The subdomain of the external environment examined in this paper is "mediated information," not only that which is intentionally educational (such as a computer-based lesson) but other information embedded in books, television programs, etc. Not directly addressed by this review is information embedded in what are sometimes called "authentic situations" (Brown, Collins, and Duguid, 1989), though the thesis developed in this paper complements learning in such situations. Nor does the article examine the larger social environment within which mediated interactions occur (Perkins, 1985). Ultimately, it may be these contexts, and the ways media are integrated into them, that have the greatest impact on how people think and learn. While these broader contexts will be referenced from time to time, the primary focus of this paper is finer grained: specific episodes within which a learner interacts with mediated information to influence learning.