Authors, Year, Country, Reference	Language	Setting, Provider	Sample Characteristics	Interventions	Length of Intervention	Outcomes
Allen, 2013, USA [63]	English/American	Setting: developmental preschool, “Head Start”, preschool, “Childcare, home Provider: Speech therapists and researcher-trained assistants	Population N = 54 with SSD (M = 39, F = 15); Age range = 3–5.5 years; Mean age = 4.4 years	Three arms: P1 = one-time-per-week phonological intervention P3 = three-times-per-week phonological intervention; C = active control	Intervention: P1 24 weeks P3 8 weeks C 8 weeks Follow-up: P1 and P3 were re-examined after a six-weeks maintenance period	Phonological skills (PCC primary measure)
Lousada et al., 2013, Portugal [64]	Portuguese	Setting: University of Aveiro Provider: Speech therapist	Population N = 14 with phonologically based SSD; M = 10, F = 4; Age range = 4–6.7 years; Mean age = 5.2 years	Two arms: -Phonological therapy (combination of PA activities and auditory discrimination and listening tasks). -- Articulation intervention (Van Riper method)	Intervention: 25 (45 min) individual sessions (one per week) with the same therapist (blind to the objectives of the study)	Phonological skills (PCC primary measure)
Diaz-Williams, 2013, USA [65]	English/American	Setting: structured environment in school Provider: School intervention: speech therapist Home intervention: parents	Population N = 30 speech impaired (in expressive but not receptive language skills) based on the school district identification process; M = 26, F = 4; age range = 3.6–5.3 years; Mean age = 4.5 years	School-based traditional phonological intervention associated with three different types of homework intervention procedures: -Gross Motor Activity: production of target phonemes in association with a motor activity; -Structured table activities: words incorporated in table activities; -Structured Table with Letter-Tracing Activities: included a card with the target sound for finger tracing	Intervention: 12 weeks School intervention: 1hr twice a week Home intervention: five times a week (60 sessions)	Phonological competence measured with the HAPP-3 test [90]
Wren and Roulstone, 2008, UK [66]	English	Setting: school Provider: speech therapist	Population A total of 33 children participated to the study (N = 33; M = 25, F = 8; Age range = 4.2–7.8 years; Mean age = 5.6 years).	Three arms: -Group 1: computer-supported therapy: interactive game and sound and word stimuli (N = 11); -Group 2: standard therapy with tabletop games with drawings and objects (N = 11); -no therapy (N = 11)	Intervention: One 30 min session per week for eight weeks Follow-up: three weeks after the end of training	Phonological competence measured with GFTA Sounds in Words subtest [91]; PCC
Jesus et al. 2019, Portugal [67]	Portoguese	Setting: School Provider: speech-language pathologist	Population = 22 with SSD (M = 18, F = 4); Mean age = 57 months	Two arms Table top group: Phonologically based intervention: combination of phonological awareness activities, phonological awareness program, auditory bombardment, and discrimination and listening tasks. Tabletop materials consisted of printed cards, board games, stuffed animals, cardboard boxes, a large dice, fishing rods, and other similar materials used in traditional therapy. Tablet group: Phonologically based intervention (as above). The method of presenting the materials is by tablet. All the activities were run on an 8-in screen ASUS MeMO Pad 8	Intervention: 3 months. 12 weekly 45 min. individual sessions. Intervention was divided into two 6-session blocks: T0 = baseline T1 = first assessment at baseline T2 = 3-month waiting period T3 = post intervention	Phonological skills measured by University of Aveiro’s Case History Form for Child Language [101], the TFF-ALPE phonetic–phonological test [102], the TL-ALPE language test [103], and the PAOF oromotor abilities test [104]. PCC, percentage of vowels correct, and percentage of phonemes correct
