A review of the literature on bilingualism and second-language learning reveals the following key findings:

• Bilingualism is pervasive throughout the world; there is nothing unusual about it. It varies according to the conditions under which people become bilingual, the uses they have for their various languages, and the social status of the languages. For example, some children learn two languages from the onset of language acquisition, while others begin to acquire a second language when they arrive in school.

• Bilingualism shows no negative effects on the overall linguistic, cognitive, or social development of children, and may even provide general advantages in these areas of mental functioning.

• Second-language acquisition is a complex process because language is so central to human functioning. For example, second-language learning can be viewed as a linguistic and cognitive accomplishment, but social variables also affect language use and structure.

• An important dimension of second-language acquisition is the age and concomitant cognitive skills of the second-language learner. Because of their more advanced cognitive skills, older children acquire a second language at a more rapid rate than younger children.

• Second-language abilities should be assessed in relation to the uses of language the learner will require, rather than in isolation as an abstract competence.

• Individual and group factors such as age of learning, intelligence, attitudes, and personality have been examined in hopes of explaining individual differences in language learning. Age of learning and intelligence are related to certain aspects of second-language acquisition, but attitudes and personality are not promising explanations.

• Many bilinguals in the United States show a strong preference for English in most conversational situations, and this shift in preference from the native language to English results in a monolingual English upbringing for their children.

• Evidence from preschool programs reviewed in this chapter suggests that use of the child's native language does not impede the acquisition of English.