calibration, we refined our inclusion/exclusion criteria to increase reliability. When this step was complete, two research team members independently screened the rest of the publication titles and abstracts using the inclusion/exclusion criteria (see Table 1), with disagreements resolved by consensus. We then retrieved the full text for publications that passed this screening level. Next, two research team members independently screened full texts, with disagreements again resolved by consensus. Figure 1 summarizes the flow of information through the retrieval and screening stages.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart.

Data Extracting/Charting Process

We developed surveys in Qualtrics (Qualtrics; qualtrics.com), a web-based survey development tool, to extract our data. We tested several survey versions, refining the survey after each test, to ensure that we could reliably extract the necessary data. After several trials, we determined that it was most efficient and reliable to have two researchers extract from each publication in tandem. This approach allowed the researchers to discuss any discrepancies immediately and avoid differences in data extraction that may have cascading effects. For example, if one researcher failed to identify a relevant group, they would also not report on the group characteristics. For each study, thus, two members of our team opened separate Qualtrics surveys on their own computer. Each independently completed each page of the survey. As they finished each page, they compared responses before proceeding to the next page. A total of five researchers extracted the data. Data extracted included information regarding participant demographics, intervention characteristics and type of outcomes measured. Table 2 lists the data extracted from each publication.

Table 2.

Data extracted from studies by domain.

Extraction domain	Data extracted
Study characteristics	Year of publication Country in which study took place Study design: (a) RCT, (b) non-RCT, or (c) single group
Caregiver characteristics	Relationship to the child Age Gender Race Special characteristics (e.g., low income and identified disability)
Child characteristics	Age Gender Race Special characteristics (e.g., diagnosed as being on the autism spectrum)
Intervention characteristics	Person delivering the intervention Language used to deliver the intervention Location (e.g., home, clinic, and university setting) Dosage (i.e., number of sessions, length of session, and duration of intervention) Delivery method (e.g., in-person and telehealth) Delivery format (e.g., group and one-on-one) Instructional methods (e.g., information and live feedback) Strategies taught (e.g., models, expansions, and following the child's lead) and information provided to caregivers Specific context (e.g., play routines and shared book reading)
Caregiver communication outcomes	Outcome name Measurement context (e.g., caregiver–child interaction) Communication domain: Nonverbal: Communicative behaviors that do not involve speech (e.g., gestures) Spoken language input: Communicative behavior involving verbal language (e.g., MLU and adult word count) Global: Captured the overall language environment (e.g., HOME) Interactional: Communication behaviors that are contingent on child communicative acts (e.g., conversational turns and responsivity) Maintenance and/or generalization outcome, if applicable
Child communication outcomes	Outcome name Measurement context (e.g., caregiver–child interaction) Communication domain: (a) expressive language, (b) receptive language, (c) social/pragmatic language, or (d) global language (e.g., mix of expressive and expressive language) Maintenance and/or generalization outcome, if applicable

Note.  RCT = randomized control trial; MLU = mean length of utterance.

We also assessed the quality of each communicative outcome and assigned an evidence-level rating. Using ratings adapted from a scoping review conducted by Guiberson and Ferris (2019) and our consensus method, we rated each outcome as compelling, promising, or lacking. We based our ratings on study design, statistical significance, and effect sizes. Statistical significance and effect sizes were determined in relation to the study's comparison group(s), which in some cases was a no communication intervention control group and in other cases was another communication treatment group. An outcome was rated as compelling if the study demonstrated experimental control (e.g., quasi-experimental design or RCT), had a standard effect size (Cohen's d) > 0.25, and/or there was a significant difference between groups. An outcome was coded as promising, if there were moderate to large effects, but no experimental control. Outcomes were coded as lacking, if there was no intervention effect on the outcome (i.e., effect size < 0.25), or analyses did not include or enable the calculation of effect sizes. When a study included a communication treatment control group, we only rated the evidence level for the treatment group identified by the study authors as being the primary intervention group. We included broad indications of outcome measure quality to ensure that each of the studies included in our scoping review was minimally associated with at least one positive caregiver outcome. As we aimed to better understand the composition caregiver-implemented communication interventions, we excluded studies with only outcomes associated with lacking evidence (no experimental control, no significant effect, and small effect size). If a study included follow-up data, communication outcomes were also evaluated to determine if effects maintained, decreased, or increased. This was based on how each study analyzed their results (e.g., some studies evaluated pretest/baseline to follow-up, whereas others evaluated posttest to follow-up). Our full data extraction manual is available on our OSF project page.

Finally, we characterized each intervention using the system developed by Sandbank et al. (2020). Three researchers independently characterized each of the intervention groups as Behavioral (i.e., grounded in operant theories of learning or comprising predominantly behavioral techniques), developmental (i.e., grounded in constructivist theories of learning or primarily child-led), Naturalistic Developmental Behavioral Intervention (NDBI; i.e., combination of adult-led behavioral teaching approaches and child-led activities embedded in natural contexts and follow a natural developmental sequence), or sensory-based intervention (i.e., incorporated exposure to sensory stimuli, including auditory, tactile, or visual). Following Sandbank et al.'s system, we characterized any intervention, which the authors identified as TEACCH (Treatment and Education of Autistic and Related Communication Handicapped Children) as such. If a study did not include adequate information to characterize the intervention, we noted this. Upon independently characterizing the interventions, the researchers discussed discrepancies to come to a final consensus.

Results

After duplicates were removed, a total of 5,703 citations were identified from the searches of the electronic databases. On the basis of the title and the abstract, 4,838 were excluded, with 865 full-text articles to be retrieved and assessed for eligibility. Of these, 805 were excluded for the following reasons: 228 did not include a caregiver language or communication outcome measure, 169 did not include children 0 through 48 months of age, 119 did not include a study group comprising children with an identified language or communication impairment or condition closely associated with such, 66 did not include a caregiver language or communication intervention, 155 were not group studies, 45 did not include a language or communication intervention, 11 were not reported in English, and eight were ongoing studies with no study results. We identified an additional five studies as duplicates. The remaining 59 studies were considered eligible for the purposes of this review (see Figure 1). Supplemental Material S9 includes the complete reference list for all studies included in the review.

Overall Study Characteristics

The 59 studies identified were published between 1987 and 2021, with the majority (n = 42) published after 2010. The identified studies were most commonly reported to be conducted in the United States (n = 32), Canada (n = 10), the United Kingdom (n = 9), Australia (n = 2), and India (n = 2). Other locations included Italy, Northern Ireland, Saudi Arabia, and Turkey (ns = 1). The studies included 30 RCTs, 11 non-RCTs, and 18 single-group studies. There were nine studies that had more than one intervention group meeting our criteria, yielding a total of 72 unique groups that included children identified as having communication impairment who were receiving some type of caregiver-implemented communication intervention. Of the nine studies with more than one identified treatment group with children with communication impairment, the treatment groups for three studies differed based on participant characteristics (e.g., different etiologies), the groups for one study differed based on treatment intensity (i.e., dosage), and the groups for the remaining five studies differed based on the treatment approach delivered.

Specific Study Question Results

For each of our study questions, we synthesized studies according to four groups based on child age due to supposed differences in intervention approaches to match the child's stage of language development as follows: 0 through 11 months (n = 1), 12 through 23 months (n = 10), 24 through 35 months (n = 23), and 36 through 48 months (n = 26). Grouping by age also helped to reduce variability in intervention types as well as caregiver and child language outcome measures to yield more specific syntheses. We determined the groupings based on the mean child age of each caregiver-implemented communication intervention group. For studies in which the mean age was not reported, we used the midpoint between the minimum and maximum ages reported. There was one study (i.e., Tannock et al., 1992) with intervention groups representing two different age groups and thus are reported in both age groups. Next, we created subgroups within each age group based on child diagnostic characteristics. The broad subgroups included developmental disorder (e.g., Down syndrome, unspecified developmental disorder), autism (i.e., inclusion of children diagnosed with autism), and language delay/disorder (i.e., specified significant weaknesses in language development).

For our final synthesis, we only included studies for which there was at least one adult communication-based outcome measure rated as providing compelling or promising evidence (see Table 3). In our synthesis, there were four communication intervention groups that served as treatment control groups and for which no evidence ratings were completed (i.e., 12 through 23 months: Fey et al., 2013; and Rogers et al., 2019; 36 through 48 months: Ingersoll et al., 2016). Table 4 contains the characteristics of studies included in the synthesis. Table 5 contains key details of child and caregiver characteristics. Tables 6 and 7 include information regarding the intervention components. Tables 3 and 8 contain the number of caregiver and child outcome measures associated with each study that were rated as compelling, promising, or lacking, categorized by communication domain, respectively. For a summary of the study, child, caregiver characteristics, intervention components, and outcomes measures for studies with no compelling or promising adult outcome measures, see Supplemental Materials S3–S9.

Table 3.

Number of caregiver outcomes for each study by evidence level and outcome domain.

Study	Targeted treatment (TT) and treatment comparison (TC) or other comparison (OC) study groups	Evidence level and outcome domain
		Compelling				Promising				Lacking
		NV	SLI	GL	IN	NV	SLI	GL	IN	NV	SLI	GL	IN
12 through 23 months
Developmental disorder
Fey et al., 2013	a. Milieu Communication Teaching - High Intensity (TT)			1	2
	b. Milieu Communication Teaching - Low Intensity (TC*)
	Follow-up (6 months)			1/1	2/2
	Follow-up (15 months)			1/1	2/2
Mahoney & Powell, 1988	a. Transactional Intervention Program (TT)							2	5
Yoder & Warren, 2002	a. Responsivity Education and Prelinguistic Milieu Teaching (TT)				2
	b. Control Group (OC)
Autism
Brian et al., 2016	a. Social ABCs (TT)							2
	Follow-up (3 months)							2/2
Carter et al., 2011	a. Hanen More Than Words (TT)								1
	b. Business as Usual (OC)
	Follow-up (4 months)								1/1
Stahmer et al., 2020	a. Project ImPACT for Toddlers (TT)			1	10
	b. Treatment as Usual (OC)
	Follow-up (3 months)				3/3
Language delay/disorder
Rajesh & Venkatesh, 2019	a. Low-Intensity Parent Training Program (TT)						3				4		1
	Follow-up (2.5 months)						1/3 2/3 +				3/4 1/4 +		1/1
24 through 35 months
Developmental disorder
Cycyk et al., 2020	a. Language and Play Every Day en Español Intervention (TT)							1	3			1	2
Fey et al., 2006	a. Responsivity Education/PMT – Down syndrome (TT)				1
	b. Responsivity Education/PMT – Other Etiology (TC)												1
	c. Responsivity Education/PMT – Entire sample (TC*)
Iven et al., 1989	a. Pragmatic Interaction Strategies Intervention (TT)						2				2	2	2
Pennington et al., 2009	a. It Takes Two to Talk (TT)						2		1		4		1
	Follow-up (4 months)						2/2		1/1		4/4		1/1
Romski et al., 2010	a. PI Communication Intervention – Augmented Communication (TT)				1		1				1
	b. PI Communication Intervention – Spoken communication (TT)*
	c. Augmented Communication Output (TT)				1		1				1
Yang, 2016	a. Musical Bonds Program (TT)								2
Autism
Barrett et al., 2020	a. Pivotal Response Intervention for Social Motivation (TT)				1
	b. Waitlist Control (OC)
Liu & Schertz, 2021	a. Joint Attention Mediated Learning (TT)				2							1	1
	b. Business as Usual (OC)
Rogers et al., 2019	a. Enhanced Parent-Implemented Early Start Denver Model (TT)							1
	b. Parent-Implemented Early Start Denver Model (TC*)
Rollins et al., 2019	a. Pathways (TT)								1
	b. Treatment as Usual (OC)
Language delay/disorder
Baxendale et al., 2003	a. Hanen Parent Program (TT)								1				1
	b. Conventional Clinic (TC)
	Follow-up (6 months)								1/1				1/1
Ciccone et al., 2012	a. Parent-Focused Early Intervention Program (TT)								1
Falkus et al., 2016	a. Parent–child Interaction Therapy (TT)							1	1
Gibbard & Smith, 2016	a. Enhanced Parent-Based Intervention (TT)							1
Girolametto et al., 1996	a. Hanen Program for Parents (TT)		4				1				1
	b. Delayed Treatment (OC)
McDade & McCartan, 1998	a. Hanen Program (TT)						2				2
	b. Control Group (OC)
Pearce et al., 1996	a. Hanen Program for Parents (TT)		1	3	2		1				1	1
	b. Delayed Treatment (OC)
Roberts & Kaiser, 2012	a. PI Enhanced Milieu Teaching (TT)			3	3
	b. LI – business as usual (OC)
	c. TD – business as usual (OC)
Roberts & Kaiser, 2015	a. Enhanced Milieu Teaching (TT)			3	3
	b. Business as Usual (OC)
Suttora et al., 2021	a. Oltre il Libro – Dialogic Book Reading (TT)		1		2		2		1		1		1
	b. Treatment as Usual (OC)
Tannock et al., 1992	a. Hanen Early Language Parent Program (TT)		1	1	3				1
	b. Wait List Control (OC)
	Follow-up (4 months)		-	1/1	1/1				1/1
36 through 48 months
Developmental disorder
Girolametto et al., 1998	a. Hanen Program (TT)						3				2
	b. Delayed Treatment (OC)
Girolametto, 1988	a. Hanen Early Language Parent Program (TT)						2		2		2
	b. Delayed Treatment (OC)
Kaiser & Roberts, 2013	a. Parent + Therapist Enhanced Milieu Teaching (TT)		2	2	4
	b. Therapist Only Enhanced Milieu Teaching (OC)
	Follow-up (6 months)		2/2	2/2	4/4
	Follow-up (12 months)		2/2	2/2	4/4
Kot & Law, 1995	a. Parent Linguistic Input (TT)						1				3		1
	b. Group Only – No parent training (OC)
Weistuch et al., 1991	a. Language Interaction Intervention Program – Site 1 (TT)						1						2
	b. Language Interaction Intervention Program – Site 2 (TT)						1						2
	c. Control Group (OC)
Autism
Aldred et al., 2004	a. Social Communication Intervention (TT)				2							1
	b. Routine Care (OC)
Alquraini et al., 2018	a. Responsive Teaching (TT)				1
	b. Standard Community Services (OC)
Braiden et al., 2012	a. Forward Steps Early Intervention Program with TEACCH (TT)							4
Casenhiser et al., 2013	a. Milton & Ethel Harris Research Initiative (TT)			1	1
	b. Business as Usual/Delayed Treatment (OC)
Green et al., 2010	a. Preschool Autism Communication Trial (TT)								2
	b. Treatment as Usual (OC)
Hampton et al., 2020	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device (TT)							1	3				1
	b. Business as Usual (OC)
	Follow-up (4 months)							1/1	1/3 2/3 −				1/1 +
Ingersoll & Wainer, 2013	a. Project ImPACT (TT)						1	3	1
Ingersoll et al., 2016	a. Therapist-Assisted ImPACT Group (TT)			1
	b. Self-Directed ImPACT Group (TC*)
	Follow-up (3 months)			1/1
Matthews et al., 2018	a. JumpStart (TT)			1
	b. Waitlist Control (OC)
	Follow-up (3 months)			1/1
McGarry et al., 2020	a. Pivotal Response Training (TT)							1
Minjarez et al., 2011	a. Pivotal Response Training (TT)							1
Noyan Erbas et al., 2020	a. Hanen More Than Words (TT)							1	1			1
	Follow-up (1 months)							0/1	0/1			1/1
Sengupta et al., 2020	a. Project ImPACT (TT)								5
Venker et al., 2012	a. Hanen More Than Words (TT)			2	2
	b. Delayed Treatment (OC)
Wainer et al., 2021	a. Stepped-care Online Reciprocal Imitation Training (TT)			2
	b. Treatment as Usual (OC)
Language delay/disorder
Tannock et al., 1992	a. Hanen Early Language Parent Program (TT)		1	1					2				2
	b. Wait List Control (OC)
	Follow-up (4 months)		-	1/1					1/1				1/1