Roden et al. 2019, Germany [68]	German	Setting: School Provider: Preschool teachers	Population: ASTM group: N = 40 (M = 24, F = 16); mean age = 4.52 years; PA group: N = 24, (M = 16, F = 8); mean age = 4.54 years; Control group: N = 37 (M = 22, F = 15); mean age = 4.51 years	Experimental group: “Auditory Stimulation Training with Technically Manipulated Musical Material”: listening, over earphones, to music acoustically modified, particularly (1) only high frequency, (2) electronic filters removing low frequency (<1000 Hz) and boosted medium and high frequency (>2000 Hz), (3) medium and high frequency were lateralized. Pedagogical activity program: preparation of primary school skills Control group: no treatment	Intervention: 3 30-min weekly session for 12 weeks	Digit span, non-word recall and recall of sentence (HASE) [105], Phoneme discrimination test with and without background noise, speech perception at high frequency
Smeets et al., 2012, Netherlands [69]	Dutch	Setting: structured environment in kindergarden (both)	Population Exp. 1: N = 29 children with DLD; M = 24, F = 5; Age range = 60–80 months; Exp. 2: N = 23) children with DLD (who did not participate in exp. 1); M = 13, F = 12; Age range = 60–90 months)	Exp. 1: Three conditions (randomized within subjects): 1. Two electronic storybooks in a static format; 2. Two electronic storybooks in a video format; 3. Control: no presentation Exp. 2: Four conditions (randomized within subjects): static books without background music or sounds (1) or with background music or sounds (2), video books without background music or sounds (3), or with background music or sounds (4).	Intervention Exp. 1: Eight sessions (two per week) —four weeks Exp. 2: Two periods of four weeks with eight sessions each (two per week) were used to counterbalance presentation of intervention materials	Exp. 1: Target vocabulary test designed for the study, and the Peabody Picture Vocabulary Test Exp. 2: Target vocabulary test (as in Exp 1), Phonological NWR Working Memory, Digit span, CELF-4-NL [106]
Plante et al., 2014, USA [70]	English/American	Setting: University clinic Provider: trained clinicians	Population Experimental group: N = 9; M = 6, F = 3; Age range = 4.3–5.7 years; Mean age = 5.2 years; Control group: N = 9 children (M = 5, F = 4; Age range = 4.0–5.9 years; Mean age = 4.9 years)	Two arms: -high-variability condition: clinicians used 24 unique verbs during recasts of child utterances. -low-variability condition, clinicians used 12 unique verbs, each recast twice.	25 min. individual daily sessions for six weeks (for a maximum of 25 sessions)	Percentage-of-correct-use data from materials and verbs not used during treatment; number of correct spontaneous uses of treated and control morphemes
Fey et al., 2016, USA [71]	English/American	Setting: University Provider: Study staff	Population: N = 20 with DLD; M = 14, F = 6 monolingual; Mean age = 3.8 years; Experimental group: N = 9, M = 6, F = 3; Mean age = 3.8 years; Control group: N = 11 children; M = 8, F = 3; Mean age = 3.7 years	Group 1: Competing sources of input;Three treatment sections for each target morpheme (the auxiliary “is” and the suffix of the third person singular/3S); past tense “-ed” was monitored as a control: -“comprehension” through a game on the Ipad with 10 items “is/was” and 10 items “does/did”, focused on time contrast, with questions related to 3 images presented in sequence; -“story model” involved listening to a short story with 12 declarative sentences for is and 12 for 3S; -retell-recast” included 8 declarative restructurings, both for “is” and 3S with the characters and events of the story. Group 2: traditional focused stimulation (TRAD)	Intervention: 12 weeks Frequency: 2 sessions per week (30–40′)	Morphological and syntactic expressive skills
Smith-Lock et al., 2015, Australia [72]	English/Australian	Setting: schools for children with language difficulties Provider: Speech-language pathologist, classroom teachers, and education assistants	Population Children with a DLD—diagnosis made by a speech-language pathologist; Experimental group: N = 17; M = 13, F = 4; Mean age = 5.1 years), Control group: N = 14; M = 12, F = 2; Mean age = 5.1 years)	Two conditions: -cueing procedure: pre-planned scaffolding hierarchy designed to elicit a correct answer. -recasting procedure: the correct answer was provided to the child after an error, but no attempt was made to have the child produce the target correctly	Intervention: weekly 1-hr sessions for 8 weeks; both whole-class (approximately 12 children) and small-group activities Follow up: 8 weeks after the end of therapy	Grammatical tests (Grammar Screening Test, the Articulation Screening Test, and the Gram- mar Elicitation Test) [93]
