Traditional theories of delayed matching-to-sample performance do not predict that accuracy will improve when absolute levels of reinforcement are increased. This prediction emerges only when reinforcement context is considered (J. A. Nevin, M. Davison, A. L. Odum, & T. A. Shahan, 2007). To provide quantitative data, the authors factorially manipulated between conditions the probability and duration of reinforcement for correct choices by pigeons. In Experiment 1, increasing the value of either variable improved initial discriminability of the forgetting functions, but did not affect the rate of forgetting. In Experiment 2, initial discriminability covaried with changes in choice immediacy and trial completion rate, suggesting a relationship with response strength consistent with Nevin et al.'s behavioral momentum model. Adding reinforcement context to K. G. White and J. T. Wixted's (1999) model also generates predictions consistent with the present experiments and with the effects of manipulating extraneous reinforcement. The inclusion of reinforcement context thus improves predictions of delayed matching-to-sample performance.