An N-of-1 Randomized Controlled Trial of Interventions for Children With Inconsistent Speech Sound Errors

Purpose The aim of this study was to test the hypothesis that children with inconsistent speech errors would respond differentially to 1 of 3 specific interventions depending on their primary underlying impairment: Children with deficient motor planning were expected to respond best to an auditory-motor integration (AMI) intervention, and children with deficient phonological planning were expected to respond best to a phonological memory and planning (PMP) intervention. Method Twelve participants were diagnosed with a motor planning (n = 7) or phonological planning (n = 5) deficit based on a comprehensive assessment, which included the Syllable Repetition Task as an important source of diagnostic evidence. An N-of-1 randomized controlled trial was used. Each child experienced all 3 interventions: AMI, PMP, and control (CTL); however, these interventions were randomly allocated to sessions within weeks (3 sessions per week × 6 weeks for 18 sessions). The AMI intervention procedures targeted knowledge of the acoustic-phonetic target and integration of auditory and somatosensory feedback during speech practice. The PMP intervention procedures targeted segmenting and recompiling the phonological plan for each word. The CTL intervention was standard drill practice. The child was taught 5 pseudowords in a meaningful context in each intervention condition. Results Same-day (SD) probes assessed transfer from taught pseudowords to untaught real words, and next-day (ND) probes assessed retention of that learning. Nonparametric resampling tests with pooling of p values across children with the same diagnosis were used to assess the results. Pooled p values indicated a significant benefit of AMI over PMP for the group with a motor planning deficit (p = 2.01E-04 for SD probes and 2.97E-03 for ND probes) and a significant benefit of PMP over AMI for the group with a phonological planning deficit (p = 1.22E-02 for SD probes and 1.32E-02 for ND probes). Response to the CTL intervention was variable within groups. Conclusion In this study, the child's underlying psycholinguistic deficit helped to predict response to intervention.