Published March 11, 2026 · Teaching Methods
Spaced repetition is the most scientifically validated method for long-term vocabulary retention. Research spanning over 130 years — from Ebbinghaus's pioneering memory experiments in 1885 to modern cognitive science studies — consistently shows that distributing review sessions over increasing intervals dramatically improves long-term retention compared to massed practice (cramming).
Yet most ESL/EFL teachers still rely on word lists, translation drills, or hope that students will "pick up" vocabulary through exposure alone. This guide explains the science behind spaced repetition, how the SM-2 algorithm works, and how you can implement it in your teaching practice using digital flashcard systems.
In 1885, German psychologist Hermann Ebbinghaus conducted the first systematic study of memory. He discovered the "forgetting curve" — a mathematical model showing that newly learned information fades rapidly from memory unless actively reviewed. Within 24 hours, approximately 70% of new information is forgotten. Within a week, over 90% is lost.
However, Ebbinghaus also discovered that each time you successfully retrieve information from memory, the forgetting curve flattens — the memory becomes more durable. The key insight: the best time to review is just before you would have forgotten. Reviewing too early wastes time (the memory is still strong). Reviewing too late means you've forgotten and must relearn from scratch.
This "sweet spot" of optimal review timing is what spaced repetition systems exploit.
The forgetting curve follows an exponential decay pattern. Without review, memory strength drops rapidly at first, then more slowly:
With spaced repetition, each review "resets" the curve at a higher level. After 5-6 well-timed reviews, the memory becomes essentially permanent, with review intervals stretching to months or years.
SM-2 (SuperMemo 2) is the algorithm used by Edooqoo's flashcard system. Developed by Piotr Woźniak in 1987, it's the same algorithm used by Anki, the world's most popular flashcard application. Here's how it works in simple terms:
The result: easy words quickly move to long intervals (reviewed rarely), while difficult words stay at short intervals (reviewed frequently). Each student's review schedule is uniquely personalized to their actual learning patterns.
Here's a practical workflow for using spaced repetition with your English students:
| Aspect | Digital (Edooqoo/Anki) | Paper |
|---|---|---|
| Scheduling | Automatic SM-2 algorithm | Manual — students forget to review |
| Tracking | Detailed statistics per word | No tracking |
| Accessibility | Phone, tablet, computer — anywhere | Physical cards needed |
| Content | Example sentences, audio, images | Limited space |
| Teacher insight | See student progress remotely | Only if student brings cards |
| Kinesthetic learners | Less tactile engagement | Writing and handling aids memory |
Edooqoo's flashcard system tracks multiple metrics per word and per student:
5-15 minutes is optimal. Short, frequent sessions are more effective than long, infrequent ones. Edooqoo's Student Hub makes it easy for students to do quick review sessions on their phone.
Digital flashcards work well for students aged 12+. Younger students benefit more from physical flashcard activities with a teacher present. Edooqoo is designed for adult learners.
Yes. Create flashcards with grammar rules, example sentences, and common errors. However, grammar is better practiced through exercises (sentence transformation, error correction) with vocabulary reinforcement through flashcards.
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