In search of competition between lexical and grammatical growth.

Relations between lexical and grammatical growth were examined in a Dutch boy from age 1:0 to 2:6. The overall shape of lexical growth was a pronounced increase in rate until age 2:2 approximately and a slight decrease in rate thereafter. Two measures of early grammatical growth (the percentage of obligatory plural contexts in which plurals were used and mean length of utterances) reached high levels well before the age of 2:2. Further, there was no evidence for a relation between the change from one week to the next in the number of new words and the change from one week to the next on the two grammatical measures. Thus, no evidence for competition between lexical and grammatical growth was found on both a larger and a smaller time scale. Patterns of lexical and grammatical growth suggestive of competition may be especially likely when the productive lexicon grows very fast initially.