Note. Only studies where the language intervention group had promising or compelling evidence are included in the table. NV = nonverbal; SLI = spoken language input; GL = global; IN = interactional; PI = parent implemented; PMT = prelinguistic milieu teaching; TEACHH = Treatment and Education of Autistic and Related Communication Handicapped Children; ImPACT = Improving Parents as Communication Teachers.

^*Denotes language intervention groups without evidence ratings included in syntheses. For studies with a follow-up, the denominator represents the total number of outcomes assessed at follow-up for a given outcome category.

⁺ Indicates a significant positive change at follow-up.

⁻ Indicates significant negative change at follow-up.

Table 4.

Characteristics of studies with compelling or promising evidence.

Study	Country or territory	Study design	Number of study groups	Caregiver–child language intervention name
12 through 23 months
Developmental disorder
Fey et al., 2013	USA	RCT	2	a. Milieu Communication Teaching - High Intensity
				b. Milieu Communication Teaching - Low Intensity
Mahoney & Powell, 1988	USA	SG	1	a. Transactional Intervention Program
Yoder & Warren, 2002	USA	RCT	2	a. Responsivity Education and Prelinguistic Milieu Teaching
Autism
Brian et al., 2016	Canada	SG	1	a. Social ABCs
Carter et al., 2011	USA	RCT	2	a. Hanen More Than Words
Stahmer et al., 2020	USA	Non-RCT	2	a. Project ImPACT for Toddlers
Language delay/disorder
Rajesh & Venkatesh, 2019	India	SG	1	a. Low-Intensity Parent Training Program
24 through 35 months
Developmental disorder
Cycyk et al., 2020	USA	SG	1	a. Language and Play Every Day en Español Intervention
Fey et al., 2006	USA	RCT	6	a. Responsivity Education/Prelinguistic Milieu Teaching - Down syndrome
				b. Responsivity Education/Prelinguistic Milieu Teaching - Other Etiology
Iven et al., 1989	USA	SG	1	a. Pragmatic Interaction Strategies Intervention
Pennington et al., 2009	Australia UK	SG	1	a. It Takes Two to Talk
Romski et al., 2010	USA	RCT	3	a. Parent-Implemented Communication Intervention - Augmented Communication Input
				b. Parent-Implemented Communication Intervention - Spoken communication
				c. Augmented Communication Output
Yang, 2016	USA	SG	1	a. Musical Bonds Program
Autism
Barrett et al., 2020	USA	RCT	2	a. Pivotal Response Intervention for Social Motivation
Liu & Schertz, 2021	USA	RCT	2	a. Joint Attention Mediated Learning
Rogers et al., 2019	USA	RCT	2	a. Enhanced Parent-Implemented Early Start Denver Model
				b. Parent-Implemented Early Start Denver Model
Rollins et al., 2019	USA	RCT	2	a. Pathways
Language delay/disorder
Baxendale & Hesketh, 2003	UK	Non-RCT	2	a. Hanen Parent Program
				b. Conventional Clinic
Ciccone et al., 2012	Australia	SG	1	a. Parent-Focused Early Intervention Program
Falkus et al., 2016	UK	SG	1	a. Parent–child Interaction Therapy
Gibbard & Smith, 2016	UK	SG	1	a. Enhanced Parent-Based Intervention
Girolametto et al., 1996	Canada	RCT	2	a. Hanen Program for Parents
McDade & McCartan, 1998	UK	Non-RCT	2	a. Hanen Program
Pearce et al., 1996	Canada	RCT	2	a. Hanen Program for Parents
Roberts & Kaiser, 2012	USA	RCT	3	a. Parent-implemented Enhanced Milieu Teaching
Roberts & Kaiser, 2015	USA	RCT	2	a. Enhanced Milieu Teaching
Suttora et al., 2021	Italy	Non-RCT	2	a. Oltre il Libro – Dialogic Book Reading
Tannock et al., 1992	Canada	RCT	4	a. Hanen Early Language Parent Program
36 through 48 months
Developmental disorder
Girolametto et al., 1998	Canada	RCT	2	a. Hanen Program
Girolametto, 1988	Canada	RCT	2	a. Hanen Early Language Parent Program
Kaiser & Roberts, 2013	USA	RCT	2	a. Parent + Therapist Enhanced Milieu Teaching
Kot & Law, 1995	UK	RCT	2	a. Parent Linguistic Input
Weistuch et al., 1991	USA	Non-RCT	3	a. Language Interaction Intervention Program – Site 1
				b. Language Interaction Intervention Program – Site 2
Autism
Aldred et al., 2004	UK	RCT	2	a. Social Communication Intervention
Alquraini et al., 2018	Saudi Arabia	RCT	2	a. Responsive Teaching
Braiden et al., 2012	Northern Ireland	SG	1	a. Forward Steps Early Intervention Program with TEACCH Approach
Casenhiser et al., 2013	Canada	RCT	2	a. Milton & Ethel Harris Research Initiative
Green et al., 2010	UK	RCT	2	a. Preschool Autism Communication Trial
Hampton et al., 2020	USA	RCT	2	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device
Ingersoll & Wainer, 2013	USA	SG	1	a. Project ImPACT
Ingersoll et al., 2016	USA	RCT	2	a. Therapist-Assisted ImPACT Group
				b. Self-Directed ImPACT Group
Matthews et al., 2018	USA	Non-RCT	2	a. JumpStart
McGarry et al., 2020	USA	SG	1	a. Pivotal Response Training
Minjarez et al., 2011	USA	SG	1	a. Pivotal Response Training
Noyan Erbas et al., 2020	Turkey	SG	1	a. Hanen More Than Words
Sengupta et al., 2020	India	SG	1	a. Project ImPACT
Venker et al., 2012	USA	RCT	2	a. Hanen More Than Words
Wainer et al., 2021	USA	RCT	2	a. Stepped-care Online Reciprocal Imitation Training
Language delay/disorder
Tannock et al., 1992	Canada	RCT	4	a. Hanen Early Language Parent Program

Note.  RCT = randomized control trial; SG = single group; TEACCH = Treatment and Education of Autistic and Related Communication Handicapped Children; ImPACT = Improving Parents as Communication Teachers.

Table 5.

Caregiver and child characteristics.

