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infant-directed and adult-directed utterances for the categories described above (only pre-
serving the “melody” of the message), Fernald found that adult listeners were more accurate
in recognizing these affective categories in infant-directed speech than in adult-directed
speech. This suggests that the relation of prosodic form to communicative function is made
uniquely salient in the melodies of mother’s speech, and that these intonation contours
provide the listener with reliable acoustic cues to the speaker’s intent.
Fernald has used the results of such studies to argue for the adaptive significance of
prosody in child language acquisition, as well as in the development and strength of the
parent-offspring relationship. Caregivers are very good at matching the acoustic structure of
their speech to communicative function. Fernald suggests that the pitch contours observed
have been designed to directly influence the infant’s emotive state, causing the child to
relax or become more vigilant in certain situations, and to either avoid or approach objects
that may be unfamiliar. Auditory signals with high frequency and rising pitch are more
likely to alert human listeners than signals lower in frequency and falling pitch (Ferrier,
1985). Hence, the acoustic design of attentional bids would appear to be appropriate to the
goal of eliciting attention. Similarly, low mean pitch, narrow pitch range, and low intensity
(all characteristics of comfort vocalizations) have been found to be correlated with low
arousal (Papousek et al., 1985). Given that the mother’s goal in soothing her infant is to
decrease arousal, comfort vocalizations are well-suited to this function. Speech having a
sharp, loud, staccato contour, low pitch mean, and narrow pitch range tend to startle the
infant (tending to halt action or even induce withdraw) and are particularly effective as
warning signals (Fernald, 1989). Infants show a listening preference for exaggerated pitch
contours. They respond with more positive affect to wide range pitch contours than to
narrow range pitch contours. The exaggerated bell-shaped prosody contour for approval is
effective for sustaining the infant’s attention and engagement (Stern et al., 1982).
By anchoring the message in the melody, there may be a facilitative effect on “pulling”
the word out of the acoustic stream and causing it to be associated with an object or
event. This development is argued to occur in four stages. To paraphrase Fernald (1989),
in the first stage, certain acoustic features of speech have intrinsic perceptual salience for
the infant. Certain maternal vocalizations function as unconditioned stimuli in alerting,
soothing, pleasing, and alarming the infant. In stage two, the melodies of maternal speech
become increasingly more effective in directing the infant’s attention and in modulating the
infant’s arousal and affect. The communication of intention and emotion takes place in the
third stage. Vocal and facial expressions give the infant initial access to the feelings and
intentions of others. Stereotyped prosodic contours occurring in specific affective contexts
come to function as the first regular sound-meaning correspondences for the infant. In the
fourth stage, prosodic marking of focused words helps the infant to identify linguistic units
within the stream of speech. Words begin to emerge from the melody.