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Infrequent Child-Directed Speech Is Bursty and May Draw Infant Vocalizations

Margaret Cychosz, Adriana Weisleder

Abstract

Children in many parts of the world hear relatively little speech directed to them, yet still reach major language development milestones. What differs about the speech input that infants learn from when directed input is rare? Using longform, infant-centered audio recordings taken in rural Bolivia and the urban U.S., we examined temporal patterns of infants' speech input and their pre-linguistic vocal behavior. We find that child-directed speech in Bolivia, though less frequent, was just as temporally clustered as speech input in the U.S, arriving in concentrated bursts rather than spread across the day. In both communities, infants were most likely to produce speech-like vocalizations during periods of speech directed to them, with the probability of infants' speech-like vocalizations during target child-directed speech nearly double that during silence. In Bolivia, infants' speech-like vocalizations were also more likely to occur during bouts of directed speech from older children than from adults. Together, these findings suggest that the developmental impact of child-directed speech may depend not only on quantity, but on temporal concentration and source, with older children serving as an important source of input in some communities, including where adult speech to infants is less frequent.

Infrequent Child-Directed Speech Is Bursty and May Draw Infant Vocalizations

Abstract

Children in many parts of the world hear relatively little speech directed to them, yet still reach major language development milestones. What differs about the speech input that infants learn from when directed input is rare? Using longform, infant-centered audio recordings taken in rural Bolivia and the urban U.S., we examined temporal patterns of infants' speech input and their pre-linguistic vocal behavior. We find that child-directed speech in Bolivia, though less frequent, was just as temporally clustered as speech input in the U.S, arriving in concentrated bursts rather than spread across the day. In both communities, infants were most likely to produce speech-like vocalizations during periods of speech directed to them, with the probability of infants' speech-like vocalizations during target child-directed speech nearly double that during silence. In Bolivia, infants' speech-like vocalizations were also more likely to occur during bouts of directed speech from older children than from adults. Together, these findings suggest that the developmental impact of child-directed speech may depend not only on quantity, but on temporal concentration and source, with older children serving as an important source of input in some communities, including where adult speech to infants is less frequent.
Paper Structure (13 sections, 3 figures, 2 tables)

This paper contains 13 sections, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. Participants
  4. Data Collection
  5. Data Annotation
  6. Computation of burstiness
  7. Results
  8. Is child-directed speech more temporally clustered (burstier) in Bolivia, where it is rarer?
  9. Do infants in both communities produce more speech-like vocalizations when they hear speech directed right to them than when they hear speech directed to other children or adults, even if that directed speech is less frequent overall?
  10. Does the source of child-directed speech to the target infant, stemming from an adult versus an older child, predict the occurrence of infants' speech-like vocalizations across these two communities?
  11. Discussion
  12. Child-directed speech is burstier in the Bolivian community, where it is rarer
  13. Infants vocalize more in the presence of directed speech, including from older children

Figures (3)

  • Figure 1: Daily speech register patterns for two representative infants in Bolivia (left) and the U.S. (right). Y-axis=the proportion of a 5-minute rolling window containing a given register. Dashed line indicates the mean proportion of each register or vocalization rate over the entire recording period.
  • Figure 2: Temporal distribution of speech registers and target infant vocalizations for two representative infants in Bolivia (left) and the U.S. (right). Each vertical slice represents the presence or absence of the register/vocalization within a single 30-second annotation bin. White space indicates silence (no speech present in the segment). Green tick marks above the register bar indicate bins containing a speech-like vocalization from the target infant.
  • Figure 3: Conditional probability of target infant vocalization given each speech register, by community. Points represent individual infants. Vocalizations are more likely to co-occur with TCDS than most other registers, in both communities (see Table 2 for detail). TCDS = speech directed to the target infant and no other child. CDS incl. = child-directed speech to the target child and other children. CDS excl. = child-directed speech to other children only. ADS = adult-directed speech.