One basic reason for baby talk is that it catches an infant's attention more readily than regular speech does. Some researchers, including Rima Shore (1997) believe that baby talk is an important part of the emotional bonding process.
Shore and other researchers also believe that baby talk contributes to mental development. They say it plays a role in teaching the child the basic function and structure of language. Studies have found that even replying to babble with meaningless babble aids language acquisition, because even though the babble itself conveys no logical meaning, the interaction teaches infants that speech is bidirectional communication. Some experts advise that parents should not talk to infants and young children solely in baby talk, but include some normal adult speech as well. The high pitch of motherese gives it special acoustic properties which may be appealing to the infant (Goodluck 1991). Motherese may also serve to aid a child in the acquisition and/or comprehension of language-particular rules which are otherwise unpredictable utilizing principles of universal grammar (Goodluck 1991).
Other researchers have pointed out that motherese is not universal among the world's cultures, and argue its role in "helping children learn grammar" has been overestimated. In some societies (such as certain Samoan tribes; see first reference) adults do not speak to their children at all until they have reached a certain age. In others, it is more usual to speak to children as one would speak to anyone else, with some vocabulary simplifications. Furthermore, even where baby-talk is used, sometimes the parent simplifies words making it full of complicated grammatical constructs, mispronounced or non-existent words. Often parents will tend to refer only to objects and events in the immediate vicinity. Baby-talk often has the parent repeating the child's utterances back to him/her, and since children employ a wide variety of phonological and morphological simplifications (mostly distance assimilation or reduplication) in learning to speak, this results in "classic" baby-words like na-na for grandmother or din-din for dinner, where the child has seized on a stressed syllable of the input and then repeated it to make a word.
