Perception of conversations: the importance of semantics and intonation in children's development.

In conversations, adults readily detect and anticipate the end of a speaker's turn. However, little is known about the development of this ability. We addressed two important aspects involved in the perception of conversational turn taking: semantic content and intonational form. The influence of semantics was investigated by testing prelinguistic and linguistic children. The influence of intonation was tested by presenting participants with videos of two dyadic conversations: one with normal intonation and one with flattened (removed) intonation. Children of four different age groups--two prelinguistic groups (6- and 12-month-olds) and two linguistic groups (24- and 36-month-olds)--and an adult group participated. Their eye movements were recorded, and the frequency of anticipated turns was analyzed. Our results show that (a) the anticipation of turns was reliable only in 3-year-olds and adults, with younger children shifting their gaze between speakers regardless of the turn taking, and (b) only 3-year-olds anticipated turns better if intonation was normal. These results indicate that children anticipate turns in conversations in a manner comparable (but not identical) to adults only after they have developed a sophisticated understanding of language. In contrast to adults, 3-year-olds rely more strongly on prosodic information during the perception of conversational turn taking.