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This research describes the acquisition of 5 noun and verb inflections by 3 subjects of a longitudinal study. Criteria were established for asserting that inflections were required in particular utterances, and the proportion of supplied to omitted inflections was charted over time. Plurals appear before possessives, and each appears first in particular linguistic contexts. Present progressives appear before pasts and present indicatives. When rate of acquisition is compared across children, different results are obtained if chronological age or mean length of utterance is held constant. These findings, and a categorization of errors of commission according to the levels of generative grammar, are discussed.
Courtney B. Cazden (Sat,) studied this question.