In this set of studies, we ask whether monolingual English-learning 6-month-olds are able to pull out conjugated verbs (i.e., ‘smile’ in ‘Mommy smiles’) in stories where they follow the familiar word “mommy/mama”. Our results show that not only can 6-month-olds pull out these verbs, they can also relate them to the bare form of the verb ‘smile’. Our results show that infants can segment verbs and decompose the root of the verb (‘smile’) and the grammatical morpheme (-s) at a very young age (6 months). These results have implications on verb acquisition and morpheme learning. We also tested if infants can relate any part word to a word, e.g. the word bab to the nonsense sequence babsh but they do not. Therefore, English-learning 6-month-olds know that word final –s is special, and used as a grammatical marker in English.
Currently we are also testing the endings –ing, -ed, and plural -s, and we are trying to determine whether they know that–s, –ing, and -ed go after verbs by testing them on babs, babbing, and babbed, and whether they know that possessive ‘s goes after nouns by testing them on ‘Mommy’s babs’. We are testing 6mo, 8mos, 12mos, and 14mos to determine the timing of acquisition of those morphemes. So far we have found that infants before 14mos treat 3rd person singular –s like plural –s, i.e., they can’t tell them apart yet by looking at the linguistic context. But they start to become sensitive to this difference by 14mos. We are currently developing stimuli to test other potential inflections in English.