Core vocabulary therapy for the treatment of inconsistent phonological disorder: Variations in service delivery

Approximately 10% of children with a speech sound disorder present with an inconsistent phonological disorder, characterized by inconsistent production of words across multiple trials. A number of studies have provided evidence of the efficacy of core vocabulary therapy for the remediation of this speech sound disorder with a dosage of two speech-language therapy sessions per week. The present study aimed to investigate if two variations of core vocabulary therapy under real world conditions were effective in improving consistency in the speech of children with inconsistent phonological disorder. Variation A was based on standard administration of core vocabulary therapy (with the addition of a third session per week) and Variation B involved one therapy session per week with a speech-language therapist and an imitation based home program delivered by caregivers. This effectiveness study involved five participants (four males, one female) with inconsistent phonological disorder. The ages of the participants ranged from 39 to 59 months at baseline. One child participated in Variation A and four children participated in Variation B. Changes in consistency of speech between baseline and post-therapy were analysed using the Wilcoxon signed-rank test. Consistency of speech improved significantly between and pre- and post-test assessment for four out of five participants treated with either variation A or B. These results suggest that core vocabulary therapy delivered once per week with a speech language therapist and using imitation home practice may be an alternative therapy option for children with inconsistent phonological disorder, with implications for the cost and time required. These findings also challenge our theoretical understanding of the locus of impairment in inconsistent phonological disorder. Given the small number of participants in the study, there is a need for replication of these research findings using a larger number of participants.