Why is spaced practice more effective than massed practice?

When students utilize spaced practice, they are studying for shorter periods of time with rest periods in between. These multiple rest periods allow the new information to be created and allow for this new information to be stored in different places. Additionally, multiple practice periods create many primacy and recency effects.

When students study for one long period of time with no rest periods in between, students will experience interference, which will lead to retrieval problems. In addition, frustration and fatigue will only exacerbate interference and further prevent accurate retrieval. Massed practice does not afford the brain adequate time to store memories, which will inevitably cause problems with retrieval come exam time.