The acquisition and evolution of speech and gesture: Studying normal and pathological subjects as a window to mechanisms and functions

In the first two years of life, most children develop the phonetic tools scaffolding first language acquisition, both at the segmental and prosodic level. In doing so, children face the following challenges:

  1. perceptually parse the incoming speech sounds into words,
  2. produce and respond to phatic utterances,
  3. employ a functional “protolanguage” (see work by Oller et al., 2013) practicing a perception-production feedback loop until their vocalizations are similar enough to the sound patterns of the language they’re exposed to,
  4. use facial and pointing gestures to either replace or accompany their utterances. Critically, infants and children start to use their newly acquired linguistic skills in an interactive way.

They hence show an early functional flexibility, and even species-specific signals homologous to vocal calls in other primates. At the same time, they learn to use co-speech gestures, such as pointing, facial expressions (Esteve-Gibert et al. 2014, 2017), as well as head and eyebrow movement (Esteve-Gibert et al., in preparation) in order to mark prominent events in the utterance. How does all this happen? In order to enhance our understanding language acquisition in infants we will address Tinbergen’s four questions (Tinbergen, 1963)