Second language learners can make judgments as to the acceptability of verbal sequences in a target language text. However, such judgments are often different from judgments of the same text by native speakers of the target language. These differences can be interpreted as a gauge of differences between the learners' transitional competence and the competence of native speakers. Similarly, changes in learner judgments may indicate changes in transitional competence. The latter part of this paper reports a study in which learner judgments are used to test a model of change in learner competence proposed by S. Pit Corder (1971) and an extension of that model proposed by Jacquelyn Schachter, Adele F. Tyson, and Frank J. Diffley (1976).