16) Young, S., Schmitz, S., Corley, R.P., & Fulker, D.W. (2001). Language and Cognition. In R. Emde & J. Hewitt (Eds.), Infancy to Early Childhood: Genetic and Environmental Influences on Developmental Change (pp 221-240). Oxford University Press: New York, New York.

Language and Cognition
This chapter examines the genetic and environmental contributions to language acquisition in infants. Researchers looked at two aspects of language development; expressive language, which requires imitation or production of sounds and words, and receptive language, which requires the ability to discriminate or understand words and commands. Researchers found that expressive language was more influenced by genetic factors, and that new genetic effects were expressed over time as the children aged from 14 months to 36 months. They found that receptive language was largely influenced by environmental factors in infancy. Gender differences were also observed, as female subjects were consistently advanced in expressive and receptive language skills, as well as general cognitive ability during the developmental period from 14 months to 36 months. Although expressive language and general cognitive ability were more influenced by genetics than receptive language, all were affected by persistent influences in the environment.