Diagnosing inconsistent phonological disorder: quantitative and qualitative measures.

Area of Science:

• Speech-Language Pathology
• Developmental Psychology
• Linguistics

Background:

• Speech sound disorder (SSD) identification relies on analyzing children's word production consistency.
• Inconsistent errors characterize two groups: childhood apraxia of speech (CAS) and inconsistent phonological disorder (IPD).
• IPD is hypothesized to stem from impaired phonological planning.

Purpose of the Study:

• To describe and compare the inconsistent word productions of children with IPD to those of typically developing (TD) children.
• To investigate the characteristics of inconsistent speech errors in children with IPD.
• To explore the effect of word complexity on inconsistency in children with IPD.

Main Methods:

• Two studies involving 135 children with suspected SSD were conducted.
• 22 children meeting criteria for IPD (≥40% inconsistent word productions across three trials) were analyzed.
• Participants had no CAS symptoms, were monolingual, and spoke Australian- or Irish-English. Productions were assessed for consistency, and qualitative analyses examined error types and word characteristics.

Main Results:

• Children with IPD produced 52% of words with variable errors across trials.
• While 56% of phoneme errors were developmental, atypical errors (e.g., default sounds, word structure errors) were common in IPD.
• Words with more phonemes, syllables, and consonant clusters were more prone to inconsistency.

Conclusions:

• Children with IPD demonstrate distinct quantitative and qualitative speech error profiles compared to TD children.
• These findings support IPD as a valid diagnostic category within SSD.
• Qualitative analyses align with the hypothesis of a phonological planning deficit in children with IPD.