The Ontogeny of Grammatical Variation
To illustrate grammatical variation, consider Spanish subject pronouns, which can be expressed or omitted, as in yo voy ~ voy ‘I go’. This variation is probabilistically conditioned by multiple linguistic factors. More specifically, subject pronouns are likelier to be expressed when (i) the referent of the subject is different from that of previous subject, (ii) the subject is 1sg, (iii) the verb is a copula, and (iv) the verb is in the imperfective past tense. Such patterns of grammatical variation are highly systematic across communities of Spanish-speaking adults. Nevertheless, we still know very little about how such patterns develop during childhood.
In order to explore the ontogeny of grammatical variation, I first discuss studies of school-age Spanish-speaking children’s subject pronoun expression and subject-verb ~ verb-subject word order. The studies indicate that linguistic factors that constrain variation emerge over time, with discourse factors emerging earlier than morphological or verb class factors. The findings also suggest that some patterns of variation emerge first with frequent verbs and only later with infrequent ones, which supports the interpretation that high frequency items provide more evidence for learning patterns.
In the second half of the talk I make predictions for how grammatical variation develops during early childhood based on usage-based research on the acquisition of grammar. I propose three stages of development: (i) initially children show no evidence of variation, (ii) variation is restricted to item-specific constructions, and (iii) variation generalizes across items. I provide preliminary evidence of the early stages by drawing on natural conversation data produced by a young child in Spain, ages 1;7-2;3. Finally, I discuss ways to explore whether linguistic factors constrain variation during the earliest stages of language development.