On the biological, environmental and neurogenetic factors determining early language acquisition: evidence from signed and spoken language.
Laura Ann PETITTO

Data on very signed and spoken language acquisition are presented. The results demonstrate strong parallels in the maturation time course, structure and semantic content of early language acquisition across these two modalities. Such results indicate that the biological mechanisms that underlie early human language acquisition do not appear to differentiate between spoken versus signed language input. Indeed, at birth, there is a stunning equipotentiality of the signed and spoken modalities to receive and produce natural language. In order for signed and spoken languages to be acquired in the same manner, human infants may be sensitive to what is encoded within the modality –regardless of whether it is signed or spoken. Specifically, infants may be born with sensitivity to particular distributional, rhythmical and temporal patterns that happen to correspond to aspects of natural language structure. I further suggest that early language acquisition begins as a result of the complex interplay of 3 critical factors : (i) the infant’s general perceptual and motoric capacities, (ii) environmental factors, and (iii) the infant’s innate sensitivities to specific patterns corresponding to aspects of natural language. This mecanism is under genetic and environmental control. In very early life, genetically controlled neural substrates initially determine the nature of the distributional, rhythmical and temporal patterns in the input that will be most salient to the infant and provide the nascent neural architecture to lay down this information in memory. Environmental input prunes and expands the underlying neural substrates, an epigenetic process that ultimately constitutes the brain-based capacity for language in our species. Thus the infant is born with an initial sensitivity to very particular patterns. Regardless of whether they encounter these patterns on the hands or on the tongue, they will then attempt to produce them. One intriguing implication of theses studies is that language modality, be it spoken or signed, is neurologically plastic and may be neurologically set after birth.