Study	Caregiver–child language intervention name	Group sample size	Mean child age at enrollment (months)	Child characteristics	Child gender	Caregiver relationship	Mean caregiver age (years)	Family race
12 through 23 months
Developmental disorder
Fey et al., 2013	a. Milieu Communication Teaching - High Intensity	33	21.83	DD; DS	M = 61% F = 39%	Parent	—	—
	b. Milieu Communication Teaching - Low Intensity	31	23	DD; DS	M = 65% F = 35%	Parent	—	—
Mahoney & Powell, 1988	a. Transactional Intervention Program	41	17.6	DS; cerebral palsy; spina bifida; hydrocephalus; congenital infectious diseases; undiagnosed etiologies	—	Mother; father	Mother: 30.2 Father: 32.3	White = 100%
Yoder & Warren, 2002	a. Responsivity Education and Prelinguistic Milieu Teaching	19.5	21	DD; DS; cerebral palsy; encephalitis	M = 56% F = 44%	Mother; father; foster parent; grandparent	—	Black = 48% White = 48% Other = 4%
Autism
Brian et al., 2016	a. Social ABCs	20	22.05	Autism; at risk for autism	M = 70% F = 30%	Parent	—	Asian/Pacific Islander = 10% White = 75% East Indian = 15%
Carter et al., 2011	a. Hanen More Than Words	32	21.11	Autism; at risk for autism	M = 82% F = 18%	Parent	—	—
Stahmer et al., 2020	a. Project ImPACT (Improving Parents as Communication Teachers) for Toddlers	12	23.08	DD; autism	M = 92% F = 8%	Parent	—	Asian/Pacific Islander = 25% White = 33% Latino = 50% Multiracial = 8% Other = 33%
Language delay/disorder
Rajesh & Venkatesh, 2019	a. Low-Intensity Parent Training Program	10	18.2	Language delay	M = 70% F = 30%	Mother; father	—	—
Average (SD) Min-max		24.81 (11.04) 10–41	20.98 (2.05) 17.6–23.08		M = 71% F = 29%		31.25 (1.48) 30.2–32.3	Asian/Pacific Islander = 18% Black = 48% East Indian = 15% Latino = 50% White = 64% Multiracial = 8%
24 through 35 months
Developmental disorder
Cycyk et al., 2020	a. Language and Play Every Day en Español Intervention	8	35.1	DD; language delay (confirmed or at risk)	M = 75% F = 25%	Mother; father; grandparent	45.9	Latino = 100%
Fey et al., 2006	a. Responsivity Education/Prelinguistic Milieu Teaching - Down syndrome	13	25.31	DS	—	Parent	—	Black or Asian/Pacific Islander = 16%
	b. Responsivity Education/Prelinguistic Milieu Teaching - Other Etiology	12	27.17	DD	—	Parent	—	Black or Asian/Pacific Islander = 16%
Iven et al., 1989	a. Pragmatic Interaction Strategies Intervention	7	27	DD: DS; cerebral palsy; DHH; language delay	—	Parent	—	—
Pennington et al., 2009	a. It Takes Two to Talk	11	26	Cerebral palsy; myopathy	M = 73% F = 27%	Mother	—	—
Romski et al., 2010	a. Parent-Implemented Communication Intervention - Augmented Communication Input	21	29	DS; cerebral palsy; language delay	M = 68% F = 32%	Mother; father	37.33	Black = 29% Asian/Pacific Islander = 10% White = 62%
	b. Parent-Implemented Communication Intervention - Spoken communication	21	29	DS; cerebral palsy; language delay	M = 68% F = 32%	Mother; father	37.33	Black = 29% Asian/Pacific Islander = 10% White = 62%
	c. Augmented Communication Output	20	30	DS; cerebral palsy; language impairment (at risk)	M = 72% F = 32%	Mother; father	37.33	Black = 30% Asian/Pacific Islander = 10% White = 60%
Yang, 2016	a. Musical Bonds Program	26	27.96	DD; autism; DHH; DLD; motor delay	M = 77% F = 23%	Mother	34.38	Black = 23% White = 58% Latino = 8% Other = 12%
Autism
Barrett et al., 2020	a. Pivotal Response Intervention for Social Motivation	12	35.75	Autism	M = 92% F = 8%	Parent	—	Asian/Pacific Islander = 8% White = 75% Latino = 17%
Liu & Schertz, 2021	a. Joint Attention Mediated Learning	30	24.77	Autism	M = 87% F = 13%	Parent	30.6	Black = 17% White = 70% Latino = 3% Multiracial = 10%
Rogers et al., 2019	a. Enhanced Parent-Implemented Early Start Denver Model	21	25.2	Autism	M = 71% F = 29%	Parent	—	Black = 14% Asian/Pacific Islander = 5% White = 38% Other = 19% Not Reported = 33%
	b. Parent-Implemented Early Start Denver Model	24	25.2	Autism	M = 67% F = 33%	Parent	—	Asian/Pacific Islander = 4% White = 50% Other = 13% Not Reported = 33%
Rollins et al., 2019	a. Pathways	32	28.8	Autism	M = 69% F = 31%	Parent	—	Black = 6% Asian/Pacific Islander = 22% White = 22% Latino = 50%
Language delay/disorder
Baxendale et al., 2003	a. Hanen Parent Program	19	31.5	Language delay	M = 74% F = 26%	Parent	—	White = 100%
	b. Conventional Clinic	18	34.3	Language delay	M = 89% F = 11%	Parent	—	White = 100%
Ciccone et al., 2012	a. Parent-Focused Early Intervention Program	18	33.4	Language delay	M = 67% F = 33%	Mother; father	—	—
Falkus et al., 2016	a. Parent–child Interaction Therapy	18	29.6	Language delay	M = 83% F = 17%	Parent	—	—
Gibbard & Smith, 2016	a. Enhanced Parent-Based Intervention	18	30	Language delay	—	Parent; caregiver	—	—
Girolametto et al., 1996	a. Hanen Program for Parents	12	28.7	Language delay	—	Mother	35	—
McDade & McCartan, 1998	a. Hanen Program	11	24	DLD	—	Mother	—	—
Pearce et al., 1996	a. Hanen Program for Parents	8	30.3	DLD	M = 63% F = 38%	Mother	32	—
Roberts & Kaiser, 2012	a. Parent-implemented Enhanced Milieu Teaching	16	31	DD; DLD	M = 88% F = 13%	Mother; father	32.69	—
Roberts & Kaiser, 2015	a. Enhanced Milieu Teaching	45	30.3	DD; language delay	M = 82% F = 18%	Caregiver	—	—
Suttora et al., 2021	a. Oltre il Libro – Dialogic Book Reading	24	30.86	Language delay (confirmed or at risk)	M = 58% F = 42%	Mother; father	Mother: 40.04 father: 42.00	—
Tannock et al., 1992	a. Hanen Early Language Parent Program	8	24.8	language delay (confirmed or at risk)	M = 50% F = 50%	Mother	36.9	—
Average (SD) Min-max		18.19 (8.70) 7–45	29.04 (3.29) 24–35.75		M = 74% F = 26%		36.79 (4.36) 30.6–45.9	Asian/Pacific Islander = 10% Black = 21% Black or Asian/Pacific Islander = 16% Latino = 36% White = 63% Multiracial = 10% Other = 15% Not reported = 33%
36 through 48 months
Developmental disorder
Girolametto et al., 1998	a. Hanen Program	6	39.2	DS	M = 83% F = 17%	Mother	32	—
Girolametto, 1988	a. Hanen Early Language Parent Program	9	39	DD; DS	M = 56% F = 44%	Mother	34.7	—
Kaiser & Roberts, 2013	a. Parent + Therapist Enhanced Milieu Teaching	39	40.05	DD; autism; DS	M = 74% F = 26%	Mother; father	36	—
Kot & Law, 1995	a. Parent Linguistic Input	7	39	DD; DLD	—	Parent	—	—
Weistuch et al., 1991	a. Language Interaction Intervention Program – Site 1	16	42	DD; DS	—	Mother	—	—
	b. Language Interaction Intervention Program – Site 2	10	42	DD; DS	—	Mother	—	—
Autism
Aldred et al., 2004	a. Social Communication Intervention	14	48	Autism	M = 93% F = 7%	Parent	—	Black = 7% White = 93%
Alquraini et al., 2018	a. Responsive Teaching	13	42	Autism	M = 85% F = 16%	Mother	38.5	—
Braiden et al., 2012	a. Forward Steps Early Intervention Program with TEACCH Approach	18	38	Autism	M = 94% F = 6%	Parent	—	—
Casenhiser et al., 2013	a. Milton & Ethel Harris Research Initiative	25	42.52	Autism	—	Parent	—	—
Green et al., 2010	a. Preschool Autism Communication Trial	77	45	Autism	M = 92% F = 8%	Parent	33	White = 60% Other = 40%
Hampton et al., 2020	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device	34	43	Autism	M = 76% F = 24%	Mother; father; grandparent	—	White = 64% Not reported = 36%
Ingersoll & Wainer, 2013	a. Project ImPACT	24	44.9	Autism	M = 88% F = 13%	Parent	—	—
Ingersoll et al., 2016	a. Therapist-Assisted ImPACT Group	14	41.57	Autism	M = 79% F = 21%	Mother	—	—
	b. Self-Directed ImPACT Group	13	46.08	Autism	M = 61% F = 39%	Mother; father	—	—
Matthews et al., 2018	a. JumpStart	18	40.83	Autism (diagnosed or at risk)	—	Mother; father	34.61	—
McGarry et al., 2020	a. Pivotal Response Training	11	36.82	Autism	M = 73% F = 27%	Mother; father	—	Asian/Pacific Islander = 18% White = 27% Latino = 36% Multiracial = 10% Other = 10%
Minjarez et al., 2011	a. Pivotal Response Training	17	47	Autism	—	Parent	—	Asian/Pacific Islander = 28% White = 33% Latino = 11% Other = 28%
Noyan Erbas et al., 2020	a. Hanen More Than Words	16	36.14	Autism	—	Parent	33	—
Sengupta et al., 2020	a. Project ImPACT (Improving Parents as Communication Teachers)	57	43.2	Autism	M = 84% F = 16%	Mother	34.18	—
Venker et al., 2012	a. Hanen More Than Words	7	41.14	Autism	—	Mother; father	—	—
Wainer et al., 2021	a. Stepped-care Online Reciprocal Imitation Training	10	40.1	Autism	M = 80% F = 20%	Mother	—	Asian/Pacific Islander = 10% Black = 40% Latino = 40% Multiracial = 10%
Language delay/disorder
Tannock et al., 1992	a. Hanen Early Language Parent Program	8	40.3	Language delay (confirmed or at risk)	M = 53% F = 47%	Mother	33.6	—
Average (SD) Min-max		20.13 (17.21) 6–77	41.65 (3.09) 36.14–48		M = 78% F = 22%		34.40 (1.93) 32.00–38.50	Asian/Pacific Islander = 19% Black = 24% Latino = 29% White = 56% Multiracial = 10% Other = 26% Not reported = 36%

Note. Only studies where the language intervention group had promising or compelling evidence are included in the table. Em dashes indicate data not reported. DD = developmental delay; DS = Down syndrome; DLD = developmental language disorder; F = female; M = male; TEACCH = Treatment and Education of Autistic and Related Communication Handicapped Children; ImPACT = Improving Parents as Communication Teachers.

Table 6.

Summary of intervention trainer, language, location, and dosage.

Study	Caregiver–child language intervention name	Intervention trainer	Language of intervention	Intervention location	Intervention dosage
					Number of sessions	Session length	Duration of intervention	Frequency of sessions
12 through 23 months
Developmental disorder
Fey et al., 2013	a. Milieu Communication Teaching - High Intensity	Trained paraprofessionals	English	Home	9	1 hr	3 months	Weekly
	b. Milieu Communication Teaching - Low Intensity	Trained paraprofessionals	English	Home	9	1 hr	3 months	Weekly
Mahoney & Powell, 1988	a. Transactional Intervention Program	Teacher consultant	English	Home	—	—	11.5 months	Weekly
Yoder & Warren, 2002	a. Responsivity Education and Prelinguistic Milieu Teaching	Researcher	English	Unspecified location	12	—	—	—
Autism
Brian et al., 2016	a. Social ABCs	Parent educator	English	Home	12	1–1.5 hr	8.7 months	3/week, then taper
Carter et al., 2011	a. Hanen More Than Words	Speech-language pathologist	English	Home; unspecified location	3 home; 8 group	—	3.5 months	—
Stahmer et al., 2020	a. Project ImPACT for Toddlers	Trained early intervention providers	English	Home; early childhood education setting	—	2.5 hr/week	12 weeks	—
Language delay/disorder
Rajesh & Venkatesh, 2019	a. Low-Intensity Parent Training Program	—	English; Tamil	Home	3	1 hr	1 week	3/week
Average (SD) Min–max					Sessions: 9.33 (3.39) 3–12	Minutes: 81.0 (39.12) 60–150	Weeks: 19.4 (16.86) 1–50
24 through 35 months
Developmental disorder
Cycyk et al., 2020	a. Language and Play Every Day en Español Intervention	Speech-language pathologist; Bilingual graduate students	English; Spanish	Home; Community location	Group: 6; individual: 2	1–2 hr	3 months	—
Fey et al., 2006	a. Responsivity Education/Prelinguistic Milieu Teaching - Down syndrome	Speech-language pathologist	English	Home	8	1 hr	6 months	—
	b. Responsivity Education/Prelinguistic Milieu Teaching - Other Etiology	Speech-language pathologist	English	Home	8	1 hr	6 months	—
Iven et al., 1989	a. Pragmatic Interaction Strategies Intervention	—	English	—	4	1 hr	4 weeks	Weekly
Pennington et al., 2009	a. It Takes Two to Talk	Speech-language pathologist	English	Home; unspecified location	Home: 3; group: 7–8	Group: 2.5 hr	13 weeks	—
Romski et al., 2010	a. Parent-Implemented Communication Intervention - Augmented Communication Input	Trained interventionist	English	Home; university setting	Home: 6; university: 18	30 min	12 weeks	Home: 2/week; University: 3/week
	b. Parent-Implemented Communication Intervention - Spoken communication	Trained interventionist	English	Home; university setting	Home: 6; university: 18	30 min	12 weeks	Home: 2/week; University: 3/week
	c. Augmented Communication Output	Trained interventionist	English	Home; university setting	24	30 min	12 weeks	Home: 2/week; University: 3/week
Yang, 2016	a. Musical Bonds Program	Music therapist	English	Home	6	40 min	6 weeks	Weekly
Autism
Barrett et al., 2020	a. Pivotal Response Intervention for Social Motivation	Graduate student clinician	English	—	—	8 hr/week	6 months	—
Liu & Schertz, 2021	a. Joint Attention Mediated Learning	Intervention coordinators	English	Home	32	1 hr	8 months	Weekly
Rogers et al., 2019	a. Enhanced Parent-Implemented Early Start Denver Model	Psychologist; speech-language pathologist; behavior analysts family therapist	English	Home; clinic	24	1.5 hr	12 weeks	2/week
	b. Parent-Implemented Early Start Denver Model	Psychologist; speech-language pathologist; behavior analysts family therapist	English	Clinic	12	1.5 hr	12 weeks	Weekly
Rollins et al., 2019	a. Pathways	Clinician	English; Spanish	Home	11	1.5 hr	—	Weekly
Language delay/disorder
Baxendale et al., 2003	a. Hanen Parent Program	Speech-language pathologist	English	Group based: Not reported; Home	Group: 8; home: 3	Group: 2.25 hr	11 weeks	Group: Weekly
	b. Conventional Clinic	Speech-language pathologist	English	Clinic; nursery	8–12	45 min	8–12 weeks	Weekly
Ciccone et al., 2012	a. Parent-Focused Early Intervention Program	Speech-language pathologist; trained students	English	School classroom	6	1.25 hr	6 weeks	Weekly
Falkus et al., 2016	a. Parent–child Interaction Therapy	Therapist	English	Clinic	4	1 hr	10 weeks	—
Gibbard & Smith, 2016	a. Enhanced Parent-Based Intervention	Speech-language pathologist; teacher	English	Home; Early childhood education setting	20	1.5 hr	20 weeks	Weekly
Girolametto et al., 1996	a. Hanen Program for Parents	speech-language pathologist; parent associate	English	Home; unspecified location	8 group; 3 individual	Group: 2.5 hr	11 weeks	—
McDade & McCartan, 1998	a. Hanen Program	—	English	Home; unspecified location	Home: 3; other: 9	—	12 weeks	—
Pearce et al., 1996	a. Hanen Program for Parents	Speech-language pathologist (Hanen certified)	English	—	Group: 7; individual: 3	—	—	—
Roberts & Kaiser, 2012	a. Parent-implemented Enhanced Milieu Teaching	Speech-language pathologist	English	Home; clinic	28	1 hr	3 months	2/week
Roberts & Kaiser, 2015	a. Enhanced Milieu Teaching	Trained interventionist	English	Clinic; home	Clinic: 4; home: 24	1 hr	3 months	2/week
Suttora et al., 2021	a. Oltre il Libro – Dialogic Book Reading	Psychologist	Italian	—	6	2 hr	2 months	—
Tannock et al., 1992	a. Hanen Early Language Parent Program	Parent educator; speech-language pathologist	English	Home; unspecified	Group: 9; individual: 3	Group: 2.5 hr	12 weeks	Weekly
Average (SD) Min-max					Sessions: 14.40 (8.50) 4–32	Minutes: 78.90 (37.92) 30–150	Weeks: 13.46 (6.62) 4–32
36 through 48 months
Developmental disorder
Girolametto et al., 1998	a. Hanen Program	Speech-language pathologist (Hanen certified)	English	Clinic; home	Group: 9; home: 4	Group: 2.5 hr	13 weeks	Weekly
Girolametto, 1988	a. Hanen Early Language Parent Program	Speech-language pathologist; parent assistant	—	Program center; home	Group: 8; individual: 3	Group: 3 hr	11 weeks	—
Kaiser & Roberts, 2013	a. Parent + Therapist Enhanced Milieu Teaching	Trained interventionist	English	Clinic; home	Workshop: 1; clinic: 24; home: 12	Workshop: 2–3 hr; Home: 20 min	3 months	Clinic: 2/Week; Home: Weekly
Kot & Law, 1995	a. Parent Linguistic Input	Speech-language pathologist; child development worker	English	—	7	—	7 weeks	Weekly
Weistuch et al., 1991	a. Language Interaction Intervention Program – Site 1	Speech-language pathologist	English	Early childhood education setting	40	2 hr	—	Weekly
	b. Language Interaction Intervention Program – Site 2	Speech-language pathologist	English	Early childhood education setting	40	2 hr	—	Weekly
Autism
Aldred et al., 2004	a. Social Communication Intervention	Therapist	English	—	9 + workshops	—	12 months	Monthly then bi-monthly
Alquraini et al., 2018	a. Responsive Teaching	Trained interventionist	Arabic	Home; center	16	1 hr	4 months	Weekly
Braiden et al., 2012	a. Forward Steps Early Intervention Program with TEACCH Approach	Trained TEACCH facilitators	English	Home; unspecified location	Home: 8; other: 6	Home; 1–2 hr; Other: 2–3 hr	10 weeks	Weekly
Casenhiser et al., 2013	a. Milton & Ethel Harris Research Initiative	Speech-language pathologist; occupational therapist	English	—	52	2 hr	12 months	Weekly
Green et al., 2010	a. Preschool Autism Communication Trial	Speech-language pathologist	English	Home; clinic	18	2 hr	1 year	6 mo: 2/week; 6 mo: monthly
Hampton et al., 2020	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device	Master-level clinician	English	Home; clinic	40	40–90 min	4 months	3/Week
Ingersoll & Wainer, 2013	a. Project ImPACT	Teacher	English	Central location in school district	Group: 6; individual: 6	Group: 2 hr; Individual: 45 min	12 weeks	Weekly
Ingersoll et al., 2016	a. Therapist-Assisted ImPACT Group	Trained interventionist	English	Home	Online: 12; video conferencing: 24	Online: 1.25 hr Video: 30 min	6 months	3/Week
	b. Self-Directed ImPACT Group	NA	English	Home	12	1.25 hr	6 months	Weekly
Matthews et al., 2018	a. JumpStart	BCBA clinician; trained interventionist	English	Clinic	8	2.5 hr	4 weeks	2/Week
McGarry et al., 2020	a. Pivotal Response Training	—	English	Online	6	15–30 min	9.5 weeks	Weekly
Minjarez et al., 2011	a. Pivotal Response Training	Psychologist specializing in PRT	English	Clinic	Group: 10; individual: 1	Group: 1.5 hr; individual: 50 min	11 weeks	Weekly
Noyan Erbas et al., 2020	a. Hanen More Than Words	Researcher; Hanen therapist	Turkish	University setting; home	Group: 8; video: 3	—	—	—
Sengupta et al., 2020	a. Project ImPACT	Speech-language pathologist; occupational therapist; psychologist; special educators	English; Hindi	Child development center	Group: 6; individual: 6	Group: 2 hr; individual: 1 hr	6 weeks	Weekly
Venker et al., 2012	a. Hanen More Than Words	Speech-language pathologist (Hanen certified)	English	University setting	Group: 5; individual: 2; small group: 14	Parent Group: 2 hr; individual: 45 min; Small group: 1 hr	—	—
Wainer et al., 2021	a. Stepped-care Online Reciprocal Imitation Training	Researcher	English	Home	Self-paced: 5; telecoaching: 5	—	10 weeks	Weekly
Language delay/disorder
Tannock et al., 1992	a. Hanen Early Language Parent Program	Parent educator speech-language pathologist	English	Unspecified group location home	Group: 9; individual: 3	Group: 2.5 hr; individual: Not reported	12 weeks	Weekly
Average (SD) Min-max					Sessions: 19.48 (13.65) 6–52	Minutes: 90.5 (45.83) 20–180	Weeks: 18.82 (14.38) 6–52

