The acquisition of inflectional suffixes in Japanese adjectives

This dissertation investigates the acquisition of two inflectional classes of Japanese adjectives. In predicative use, inflectional Class 1 (C1) adjectives inflect for tense with a nonpast tense -i suffix and a past tense -katta suffix. The paradigm for inflectional Class 2 (C2), on the other hand, follows that of the copula: nonpast tense - da and past tense -datta. The class membership, however, is not necessarily predictable semantically or phonologically. The main goals of this study are: (i) to identify how Japanese-speaking children utilize morphological information to determine the class of a given adjective and (ii) to identify which class of suffixes they use as the default.;57 children (4;3–6;3) and 32 adults participated in an elicitation task experiment. The stimuli consisted of two sets of roots: real (existing) roots and novel (pseudo) roots, each of which was presented with a nonpast tense suffix (-i or -da). Real roots were presented with either a correct nonpast tense suffix (oisi-i ‘is tasty’ and kantan-da ‘is easy’) or an incorrect nonpast tense suffix (*oisi-da and * kantan-i). Novel roots were also presented with either a C1 or C2 nonpast suffix. The subjects were asked to provide the past tense forms of the given adjectives.;The results show that two-thirds of the children did not recognize the class membership information carried by the incorrectly suffixed existing roots and did not utilize morphological information (i.e., suffix) in the stimuli as effectively as adults in determining the class membership of the novel adjectives. Therefore, more children resorted to using default suffixes than the adults. The results also show that the adults' default suffix is -datta (C2), while that of the children is either - datta (C2) or -katta (C1). The results, however, do not indicate any statistically significant age differences regarding their response patterns.;The results of this study lend support to lexeme-based models of morphology. This study also discusses how children distinguish and learn two classes of Japanese adjectives by considering Carstairs-McCarthy's version of the Principle of Contrast (1994). Possible reasons for the child -katta default suffix are also discussed.