PHONETIC INVENTORY CHANGES AFTER TREATING DISTINCTIONS ALONG AN IMPLICATIONAL HIERARCHY

Dinnsen, Chin, Elbert, and Powell (1990) described an implicational hi erarchy of feature distinctions that characterized five inventory type s for a group of phonologically disordered children. The presence of a feature associated with a more complex phonetic inventory implied the presence of all the distinctive features from less complex levels. In the present study two phonologically impaired subjects, ages 2;8 and 2;10, with limited phonetic inventories, received treatment to add pho netic distinctions based on this implicational hierarchy. One subject was treated on a distinction from a more complex level in the hierarch y and the other on a less complex distinction. Treatment was applied i n two 9-week blocks separated by 5-week withdrawal periods in which ge neralization probes were administered. Both children learned their tar get sounds; however, only the child treated on the complex distinction added sounds reflecting less complex distinctions without direct trea tment. This subject added 12 sounds compared to his baseline inventory . Change observed in both subjects' phonological systems supports the application of implicationally related feature distinctions in treatme nt to expand phonetic inventories. Results also lend support to planne d no-treatment periods as facilitative of system-wide phonological cha nge.