Children with speech sound disorder show diminished accuracy and intelligibility in spoken communication and may thus be perceived as less capable or intelligent than peers, with negative consequences for both socioemotional and socioeconomic outcomes. While most speech errors resolve by the late school-age years, between 2-5% of speakers exhibit residual speech errors (RSE) that persist through adolescence or even adulthood, reflecting about 6 million cases in the US. Both affected children/families and speech-language pathologists (SLPs) have highlighted the critical need for research to identify more effective forms of treatment for children with RSE. In a series of single-case experimental studies, research has found that treatment incorporating technologically enhanced sensory feedback (visual-acoustic biofeedback, ultrasound biofeedback) can improve speech in individuals with RSE who have not responded to previous intervention. A randomized controlled trial (RCT) comparing traditional vs biofeedback-enhanced intervention is the essential next step to inform evidence-based decision-making for this prevalent population. Larger-scale research is also needed to understand heterogeneity across individuals in the magnitude of response to biofeedback treatment.

The overall objective of this proposal is to conduct clinical research that will guide the evidence-based management of RSE while also providing novel insights into the sensorimotor underpinnings of speech. The central hypothesis is that biofeedback will yield greater gains in speech accuracy than traditional treatment, and that individual deficit profiles will predict relative response to visual-acoustic vs ultrasound biofeedback. This study will enroll n = 118 children who misarticulate the /r/ sound, the most common type of RSE. This first component of the study will evaluate the efficacy of biofeedback relative to traditional treatment in a well-powered randomized controlled trial. Ultrasound and visual-acoustic biofeedback, which have similar evidence bases, will be represented equally.

Randomized Trial Component: Previous findings suggest that biofeedback interventions can outperform traditional speech therapy for children with RSE, but the research base to date is limited to small-scale studies that do not reach the level of evidence needed to support large-scale changes in practice. The primary objective of the C-RESULTS RCT is to test the working hypothesis that a group of individuals randomly assigned to receive biofeedback-enhanced treatment will show larger and/or faster gains in /r/ production accuracy than an equivalent group receiving the same dose of non-biofeedback treatment. To test this hypothesis, n=110 children will be randomly assigned to receive a standard course of intervention with or without biofeedback. Acoustic and perceptual measures will be used to test for differences in both short-term learning of treated targets (Acquisition) and longer-term carryover of learning to untreated contexts (Generalization). In addition, a survey assessing participants' socio-emotional well-being will be collected from caregivers both pre and post treatment.

Inclusion Criteria:

• Must be between 9;0 and 15;11 years of age at the time of enrollment.
• Must speak English as the dominant language (i.e., must have begun learning English by age 2, per parent report).
• Must speak a rhotic dialect of English.
• Must pass a pure-tone hearing screening at 20 decibels Hearing Level (HL).
• Must pass a brief examination of oral structure and function.
• Must exhibit less than thirty percent accuracy, based on trained listener ratings, on a probe list eliciting /r/ in various phonetic contexts at the word level.

Exclusion Criteria:

• Must not receive a T score more than 1.3 standard deviations (SD) below the mean on the Wechsler Abbreviated Scale of Intelligence-2 (WASI-2) Matrix Reasoning.
• Must not receive a standard score below 80 on the Core Language Index of the Clinical Evaluation of Language Fundamentals-5 (CELF-5).
• Must not exhibit voice or fluency disorder of a severity judged likely to interfere with the ability to participate in study activities.
• Must not have an existing diagnosis of developmental disability or major neurobehavioral syndrome such as cerebral palsy, Down Syndrome, or Autism Spectrum Disorder, or major neural disorder (e.g., epilepsy, agenesis of the corpus callosum) or insult (e.g., traumatic brain injury, stroke, or tumor resection).
• Must not show clinically significant signs of apraxia of speech or dysarthria.

From enrollment until end of follow-up, roughly 13 weeks"

This was a low-risk behavioral speech therapy trial. Adverse events were systematically monitored with safety checks at midpoint and end of treatment. Because all randomized participants were included in adverse event monitoring, all randomized participants were treated as at risk. Study definitions were consistent with ClinicalTrials.gov definitions.

All perceptual ratings will be obtained from blinded, naive listeners recruited through online crowdsourcing. Following protocols refined in previous published research, binary rating responses will be aggregated over at least 9 unique listeners per token.