Spacing Effect

The spacing effect is the well-documented finding that information is remembered better in the long term when study of it is spread out over multiple sessions separated by time, rather than concentrated into a single session, a pattern often called distributed practice. It was first documented experimentally by German psychologist Hermann Ebbinghaus in his pioneering 1885 memory research, in which he found that spaced repetitions of nonsense syllables produced far better retention than the same number of repetitions massed together. The effect has been replicated across countless subsequent studies and is now one of the most robust findings in learning science, informing spaced-repetition study software and curriculum designs that deliberately revisit material after a delay rather than teaching it once and moving on.