Note. Only studies where the language intervention group had promising or compelling evidence are included in the table. Em dashes indicate data not reported. TEACCH = Treatment and Education of Autistic and Related Communication Handicapped Children; ImPACT = Improving Parents as Communication Teachers.

Table 7.

Summary of delivery format, key intervention strategies taught and information provided to caregivers, and intervention contexts.

Study	Caregiver–child language intervention name	Intervention characteristics	Delivery format	Key intervention strategies taught (S)/ information provided (I) to caregivers	Intervention context
12 through 23 months
Developmental disorder
Fey et al., 2013	a. Milieu Communication Teaching - High Intensity	NDBI	One-on-one: In-person	(S) waiting for child to act or communicate (S) follow child's lead (S) imitate child play acts and gestures, vocalizations, and eye contact (S) comment on child's acts and objects of attention (S) put the child's nonverbal communication acts into words (linguistic mapping) (S) add semantically to the child's topic (S) copy and add structure and meaning to the child's use of words (recasts)	Familiar activities & routines
	b. Milieu Communication Teaching - Low Intensity	NDBI	One-on-one: In-person	(S) waiting for child to act or communicate (S) follow child's lead (S) imitate child play acts and gestures, vocalizations, and eye contact (S) comment on child's acts and objects of attention (S) put the child's nonverbal communication acts into words (linguistic mapping) (S) add semantically to the child's topic (S) copy and add structure and meaning to the child's use of words (recasts)	Familiar activities & routines
Mahoney & Powell, 1988	a. Transactional Intervention Program	Developmental	One-on-one: In-person	(S) turn-taking strategies: waiting for child to act, imitating child's behavior, following child's lead, and occasionally elaborating on child's activity (S) interactive match strategies: adjusting behavioral style so that it is similar to child's tempo or pace (S) engaging in activities that are within child's current range of development (S) following and responding to child's current interests (S) incorporating strategies into daily routines	—
Yoder & Warren, 2002	a. Responsivity Education and Prelinguistic Milieu Teaching	NDBI	Mixed: In-person	(S) optimal responding to children's communication acts	Play routines
Autism
Brian et al., 2016	a. Social ABCs	NDBI	One-on-one: In-person; text/emails; phone calls	(S) ABC's of learning (S) enhancing communication (S) sharing positive emotion (S) motivation and arousal (S) play and the social ABC's (S) daily care-giving activities (S) managing behavioral challenges (S) parent self-care	Familiar activities & routines; play routines
Carter et al., 2011	a. Hanen More Than Words	Developmental	Mixed: In-person	(S) responding to child's communicative attempts (S) following child's lead (S) building and participating in joint action routines in play (S) enhancing interaction during caregiving routines (S) using books and play as contexts for communication elicitation and reward (S) using visual supports to help children understand expectations (S) supporting peer interactions (S) scaffolding peer play dates	Familiar activities & routines
Stahmer et al., 2020	a. Project ImPACT for Toddlers	NDBI	One-on-one: In-person	(S) limit distractions (S) adjust animation (S) focus on child (S) comment (S) imitate child (S) model and adjust communication and play (S) create opportunities (S) help child anticipate interruptions (S) use communication temptations (S) wait (S) respond and expand (S) expands communication and play (S) help child succeed (S) provide related and clear prompts and adjust (S) provide natural and immediate rewards	Play routines
Language disorder/delay
Rajesh & Venkatesh, 2019	a. Low-Intensity Parent Training Program	Developmental	One-on-one: In-person	(S) speech-language stimulation strategies in the contexts of free play and daily routines speech and language milestones (I) play development	Familiar activities & routines; play routines
24 through 35 months
Developmental disorder
Cycyk et al., 2020	a. Language and Play Every Day en Español Intervention	Developmental	Mixed: In-person	(S) select activities that occur frequently and interest the child (S) give full attention to the activity and not rush through it (S) maintain the activity or routine for at least 5 min (S) limit distractions to communication (S) focusing on the child's interest whenever possible or acceptable (S) fully participate in the activity (S) put preferred item where the child can see it but cannot reach it (S) create opportunity for child to request help (S) offer choice of two or more objects or activities (S) give small portions of preferred items (S) do something silly in the routine (S) add something new or unexpected to a routine (S) balance turn-taking (S) limit yes/no or test questions (S) responding immediately to child verbal and nonverbal communication bids (S) expand on child's communication attempts	Familiar activities & routines; play routines;
Fey et al., 2006	a. Responsivity Education/Prelinguistic Milieu Teaching - Down syndrome	NDBI	One-on-one: In-person	(S) recognize real or possible child communicative attempts and respond to them meaningfully (S) how to provide recasts and linguistic mappings of child's communication acts (S) awareness of child's developing nonintentional and intentional communication behaviors (S) wait for child to produce interpretable behaviors (S) attend to child's focus of attention by following the child's lead (S) provide appropriate verbal and nonverbal consequences to child's acts	Familiar activities & routines
	b. Responsivity Education/Prelinguistic Milieu Teaching - Other Etiology	NDBI	One-on-one: In-person	(S) recognize real or possible child communicative attempts and respond to them meaningfully (S) how to provide recasts and linguistic mappings of child's communication acts (S) awareness of child's developing nonintentional and intentional communication behaviors (S) wait for child to produce interpretable behaviors (S) attend to child's focus of attention by following the child's lead (S) provide appropriate verbal and nonverbal consequences to child's acts	Familiar activities & routines
Iven et al., 1989	a. Pragmatic Interaction Strategies Intervention	NDBI	Group: In-person	(S) reference - direct child's attention to an object or event through gestures or verbalizations (S) model - label items or events in the environment not contingent upon a request for information (S) imitation - repeat exactly or partially child's verbal and/or nonverbal behaviors (S) description - provide child with more information about items or events, including adjectives, prepositions and adverbs (S) parallel talk - describe actions of self and child as the actions are occurring (S) expansion - repeat child utterance while adding new words to make it more grammatically complete	Play routines
Pennington et al., 2009	a. It Takes Two to Talk	Developmental	Mixed: In-person	(S) strategies to facilitate child language development (S) strategies to maximize child communication opportunities	Familiar activities & routines; play routines
Romski et al., 2010	a. Parent-Implemented Communication Intervention - Augmented Communication Input	NDBI	One-on-one: In-person	(S) model augmented and spoken word use of the individualized target vocabulary via an SGD (S) avoid direct communication demands of the child (S) provide the child with natural reinforcers (S) shorten utterance length (S) give child choice between two toys or books or snacks (S) pause and slow interactions so that child has a chance to communicate	Mealtimes; play routines; shared book reading
	b. Parent-Implemented Communication Intervention - Spoken communication	NDBI	One-on-one: In-person	(S) visually, verbally, and physically prompt child to produce augmented words for an individualized target set of vocabulary (S) hand-over-hand prompting (S) shorten utterance length (S) give child choice between two toys or books or snacks (S) pause and slow interactions so that child has a chance to communicate	Mealtimes; play routines; shared book reading
	c. Augmented Communication Output	NDBI	One-on-one: In-person	(S) provide verbal and/or hand-over-hand prompts so that child produces communication using speech generating device. (S) use of naturalistic routines (S) use of environmental arrangement (S) provide choices (S) pause to “encourage” communication	Mealtimes; play routines; shared book reading
Yang, 2016	a. Musical Bonds Program	Sensory-based	One-on-one: In-person	(S) facilitate parent–child interactions and synchrony during musical play (S) expand musical play repertoire (S) responsiveness to child: use of affect, behavioral and developmental matching, reciprocity, shared control, and contingency	Music time
Autism
Barrett et al., 2020	a. Pivotal Response Intervention for Social Motivation	NDBI	One-on-one: In-person	(S) use social activities as reinforcement (S) noncontingent exposure (S) high affect bids verbal prompts (S) child attention (S) child choice (S) playful opportunity (S) natural reinforcement (S) contingency of reinforcement (S) reinforcing attempts	Social activities
Liu & Schertz, 2021	a. Joint Attention Mediated Learning	NDBI	One-on-one: In-person	(S/I) mediated learning principles (S) how to address child's social challenges (S) how to distinguish social versus nonsocial acts	Familiar activities & routines; play routines
Rogers et al., 2019	a. Enhanced Parent-Implemented Early Start Denver Model	NDBI	One-on-one: In-person	(S) increasing child's attention and motivation (S) using sensory social routines (S) promoting dyadic engagement and joint activity routines (S) enhancing nonverbal communication (S) building imitation skills (S) facilitating joint attention (S) promoting speech development (S) using antecedent behavior-consequence relationships (“ABC's of learning”) (S) employing prompting, shaping, and fading techniques (S) conducting functional assessment of behavior to develop new interventions	Familiar activities & routines; mealtimes; play routines; shared book reading
	b. Parent-Implemented Early Start Denver Model	NDBI	One-on-one: In-person	(S) increasing child's attention and motivation (S) using sensory social routines (S) promoting dyadic engagement and joint activity routines (S) enhancing nonverbal communication (S) building imitation skills (S) facilitating joint attention (S) promoting speech development (S) using antecedent behavior-consequence relationships (“ABC's of learning”) (S) employing prompting, shaping, and fading techniques (S) conducting functional assessment of behavior to develop new interventions	Familiar activities & routines; mealtimes; Play routines; shared book reading
Rollins et al., 2019	a. Pathways	NDBI	One-on-one: In-person	(S) following child's lead, limiting of distractions, use of wait time (S) face-to-face dyadic interactions and social sensory routines (S) reinforcement of activities, with behaviors as reinforced immediately and consistently (S) facilitation of social eye contact without aversive prompts (S) use of animation (S) contingent imitation of the child vocalizations, words, and gestures (S) use of imitation, modeling, and expansion of language	Play routines
Language delay/disorder
Baxendale et al., 2003	a. Hanen Parent Program	Developmental	Mixed: In-person	(S) strategies focused on enhancing parents' language and interaction style	Play routines
	b. Conventional Clinic	NDBI	In-person	(S) modeling (S) imitation (S) expansion (S) focusing attention through play	Play routines
Ciccone et al., 2012	a. Parent-Focused Early Intervention Program	NDBI	Mixed: In-person	(S) following the child's lead (S) encouraging participation (S) language modelling strategies (S) focused stimulation (S) using music and using books	—
Falkus et al., 2016	a. Parent–child Interaction Therapy	Developmental	One-on-one: In-person	(S) letting child choose toy (S) following what child wants to do with toy (S) sitting where child can easily see you (S) waiting for child to start the talking with words/sounds/gestures (S) giving child enough time to talk (S) showing child you are listening by repeating or answering (S) commenting on what child is doing (S) not asking child questions (S) praising child (S) talking slowly so child understands	Familiar activities & routines; play routines
Gibbard & Smith, 2016	a. Enhanced Parent-Based Intervention	Cannot be Determined	Mixed: In-person	(S) strategies to facilitate language development through interaction, daily routines, naturally occurring situations and parenting activities (I) increased awareness of role and importance in child's language development	Familiar activities & routines
Girolametto et al., 1996	a. Hanen Program for Parents	Developmental	Mixed: In-person	(S) incorporate 10 target words into existing daily routines (S) repeat target word at least five times during each interaction (S) join in the child's play (S) model targets using labels, short comments, or expansions (S) set up new routines to model target words in many different contexts using different exemplars (S) select additional lexical targets once the child had used the target word spontaneously at least three times in three different situations within one week (S) model two-word combinations	Familiar activities & routines
McDade & McCartan, 1998	a. Hanen Program	Developmental	Mixed: In-person	(S) interaction-promoting strategies: taking one turn and waiting expectantly for child to respond, signaling child nonverbally to take a turn (S) language modeling strategies: responsive labels, comments, expansions, extensions, parallel talk (S) child-oriented strategies: follow child's lead, interpret child's cues, respond to child's focus of attention, and reduce directiveness	Familiar activities & routines
Pearce et al., 1996	a. Hanen Program for Parents	Developmental	Mixed: In-person	(S) use target words in labels, comments, or expansions during naturalistic routines (S) model target words in many different contexts (S) use different exemplars (S) express different intentions (e.g., request, comment)	Familiar activities & routines; Play routines; shared book reading
Roberts & Kaiser, 2012	a. Parent-implemented Enhanced Milieu Teaching	NDBI	One-on-one: In-person	(S) use of modeling and expanding communication (S) time delay strategies (S) prompting strategies	Familiar activities & routines; mealtimes; play routines; shared book reading
Roberts & Kaiser, 2015	a. Enhanced Milieu Teaching	NDBI	Mixed: In-person	(S) Enhanced Milieu Teaching strategies (S) promote language acquisition in everyday interactions	Familiar activities & routines
Suttora et al., 2021	a. Oltre il Libro – Dialogic Book Reading	NDBI	Group: In-person	(S) turn-taking skills (S) use of extra-verbal cues as intonation, rhythm, and gestures (S) adjust speech to child's linguistic skills (S) use simple sentences and redundant lexicon (S) use open-ended, wh-questions (S) focused stimulation on target words that are already understood but not produced by child (S) expand child's verbal productions	shared book reading
Tannock et al., 1992	a. Hanen Early Language Parent Program	Developmental	Mixed: In-person	(S) interaction-promoting strategies: taking one turn and waiting expectantly for child to respond, signaling the child nonverbally to take a turn, avoid adult dominance of the interaction (S) language-modeling strategies: responsive labels and comments, expansions, extensions, parallel talk (S) child-oriented strategies: follow child's lead, interpret child's cues, respond to child's focus of attention, and reduce directiveness	—
36 through 48 months
Developmental disorder
Girolametto et al., 1998	a. Hanen Program	Developmental	Mixed: In-person	(S) incorporating target words into existing daily routines (S) using target words in response to the child's interest or activity (S) join in child's play and model words using labels, short comments, or expansions (S) use routines to model target words in many different contexts (S) strategies to select target words (S) model two-word combinations	Familiar activities & routines
Girolametto, 1988	a. Hanen Early Language Parent Program	Developmental	Mixed: In-person	(S) observe (S) follow child's lead (S) use play, games, art, books, and music (S) respond contingently to child's communicative attempts (S) promote turn taking (S) use conversational repair signals (S) provide clear linguistic models (I) increase awareness of the form, content, and use of child's communication system	Play routines
Kaiser & Roberts, 2013	a. Parent + Therapist Enhanced Milieu Teaching	NDBI	One-on-one: In-person	(S) arrange environment to set stage for adult–child interactions (S) model specific language targets appropriate to child's skill level (S) expand child communication forms by adding words to child utterances (S) respond to child's requests with prompts for elaborated language (S) functional reinforcement of child's production of prompted target forms	Familiar activities & routines; mealtimes; play routines; shared book reading
Kot & Law, 1995	a. Parent Linguistic Input	Developmental	Mixed: In-person	(S) increase frequency and saliency of linguistic input with relevance to child's focus of attention (word-mapping opportunities)	—
Weistuch et al., 1991	a. Language Interaction Intervention Program – Site 1	Developmental	Group: In-person	(S) how to help child form word categories (S) use words across a range of communicative intents (S) build from words to content categories that govern word combinations	—
	b. Language Interaction Intervention Program – Site 2	Developmental	Group: In-person	(S) how to help child form word categories (S) use words across a range of communicative intents (S) build from words to content categories that govern word combinations	—
Autism
Aldred et al., 2004	a. Social Communication Intervention	Developmental	Mixed: In-person	(S) shared attention (S) sensitivity (S) modelling (S) consolidation (S) elaboration	—
Alquraini et al., 2018	a. Responsive Teaching	NDBI	One-on-one: In-person	(S) contingency (S) affect (S) match	Play routines
Braiden et al., 2012	a. Forward Steps Early Intervention Program with Treatment and Education of Autistic and Related Communication Handicapped Children (TEACCH) Approach	TEACCH	One-on-one: In-person	(S) visual cues (I) understanding child's autism	—
Casenhiser et al., 2013	a. Milton & Ethel Harris Research Initiative	Developmental	In-person	(S) co-regulation (S) expression of enjoyment of child (S) sensory-motor supports (S) joining (S) use of affect (S) support of reciprocity (S) support of independent thinking	—
Green et al., 2010	a. Preschool Autism Communication Trial	Developmental	One-on-one: In-person	(S) increase sensitivity and responsiveness to child communication (S) reduce mistimed parental responses (S) use action routines (S) use familiar repetitive language (S) pause	—
Hampton et al., 2020	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device	NDBI	One-on-one: In-person	(S) matched turns (S) target-level language (S) expansions (S) time delays (S) milieu prompting (S) engagement and play strategies (S) using joint attention and gestures	Familiar activities & routines; mealtimes; play routines; shared book reading
Ingersoll & Wainer, 2013	a. Project ImPACT	NDBI	Mixed: In-person	(S) use a blend of developmental and naturalistic behavioral intervention strategies (S) promote child's social engagement (S) promote language (S) use imitation (S) use strategies in play and daily routines	Familiar activities & routines
Ingersoll et al., 2016	a. Therapist-Assisted ImPACT Group	NDBI	One-on-one: Self-paced tutorials	(S) targets social communication using a naturalistic, developmental-behavioral intervention	—
	b. Self-Directed ImPACT Group	NDBI	One-on-one: Self-paced tutorials	(S) targets social communication using a naturalistic, developmental-behavioral intervention	—
Matthews et al., 2018	a. JumpStart	Behavioral	Mixed: In-person	(S/I) applied behavior analysis (S/I) pivotal response treatment (S/I) disruptive behaviors (S/I) toilet training What is autism? accessing services (I) Individualized Education Plans	—
McGarry et al., 2020	a. Pivotal Response Training	NDBI	One-on-one: Self-paced tutorials	(S) set up a learning opportunity PRT strategies: child choice/shared control, clear learning opportunities, interspersing maintenance and acquisition tasks (S) respond to child's language PRT strategies: natural reinforcers, reinforcing attempts, immediate/contingent reinforcement (S) choose a treatment plan identifying a developmentally appropriate target skill (S) use model, open-ended, and time-delay prompts (S) using social reinforcers Incorporating child interests within social activities	Familiar activities & routines; play routines
Minjarez et al., 2011	a. Pivotal Response Training	NDBI	Mixed: In-person	(S/I) Pivotal Response Training	Play routines
Noyan Erbas et al., 2020	a. Hanen More Than Words	Developmental	Mixed: In-person	(S) follow child's lead (S) strategies to keep interactions going (S) observe, wait, and listen to child (S) how to help child learn daily routines (S) how to use strategies to teach toy play (S) how to help child with peer interactions (S) how to use books for interaction (S) how to transfer newly learned interaction skills to practical applications with child in daily environment	Familiar activities & routines; play routines
Sengupta et al., 2020	a. Project ImPACT	NDBI	Mixed: In-person; texts & emails	(S) follow child's lead (S) face to face (S) imitate child (S) join in child's play and make interactive (S) use animation (S) model and expand child's language (S) use communicative temptations to create opportunities for communication and increase social engagement (S) prompts and reinforcement to increase complexity of child's response (S) taking turns during play (I) stages of play	Familiar activities & routines
Venker et al., 2012	a. Hanen More Than Words	Developmental	Mixed: In-person	(S) be verbally responsive by talking about child's play (follow-in commenting) (S) respond to child's communication acts using linguistic mapping and expansions (S) use of strategies to engage child in play: establishing play routines and supporting object-focused engagement (S) prompt communication: arrange environment with favored items in sight but out of reach, provide choices, give pieces of toys bit by bit, and insert pauses during familiar verbal routines (S) strategies to establish interactive “people games” that provide child with predictable social turn-taking routines (S) decrease redirects of child's attention away from a toy of interest	Play routines
Wainer et al., 2021	a. Stepped-care Online Reciprocal Imitation Training	NDBI	One-on-one: Self-paced tutorial; telehealth/video conferencing coaching	(S) select activities and antecedent controls (S) schedule practice time (S) ensure a support system (S) imitate child (S) describing play using linguistic mapping, simple and descriptive language at or slightly above child's linguistic level (S) use modeling, prompting, and reinforcement to teach a target skill, and pace the interaction	Play routines
Language delay/disorder
Tannock et al., 1992	a. Hanen Early Language Parent Program	Developmental	Mixed: In-person	(S) interaction-promoting strategies: taking one turn and waiting expectantly for child to respond, signaling the child nonverbally to take a turn, avoid adult dominance of the interaction (S) language-modeling strategies: responsive labels and comments, expansions, extensions, parallel talk (S) child-oriented strategies: follow child's lead, interpret child's cues, respond to child's focus of attention, and reduce directiveness	—

