Forgetting is fast. Spacing beats it. Half of what you learn today is gone by tomorrow. Four short reviews, spread across a month, hold on to roughly four-fifths of it

Learning Science • Memory

Forgetting is fast. Spacing beats it.

Half of what you learn today is gone by tomorrow. Four short reviews, spread across a month, hold on to roughly four-fifths of it — without adding study time.

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What one month does to a memory

Learned once Reviewed on a schedule

[Retention Curve Visualization: D1, D3, D7, D16 Review Intervals]

Reviewed schedule retains 79% of memory, compared to just 16% not reviewed (yielding 5x MORE HELD).

1 THE CLIFF

Nearly half is gone within 24 hours — before you ever reopen the material.

2 THE RESET

Every review snaps you back to full, and flattens the decline that follows.

3 THE FLATTENING

After four reviews the curve barely falls. Gaps can stretch into weeks.

R = (1 + t/c)^-b

Retention falls steeply at first, then flattens. Each review shrinks b — the decay rate — so the next drop is gentler and the gap between reviews can grow.

The Schedule • Intervals Expand as Memory Strengthens

1

Day 1

First review, one day after learning

2

Day 3

Wait 2 days

3

Day 7

Wait 4 days

4

Day 16

Wait 9 days

5

Day 35

Wait 19 days, and keep doubling

Why It Works • 01

Effort is the point

Pulling an answer out of your head strengthens it. Re-reading feels productive but leaves the memory untouched.

Why It Works • 02

Review at the edge

The best moment to review is just before you'd forget. Too early is wasted effort; too late and you are relearning.

Why It Works • 03

Sleep does the filing

Consolidation happens overnight, which is why intervals measured in days beat cramming measured in hours.

Curve modelled on Ebbinghaus (1885) • Spacing effect after Cepeda et al. Illustrative model, not measured data (2006)