Child speech articulation development: Integrative and cross-language perspectives

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Objectives: My research program investigates developmental mechanisms of child speech articulation behaviour. Building on my previous research on the acoustics of child speech production, the short term goals of this research program are to 1) characterize children's tongue motor control over time and across languages for the underlying mechanisms that govern speech articulation development in children regardless of the language they speak and to 2) identify the relationship between tongue motor control, manual movement, speech perception, and language environment. The long-term goal is to construct a coherent and comprehensive theory of speech acquisition that is evolutionarily informed and biologically valid. Scientific approach: To achieve these goals, speech production by monolingual children speaking English, Japanese, or Mandarin Chinese will be examined using ultrasound imaging technique and acoustic measurements. The ultrasound technique offers direct assessment on tongue position and posture during articulation processes. Children's tongue surface curvature will be traced while they are engaged in speech production experiments that sample the phoneme inventory of their native language. Children's speech will also be simultaneously audiorecorded for acoustic analysis, which provides another index of tongue movement pattern. Both the ultrasound and acoustic data will be compared over time within an individual, across individuals, and across languages for common developmental patterns. In addition to articulatory measurements, children's hand movement and dexterity will be evaluated to substantiate the link between oral and manual motor control. Children's ability to perceive speech sound distinctions will then be measured using speech perception experiments utilizing the eye-tracking techniques. Last but not least, children and their parents will be recorded using the LENA (Language Environment Analysis) device which affords automatic analysis of the child's home language environment over an extended period of time. Significance: Speech is the defining feature of humans, but our understanding of how this capacity emerges in children is limited. The proposed research program addresses a critical missing piece in deciphering this puzzle, namely, the ontogeny of children's tongue motor control and its interaction with language-specific environment. This research will illuminate evolutionary theory of language in general and of phonological theories in particular, as well as bear significant scientific and technological implications.