In a Successive Bilingual system, a child that has been exposed almost exclusively to a primary language, i.e. monolingual, is thrust into an immersive second language experience. This new immersion needn't be total, but should last for a significant period of time on a daily or at least frequent and regular basis. The most common example of this involves children who speak one language at home, and are exposed to a second when they begin schooling. which language will become dominant depends on the strength of the developing relationships. If the child develops strong ties with new peers, the second language will often dominate, while stronger familial and cultural ties result in a predominance of the original.
Children use their first language as a linguistic resource in developing the second, which is commonly influenced by what they have previously learned. This process is called transfer, and is often most noticeable with pronunciations in the new language. This is especially apparent when the second language contains sounds that are not used in the first, and the pronunciation is adjusted to conform to familiar patterns. These transfers tend to fade away as differentiation between the two systems crystallizes.
Exposure to the second language before 3 years old leads to greater initial confusion than exposure later in life, such as with an adult taking a class, but proficiency eventually becomes notably greater for the young child if exposure to both languages remains consistent. If the second exposure does not occur before 5 years of age, they typically understand the new language long before being able to speak it, often with significant proficiency not occurring until the child is 10 or 11 years old.