Active recall and spaced repetition, explained

What is active recall?

Active recall (also called retrieval practice or practice testing) is trying to remember information without looking at it. Covering your notes and explaining a topic, answering past exam questions and using flashcards are all forms of it.

It works better than rereading for long-term learning. In a well-known study, students who practised recalling a passage remembered much more of it a week later than students who spent the same time rereading it (Roediger & Karpicke, 2006). Rereading can feel more effective, because familiar text is easy to recognise — but recognising isn't recalling.

What is spaced repetition?

Spaced repetition is reviewing material several times, with gaps between reviews that grow as you learn it. Spreading study out generally leads to better long-term retention than the same amount of study crammed together — one of the most consistent findings in learning research (Cepeda et al., 2006).

A large review of study techniques rated both practice testing and distributed (spaced) practice as "high utility", while rereading and highlighting were rated low (Dunlosky et al., 2013).

How they work together

	Active recall	Spaced repetition
Answers the question	How should I study?	When should I study it again?
What you do	Answer from memory before checking	Review at growing intervals
Example	A flashcard asks "What does ATP synthase do?"	You see that card again in 1 day, then 3, then 8…

You can do either without the other, but they're strongest together — which is exactly what a spaced-repetition flashcard app does.

What makes a good flashcard?

• One idea per card. If the answer is a paragraph, split it.
• A specific question. It should have one clear answer you can check yourself against.
• In your own words where possible — rewording shows you understand it.
• Hide labels, not whole diagrams. Image occlusion turns one diagram into several small recall tests.
• Be honest when you rate it. If you hesitated or half-knew it, rate it lower so it comes back sooner.

How often should I review flashcards?

There's no single right schedule, but the pattern is: review new cards again soon (within a day), then at longer and longer gaps as you keep getting them right — days, then weeks, then months. Short daily reviews are easier to keep up than occasional long ones. A spaced-repetition app handles the timing for you; your job is to review the cards that are due.

What to look for in a spaced-repetition app

• It schedules reviews for you based on how well you knew each card.
• Creating cards is quick, whether that's typing, importing or generating from your notes.
• It fits how you study: on a laptop, on your phone, or in short breaks.
• Its scheduler is clear. Some apps, like Anki and RemNote, offer FSRS, an adaptive algorithm; others use simpler SM-2-based schedulers.

Our comparison of flashcard apps covers the main options.

How FlashStacks schedules reviews

FlashStacks uses an SM-2-style scheduler. After you see the answer, you rate the card Again, Hard, Good or Easy (or swipe right for Easy, left for Hard):

• Again brings the card back in about a minute and makes future gaps grow more slowly.
• Good schedules the next review in 1 day, then 3 days, then a gap that grows each time by the card's ease factor.
• Easy jumps further ahead (4 days for a new card) and makes future gaps grow faster.
• Hard grows the gap only a little.

Gaps stop growing at one year. FlashStacks doesn't use FSRS and has no scheduling settings to tune. On top of scheduled reviews, its widgets keep cards from a stack in front of you through the day, which adds extra recall practice between sessions.