Variability and Inconsistency in Children with and Without Speech Sound Disorders

Objectives: This study aimed to quantify and examine consistent and correct word production in children with and without speech sound disorders (SSD) and by subgroups of SSD in order to differentiate between normal variability and inconsistent productions. Methods:This study included 209 typically developing children and 99 children with SSD. The children with SSD were classified into four subgroups based on linguistic symptomatology. All children were asked to produce 22 words on three separate occasions and their responses were categorized by four types and calculated into scores based on consistency and correctness of word production. This study examined whether proportion of each response and consistency-correctness scores reveal group and age differences. Results: Both children with and without SSD showed high proportions of consistent correct responses, which increased with age. Children produced more consistent correct responses and fewer variable-no hits as they got older. Children with SSD produced fewer consistent correct responses and more variable-no hits than typically developing children. Children with inconsistent phonological disorders produced the highest proportions of variable-no hits, differentiating from other three subgroups of SSD. Conclusion: This study indicated developmental patterns of normal variability by age and inconsistent phonological disorders showed atypical inconsistent productions which are different from normal variability. This study suggested a foundation for differential diagnosis of subgroups of SSD.