Variability in the language input to children enhances learning in a treatment context
Plante, E., Ogilvie, T., Vance, R., Aguilar, J. M., Dailey, N. S., Meyers, C., Lieser, A. M., & Burton, R. (2014). American Journal of Speech-Language Pathology, 23(4), 530-545. https://doi.org/10.1044/2014_AJSLP-13-0038.
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examining18Students, gradePK
Practice Guide
Review Details
Reviewed: May 2026
- Practice Guide (findings for High variability conversational recast therapy for morpheme errors - Plante et al. (2014))
- Randomized Controlled Trial
- Meets WWC standards without reservations because it is a randomized controlled trial with low attrition.
This review may not reflect the full body of research evidence for this intervention.
Evidence Tier rating based solely on this study. This intervention may achieve a higher tier when combined with the full body of evidence.
Findings
|
Outcome measure |
Comparison | Period | Sample |
Intervention mean |
Comparison mean |
Significant? |
Improvement index |
|---|---|---|---|---|---|---|---|
|
Accuracy of target morphemes (Plante et al., 2014) |
High variability conversational recast therapy for morpheme errors - Plante et al. (2014) vs. Low variability conversational recast therapy for morpheme errors - (Plante et al., 2014) |
0 Days |
Full sample;
|
35.90 |
12.60 |
No |
-- |
|
Unique spontaneous use of target morphemes (Plante et al., 2014) |
High variability conversational recast therapy for morpheme errors - Plante et al. (2014) vs. Low variability conversational recast therapy for morpheme errors - (Plante et al., 2014) |
0 Days |
Full sample;
|
18.00 |
10.50 |
No |
-- |
|
Total spontaneous use of target morphemes (Plante et al., 2014) |
High variability conversational recast therapy for morpheme errors - Plante et al. (2014) vs. Low variability conversational recast therapy for morpheme errors - (Plante et al., 2014) |
0 Days |
Full sample;
|
23.60 |
18.90 |
No |
-- |
Evidence Tier rating based solely on this study. This intervention may achieve a higher tier when combined with the full body of evidence.
Sample Characteristics
Characteristics of study sample as reported by study author.
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Female: 39%
Male: 61% -
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Arizona
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Race Other or unknown 100% -
Ethnicity Other or unknown 100% -
Eligible for Free and Reduced Price Lunch Other or unknown 100%
Study Details
Setting
The study took place at a university-based clinic in Arizona. Participants were also enrolled in a half-day summer preschool on the University of Arizona campus, which was developed and directed by a member of the research team.
Study sample
The researchers randomly assigned 9 preschool children to the intervention group and 9 preschool children to the comparison group. All children were screened on several assessments to verify that they had a speech or language impairment that was not associated with other conditions, such as intellectual disability. All children were native English speakers between 4 and 6 years old. Approximately 61% of the children were male and 39% were female.
Intervention Group
The intervention consisted of a conversational recast treatment to reduce grammatical morphology errors. Conversational recast is a one-on-one speech therapy intervention where a clinician responds to a child's utterance by repeating part or all of it, while correcting any errors in the targeted morpheme. A targeted morpheme, the smallest meaningful unit in language, was identified for each child during three consecutive pretreatment sessions. During subsequent sessions, clinicians provided a model of the correct grammatical form within a natural conversation, allowing the child to learn by hearing the accurate usage without direct instruction or correction. There are two variations of this intervention: high-variability and low-variability recast. The high-variability condition is the intervention condition in this review. In the high-variability condition, children heard their target morpheme recast through the use of 24 unique verbs during each treatment session. Each of the 24 verbs was used in a conversational recast just once within the session. Treatment sessions lasted 30 minutes over the course of six weeks for a total of 20-25 sessions per child. Sessions included three activities such as dialogic book reading, board games, craft projects, dress-up, flash card activities, and free play, during which the clinician recast the child’s correct or incorrect elicited or spontaneous attempts at the treatment morphemes. All participating children also received a daily, half-day summer preschool program that taught vocabulary development, sound awareness skills, and articulation. The preschool program was also developed by the researchers.
Comparison Group
Participants in the comparison group received the low-variability conversational recast treatment. The treatment was similar to that provided to the high-variability group in terms of length, duration, structure, and content of the sessions, except the children in the low-variability group heard their target morpheme recast through the use of 12 unique verbs during each session. Each of the 12 verbs was used in a conversational recast twice within the session.
Support for implementation
The intervention was implemented by eight undergraduate and graduate student clinicians. Each clinician provided treatment to children in both the high- and low-variability conditions. Clinicians attended two half-day training sessions before the start of the intervention and were supervised by a certified speech-language pathologist. Eleven percent of all treatment sessions were coded by a second observer to assess treatment fidelity and scoring reliability. Treatment fidelity was 96.6 percent and 97.3 percent for the low-variability and high-variability conditions, respectively.
An indicator of the effect of the intervention, the improvement index can be interpreted as the expected change in percentile rank for an average comparison group student if that student had received the intervention.
For more, please see the WWC Glossary entry for improvement index.
An outcome is the knowledge, skills, and attitudes that are attained as a result of an activity. An outcome measures is an instrument, device, or method that provides data on the outcome.
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The sample on which the analysis was conducted.
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The mean score of students in the comparison group.
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Study findings for this report.
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