The spacing effect is the finding that distributed study or practice yields better long-term retention than massed study of the same material. Spreading learning sessions across time is more effective than cramming.

Ebbinghaus noted the advantage more than a century ago; subsequent research has confirmed it across a wide range of materials, ages, and retention intervals. Spacing allows time for consolidation, reduces fatigue, and provides multiple distinct contexts that enrich retrieval cues. The optimal interval depends on how long the information must be retained: longer retention intervals benefit from longer spacing.

Students who review material over successive days outperform those who spend the same total time in a single session. The effect holds for motor skills as well as for verbal and conceptual learning. Despite its robustness, massed practice remains common because it produces rapid short-term gains that feel satisfying even though they fade quickly.

Learning that is spread out lasts longer than learning that is compressed.