Why a flashcard should hold exactly one fact

A card that asks two things at once cannot be graded honestly. Your child remembers one and forgets the other, and there is no button for that — so whichever they press, the schedule that follows is built on a wrong answer.

At a glance

The rule, and where it comes from

This is not a house style. It is the oldest and most-repeated rule in spaced repetition, set out by Piotr Woźniak in SuperMemo's Twenty rules of formulating knowledge: keep each item as small as it can usefully be. Every serious system since has restated it, because everyone who has built a large deck has learned the same lesson the hard way.

The reason is mechanical rather than aesthetic. Spaced repetition works by asking your child to grade their own recall, and using that grade to pick the next gap. The grade has to mean something. On a card with three facts, "how did that go?" has no true answer.

What actually goes wrong

Picture a card that says Name the three main strands of KS3 maths. Your child remembers two. Now:

• If they press Got it, the card disappears for weeks with a third of it unlearned.
• If they press Tricky, the whole card restarts — including the two parts they knew perfectly well, which they will now be tested on again tomorrow for no reason.

Either way effort is wasted, and the schedule no longer reflects what your child knows. Multiply that across a deck of a hundred cards and the whole system quietly stops working. This is the single most common reason a home-made deck gets abandoned: not laziness, but cards that cannot be graded.

Splitting is almost always the fix

The three-strand card becomes three cards, each asking for one strand in a way that has exactly one answer. That sounds like more work, and in raw card count it is. In review minutes it usually is not, because each card gets its own honest schedule — the two your child knows will drift out to term-long gaps while the third keeps coming back.

That is the hidden efficiency of atomic cards: the difficulty is tracked per fact, so easy material stops consuming attention.

How this is enforced here

Because the tutor writes the cards, the rule can be enforced before your child ever sees them. Every card is checked as it is made, and a question that asks for several things at once is rejected outright rather than softened.

The check is deliberately conservative — it is better to let a borderline card through than to reject a good one — and it looks for the tells of a multi-fact question: an explicit count ("name three"), a list, or two questions joined together. A rejected card is rewritten, not dropped, so the material still gets covered.

There is a second check as well, for a subtler failure: a hint that gives the answer away. A hint should narrow the search, not end it, so a hint containing the answer is stripped before the card is saved.

What "one fact" does not mean

It does not mean cards must be trivial. "Why does dividing the top and bottom of a fraction by the same number leave its value unchanged?" is a single question with a single answer, and it is a much better card than anything asking your child to recite a definition. Atomic is about the shape of the question, not the difficulty of it.

It also does not mean context is banned. A card can carry extra material for after the answer is revealed — a worked line, a note about where the idea lives in the curriculum. That content is not part of the recall test; it is there for the moment of understanding that follows.

Why this matters more for a child than an adult

An adult with a badly-written deck grumbles, edits the card, and moves on. A twelve-year-old does not diagnose the card — they conclude they are bad at the subject. A card that cannot be answered honestly does not read as a broken card; it reads as a failure. Getting card quality right is therefore not a polish issue. It is the difference between a tool that builds confidence and one that erodes it.

FAQ

What is the minimum information principle?

A rule from SuperMemo's twenty rules of formulating knowledge: each card should carry the smallest possible piece of knowledge, so that recalling it is a single act rather than several.

What is wrong with a card that lists three things?

There is no honest grade for it. Remember two of three and neither Got it nor Tricky is true, so whichever button your child presses, the schedule is now wrong.

Does aitutors.me stop bad cards being made?

Yes. A card whose question asks for several things at once is rejected at the moment it is written, before it ever reaches your child.