Two experiments examined how children and adults produce acoustic correlates for phrase boundaries during speech. Adult and children (ages 5 and 7) were asked to describe groupings of colored blocks, first in a relatively spontaneous manner and next under more structured conditions designed to elicit grouping information concerning "which blocks go together." In the spontaneous condition, adults gave elaborate descriptions of block positions and color, whereas children produced short descriptions such as "pink, green, white;" "pink, green, and white;" and "pink and green and white." In the structured condition, all subjects produced utterances corresponding to three syntactic bracketings of the phrase "pink and green and white:" [pink and (green and white)]; [(pink and green) and white]; and [pink and green and white]. Acoustic analyses indicated that adults reliably control both duration and fundamental frequency (F0) to signal phrase boundaries, whereas children of both age groups demonstrate little evidence of either type of information being used. We interpret these finding as suggesting that children as old as age 7 do not produce prosodic cues for this type of standing ambiguity in their everyday speech. Possible reasons for this lack of phrase boundary prosodic correlates are examined.

Although recent evidence suggests that young children use prosodic information to ‘‘bootstrap’’ themselves into syntactic comprehension, little is known about how children use prosody to signal syntactic boundaries in their spoken utterances. A speech elicitation task examined the extent to which children and adults control duration and intonation to mark phrase boundaries in spontaneous speech. Adults and young children (ages 5 and 7) were asked to describe groupings of colored blocks in a manner such that a blindfolded listener could tell ‘‘which blocks go together.’’ This procedure elicited utterances corresponding to three syntactic bracketings of the phrase ‘‘pink and green and white.’’ Acoustic analysis of subjects’ productions indicated that adults reliably controlled duration (i.e., syllable lengthening, pauses) and intonation fall–rise patterns to signal phrase boundaries. In contrast, children’s productions were highly variable and showed no evidence of intonation cues being involved. Individual subject analyses suggested that some of the 7-year-old children used duration cue to signal phrase boundaries, although the contrasts were not as marked as in the adult data. The results were interpreted as showing that by age 7, most children have not yet mastered prosodic cues for phrasal boundaries in their speech production.