Note. Only studies where the language intervention group had promising or compelling evidence are included in the table. Em dashes indicate data not reported. NDBI = naturalistic developmental behavioral intervention; TEACCH = Treatment and Education of Autistic and Related Communication Handicapped Children; ImPACT = Improving Parents as Communication Teachers.

Table 8.

Number of child outcomes for each study by evidence level and outcome domain.

Study	Targeted treatment (TT) and treatment comparison (TC) or other comparison (OC) study groups	Evidence level and outcome domain
		Compelling				Promising				Lacking
		EX	RE	S/P	GL	EX	RE	S/P	GL	EX	RE	S/P	GL
12 through 23 months
Developmental disorder
Fey et al., 2013	a. Milieu Communication Teaching – High Intensity (TT)									6	1
	b. Milieu Communication Teaching – Low Intensity (TC*)
	Follow-up (6 months)									6/6	1/1
	Follow-up (15 months)									6/6	1/1
Yoder & Warren, 2002	a. Responsivity Education and Prelinguistic Milieu Teaching (TT)									7
	b. Control Group (OC)
Autism
Brian et al., 2016	a. Social ABCs (TT)					4	1			1	1
	Follow-up (3 months)					4/4	1/1			1/1	1/1
Carter et al., 2011	a. Hanen More Than Words (TT)									3		1
	b. Business as Usual (OC)
	Follow-up (4 months)									3/3		1/1
Stahmer et al. 2020	a. Project ImPACT for Toddlers (TT)	3	1	2	2					1		1
	b. Treatment as Usual (OC)
	Follow-up (3 months)	3/3	1/1	2/2	2/2					1/1 +		1/1
24 through 35 months
Developmental disorder
Cycyk et al., 2020	a. Language and Play Every Day en Español Intervention (TT)					3	1			1
Fey et al., 2006	a. Responsivity Education/Prelinguistic Milieu Teaching – Down syndrome (TT)	1				4				1
	b. Responsivity Education/Prelinguistic Milieu Teaching – Other Etiology (TC*)					3				3
	c. Responsivity Education/Prelinguistic Milieu Teaching – Entire sample (TC)
Pennington et al., 2009	a. It Takes Two to Talk (TT)					4		1		1
	Follow-up (4 months)					4/4		1/1		1/1
Romski et al., 2010	a. Parent-Implemented Communication Intervention – Augmented Communication Input (TT)	4				2				4
	b. Parent-Implemented Communication Intervention – Spoken communication (TT)*
	c. Augmented Communication Output (TT)	4				2				4
Yang, 2016	a. Musical Bonds Program (TT)					1
Autism
Barrett et al., 2020	a. Pivotal Response Intervention for Social Motivation (TT)	2			1					1
	b. Waitlist Control (OC)
Rogers et al., 2019	a. Enhanced Parent-Implemented Early Start Denver Model (TT)												3
	b. Parent-Implemented Early Start Denver Model (TC*)
Language delay/disorder
Baxendale et al., 2003	a. Hanen Parent Program (TT)									1			1
	b. Conventional Clinic (TC)
	Follow-up (6 months)									1/1			1/1
Ciccone et al., 2012	a. Parent-Focused Early Intervention Program (TT)					1	1	1	1
Falkus et al., 2016	a. Parent–child Interaction Therapy (TT)					1
Gibbard & Smith, 2016	a. Enhanced Parent-Based Intervention (TT)					1
Girolametto et al., 1996	a. Hanen Program for Parents (TT)	4				8
	b. Delayed Treatment (OC)
McDade & McCartan, 1998	a. Hanen Program (TT)					1			1	1	1
	b. Control Group (OC)
Roberts & Kaiser, 2012	a. Parent-implemented Enhanced Milieu Teaching (TT)	4	1		1
	b. LI – business as usual (OC)
	c. TD – business as usual (OC)
Roberts & Kaiser, 2015	a. Enhanced Milieu Teaching (TT)	1	2							3
	b. Business as Usual (OC)
Suttora et al., 2021	a. Oltre il Libro – Dialogic Book Reading (TT)	3
	b. Treatment as Usual (OC)
Tannock et al., 1992	a. Hanen Early Language Parent Program (TT)	1				2	1			6
	b. Wait List Control (OC)
	Follow-up (4 months)	1/1				2/2	1/1 +			5/6 1/6 +
36 through 48 months
Developmental disorder
Girolametto et al., 1998	a. Hanen Program (TT)					2				2
	b. Delayed Treatment (OC)
Girolametto, 1998	a. Hanen Early Language Parent Program (TT)					5				2
	b. Delayed Treatment (OC)
Kaiser & Roberts, 2013	a. Parent + Therapist Enhanced Milieu Teaching (TT)	3				4				7	2
	b. Therapist Only Enhanced Milieu Teaching (OC)
	Follow-up (6 months)	3/3				2/4 2/4 +				6/7 1/7 +	2/2
	Follow-up (12 months)	3/3				2/4 2/4 +				6/7 1/7 +	2/2
Kot & Law, 1995	a. Parent Linguistic Input (TT)					1				4		1
	b. Group Only – No parent training (OC)
Weistuch et al., 1991	a. Language Interaction Intervention Program – Site 1 (TT)					1
	b. Language Interaction Intervention Program – Site 2 (TT)					1
	c. Control Group (OC)
Autism
Aldred et al., 2004	a. Social Communication Intervention (TT)	2									1
	b. Routine Care (OC)
Alquraini et al., 2018	a. Responsive Teaching (TT)			1	1
	b. Standard Community Services (OC)
Braiden et al., 2012	a. Forward Steps Early Intervention Program with TEACCH (TT)					2	2
Casenhiser et al., 2013	a. Milton & Ethel Harris Research Initiative (TT)			1									1
	b. Business as Usual/Delayed Treatment (OC)
Green et al., 2010	a. Preschool Autism Communication Trial (TT)					2	1	3	1	1	1		1
	b. Treatment as Usual (OC)
Hampton et al., 2020	a. Joint Attention, Structured Play, Engagement and Regulation plus Enhanced Milieu Teaching plus Speech-Generating Device (TT)							1		3	1
	b. Business as Usual (OC)
	Follow-up (4 months)							0/1		2/3 1/3 +	1/1
Ingersoll & Wainer, 2013	a. Project ImPACT (TT)					2		5	2			1
Ingersoll et al., 2016	a. Therapist-Assisted ImPACT Group (TT)							1		2			1
	b. Self-Directed ImPACT Group (TC)
	Follow-up (3 months)							1/1		2/2			1/1
Matthews et al., 2018	a. JumpStart (TT)	1
	b. Waitlist Control (OC)
	Follow-up (3 months)	1/1
McGarry et al., 2020	a. Pivotal Response Training (TT)					1		1
Minjarez et al., 2011	a. Pivotal Response Training (TT)					1
Noyan Erbas et al., 2020	a. Hanen More Than Words (TT)					2	1		2	1
	Follow-up (4 weeks)					2/2	1/1		2/2	1/1 +
Sengupta et al., 2020	a. Project ImPACT (Improving Parents as Communication Teachers; TT)					1	1	4
Venker et al., 2012	a. Hanen More Than Words (TT)	1			1							1
	b. Delayed Treatment (OC)
Wainer et al., 2021	a. Stepped-care Online Reciprocal Imitation Training (TT)			2
	b. Treatment as Usual (OC)
Language delay/disorder
Tannock et al., 1992	a. Hanen Early Language Parent Program (TT)					1				8	1
	b. Wait List Control (OC)
	Follow-up (4 months)									7/8 1/8 +	1/1 +

