Vocabulary · Learning Science
Spaced Repetition System
The science-backed method behind IELTS Memo's vocabulary flashcards — used by medical students, law students, and language learners worldwide to retain thousands of words long-term.
The problem with vocabulary
Your brain forgets 80% of new words within 24 hours.
This is called the Forgetting Curve, discovered by psychologist Hermann Ebbinghaus in 1885. No matter how many times you read a word list, passive exposure doesn't stick. Memory only strengthens through active recall — being forced to retrieve the word from your own memory.
For IELTS candidates, this is a critical problem. The Lexical Resource criterion — worth 25% of your writing score — rewards precise, varied, and sophisticated vocabulary use. Reading word lists is not enough. You need to own the words.
How spaced repetition fixes it
Review each word just before you forget it.
Every time you successfully recall a word, the memory trace strengthens and the next review is scheduled further in the future. Fail to recall it, and it comes back sooner. Over time, the words you know well appear less and less — and the ones you struggle with keep coming back until they stick.
This is the method used by medical students memorising thousands of drug names, law students learning case precedents, and language learners worldwide. Apps like Anki and Duolingo are built on the same principle.
How the algorithm works
Each rating changes when you see a word next.
IELTS Memo uses a simplified version of SM-2, the algorithm behind Anki — the most popular flashcard app used by medical and language students. Every word has two hidden numbers: an interval (days until next review) and an ease factor (how fast the interval grows). Your rating after each card adjusts both.
Interval resets to 1 day. Ease factor is unchanged.
Use this when you had no idea — the word comes back tomorrow.
Interval grows slowly (×1.2). Ease factor drops slightly.
Use this when you recalled it but it took effort. Next review in ~2 days.
Interval multiplies by the ease factor (starts at ×2.5). Ease factor rises.
Use this when you knew it instantly. Gaps grow: 1 → 6 → 15 → 38 days…
A word's journey
What happens to a word you keep rating Easy.
A word you find hard might be reviewed 8–10 times before it's truly learnt. A word you already know will fade into the background after 2–3 reviews — freeing up your sessions for the ones that matter.
The one rule
Be brutally honest with your ratings.
The algorithm only works if your ratings reflect what you actually knew before flipping the card — not what you recognised after seeing the answer. Giving yourself Easy when you struggled feels good in the moment but pushes the word away when you still need to practice it. The system has no way to know you cheated — but your IELTS examiner will.
Why 10 words a day
Consistency beats intensity every time.
Research on spaced repetition consistently shows that short, daily sessions outperform long, infrequent ones. Ten words takes about three minutes. That's a habit you can actually keep — on the bus, before bed, between tasks. Miss a day and the due queue grows, but the algorithm catches up gracefully.
At 10 words per day, you'll encounter every word in the 1500-word bank within 150days — and the words you've already learnt will only resurface when they actually need it.