The impact of age on the naturalness of /r/ productions

This study investigated the influence of speech therapy introduced in early childhood versus introduced later in childhood. Specifically, this study compared children who started speech therapy for the production of the /r/ sound at age 4-5 as compared to those who started at age 7-8. This research included 2 types of measures: objective acoustic measures and subjective perceptual judgments. First, naturalness was assessed objectively by analyzing the acoustic properties of the /r/ sound (e.g. F2-F3 distance and duration). Second, recruited adult participants were asked to make judgments about the naturalness of the /r/ production of these recordings of younger and older children producing the /r/ sound before and after treatment. The participants were asked to rate each production on a scale of 1 to 7, with 1 representing highly unnatural sounding speech and 7 representing highly natural sounding speech. Finally, the acoustic measures and perceptual judgments were examined side by side to see if they correlated with one another. The results of this study suggest that it is better for children to start speech therapy at an earlier age in childhood (ages 4-5) in order to have the best outcome for naturalness, in terms of acoustic measurements and perceptual judgments. These findings are the start to helping speech-language pathologists determine the right age to enroll a child in speech therapy for the /r/ sound.