11-month-old infants' use of function morphemes to identify word boundaries

11-month-old infants' use of the prosodic and phonological characteristics of function morphemes was investigated in four studies. This was done by familiarizing infants with sentences that either contained the English functor the in the determiner position or a nonsense word. Following the familiarization phase of the experiment, the syllables that immediately followed the syllables in the functor position were presented in isolation. In addition, two novel distractor syllables were also presented. To determine the effects of the prosodic and phonological characteristics on infants' ability to recognize the word following the syllable, these qualities were varied across the four experiments. In the first experiment, the nonsense functor was unnatural in both its prosodic and phonological characteristics; in the second experiment, the nonsense functor had unnatural phonological characteristics and natural prosodic characteristics; in the third experiment, the nonsense functor had natural phonological characteristics and unnatural prosodic characteristics; and in the fourth experiment, the nonsense functor was natural in both its prosodic and phonological characteristics. In Experiment 1, infants exhibited longer looking times in the direction of distractor syllables and syllables extracted from the familiarization sequences containing nonsense functors than the syllables extracted from the familiarization sequences containing English functors. There were no significant main effects in the three subsequent experiments. The general analysis did however reveal that infants looked longer in the direction of distractor syllables than syllables extracted from sequences containing English functors, indicating that they were treating these syllables as familiar. Prelinguistic awareness of function words would provide infants with a powerful tool for identifying important linguistic units, such as words, phrases, and clause in the speech stream.