Variable vs. consistent input: Comprehension of plural morphology and verbal agreement in children

This chapter presents an experimental study that tests Chilean and Mexican children's comprehension of nominal plural morphology and subjectverb agreement. The main results of the study are that children exposed to reliable input associate the plural morpheme to an interpretation of 'more than one' by at least four years of age, while children exposed to variable and unreliable input are delayed in their comprehension of plural morphology. Instead, these children rely on subject-verb agreement when assigning number to nouns. The results of this research strongly indicate that variable and unreliable input delays the acquisition of grammatical morphology that is affected by that variability.