At the center of studies of the mind is the problem of representation. It has always seemed that if we could unravel the mystery of how knowledge is stored it would lead irrevocably to understanding how it is learned, how it is used, and, perhaps most intractably of all, how it is made conscious. The form that language takes when it is laid down as traces of long-term memory is a key to understanding its role in human development, intelligence, and socialization.

How is language represented? Are semantic features of words stored as entries in a lexicon or as part of our knowledge of concepts? How do words and meanings combine so that we can use language meaningfully and express thoughts verbally? Why do contexts change the way we interpret language? These are some of the questions that have fueled the inquiry into psycholinguistic processes and each one has a noble tradition in research and theory. Because the questions are difficult and the solutions impossible to observe directly, the research is intricate and the conclusions are inferential. However, the vast majority of that literature is based on a simplifying assumption: people have only one language. Again the story becomes more complex when these questions are asked about speakers who have two or more languages.

There is another complicating factor. Psycholinguistic research has typically approached research questions by examining and attempting to understand the stable state, namely, the adult mind. Developmental processes are always more difficult to observe and to understand.