Washington et al., 2011, Canada [73]	English	Setting: Not specified Provider: speech therapist	Population Group 1 (C-AT): N = 11; M = 8, F = 3; Mean age = 4.4 years) Group 2 (nC-AT): N = 11; M = 8, F = 3; Mean age = 4.5 years; control group (NT): N = 12; M = 11, F = 1; Mean age = 4.1 years	Experimental Group 1 (C-AI): Computer-Assisted program, “My Sentence Builder”, includes social content embedded in a series of activities useful for sentence production. Experimental Group 2 (nC-AT): Table-top procedures for sentence elicitation with predominant use of verbal instructions; use of objects/toys Control group: no treatment	Intervention: 10 individual weekly sessions of 20′ Follow up: Three months after the end of therapy	Structured Photographic Expressive Language Test-Preschool (SPELT-P; [94]; Developmental Sentence Scoring (DSS; [95])
Washington et al., 2013, Canada [74]	English	Setting: Not specified Provider: speech therapist	Population Groups 1 and 2 as in [73]	Same as Groups 1 and 2 as in [73]	Same as in [73]	session-to-session progress in terms of efficiency and syntactic growth
Yoder et al., 2011, USA [75]	English/American	Setting: university clinic Provider: speech therapists trained in the treatments	BTR group: N = 34; Mean age = 3.6 years; MLT group: N = 28; Mean age = 3.6 years	Milieu language teaching (MLT; [107]) focuses on child-lefted play to elicit the child’s use of utterances containing preselected grammatical targets. Broad Target Recasts (BTR [108]) is an intervention which follows child’s play with the aim of grammatically recasting the child’s utterances	Individual 30-min sessions three times a week for a period of 6 months.	Progressive grammar as assessed by the Index of Productive Syntax (IPSyn) from 2 conversational language samples
Finestack and Fey, 2009, USA [76]	English/American	Setting: at home or at school Provider: Not specified	Deductive group: N = 16; M = 9, F = 7; Mean age = 7.3 years; Inductive group: N = 16; M = 10, F = 6; Mean age = 7.4 years	Explicit instruction: Sessions 1 and 2: the researcher teaches a new grammatical morpheme (-pa or -po that do not exist in English associated with masculine or feminine) with the modeling technique associated with an explicit auditory prompt; Sessions 3 and 4: the researcher requires the production of the new grammatical morpheme with pictures and explicit auditory prompt Implicit instructions: Same intervention as above but auditory prompt in task with modeling and with recast is implicit	Four individual teaching sessions within a 2-week period	Learning the new grammar rule measured as the percentage of correct answers and classifying children into: pattern, undifferentiated, and bare stem users
Finestack, 2018, USA [77]	English/American	Setting: at home or at school Provider: Not specified	25 children Explicit-implicit group (E-I): N = 12; M = 10, F = 2; Mean age = 6.77 years; Implicit-only group (I-O): N = 7; M = 6, F = 6; Mean age = 7.35 years	Training of three novel grammatical forms (gender, aspect and first person). Each session included a learning check, followed by a teaching task and an acquisition probe (presented via computer to ensure consistency of delivery). For the E-I group the computer presented participants the rule guiding use of the novel target form. The I-O group received a filler instruction. Prompts (and feedback) was provided in the second part of the teaching session An acquisition probe (with no feedback) was given at the end of each teaching session	Five computer-based teaching 20 min. sessions for each of the three novel grammatical targets. 1 week of waiting period after completion of each target	Learning of the novel grammatical rule. Children were classified as pattern user (PU: at least 80% performance) or non-pattern user (non-PU) for each of the three grammatical targets separately for the acquisition, maintenance and generalization probe
Tyler et al., 2002, USA [78]	English/American	Setting: school context Provider: speech therapy student under the supervision of a speech therapist	- Group with morpho-syntactic intervention first: N = 10; Mean age = 4.3 years - Group with phonological intervention first: N = 10; Mean age = 4.1 years - Control group with no treatment: N = 7	Combined morpho-syntactic and phonological interventions carried out in sequence -morpho-syntactic intervention: auditory awareness activities, focused stimulation activities and activities to elicit production -phonological intervention: auditory awareness activities, conceptual activities, activities to elicit production and phonological awareness activities	Intervention: individual session of 30 min and group session of 45 min–2 times a week Follow-up: 12 weeks and 24 weeks; for the control group: 12–15 weeks post-treatment	Morpho-syntactic test based on free speech Phonological evidence measured with the standardized test BBTOP
