Poster #116 - The Sensorimotor Coordination of Vocal Production in Late Infancy

• In Event: 3-159 - Poster Session 12
  In Poster Session: PS 12 Section - Language, Communication

Integrative Statement

Infant vocal production requires the coordination of multiple effectors in a rapidly growing and changing body. Like adults and other mammals, infants coordinate their vocal production by vibrating the vocal folds of the larynx and pushing air through the vocal-tract airways. These two basic components interact to generate a wide range of sounds. Little is known, however, of how these effectors interact with the larger coordination of the head in which they are situated. Here we examine how infants coordinate their head movement during vocal production in dyadic toy play with their caregiver. We studied 3,464 vocalizations emitted by 46 unique infants across a total of 153 sessions. To capture their movement patterns, we affixed a motion capture sensor to the infant’s head. We first demonstrate that the frequency and number of infant vocalizations increase across development (Figure 1A-B). From 9-15 months of age, there is an increase in the duration of vocalizations produced and from 18-24 months of age, vocalization duration decreases (Figure 1C). There are also developmental differences in how infants coordinate their head movements to produce vocalizations. We calculated the baseline rotational speed of the head when no vocalization was occurring (Figure 2, shaded regions). We then calculated the average rotational speed for the period 1-second pre-vocalization, during the vocalization, and post-vocalization. Both 9 and 12-month-old infants quickened the speed of their head during a vocalization, which continued post-vocalization (Figure 1A). Both during and after the vocalization, the observed rotational speed was significantly different from baseline (Wilcoxon rank sum test p<0.001). The disruption in head speed during vocal production is not evident for infants starting at 15 months of age. The increase in vocalization-related head movement present at 9 and 12 months and its persistence after the vocalization, suggests immature motor control. Parallel to this immature motor control, the duration of vocalizations produced from 9-15 months of age steadily increase in duration (Figure 1C). After 15 months of age, when motor control during vocal behavior has developed, the duration of vocalizations produced decreases. Together our results suggest that one constraint driving infant vocal production is the ability to control their head movements. Immature infants still developing head control produce longer vocalizations while those with more mature head stability can produce shorter vocalizations. Taken together, these results suggest that, in addition to control of the larynx and vocal tract, infants must develop mature head stability to produce mature-like vocalizations.

Authors

• Jeremy Isaac Borjon, Indiana University
  Presenting Author

• Drew Abney, Indiana University
  Non-Presenting Author

• Andres Méndez, Espacio Interdisciplinario, Universidad de la República
  Non-Presenting Author

• Chen Yu, Indiana University
  Non-Presenting Author

• Linda B Smith, Indiana University
  Non-Presenting Author