The effectiveness of phonological intervention in preschool children: a single-subject design study.

The purpose was to investigate an intervention model for treating preschool children with phonological processes. Six children, three girls and three boys, between 4y 1m and 5y 7m, with similar developmental phonological disorder (PD) received an individually adjusted intervention including articulatory, phonological, and meta-phonological approaches. A single-subject multiple-baseline design with /f/ and /s/ as target phonemes and velar plosives and /r/ as control phonemes was used. An improved production of the treated phonemes was found in five of the children, while one girl established /f/ but not /s/. The control phonemes remained unchanged for all children. Six to 18 therapy sessions were needed to reach the intervention goal. The study highlights the importance of considering heterogeneity in children with PD.