Relearning attenuates the benefits and costs of spacing.

The literature on spacing effects is vast, but no prior research has examined the effects of initial spacing when students learn to criterion and then subsequently relearn items. In addition, minimal research has evaluated the costs associated with spaced practice as well as the benefits. Accordingly, in the current research, we examined the benefits and costs of initial spacing using Bahrick's (1979) method of successive relearning. Across 3 experiments, 567 students practiced key term definitions via test-restudy practice until items were correctly recalled 1 or 3 times during initial learning. Practice trials during initial learning were either massed or spaced (including relatively longer lags in all experiments as well as intermediate lags in Experiment 1). All students then relearned items in 2-3 subsequent relearning sessions (across experiments, almost 40,000 short-answer recall responses were collected and hand scored). The benefits of initial spacing were measured by interim cued recall tests and a final test administered days or weeks after relearning, and costs were measured by total practice time across sessions. A consistent qualitative pattern emerged: The benefits of initial spacing were substantial prior to relearning but were significantly attenuated after relearning. Moreover, the costs associated with achieving criterion via spaced practice during initial learning were also substantially attenuated by faster relearning in subsequent sessions.