Categorization and feature specification in phonological acquisition.

Distinctive feature specification and representation in phonological acquisition are examined in the context of underspecification theory. Subjects were 30 children aged (3;1 to 5;10) who exhibited systematic differences in their linguistic knowledge of target phonological contrasts. A free classification task was used to tap children's conceptual knowledge of these contrasts, with features of place and manner experimentally manipulated. Three questions were addressed: which features do children use to categorize segmental information, do the defining features of a category shift as the phonological system advances, and which framework of underspecification theory best accounts for the results? All children categorized segments on the basis of marked nonredundant featural properties, and used only one feature value to define category membership consistent with radical underspecification. Linguistic knowledge and linguistic input both influenced children's category judgements, but to different degrees. The emergence of phonological categories involved increasing feature differentiation as the child's productive phonology advanced.