Maggiolo et al., 2003 Chile [79]	Spanish	Setting: schools Provider: teachers	Population 14 children (M = 4, F = 10; Mean age = 4.6 years) Intervention group: N = 7 Control group: N = 7	Intervention group: interaction activities with the child; development of the experimental program (structured into five mini-programs: temporal relationships; causal and purpose relationships; story presentation; storytelling; and storytelling structure); and interactive storytelling. Control group: no treatment.	Intervention: Sixteen session (2 sessions per week-45′)	Narrative skills (clinical test of the authors)
Dawes et al., 2019 Australia [80]	English	Setting: school Provider: Researcher	Experimental group (ICI): N = 19 Control group (PA) N = 18 Total: N = 37 (27 males) Mean Age 5.5	Experimental group (ICI): Inferential comprehension intervention (ICI) focused on book sharing, shared creation of a story map, retelling part of the story using the story map, discussion about character emotions and linking emotions to personal experiences, prediction (after the end of the story) Control group (PA): Gillon Phonological Awareness Training Program [109]	Intervention: 16 sessions (2 sessions a week over 8 weeks) Follow up: 8–9 weeks post-intervention	Inferential comprehension of narratives: questions requiring causal reasoning (including inferring emotions), prediction, and evaluative reasoning. Squiller Story Narrative Comprehension Assessment and Peter and the Cat Narrative Comprehension Assessment (NCA [110,111]
Hesketh et al., 2007 UK, [81]	English	Setting: home or school context (depending on parents’ preference) Provider: Speech therapists	Population Intervention group: 22 children (M = 17, F = 5; Mean age = 4.2 years). Control group (N = 20; M = 17, F = 3; Mean age = 4.3 years)	Intervention group: specific training on meta-phonological skills. The tasks focused first on syllables and rhymes, then on the recognition of the first and last phoneme of the word, and, finally, on the phonological manipulation of adding or deleting phonemes in the word. Control group: language stimulation (LS) program with activities of linguistic comprehension, knowledge of writing, verbalization of emotions and development of vocabulary and semantics.	Intervention: 20 individual sessions (20′-30′), two or three session per week	Meta-phonological skills (Syllable and phoneme) Phoneme Addition and Deletion task Primary and Pre-school Inventory of Phonological Awareness (PIPA) [112] Metaphon Screening Assessment [113]
Hund-Reid and Schneider, 2013, Canada, [82]	English	Setting: home or school context (depending on parents’ preference) Provider: Speech therapists	Population Experimental group: N = 22; M = 17, F = 5; Mean age = 5.6 years Control group: N = 15; M = 10, F = 5; Mean age = 5.3 years	Experimental group: the phonological awareness program: “Road to the Code” [85], based on principles that include, in each session, explicit teaching of one or two types of phoneme manipulations (e.g., initial sound isolation and/or initial sound identification) and fusion and segmentation, as well as sound-symbol awareness activities (manipulation of phonemes with letters). Control group: no treatment	Intervention: In groups of two, 20-minutes sessions with penta-weekly frequency, for 14 weeks	Phonological awareness (Dynamic Indicators of Basic Early Skills, DIBELS) [114]
Roberts et al. 2012, USA, [83]	English	Setting: Clinic and home Provider: Parents (specifically trained by therapists and educators)	Experimental group: N = 16; M = 14, F = 2; Mean age = 2.6 years Control group of children with DLD: N = 18; M = 13, F = 5; Mean age = 2.6 years Control group of children with typical language development: N = 28; M = 26, F = 2; Mean age = 2.5 years	Experimental group: “Enhanced Milieu Teaching” (EMT) in 4 phases: setting the basics for communication; shaping and broadening communication; time delay strategies; and, finally, prompt strategies. Control groups: no treatment	Intervention: Bi-weekly 1-hr sessions (one in the clinic and one at home) for a total of 24 sessions over 3 months.	Receptive and expressive skills (Preschool Language Scale-fourth edition, PLS-4) [115]