Note. Only studies where the language intervention group had promising or compelling evidence are included in the table. EX = expressive; RE = receptive; S/P = social/pragmatic; GL = global (receptive & expressive); LI = language impairment; TD = typical development; ImPACT = Improving Parents as Communication Teachers.

^*Denotes language intervention groups without evidence ratings included in syntheses.

⁺ Indicates a significant positive change in outcome between posttest and follow-up analyses.

Zero Through 11 Months

There were no studies with children in the 0- through 11-month-old age range identified in our review that yielded an adult language outcome measure with promising or compelling evidence. The only study identified with children under 12 months of age (Barrera et al., 1987) lacked any compelling or promising adult communication outcomes measures to support a caregiver-implemented communication intervention. The Barrera study was a non-RCT evaluating a developmental Home Responsiveness Intervention for children with Down syndrome (see Supplemental Materials S3–S7 for further information on the Barrera et al. [1987] study).

Twelve Through 23 Months

Study, Child, and Caregiver Characteristics

There were 10 studies that yielded 12 caregiver-implemented communication intervention groups for children 12 through 23 months identified as having communication impairment. Of the 10 studies, three did not report outcomes with compelling or promising evidence, yielding seven studies for our synthesis comprising eight intervention groups. The three excluded studies included children with language delay or disorder; two were RCTs and one was a non-RCT; and two evaluated developmental interventions and two evaluated NDBIs. Of the seven studies included, one included two intervention groups, yielding a total of eight intervention groups. The included studies were published from 1988 through 2020 and were conducted in three different countries or territories, including the United States (n = 5), Canada (n = 1), and India (n = 1). Three studies were RCTs, two were a non-RCTs, and two were single-group studies. See Table 4.

The number of children in the intervention groups ranged from 10 to 41 with an average of 24.81 (SD = 11.04) children per group. The average age of the children in the intervention group was 20.98 months (SD = 2.05; min–max: 17.6–23.08). Four groups comprised children with developmental disorder, three comprised children on the autism spectrum, and one comprised children language delay or disorder. For seven groups, child gender was reported with males and females comprising 71% and 29% of the groups, respectively.

Caregivers typically included an unspecified parent (n = 5). For two study groups, it was specified that the caregivers included both mothers and fathers, and for one group, the caregivers included foster parents and grandparents in addition to mothers and fathers. Caregiver age was reported for one group (mother: 30.2 years; father: 32.3 years). Four studies reported the race of their participant groups (n = 4 groups reporting), with, on average, 64% (SD = 29.63) of participants within these groups being identified as White (n = 4 groups reporting), 48% as Black (n = 1 group reporting), 15% as East Asian (n = 1 group reporting), 50% as Latino (n = 1 group reporting), and 12% (SD = 8.10) as Asian or Pacific Islander (n = 7 groups reporting). See Table 5.

Intervention Components

Three of the interventions were identified as being variations of milieu teaching, all of which were in the developmental delay subgroup. The other interventions delivered had unique names. The person who trained caregivers to implement the intervention varied across studies including the following: trained paraprofessionals (n = 2 groups), speech-language pathologists (n = 1 group), trained early intervention providers (n = 1 group), teacher consultants (n = 1 group), researchers (n = 1 group), and parent educators (n = 1 group). For all groups, the intervention was delivered in English (n = 8 groups). For the one study (n = 1 group), in the language delay/disorder subgroup, the intervention language was also delivered in Tamil. For six groups, the intervention was delivered in family homes. For two of these groups, intervention was also delivered in an early childhood education setting (n = 1 group) and an unspecified location (n = 1 group). For one group, no location was specified. See Table 6.

The number of intervention sessions ranged from three to 12 with an average of 9.33 sessions (SD = 3.39), with two groups unreported. Session lengths ranged from 1 to 2.5 hr with an average length of 81.0 min (SD = 39.12), with three groups unreported. The most common session length was 1 hr (n = 4 groups). The duration of the intervention ranged from 1 to 50 weeks with an average duration of 19.4 weeks (SD = 16.86). Duration was not reported for one group. Frequency of sessions was reported for five groups, with three groups receiving weekly sessions and two receiving sessions 3 times per week. See Table 6.

The most common delivery format included one-on-one, in-person (n = 6 groups). For one of these groups, the intervention was also delivered via phone calls and texts/e-mails. For two groups, the format was a mix of one-on-one and group, in-person. We characterized five of the interventions as NDBIs and three as developmental. The delivery formats and intervention characterizations were mixed across the diagnostic subgroups. All but one of the intervention groups reported teaching strategies to caregivers. One study shared both strategies and information. The depth of details regarding specific intervention strategies taught to caregivers varied across studies, ranging from broad “speech-language stimulation strategies” to specific strategies such as “following child's lead” and “comment on child's acts and objects of attention.” Information shared included speech and language milestones, and information on play development. No studies only shared information with caregivers. The contexts in which caregivers were taught to use the strategies were specified for seven of the eight groups. These contexts included familiar activities and routines (n = 5 groups) and play routines (n = 5 groups). See Table 7.

Caregiver and Child Outcome Measures

Caregiver outcomes. Across the seven studies and eight communication intervention groups, there were a total of 34 caregiver outcomes (note that for one study group evidence levels were not coded; see Table 3). There were 4.25 caregiver outcomes per group (min–max: 1–11). There were no outcome measures of nonverbal communicative behaviors (e.g., use of gestures or sign language) within this age group.

Of the three studies in the developmental disorder subgroup, none included a measure of spoken language input, whereas two included global communicative measures, yielding a total of three outcomes (compelling = 1; promising = 2). All three studies included measures based on caregiver child interactions, yielding a total of nine outcomes (compelling = 4; promising = 5). Only one study within this group included follow-up assessments, which provided evidence that caregiver communicative outcomes maintained 6 and 12 months postintervention.

Within the autism subgroup, none of the three studies included spoken language input outcomes, while two included global communicative measures, yielding a total of three outcomes (compelling = 1; promising = 2). Measures based on caregiver child interactions were assessed in two studies, yielding a total of 11 outcomes (compelling = 10; promising = 1). All three studies in the autism subgroup included follow-up assessments, with results suggesting that caregiver communicative outcomes maintained postintervention.

For the one study within this age range that was represented in the language delay/disorder subgroup, seven of the outcomes were spoken language input outcomes (promising = 3; lacking = 4) and one outcome was based on caregiver–child interactions, which provided lacking evidence. This study also included a follow-up assessment with results suggesting that caregiver communicative outcomes were maintained postintervention.

Child outcomes. Of the seven studies that had caregiver outcomes with compelling or promising evidence, five also included child outcome measures (see Table 8). There were seven communication intervention groups that yielded a total 34 outcomes with a group average of 4.86 (min–max: 3–10).

There were two studies represented in the developmental disorder subgroup, both studies included measures of expressive language, yielding a total of 13 outcomes all with lacking evidence. One study included one measure of receptive language, also providing lacking evidence. Neither study included social/pragmatic or global measures of language. One of these studies included follow-up assessments with results indicating that child communication outcomes were maintained postintervention.

All three of the studies in the autism subgroup included expressive language measures, yielding a total of 12 outcomes (compelling = 3; promising = 4; lacking = 5). Two studies included receptive language outcomes, yielding a total of three outcomes (compelling = 1; promising = 1; lacking = 1). Two studies included social/pragmatic outcomes, yielding a total of four outcomes (compelling = 3; lacking = 1). Global measures of language were only assessed in one study, yielding a total of two outcomes, both with compelling evidence. All three studies included a follow-up time point with results suggesting that child communicative outcomes were maintained postintervention.

Twenty-Four Through 35 Months

Study, Child, and Caregiver Characteristics

There were 23 studies that yielded 28 intervention groups for children 24 through 35 months identified as having communication impairment. Of the 23 studies, two did not report outcomes with compelling or promising evidence, yielding 21 studies for our synthesis comprising 26 caregiver communication intervention groups. The two excluded studies included children with language delay or disorder; one was an RCT and one was a non-RCT; and one evaluated a developmental interventions and one evaluated an NDBI. Of the 21 studies included, three included two intervention groups and one included three intervention groups. These studies were published from 1989 through 2021 and were conducted in five different countries or territories, including the United States (n = 11), the United Kingdom (n = 5), Canada (n = 3), Australia (n = 2), and Italy (n = 1). Most studies were RCTs (n = 11), followed by single-group studies (n = 7) and non-RCTs (n = 3). Study characteristics varied within the diagnostic subgroups, with the exception that all four of the studies within the autism subgroup were RCTs conducted in the United States. See Table 4.

The number of children in the intervention groups ranged from seven to 45 with an average of 18.19 (SD = 8.70) children per group. The average age of the children in the intervention group was 29.04 months (SD = 3.29; min–max: 24–35.75). Twelve of the intervention groups comprised children with language delay or disorder, nine comprised children with developmental disorder, and five comprised children on the autism spectrum. For 20 groups, child gender was reported with males and females comprising 74% and 26% of the groups, respectively. See Table 5.

Caregivers typically included an unspecified parent or caregiver (n = 13). For seven study groups, it was specified that the caregivers included both mothers and fathers, one of which also included grandparents. Six study groups only included mothers, whereas there were no study groups with only fathers. For 11 groups, caregiver age was reported with a mean of 36.79 years (SD = 4.36; min–max: 30.6–45.9). Nine studies reported the race of their participant groups (n = 14 groups reporting), with, on average, 63% (SD = 23.32) of participants within these groups being identified as White (n = 11 groups reporting), 36% (SD = 40.39) as Latino (n = 5 groups reporting), 21% (SD = 9.15) as Black (n = 7 groups reporting), 16% (SD = 0) as Black or Asian or Pacific Islander (n = 2 groups reporting), 10% (SD = 5.90) as Asian or Pacific Islander (n = 7 groups reporting), and 10% as multiracial (n = 1 group reporting). See Table 5.

