ENVIRONMENTAL CATALYSTS AND OROFACIAL KINEMATICS OF EMERGENT CANONICAL SYLLABLES

Abstract

The vocalizations and jaw kinematics of 30 infants aged 6-8 months were recorded using a Motion Analysis System and audiovisual technologies. This study represents the first attempt to determine the effect of play environment on infants' rate of vocalization and jaw movement. Four play conditions were compared: watching videos, social interaction with an adult, playing alone with small toys, and playing alone with large toys. The fewest vocalizations and the least amount of spontaneous movement was observed when infants were watching videos and social interaction with an adult. Infants vocalized most when playing with large toys. The gross motor movement (e.g. waving, banging, shaking) naturally elicited by small toys was predicted to be the reason it educed fewer vocalizations than large toy play. This study was also the first to examine the kinematics of both vocalized and non-vocalized jaw movements from infants 6-8 months of age. Infants produced many spontaneous jaw movements without vocalization. When vocalizing, infants were not likely to move their jaw. This contradicts current theories that infants' canonical-stage vocalizations are jaw-dominant. Also, the onset of canonical babbling has been predicted to be driven by a change in oromotor skill. However, no differences were found in the jaw kinematics of infants who were canonical babbling versus those who were not. Results of the current study can inform both environmental and motor theories of infants' canonical babbling.