How much input is enough? Correlating comprehension and child language input in an endangered language

This study investigated the extent to which the nature of verb input accounts for the order in which children acquire verbs. We assessed the nature of verb input using a combined sample of the speech of 57 mothers addressing their Stage I children. We assessed the order of verb acquisition using as our database a combined sample of those children's speech 10 weeks later and using as our measure of order of acquisition the frequency of verb occurrence. The first set of analyses established the validity of this measure of acquisition order by comparing it with order of acquisition data obtained from checklist and diary data. The second set of analyses revealed that three properties of the input were significant predictors of the order of acquisition of the 25 verbs that were the focus of this study. The predictive properties of input were the total frequency, final position frequency, and diversity of syntactic environments in which the verbs appeared. These findings suggest that the way verbs appear in input influences their ease of acquisition. More specifically, the effect of syntactic diversity in input provides support for the syntactic bootstrapping account of how children use structural information to learn the meaning of new verbs.