Thoughts on child-directed speech
It has been noted that child-directed speech (CDS) is often characterized by higher pitch and wider pitch range. However, these features are not universal. In Mayan society for example it has been reported that child-directed speech is characterized by a low-whispery murmuring quality. What could explain this difference?
One factor that has been largely unconsidered is the influence of sound environment on the specific choices made by speakers. An empirically verifiable theory would be that for instance the sound environment of Mayan children is more characterized by sounds within the higher pitched range, thus leading caregivers to modify their vocalisms toward the lower (and whispery) ends. It is a question of perceptual salience. The child is naturally equipped with the ability to pick out the human voice from its surrounding (cf. Belin, et al., 2000), likely by means of timbre recognition. Auditory scene analysis permits the child’s mind to pick out these features. However, if the sound environment muddies the soundscape in a particular range of frequencies, caregivers will likely veer in a different direction in order to aid the child in isolating the voice from surrounding sounds.
Reduplication and use of diminutives is often noted in CDS. Various explanations have been proposed. However, one that has yet to gain prominence regards the value of extra syllables in permitting intonational variety and contrast. What do we gain, in English for example, in transforming dog into doggy; in Czech, by rendering chlapec into chlapeček? Are we not adding greater phonetic complexity? Shouldn’t this be more difficult for the child? But this is in line with Slobin’s proposition that morphemes are more easily acquired which contain more than one phoneme. Further, we can not discount the value of intonation as contributing to the signal. It can be observed in Taiwanese Mandarin, for instance, that CDS not only contains reduplication, but that the tone is modified as well. An example that was given to me was the word /gu/ (high level tone) meaning brother. The CDS version is often /gu-gu/ (with a low followed by a high tone). Thus there is modification not only in the reduplication, but also in the change in tone, which is not lexically or phonetically determined.
