The role of baby-talk words in early language development

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BACKGROUNDAdults tend to adjust the way they speak when they are talking to babies and young children. Their speech becomes slower, higher in pitch, exaggerated in intonation patterns. Their sentences become shorter and simpler with a lot of repetition. This specific register of speech is commonly known as 'baby talk', 'motherese', or more technically, infant-directed speech. Researchers have long debated whether such modifications in speech play some facilitative role in children's language development. There are indeed some indications that infant-directed speech makes certain aspects of language more accessible to the learner. For instance, it has been demonstrated that infants can identify words more easily in slow-paced speech.One puzzling feature of infant-directed speech is the existence of 'baby-talk words', words such as 'choo-choo' and 'tummy', that are specifically used with babies. If children are ultimately to learn 'train' and 'stomach', using different words to them that mean exactly the same thing does not seem to be helpful. In fact, it is not difficult to find claims made in the media that the use of words such as 'choo-choo' and 'tummy' can hinder language development. In this project, we will examine if using baby-talk words (BTWs) has any inhibitory or facilitative effects on language learning, and then offer an explanation as to why BTWs are found in infant-directed speech across languages and cultures. Our account focuses on the sound patterns that BTWs tend to have: repeated syllables (as in 'choo-choo'), lack of consonant clusters ('tummy' as opposed to 'stomach'), and recurrent sound patterns (as in the endings in 'bunny', 'doggy', 'tummy', 'daddy'). Words with these characteristics may be easier to learn, and as such, serve as a springboard for further vocabulary development. If this is true, we can expect two things. First, infants should find words that sound like real BTWs easier to learn. Second, infants exposed to more BTWs should generally undergo faster vocabulary development at least in the earliest stage.THE STUDIESTo test the first prediction, we will carry out a series of laboratory-based experiments with infants around the age of 14 to 18 months. They will be shown video images of unfamiliar toys with made-up names. Half the names will have BTW-like features, such as repeated syllables and lack of consonant clusters (e.g., 'neenee' and 'foofoo'). The other half will have non-BTW-like features (e.g., 'proogo' and 'smoday'). By tracking the eye movement of the infants, we will be able to tell whether infants can learn the association between the toys and their names faster when the names have BTW-like features. Furthermore, by manipulating the features between the two types of names, we will be able to determine which features (such as the repetition of syllables or the lack of consonant clusters) actually make word learning easier.To test the second prediction, we will collect data from parents on their use of real BTWs and their children's receptive and productive vocabulary at four 3-month intervals starting at 9 months. This will be done by recording the mother's speech addressed to the child and having the mother complete a questionnaire that lists a range of words that are typically understood or produced by young children. If BTWs do help infants break into the process of word learning, we should find a correlation between the amount of BTWs used by parents and the growth of vocabulary in their children.