Intervention Components

Common interventions delivered included variations of the Hanen Program (n = 6 groups), with five groups in the language delay/disorder subgroup and one group in the developmental disorder subgroup receiving such, and milieu teaching (n = 4 groups), with two groups in the developmental delay subgroup and two groups in the language delay/disorder subgroup receiving such. Most frequently, the person who trained caregivers to implement the intervention was a speech-language pathologist (n = 14 groups). Other trainers included unspecified trainers/educators (n = 7 groups), psychologists (n = 3 groups), students (n = 3 groups), trained parents (n = 2 groups), behavior analysts family therapists (n = 2 groups), and teachers (n = 1 group). For the majority of the groups, the intervention was delivered in English only (n = 23 groups). For two studies (n = 2 groups), the intervention was delivered in both English and Spanish, and for one study (n = 1 group), the intervention language was Italian. For 18 groups, the intervention was delivered in family homes. For four of these groups, intervention was delivered in a second location that was not specified. Other locations included clinics (n = 6 groups), university setting (n = 3 groups), early childhood setting (n = 3 groups), and an unspecified community location (n = 1 group). For four groups, the location was not reported. See Table 6.

The number of intervention sessions ranged from four to 32 with an average of 14.40 sessions (SD = 8.50). Number of sessions was not reported for one group. Session length ranged from 30 min to 2.5 hr with an average length of 78.90 min (SD = 37.92). The most common session length was 1 hr (n = 7 groups). Session length was not reported for two groups. The duration of the intervention ranged from 4 weeks to 8 months with an average duration of 13.46 weeks (SD = 6.62). The most common intervention durations were 3 months (n = 9 groups) and 6 months (n = 3 groups). Duration was not reported for two groups. Frequency of sessions was reported for 19 groups, with nine groups receiving weekly sessions and 10 receiving sessions 2–3 times per week. See Table 6.

We characterized 16 of the interventions as NDBIs, eight as developmental, and one as sensory-based. All of the interventions in the autism subgroup were NDBIs, whereas the other subgroups included a mix of intervention types. For one group, there was not enough information available to reliably characterize the intervention. The most common delivery formats included one-on-one, in-person (n = 13 groups), and mix of one-on-one and group, in-person (n = 10 groups). Two groups used an only group, in-person format, and for one group, it was only noted that sessions were in-person (i.e., individual vs. group was not reported). For all of the autism groups, interventions were delivered one-on-one, in-person. The depth of details regarding specific intervention strategies taught to caregivers varied across studies, ranging from broad “strategies to facilitate child language development” to specific strategies such as “following child's lead” and “use of imitation, modeling, and expansion of language.” Only one study, which was in the language delay/disorder subgroup indicated that a key component of the intervention was to share information with caregivers: “increased awareness of role and importance in child's language development.” No studies only shared information with caregivers. The contexts that caregivers were taught in which to use the strategies were specified for all but two groups. These contexts included play routines (n = 15 groups), familiar activities and routines (n = 14 groups), shared book reading (n = 8 groups), mealtimes (n = 6 groups), music time (n = 1 group), and social activities (n = 1 group). See Table 7.

Caregiver and Child Outcome Measures

Caregiver outcomes. Across the 21 studies and 26 communication intervention groups, there were a total of 91 caregiver outcomes (note that for three study groups, evidence levels were not coded; see Table 3). There was an average of 3.37 caregiver outcomes per group (min–max: 1–9). There were no outcome measures of nonverbal communicative behaviors (e.g., use of gestures or sign language) within this age group.

Within the developmental disorder subgroup, three studies included measures of spoken language input, yielding a total of 14 outcomes (promising = 6; lacking = 8). Two of these studies included global communicative outcomes, yielding a total of four outcomes (promising = 1; lacking = 3). All six studies within the developmental disorder subgroup included measures based on caregiver–child interactions, yielding a total of 15 outcomes (compelling = 3; promising = 6; lacking = 6). One of these studies included a follow-up assessment, with results suggesting that caregiver communicative outcomes were maintained postintervention.

None of the four studies in the autism subgroup included spoken language input outcomes. Of these four studies, two included global communicative measures, yielding a total of two outcomes (promising = 1; lacking = 1). All four studies included measures based on caregiver–child interactions, yielding a total of five outcomes (compelling = 3; promising = 1; lacking = 1).

Of the 11 studies in the language delay/disorder subgroup, five included measures of spoken language input, yielding a total of 18 outcomes (compelling = 7; promising = 6; lacking = 5). Six of these studies included global communicative outcomes, yielding a total of 13 outcomes (compelling = 10; promising = 2; lacking = 1). Eight of these included measures based on caregiver–child interactions yielding a total of 20 outcomes (compelling = 13; promising = 5; lacking = 2). There were two studies with follow-up assessments within the language delay/disorder subgroup, both indicating that for the caregiver communicative outcomes assessed, results maintained postintervention.

Child outcomes. Of the 21 studies that had caregiver outcomes with compelling or promising evidence, 17 also included child outcome measures (see Table 8). There were 23 communication intervention groups that yielded 100 child communication-focused outcomes with a group average of 4.35 measures (min–max: 1–12).

All five of the studies in the developmental disorder subgroup included expressive language outcomes, yielding a total of 42 outcomes (compelling = 9; promising = 19; lacking =14). Only one study included one receptive language measure that provided promising evidence. One study included one social/pragmatic outcome that yielded promising evidence. None of the five studies included any global measures of language. One of these studies included follow-up assessments, with results suggesting that child communicative outcomes maintained postintervention.

Of the two studies in the autism group, one included three measures of expressive language (compelling = 2; lacking = 1). Both studies included global measures of language, yielding a total of four outcomes (compelling = 1; lacking = 3).

Each of the 10 studies in the language delay/disorder subgroup included measures of expressive language, yielding a total of 38 outcomes (compelling = 12; promising = 13; lacking =13). Five studies included measures of receptive language, yielding a total of six outcomes (compelling = 3; promising = 1; lacking = 2). One study included one social/pragmatic outcome that provided promising evidence. Four studies included a global measure of language, yielding a total of four outcomes (compelling = 1; promising = 2; lacking = 1). Of studies within the language delay/disorder subgroup, two studies included follow-up assessments, with results suggesting that child communicative outcomes were maintained postintervention.

Thirty-Six Through 48 Months

Study, Child, and Caregiver Characteristics

There were 26 studies that yielded 28 intervention groups for children 36 through 48 months identified as having communication impairment. Of the 26 studies, five did not report outcomes with compelling or promising evidence, yielding 21 studies for our synthesis comprising 23 caregiver communication intervention groups. A total of 19 studies included one such group and two included two groups. The excluded studies comprised four studies in the autism subgroup and one in the language delay/disorder subgroup, all of which were conducted in the United States with the exception of one study in the autism subgroup conducted in the United Kingdom. The studies were published from 1988 through 2021, 15 of which were published in 2010 or later. The studies were conducted in nine different countries or territories, including the United States (n = 10), Canada (n = 4), the United Kingdom (n = 3), India (n = 1), Northern Ireland (n = 1), Saudi Arabia (n = 1), and Turkey (n = 1). Most studies were RCTs (n = 13), followed by single-group studies (n = 6), and non-RCT (n = 2). See Table 5.

The number of children in the intervention groups ranged from six to 77 with an average of 20.13 (SD = 17.21) children per group. The average age of the children in the intervention group was 41.65 months (SD = 3.09; min–max: 36.14–48). Six of the intervention groups comprised children with developmental disorder, 16 comprised children on the autism spectrum, and one comprised children with language delay or disorder. For 15 of the 21 groups, child gender was reported with males and females comprising 78% and 22% of the groups, respectively. See Table 6.

Caregivers typically included an unspecified parent (n = 8) or both mothers and fathers (n = 6; plus grandparents for one group). Another nine study groups only included mothers, whereas there were no study groups with only fathers. For nine groups, caregiver age was reported with a mean of 34.40 years (SD = 1.93; min–max: 32–38.5). Six studies reported the race of their participant groups, with, on average, 55% (SD = 26.54) of participants within these groups being identified as White (n = 5 groups reporting), 29% (SD = 15.72) as Latino, 24% (SD = 23.33) as Black (n = 2 groups reporting), and 19% (SD = 9.02) as Asian or Pacific Islander (n = 3 groups reporting). See Table 6.

Intervention Components

Common interventions across studies included variations of the Hanen Program (n = 5 groups), Project ImPACT (Improving Parents as Communication Teachers; n = 4 groups), and Pivotal Response Training (n = 2 groups). Most frequently, the person who trained caregivers to implement the intervention was a speech-language pathologist (n = 10 groups), including for four of the five groups in the developmental delay subgroup. Other trainers included unspecified trainers/educators (n = 8 groups), parent educators (n = 2 groups), teachers (n = 1 group), psychologists (n = 2 group), occupational therapists (n = 2 groups), researchers (n = 2 groups), BCBA clinicians (n = 1 group), child development workers (n = 1 group), and special educators (n = 1 group). For 19 of the 23 groups, the intervention was delivered in only English. Other delivery languages included English with Hindi, Arabic, and Turkish (n = 1 group each). For one group, the language was not specified. For 12 groups, the intervention was delivered at least partially in homes; for six groups, the intervention was delivered in a clinic. Other locations included schools (n = 6 groups), university setting (n = 2 groups), unspecified community location (n = 2 groups), and online (n = 1 group). For three groups, the location was not specified. See Table 7.

The number of intervention sessions ranged from six to 52 with an average of 19.48 sessions (SD = 13.65). Session length ranged from 20 min to 3 hr, with an average length of 1.50 hr (SD = 0.76). The most common session lengths were 1 (n = 4 groups) and 2 hr (n = 5 groups). Session length was not reported for four groups. The intervention duration ranged from 1.5 months to 1 year with an average of 17.71 weeks (SD = 13.05). The most common intervention duration was 3 months (n = 3 groups). Duration was not reported for four groups. Frequency of sessions was reported for all but three groups, with 14 groups receiving weekly sessions, three receiving sessions 2–3 times per week, and three having mixed schedules. See Table 7.

We characterized 10 of the interventions as NDBIs, 11 as developmental, one as behavioral, and one as TEACHH. Five of the six interventions in the developmental delay subgroup were developmental. The most common intervention format was a mix of one-on-one and group, in-person (11 groups). Other formats included one-on-one, in-person (n = 5 groups); group, in-person (n = 2 groups); one-on-one self-paced tutorials (n = 4 groups). For one group in addition to one-on-one self-paced tutorials, telehealth video coaching was used. For one group, it was not specified if the in-person format was group or one-on-one. The specific intervention strategies taught and information provided to caregivers varied across studies. For some studies, strategies were broadly described using descriptors such as “Pivotal Response Training.” All study interventions included teaching caregiver specific strategies, such as “arrange environment with favored items in sight but out of reach, provide choices, give pieces of toys bit by bit, and insert pauses during familiar verbal routines” and “how to use books for interaction.” Five studies specified that they provided caregivers with information. Examples of information provided to caregivers include “understanding child's autism” and “Individualized Education Plans.” The contexts caregivers were taught in which to use the strategies included play routines (n = 9 groups), familiar activities and routines (n = 7 groups), shared book reading (n = 2 groups), and mealtimes (n = 2 groups). For 11 groups, the contexts were not specified. See Table 3.

Caregiver and Child Outcome Measures

Caregiver outcomes. For the 36- through 48-month group, across the 21 studies and 23 communication intervention groups with compelling or promising evidence, there were a total of 76 caregiver outcomes (see Table 3). There was an average of 3.3 caregiver outcomes per group (min–max: 1–8). There were no outcome measures of nonverbal communicative behaviors within this age group.

All five of the studies in the developmental delay subgroup included measures of spoken language input, yielding a total of 17 outcomes (compelling = 2; promising = 8; lacking = 7). One study included two outcomes based on global communicative measures, both yielding compelling evidence. Four of these studies included outcomes based on caregiver–child interactions, yielding a total of 11 outcomes (compelling = 4; promising = 2; lacking = 5). Only one study within this group included follow-up assessments; results suggested that caregiver communicative outcomes maintained postintervention.

Of the 15 studies included in the autism subgroup, only one included a spoken language input outcome, which yielded promising evidence. Twelve studies included measures of global communicative outcomes, yielding a total of 20 outcomes (compelling = 7; promising 11; lacking = 2). Nine studies included measures based on caregiver–child interactions, yielding a total of 19 outcomes (compelling = 6; promising = 12; lacking = 1). There were four studies that included follow-up assessments within the autism subgroup. Results suggest just over half of the caregiver communicative outcomes were maintained during the follow-up periods.

There was only one study within this age range that included children with a language delay/disorder. This study included one spoken language outcome and one outcome based on global communicative behaviors, both providing compelling evidence and four outcomes based on caregiver–child interactions (promising = 2; lacking = 2). Of the results assessed at follow-up, caregiver communicative outcomes were maintained postintervention.

Child outcomes. Of the 21 studies that had caregiver outcomes with compelling or promising evidence, they all also included child outcome measures (see Table 8). There were 23 language intervention groups that yielded 106 child communication-focused outcomes with a group average of 4.61 measures (min–max: 1–16).

All five studies in the developmental disorder subgroup included measures of expressive language, yielding a total of 32 outcomes (compelling = 3; promising = 14; lacking = 15). One study included two measures of receptive language both providing lacking evidence. One study included one social/pragmatic measure of language that provided lacking evidence. None of the studies included global measures of language. There was one study within this group that included follow-up assessments, with results suggesting that child communicative outcomes were maintained postintervention.

Twelve of the 15 studies in the autism subgroup included measures of expressive language, yielding a total of 22 outcomes (compelling = 4; promising = 11; lacking = 7). Six studies included measures of receptive language yielding a total of eight outcomes (promising = 5; lacking = 3). Eight studies included social/pragmatic outcomes, yielding a total of 21 outcomes (compelling = 4; promising = 15; lacking =2). Seven studies included global measures of language yielding a total of 10 outcomes (compelling = 2; promising = 5; lacking = 3). Four studies within this group included follow-up assessments with results suggesting that most child communicative outcomes were maintained postintervention.

