Interdentals to the rescue: a German four-year-old with protracted phonological development.

This paper examines the phonology of a German four-year-old with asynchronous phonological development: age-level word structure and vowels, but a restricted consonantal inventory. Both expected and unexpected developmental patterns were evident. While the absence of dorsal non-continuants and most coronal and labiodental fricatives and affricates is not unexpected in four-year-olds with PPD, less expected was his mastery of more marked /l/ and /ʁ/ and the pervasive use of ungrooved interdental fricatives (or affricates) as substitutions. Ungrooved interdentals often replace grooved fricatives and affricates, but in his system, they also replaced stops in more marked prosodic positions (unstressed initial syllables and clusters) and labiodental /f/. His case profile demonstrates the autonomy of phonological tiers (levels) but also the restrictive interactions that occur when one tier dominates, in his case, word structure. A proposed treatment plan targets new feature combinations and consonant sequences in order to address the asynchrony.