This chapter deals with research on the successive acquisition of two languages in childhood. The distinction between simultaneous and successive language acquisition is, as we have seen, a rather arbitrary one, the cutoff point being roughly 3 years. If the child is introduced to a second language before that age, I consider acquisition of the two languages to be simultaneous; if the second language is introduced after 3 years, acquisition is 5 successive--one language having been relatively well established (though by no means fully established) by that age.
The questions of interest in this chapter are similar to those that concerned us in the previous chapter. What information can be gained from case studies of children acquiring a second language? What are the developmental consequences of acquiring two languages? Does the acquisition of a second language interfere with the acquisition of the first language, or vice versa? How does the child learn to switch codes-to move from one language code to the other?
The literature on the successive acquisition of two languages is reviewed chronologically, beginning with the early case studies. As was mentioned in the previous chapter, the literature on successive acquisition of two languages in childhood includes some recent studies dealing with particular theoretical issues in second-language acquisition. Some of these are case studies, and others are studies with groups of children that employ a combination of case study and elicitation techniques.
The discussion in this chapter deals with studies of children who acquire their second language without formal instructions in a natural milieu (i.e., by living in an environment in which they are constantly exposed to the