In 1885, German psychologist Hermann Ebbinghaus conducted a series of experiments recording how quickly humans forget new knowledge. The results were discouraging: one hour after learning, you have forgotten 56%; after one day, 74%; after one week, 77%.
But he also found good news: if you review before forgetting fully happens, the memory curve resets close to full strength. After each review, the next forgetting process becomes slower. In other words, with enough reviews, memory moves toward permanence.
The best review intervals
According to Ebbinghaus's research, the most effective review points are: 1 day, 2 days, 4 days, 7 days, and 15 days after learning. Reviewing at these five moments gives the best memory effect with the least time.
ToToday's Ebbinghaus recurring tasks
When creating a new task in ToToday, choose the "Ebbinghaus memory method" recurrence rule. The system automatically generates five review tasks at 1-2-4-7-15 day intervals. You only need to:
- Learn a new knowledge point, such as an English word, a programming concept, or a math formula, record it in ToToday, and set Ebbinghaus recurrence
- The task appears after 1 day and reminds you to review
- After reviewing, check it off and wait for the next reminder
- After five reviews, the knowledge point has basically entered long-term memory
Where it works well
Language learning: Learn 10 new words every day and set Ebbinghaus review for each one, so you do not have to relearn them after forgetting.
Exam preparation: Break knowledge into small units and set recurring review for each one. Before the exam, every knowledge point has been reviewed at least five times.
Skill learning: Learn a new shortcut, an SQL command, or a Git operation, then set Ebbinghaus recurrence immediately. Two weeks later, it becomes instinctive.
Why is this better than traditional review?
The traditional learning pattern is: learn → highlight → cram before the exam. The problem is that cramming only puts knowledge into short-term memory, and it disappears after the exam.
The advantage of Ebbinghaus recurrence is that review happens just before forgetting arrives. Each review strengthens the memory trace and helps it move from short-term memory into long-term memory.
ToToday automatically calculates review times for you. You do not need to remember "when should I review this?" You only need to review when the task appears. Give memory management to the system, and keep your cognitive resources for learning itself.