Gradually increasing context-sensitivity shapes the development of children’s verb marking: A corpus study

There is substantial evidence that children’s apparent omission of grammatical morphemes in utterances such as “She play tennis” and “Mummy eating” are in fact errors of commission in which contextually-licensed unmarked forms encountered in the input are reproduced by children in a context-blind fashion. So how do children stop making such errors? It follows from this “Competing Sources of Input” account that only once children recognise the differences between unmarked forms that appear on their own and those that are part of larger constructions will they stop making errors. In other words, children’s errors and their later disappearance are the result of a late-emerging sensitivity to context. We use a pre-registered corpus analysis to explore the predictive value of different cues with regards to children’s verb-marking errors and observe a developmental pattern consistent with this account. We look at very local context-independent agreement cues — the identity of the specific verb being used — and at the relative value of more distant or abstract contextual cues. We find that the only consistent effect across a group of 2- to 3-year-olds and a group of 3- to 4-year-olds was the relative frequency of unmarked forms of specific subject+verb sequences being used. The relative frequency of unmarked forms of the verb alone was predictive only in the younger age group. This is consistent with an account in which children recover from making errors by becoming progressively more sensitive to context, at first just immediately preceding lexical contexts and eventually more distant grammatical markers.