This paper develops a stimulus selection theory, based on an extensive review of previous research, which gives weight to context change or stimulus generalization decrement. The theory assumes no special compounding or configurational process, and accounts for the learning of successive discriminations without the addition of any special process. The theory predicts the relative rates of acquiring simultaneous and successive discrimination, including the "exceptions," and leads to correct predictions in a number of other paradigms. A computer simulation which embodies the context-sensitive theory confirms the predictions of the context theory of discrimination learning which has direct implications for research on types of learning process. Component, compound, and configurational learning emerge as summary descriptions of performance in different situations, but according to the present theory are neither styles nor distinct types of learning since data from the various situations are predicted by a single process. (Author/HMV)