Normal Vowel Development Patricia

Introduction The acquisition of vowels by normally developing children is an area that has received increasing attention in the past decade, but the substitutions that characterize children’s speech remain largely undocumented. Looking at adult phonological substitutions1, we find that the range of normal substitutions is very wide, but clear. There is every reason to believe that we should find at least that same range in normal children. But existing descriptions of children’s speech show only a small sample of the systems and substitutions that could occur, and little effort has been made to determine whether children’s limitations and substitutions are coextensive with those of adult languages.2 In the discussion below, I will briefly review some of the literature on vowel acquisition, and I will consider the development of phonological systems. I will then describe known adult vowel quality substitutions in terms of a universal set of articulatorily and perceptually motivated phonological processes that govern speech production. Although these processes are universal, their effects may be limited by learning, subject to implicational conditions which reflect the phonetic motivations of the processes. In the model of phonological acquisition I will present, these processes constrain vowel inventories in adult and child language, and they account for the vowel substitutions that occur in language histories, in variation and alternation, in second-language phonology, and in normal and disordered speech development. The implicational conditions on process application are responsible for the typical shapes of vowel inventories in child and adult speech.