Petitto (1999) describes how the biological foundations and timing milestones of language acquisition between spoken languages and signed languages are similar. Studies show that when children are exposed to both signed and spoken languages, they produce their first word in both languages within hours of each other. Children acquire a signed and a spoken language in the same manner as those who acquire two different spoken languages. Moreover, babbling represents the beginning  of human language acquisition, and it is found that infants babble in the same manner regardless of which modality of a language they are acquiring. These studies suggest that the brain possesses a mechanism that allows infants to detect the patterning of language, regardless of its modality.

The Acquisition of Natural Signed Languages: Lessons in the Nature of Human Language and Its Biological Foundations; Petitto Montreal Neurological Institute, McGill University, 41-51; Please see Petitto’s published papers and abstracts here.

Keywords: biological, signed languages, language acquisition, babbling