DISENTANGLING EARLY LANGUAGE-DEVELOPMENT - MODELING LEXICAL AND GRAMMATICAL ACQUISITION USING AN EXTENSION OF CASE-STUDY METHODOLOGY

The early lexical and grammatical development of 1 male child is exami ned with growth curves and dynamic-systems modeling procedures. Lexica l development described a pattern of logistic growth (R-2 = .98). Lexi cal and plural development shared the following characteristics: Plura l growth began only after a threshold was reached in vocabulary size; lexical growth slowed as plural growth increased. As plural use reache d full mastery, lexical growth began again to increase. It was hypothe sized that a precursor model (P. van Geert, 1991) would fit these data . Subsequent testing indicated that the precursor model, modified to i ncorporate brief yet intensive plural growth, provided a suitable fit. The value of the modified precursor model for the explication of proc esses implicated in language development is discussed.