Infants’ sensitivity to non-adjacent dependencies across phonological phrase boundaries

Natural languages contain numerous non-adjacent relationships between words or morphemes in a sentence, often straddling phonological phrase boundaries (e.g., [these sheep] [have [ellipsis (horizontal)]]). Since phonological phrases are considered the main processing unit for infants, this may cause the acquisition of cross-phrase dependencies to be challenging. This study, however, shows that by 17 months of age, French-learning infants have nonetheless gained sensitivity to remote determiner-auxiliary co-occurrences that are interceded by phonological phrase boundaries. Infants thus possess a robust mechanism for tracking non-adjacent dependencies. This ability is essential for early grammatical development.