Inconsistency in speech is often cited as an indicator of speech sound disorders and as a key factor for distinguishing between different subtypes. However, research has shown that variability is also present/expected during typical speech development and is not random; it can be explained by various factors.
The theoretical background first presents the concepts of variability and inconsistency, along with the different types of variability. Then, it describes speech and language development in typically developing children, including speech sound development. Next, it outlines the typical types of variability during early speech development and explains how speech variability evolves with age. It also discusses various factors influencing variability in typical development, such as gender, word frequency and complexity, phonological similarity, mental representations, motor development, and vocabulary. Finally, it describes inconsistency as a feature of inconsistent phonological disorder and childhood apraxia of speech and presents different methods for measuring speech variability.
Our study aimed to document speech consistency in typically developing Slovenian children aged 3 to 6. We examined whether age, gender, word length, and complexity influence speech consistency. To achieve this, we developed the first Slovenian consistency test for children, in which 62 participants named 25 pictures across three repetitions, each separated by an activity. The study makes a valuable contribution to our understanding of typical speech development and offers insights into which types of variability are still considered normal.
Children's speech was 81 % consistent overall. In multiple productions, children most often produced words as consistent correct (63,9 %), followed by consistent incorrect productions (17,3 %), variable productions with hits (13,2 %), and variable productions without hits (5,6 %). Speech consistency was related to age and increased as children grew older. We also found a statistically significant relationship between variability types and age: younger children showed more consistent incorrect productions than older children. The percentage of correct consistent productions increased notably with age. A significant difference was also observed between variable productions with and without correct responses; most variable responses included at least one correct target realization. We found no significant relationship between speech consistency and gender, word length, or the presence of consonant clusters in words.
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