← Spaced RepetitionMemory fundamentals

Determining optimal spacing

There is no universal best interval. The right gap depends on how long you want the memory to last.

Key findings

  1. 01

    Spacing works because it forces reactivation. You rebuild the memory instead of riding short-term familiarity, and that produces stronger long-term retention than massing.

  2. 02

    The major scheduling mistake is acting as if one interval fits everything. Evidence shows the optimal gap shifts with the target retention interval.

  3. 03

    The useful intuition from the spacing literature is a temporal ridgeline: the best gap is often some fraction of the final test delay, not a fixed calendar rule.

  4. 04

    There is real work on optimizing schedules, not just proving the spacing effect exists. Cognitive models can outperform simpler schedules in controlled settings.

  5. 05

    Practical reviews aimed at instruction converge on the same advice: distribute practice, avoid compression, and think from the retention horizon backward.

References

5 sources
  1. 1.Distributed practice in verbal recall tasks: a review and quantitative synthesis (2006). Psychological Bulletin. doi: 10.1037/0033-2909.132.3.354.
  2. 2.Spacing effects in learning: a temporal ridgeline of optimal retention (2008). Psychological Science. doi: 10.1111/j.1467-9280.2008.02209.x.
  3. 3.

    Enhancing learning and retarding forgetting: choices and consequences (2007). Psychonomic Bulletin & Review. doi: 10.3758/bf03194050.

  4. 4.

    Using a model to compute the optimal schedule of practice (2008). Journal of Experimental Psychology: Applied.

  5. 5.

    The science of effective learning with spacing and retrieval practice (2022). Nature Reviews Psychology. doi: 10.1038/s44159-022-00089-1.