Early lexical acquisition: rate, content, and the vocabulary spurt.

The transition from slow to rapid word-learning was examined in a longitudinal study of 18 children. Beginning at age 1.2, mothers kept a diary of children's words. Diary entries were discussed during phone calls to the home every 2 1/2 weeks. A chronological record of nouns and other word classes was coded from the diary records. Thirteen children evidenced a prolonged period of up to three months during which rate of acquisition markedly increased. Almost three-quarters of the words learned during this period were nouns. Five children evidenced more gradual word-learning, and acquired a balance of nouns and other word classes. These results suggest that the terms 'vocabulary spurt' and 'naming explosion' best describe children who focus their early linguistic efforts on a single strategy: learning names for things. Other children may attempt to encode a broad range of experience with a more varied lexicon, a strategy that results in more gradual lexical growth.