Prosody

The prosody of speech includes its tempo, dynamics and intonation. Prosody is intrinsic to spoken language because all speech sounds have duration and intensity (Fernald 1991:43). Prosody serves both a social and analytic function by regulating the child's attention and marking linguistic units (Trainor et. al. 2000:194). However, it ceases to be employed once children become proficient with language, usually around the age of five (Fernald 1991:45). Current research points to the emotional content of prosody (Trainor et. al. 2000). This hypothesis is based upon the differences in the development of the auditory and visual systems. Since the auditory system matures earlier than the visual system, and because language is primarily auditory, the prosodic expression of emotion may play a major role in the emotional development of infants (Trainor et. al. 2000:194).

It has been found that the same basic acoustic features are found in infant directed speech across languages and cultures. Even children, fathers and other adults who have no experience with infants, naturally produce infant directed speech when interacting with an infant (Trainor et. al. 2000:194). Additionally, research has found that infant directed prosody changes with context and appears to show cultural differences (Trainor et. al. 2000:188). For example, adults are better able to judge the context in which a phrase was uttered when it is infant directed than when it is adult directed.

Building upon Chomsky’s theory of universal grammar, the ‘prosodic bootstrapping’ hypothesis, proposes that prelinguistic infants may use cues available in the speech signal as a starting point for segmenting in input into the appropriate syntactic units (Nazzi et. al. 2000:124). However, empirical research has shown that while there are “indications that some acoustic marking of syntactic phrases does occur in speech to adults and to infants, it is not always present or consistent” (ibid.).