Tracking Speech intelligibility Development in French-Speaking Children With and Without Speech Sound Disorders: A Longitudinal Study

1. Theoretical Framework
Speech sound disorders (SSD) are among the most common communication disorders in pediatric speech-language pathology (SLP). Children with SSD produce more speech errors than expected for their age, resulting in less intelligible speech compared to typically developing (TD) peers. In European French, we lack normative data on typical and atypical speech development. This makes longitudinal studies especially valuable, as they can draw how speech develops over time. However, of the 13 studies on French speech development, only two used a longitudinal approach—and none included children with SSD.

2. Objectives
Our longitudinal study aims to track speech development in French-speaking children with and without SSD over time. We hope to identify when and why a child might deviate from the typical path and become at risk for SSD.

3. Methods
We followed 85 children, aged three, from French-speaking preschools in Belgium. At the start and over time, we assessed their speech to classify them as either TD (63 children) or being at risk of SSD (22 children). They were reassessed every six months until the age of five, for a total of five sessions. Parents also filled out the Intelligibility in Context Scale (ICS-F), a questionnaire measuring functional intelligibility. By collecting ICS-F data every six months, we could map how speech intelligibility changed over time between 3 and 5.

4. Analysis/results
We used growth curve models (mixed models) to determine the trajectory for TD and SSD children and explore how factors like gender or socioeconomic status may influence it.