1 1Language Development Subgroup of Laboratory for Molecular Mechanism of Brain Development, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako-shi, Saitama, Japan.
2 2Department of Psychology, Concordia University, Montreal, QC, Canada.

Bilinguals need to learn two words for most concepts. These words are called translation equivalents, and those that also sound similar (e.g., banana-banane) are called cognates. Research has consistently shown that children and adults process and name cognates more easily than non-cognates. The present study explored if there is such an advantage for cognate production in bilinguals' early vocabulary development. Longitudinal expressive vocabulary data were collected from 47 English-French bilinguals starting at 16-20 months up to 27 months (a total of 219 monthly administrations in both English and French). Children produced a greater proportion of cognates than non-cognates, and the interval between producing a word and its translation equivalent was about 10-15 days shorter for cognates than for non-cognates. The findings suggest that cognate learning is facilitated in early bilingual vocabulary development, such that phonological overlap supports bilinguals in learning phonologically similar words across their two languages.