Objective: This study was designed to investigate using maximal oppositions to treat phonological disorders in children aged 3;0-6;0 with moderate to severe phonological disorders. Methods: Three participants were enrolled in a single-subject ABAB study design. The primary dependent variable was increased accuracy of targeted and untargeted speech sound errors. The secondary variable was the acquisition of untreated speech sounds. Dependent variables were measured by increased the accuracy of target speech sounds and the presence of new speech sounds. The independent variable was the maximial opposition approach. Baseline and withdrawal sessions include sham treatments, including no direct speech sound intervention. Results: Visual analysis revealed increased speech sound accuracy for all three participants. Two participants (P1 and P2) reached the 90% criterion in the first intervention phase B1: therefore, new targets were chosen for the second intervention phase B2. P3-maintained target sound accuracy during the withdrawal phase achieved during the first intervention phase B1. P3 continued to improve accuracy throughout B2. Conclusion: These findings demonstrate that the maximal opposition approach may effectively treat children with severe speech sound disorders. For two participants, the investigation became an AB design due to the change in targets. Future research could include a comparative study with several different phonological approaches.
