Abstract
This study investigated the effect of oral motor and articulation therapies on speech intelligibility of persons with Down syndrome in Ibadan, Oyo State, Nigeria. A pretest-posttest control group quasi-experimental research design with a factorial matrix of three (3) experimental groups was adopted for the study. Thirty (30) persons with Down syndrome were purposively selected from outpatients to the Audiology Clinic of the Department of Special Education, University of Ibadan, Nigeria. Participants were randomly assigned to the treatment groups (oral motor therapy and articulation therapy) and a control group. The treatment was administered for eight (8) weeks. The Arizona Articulation and Phonology Scale (Fourth Revision) was used to diagnose and evaluate speech intelligibility before and after exposure of the participants to the treatment. Therapeutic plans using oral motor therapy and articulation therapy were adopted to rehabilitate the speech intelligibility deficit exhibited by the participants. Data was analysed using the inferential statistics of Analysis of Covariance (ANCOVA) at 0.05 level of significance, while estimated marginal means was used to test the significant deference among the groups. There was a significant main effect of treatments using oral motor and articulation therapies on the speech intelligibility of persons with Down syndrome (F (2, 17) = 123.69, p <.05, η2=0.95). Oral motor therapy had the highest mean (70.77), followed by participants exposed to articulation therapy with a mean score of 65.04, while participants exposed to the control group had the lowest mean score of 40.12. Therefore, it is recommended that speech and language therapists and other relevant professionals in the field of rehabilitation should adopt oral motor and articulation therapies for rehabilitation of speech intelligibility problems among persons with Down syndrome.