Toddlers’ Verb-Marking Errors Are Predicted by the Relative Frequency of Uninflected Sequences in Well-Formed Child-Directed Speech: A Preregistered Corpus Analysis

Verb-marking errors such as she play football and daddy singing are a hallmark feature of English-speaking children's speech. We investigated the proposal that these errors are input-driven errors of commission arising from the high relative frequency of subject + unmarked verb sequences in well-formed child-directed speech. We tested this proposal via a preregistered corpus analysis and asked at what level the effects occur: Is it the relative frequency of specific subject + unmarked verb sequences in the input that is important, or is it simply that verbs become entrenched, such that their frequency of appearance with any third person singular subject accounts for errors? We found that the best predictor of children's verb-marking errors is the relative frequency of unmarked forms of specific subject + verb sequences. Our results supported the proposal that children's apparent omissions of certain grammatical morphemes are in fact input-driven errors of commission and provided insight into the mechanisms by which this occurs.