Objective public testing methods were brought into use in language programs in the 1930s, primarily to justify decisions to exclude unqualified students from high school foreign language classes. In the United States, after World War II, government language programs supported research into the assessment of language aptitude to improve selection techniques for expensive, intensive language training. While one such study by a group of psychologists failed, another led to development of usable language aptitude tests, the Modern Language Aptitude Test. This study concluded that language aptitude consisted of four distinct, measurable abilities: phonetic coding; grammar handling; rote memorization of a large number of vocabulary items; and inductive language learning ability. It also added three important dimensions to prognosis: measurement of some of the components of individual variation in language aptitude; a model showing how measurable abilities interact with goals and methods; and illustration that aptitude was only one of the factors involved in the general theory of language learning. (Contains 33 references.) (MSE)