Mental activities and information learned in one context are not necessarily available for use in another. They often have to be learned anew in the second context, although perhaps with less time and effort. The fact is, however, that relatively little is known about how the activities of the mind affect one another. The study of bilingualism, being a study of the interaction of symbol systems and the way they affect one's acquisition and use of information, promises to provide valuable information on these questions. (Author/FWB)