AN INTRODUCTION TO LATENT SEMANTIC ANALYSIS

Latent Semantic Analysis (LSA) is a theory and me:hod for extracting a nd representing the contextual-usage meaning of words by statistical c omputations applied to a large corpus of text (Landauer & Dumais, 1997 ). The underlying idea is that the aggregate of all the word contexts in which a given word does and does not appear provides a set of mutua l constraints that largely determines the similarity of meaning of wor ds and sets of words to each other. The adequacy of LSA's reflection o f human knowledge has been established in a variety of ways. For examp le, its scores overlap those of humans on standard vocabulary and subj ect matter tests; it mimics human word sorting and category judgments; it simulates word-word and passage-word lexical priming data; and, as reported in 3 following articles in this issue, it accurately estimat es passage coherence, learnability of passages by individual students, and the quality and quantity of knowledge contained in an essay.