The discovery of babbling in another modality was exciting. It confirmed the hypothesis that babbling represents a distinct and critical stage in the ontogeny of human language. The next challenge then was to figure out how to study it. I recently conducted a new study of manual babbling with my colleague at McGill, David Ostry, and students Siobhan Holowka de Belle, Lauren Sergio, Tryve Armour, and Bronna Levy. This information was then fed into the computer software that we designed to provide us with information analogous to the spectrographic representation of speech, but adapted here for the spectrographic representation of sign.
Systematic similarities exist in the timing contours of infants' manual and vocal babbling.
Thus, homologous structural organization was observed in manual and vocal babbling, even though the neural substrates for manual articulation differ from the neural substrates for the articulation of speech. Prevailing research on very young bilinguals, however, had reported that bilingual babies under 20 months exhibted language delay and confusion relative to monolingual babies because they ostensibly had a single, fused representation of their two native languages, which they were only able to sort out over the first three years of life. By contrast, my findings suggested that very young bilingual babies have highly distinct representations of their two native languages quite probably from birth.