How grammatical are 3-year-olds?

Purpose: This study investigated the level of grammatical accuracy in typically developing 3-year-olds and the types of errors they produce. Method: Twenty-two 3-year-olds participated in a picture description task. The percentage of grammatical utterances was computed and error types were analyzed. Results: The mean level of grammatical accuracy in typical 3-year-olds was ~71%, with a wide range of variability. The current study revealed a variety of error types produced by 3-year-olds, most of which were produced by fewer than 5 children. The pattern observed for most of the children was to produce a scattering of errors with no more than a few of any 1 error type. Conclusion: The level of grammatical accuracy in 3-year-olds was skewed toward the high end. Although tense marking errors were the most frequent error type, they accounted for only 1/3 of the errors produced by 3-year-olds. A more general measure of grammaticality that considers additional aspects of language might, therefore, be useful in assessing language at this age.