An important concept in the study of speech development in bilingual children, code mixing refers to confusions in the differentiation of the separate languages being learned, with regards to vocabulary, phonology and syntax. A common example would be using a Spanish word in an English sentence, and vice versa. As the bilingual child progresses such code mixing becomes mostly grammatic in nature, as the vocabularies have become sufficiently differentiated.
This gradual change is a signal of progress for the child, as they couldn't be mixing-up grammatical elements unless they were gaining proficiency in both systems. The child is remembering and understanding rules from one grammer and placing it into the context of the second. These mix-ups become less and less frequent as language development expands.
Syntax = Structure and Order of Sentence Components
Drawing on their most solidified competencies for each language, the child must engage in greater communicative association than if only a single language was being learned. Most code mixing that occurs beyond this stage of development is a result of more environmental factors, such as family, community and culture. This just means that children begin to copy the language patterns of the adults they interact with.