There was one study included in the language delay/disorder subgroup, which included nine measures of expressive language (compelling = 1; promising = 2; lacking = 6) and one receptive language outcome that yielded promising evidence. This study also included follow-up assessments, with results suggesting that child communicative outcomes were maintained postintervention.

Discussion

The primary aim of this scoping review was to better understand the nature of studies that have been conducted to evaluate caregiver-implemented communication interventions for young children with language impairment. By examining the existing research base, we aimed to identify research gaps to guide future intervention studies. Here, we summarize major findings regarding each of our study questions and relate these findings to calls for future research directions.

Summary of Evidence

Study Question 1: What Populations Have Been Represented in Research Focused on Caregiver-Implemented Communication Interventions for Children With Language Impairment in Terms of Child and Caregiver Characteristics?

We identified only one caregiver-implemented communication intervention study that involved children less than 12 months of age (Barrera et al., 1987), and this study was excluded from our synthesis because it did not yield any language outcomes with either compelling or promising evidence. Thus, there is a substantial need for more caregiver-implemented communication studies for these populations. There are several disorders typically identified prenatally or very early in development that are commonly associated with communication impairment (e.g., Down syndrome and cerebral palsy), which likely warrant very early intervention. More studies are needed to better understand how to target these populations, who may also be experiencing complicated medical issues, and to determine if interventions for children this young lead to short-term and long-term gains in communication development.

For both the 24- through 35- and 36- through 48-month groups, the majority of studies included RCTs (52% and 62%, respectively), demonstrating high-experimental control. For all groups, the majority of studies were conducted since 2020 (67%). We advocate for the continued and increased use of RCTs to allow for critical evaluation of caregiver-implemented communication interventions. However, it is important to note that the study sample sizes have been relatively small with averages of 24.81, 18.19, and 20.13 children per treatment groups for the 12- through 23-, 24- through 35-, and 36- through 48-month groups, respectively. For each of these three age groups, the most common country that the studies were conducted in was the United States (71%, 52%, and 48%, respectively). Thus, there is a need to further evaluate caregiver-implemented interventions with larger samples and in additional countries throughout the world as cultural differences may impact treatment outcomes.

In the 12- through 23-month group, majority of intervention studies fell into the developmental disorder and autism subgroups (43% in each), with only one study (14%) in the language delay/disorder subgroup. In contrast, in the 24- through 35-month group, 29% of the studies fell into the developmental disorder subgroup, 52% in the language delay/disorder subgroup, and only 19% in the autism subgroup; while in the 36- through 48-month group, 24% of intervention groups fell into the developmental disorder subgroup, 71% in the autism subgroup, and only 5% in the language delay/disorder subgroup. In the 24 through 35-month group, each of the four studies in the autism subgroup were published since 2019. Thus, future studies should continue to focus on younger children on the autism spectrum as assessments are developed to identify very young children with ASD. The synthesis also highlights a lack of studies focused on 3-year-olds with language delay/disorder as only one study, which was published in 1992, was identified in this subgroup. Thus, there is a need for future evaluations of caregiver-implemented interventions for this population.

Many of the intervention groups within the developmental delay/disorder subgroup comprised children with mixed diagnoses. For example, one study in the 12- through 23-month group comprised children with Down syndrome, cerebral palsy, spina bifida, hydrocephalus, or congenital infectious diseases. Similarly, in the 24- through 35-month group, one study comprised children with developmental disorder, Down syndrome, cerebral palsy, Deaf and hard of hearing, or language delay. Future research studies should be designed in a manner that will allow for evaluation of the intervention based on diagnosis to move our field closer to being able to better tailor treatments. To do this, we need to consider conducting more studies with study groups based on diagnosis or conducting very large-scale studies with heterogeneous samples, so that we can learn how to predict which individuals within a certain diagnostic category are most likely to benefit from a specified intervention (Bzdok et al., 2021; Lenze et al., 2020).

Additionally, in all of the groups, the majority of child participants were males, ranging from 71% to 78%, respectively. While this rate reflects the higher prevalence of boys than girls for many conditions (e.g., autism [Maenner et al., 2020] and developmental language disorder [Tomblin et al., 1997]), the lack of larger samples of girls limits the study generalizability. Similarly, examination of the caregiver characteristics revealed that for both the 24- through 35- and 36- through 48-month groups, there were intervention groups with only mothers and no groups with only fathers. Several study groups included both mothers and fathers, but often the breakdown of the sample across caregiver roles was unspecified. Future studies need to better report the composition of their targeted caregivers. Additionally, future studies should further consider the impact of caregiver characteristics on intervention outcomes (e.g., Shalev et al., 2020) and evaluate how to best serve families with diverse caregiver characteristics. Our extraction process included documenting caregiver characteristics beyond age and race; however, only two studies, neither of which were associated with promising or compelling evidence, noted unique caregiver characteristics. The caregiver characteristics of these two studies included head of single-parent home with medical or environmental risks (Armstrong, 1998) and low income (Towson & Gallagher, 2014). Thus, there is a great need for future studies to consider how caregiver characteristics relate to intervention outcomes for children with communication disorders.

Study Question 2: How Have Intervention Components of Caregiver-Implemented Communication Interventions Been Represented in the Research?

For the 12- through 23-month group, there was variability in interventionists, including trained paraprofessionals, speech-language pathologists, trained early intervention providers, teacher consultants, researchers, and parent educators, while for the 24- through 35-month and 36- through 48-month group, speech-language pathologist was the most common interventionist (54% and 48% of all groups, respectively). Across all age groups, examination of other intervention components indicates that the interventions were most commonly conducted in English in caregiver homes and comprised a mix of one-on-one and group sessions completed in-person. Additional investigations are necessary to determine if these specific components result in optimal efficiency and outcomes across different populations.

For the 12- through 23-month group, the average dosage across all study groups was 9.33 sessions, with sessions lasting an average of 1.35 hr. The average intervention duration was 19 weeks with an average of one to three sessions weekly sessions. For the 24- through 35-month group, the average dosage was 14.40 sessions that were 1.30 hr in length. The average duration was 13.5 weeks. The most common frequency of sessions was once a week followed by 2–3 times per week. For the 36- through 48-month group, the average dosages were higher than for the other groups with an average of 19.5 sessions, 1.5 hr in length over a 5-month period. For all groups, some level of dosage was reported, but it was common for studies to report on only a few of the dosage variables. Thus, more complete reporting of dosage is needed to facilitate the evaluation of optimal dosages for children and their caregivers (Warren et al., 2007). Additionally, of the studies included in our review, only one study compared intervention dosage, highlighting the need for research focused on dosage optimization.

For all but one study group, we were able to use the information provided to broadly characterize the intervention delivered. In the 12- through 23-month group, we characterized 63% as NDBIs and 37% as developmental. Similarly, in the 24- through 35-month group, we characterized 62% as NDBIs, 31% as developmental, and 1% as Sensory-based. In the 36- through 48-month group, the distribution of NDBI and developmental interventions was more even with 48% and 43% being characterized as such, respectively. The 36- through 48-month group also included one behavior intervention group and one TEACHH group. Examination of these characterizations by diagnostic subgroup revealed that the majority of the interventions for the developmental disorder and autism groups were NDBIs (63% and 70%, respectively), while the most common intervention type for the language delay/disorder group was developmental (54%) followed by NDBI (38%). Further evaluations of the intervention types are needed to determine if one intervention may be better suited for children of a certain age or diagnosis.

There was considerable variability in reporting on the level detail provided regarding the specific strategies and information provided to caregivers. There appears to be similarities in these strategies and information; however, this information was difficult to synthesize due to heterogeneity of report detail and variability in terminology used. Examples of similarities noted by reviewing Table 7 include following the child's lead (n = 4 of 8 groups for 12- through 23-month group), modeling (n = 10 of 26 groups for 24- through 35-month group), and expanding child's utterances (n = 6 of 23 groups for 36- through 48-month group). The development of a taxonomy of terms relevant to caregiver-implemented communication interventions using an approach like the Denman et al. (2021) Delphi study, which established consensus terminology to describe child language interventions used by speech-language pathologists in Australia may promote more consistency in terminology use across settings and allow for a more precise synthesis. Additionally, to facilitate more complete reporting, we urge for more studies to use the 12-item Template for Intervention Description and Replication (TIDieR) developed by Hoffmann et al. (2014). Examples of items included on the TIDieR checklist include the intervention materials, the intervention procedures, who provided the intervention, where the intervention took place, and intervention dosage. A brief review of Table 6 reveals inconsistency in reporting of the intervention location as well as each dosage element.

Study Question 3: What Caregiver and Child Outcome Measures Have Been Used to Evaluate Caregiver-Implemented Communication Interventions for Children With Language Impairment?

Across all three represented child age groups, measures based on caregiver–child interactions most commonly served as outcome measures, followed by measures of caregiver spoken language and global measures of language input and environment, respectively. Across the 24- through 35- and 36- through 48-month groups, there were three studies in each that included measures of each of these three types. Across all child age groups, there were no studies that included measures of caregiver nonverbal communication and sign language. This finding is surprising given that the use of gestures and sign language are often recommended for young children with communication impairment (e.g., McGregor, 2008). The heterogeneity of outcome measure types and inconsistency of use of the types may call for the need for a gold standard of outcome measure types (as well as specific measures) to be used in caregiver-implemented communication studies. For example, a gold standard could be set that all caregiver-implemented communication studies include at least one measure of caregiver language input, one measure of language contingent on child language output (e.g., measure derived from a caregiver-child interaction), and one global measure of the home language environment.

Examination of child language outcome measures in the 12- through 23-month group revealed that more than half (71%) of the studies that included caregiver outcome measures with compelling or promising evidence also included child outcome measures. All studies included measures of child expressive language, resulting in 25 (71%) expressive language outcomes across studies compared with four (11%) receptive language outcomes, four (11%) social/pragmatic measures, and two (6%) global measures. For the 24- through 35-month group, a larger proportion (80%) of studies included both caregiver and child language outcome measures. However, a pattern similar to the 12- through 23-month group emerged with the majority of outcomes based on child expressive language (83%), and few outcomes based on global language (8%), receptive (7%), or social/pragmatic measures (2%). In the 36- through 48-month group, all studies included adult and child communicative measures; again, the majority of child outcomes were expressive (58%); however, within this age group, there was an increase in social/pragmatic (20%) followed by receptive (10%) and global language measures (9%). Overall, studies across age ranges targeted more language measures (i.e., expressive, receptive, or global) compared with communication (i.e., social/pragmatic); future research should make sure to target both child and language communication outcomes. Consistent with our recognition for a gold standard specifying outcome domains to be reflected in caregiver outcome measure for caregiver-implemented communication studies, we advocate for developing a gold standard for child communication domains to be included in intervention studies.

Across all included studies, 13 (22%) included follow-up assessments, these ranged from 4 weeks to 15 months postintervention. Overall, results provide encouraging evidence that changes in adult and child communicative outcomes maintained postintervention. However, these results should be interpreted with caution as there was variability in how follow-up analyses were conducted, with some studies examining change between posttest and follow-up, others comparing follow-up with pretest. Future research is needed to determine the “minimum” changes needed in caregiver communicative outcomes that result in positive changes to child language development.

Study Limitations

There are a few study limitations that should be taken into consideration when interpreting the current scoping review. Due to our inclusion and exclusion criteria, our review may have been too limited in scope. Limitations in resources prompted us to only include studies on caregiver-implemented communication interventions that were available in peer-reviewed journals published in English. Inclusion of studies reported in non–peer-reviewed journals (e.g., dissertations) and in other languages would have provided a more complete description of the current research base. Due to the potential lag time between journal articles being published and then indexed in the databases (e.g., Scopus) used in this study, additional studies that meet our inclusion criteria may not have been identified (e.g., Peredo et al., 2022, was indexed after we conducted our last search update). Additionally, to focus our scoping review, we required studies to report on at least one caregiver-based outcome measure. This helped to ensure that the intervention was caregiver focused and aimed to change caregiver behavior. Including studies with caregiver-implemented communication interventions, but only child outcome measures, would likely have yielded a greater number of studies in our review. Moreover, this study reflects only a portion of our entire scoping review process. In this review, we provide an extensive overview of studies examining caregiver-implemented communication interventions for children with communication disorders to better understand the populations that have been included in previous studies as well as the intervention components. While we describe the context and modality interventionists used to instruct caregivers, there remains a need to further examine the specific strategies and approaches used for caregiver instruction. Additional papers will be forthcoming that describe reported caregiver instructional approaches, as well as those that focus on caregiver interventions for children at risk for communication impairment, that include single-case designed studies, or that provide greater detail on specific outcome measures.

Conclusions

Although many studies have examined caregiver-implemented communication intervention for children with communication impairment, particularly for children greater than 12 months of age, this scoping review highlights important research gaps and inconsistencies in study reporting that should be addressed. With this kind of attention, the evidence base can move beyond examining whether caregiver-implemented communication interventions are effective and specify the conditions under which and for whom intervention approaches are most optimal.

Author Contributions

Lizbeth H. Finestack: Conceptualization, Data curation, Investigation, Methodology, Writing – original draft. Marianne Elmquist: Conceptualization, Data curation, Investigation, Methodology, Project administration, Writing – original draft. Kirstin Kuchler: Conceptualization, Data curation, Investigation, Methodology. Andrea Boh Ford: Data curation, Investigation, Writing – original draft. Betul Cakir-Dilek: Data curation, Investigation. Amy Riegelman: Data curation, Methodology. Sarah Jane Brown: Conceptualization, Data curation, Methodology. Scott Marsalis: Data curation, Methodology.

Funding Statement

This study was supported by a research sprint conducted by the University of Minnesota Libraries. Additionally, this publication was supported in part by the Eunice Kennedy Shriver National Institute of Child Health & Human Development under Award Numbers T32HD007489 and U54 HD090256 and the University of Wisconsin–Madison.