Wake et al. 2013, 2015 Australia, [84,85]	English	Setting: Home Provider: Parents	Experimental group (N = 99, 24% F, Mean age = 4.2 years) Control group: N = 101, 36% F, mean age = 4.1 years	Experimental group: “Let’s Read” and “Let’s Learn Language” programs promoting narrative skills, vocabulary, grammar, phonological awareness and pre-reading skills; each session consists on: a) a short review of the previous week; b) activities introduced by the researcher directed to the child; c) activities for parents and children to be carried out together with the support of the researcher; and d) activities for home practice Control group: no treatment	Intervention: 18 sessions distributed in 3 blocks of 6 weeks Follow up: Wake [76] at 6 years	Receptive and expressive language (CELF-P2 [88]), phonological processing (Comprehensive Test of Phonological Processing), Letter knowledge task
Wilcox et al. 2019, USA, [86]	English/American	Setting: School Provider: Preschool teachers	Population: 289 children (202 M, 87 F, mean age 53.09 months) TELL curriculum N = 142 BAU N = 147	Experimental group: TELL (Teaching Early Literacy and Language): a whole-class curriculum that embeds incidental and explicit oral language and early teaching practices within typical preschool activities; it includes materials and structured activities in two weeks’ 14 thematic units. Control group: Business as Usual (BAU)	Intervention: 34 weeks of instruction during a school year	Receptive and expressive language (CELF-P2 [116]), vocabulary and phonological processing (TOPEL [117]), phonological awareness and letter knowledge (PALS-PreK [118]), receptive and expressive vocabulary (TELL vocabulary)
Gillam et al. 2008 [87]	English/American	Setting: school Provider: Speech-language pathologist	Population: 216 with language impairment (136 M, 80 F); mean age 7 years 6 months FFW-L N = 54 CALI N = 54 ILI N = 54 AE N = 54	Four arms Fast For Word-Language (FFW-L): children played computer games that targeted discrimination of tones, detection of individual phoneme changes, matching phonemes to a target, identifying matched syllable pairs, discriminating between minimal pair words, recalling commands, comprehending grammatical morphemes and complex sentence structures; speech and nonspeech stimuli were acoustically modified. Computer assisted Language Intervention (CALI): children played the same computer games of FFW-L without any acoustically modification. Individual Language Intervention (ILI): individual activities developed around 13 picture books, designed to target semantics, morphosyntax, narration and phonological awareness. Academic Enrichment (AE): computer games designed to teach mathematics, science and geography.	FFW-L: 1h and 40′ per day, five day per week, for six weeks; five of the seven plays each day CALI: 1h and 40′ per day, five day per week, for six weeks ILI: 1h and 40′ per day, five day per week, for six weeks AE: not specified T0 = before treatment T1 = immediately after treatment (6 weeks after T0) T2 = 3 months after treatment T3 = 6 months after treatment	Primary outcomes: Expressive and receptive language (CASL [119]); backward masking Secondary outcomes: sentence comprehension (Token Test for Children, [120]); phonological awareness (Blending Words subtest od the Comprehensive Test of Phonological Processing [121])
Cohen et al., 2005, UK, [88]	English	Setting: home Provider: Parental supervision, parents were trained by speech-language pathologist	Population: 77 children (M = 55, F = 22); mean age = 88.92 months Group A: N = 23 Group B: N = 27 Group C: N = 27	Group A—Fast ForWord Language: children played computer games designed to develop oral language comprehension and listening skills, with acoustically modified speech Group B—Computer software: children played with age appropriate educational software packages designed to encourage aspects of language development Group C—Control: no intervention	Group A: 90 minutes, 5 days a week for 6 weeks Group B: 90 minutes, 5 days a week for 6 weeks T0 = pretreatment T1 = 9-week T2 = 6 months follow up	Receptive and expressive language (CELF-3 [116], TOLD-P:3 [122]) Phonological awareness (PhAB [123]) Narrative production (Bus Story Test, [124]))
Legenda: SSD: speech-sound disorder PA: phonological awareness; PCC: percentage of correct consonants.