How to Write Better Flashcards: One Idea Per Card

Why one idea per card

You can only hold so much in mind at once. Miller (1956) noted that for many kinds of material the span of immediate memory is about seven items. Cowan (2001) later argued that the limit is closer to four chunks once rehearsal and grouping are controlled. The estimates differ because researchers measure in different ways, and the debate continues.

A chunk is a familiar unit, such as a word or a short phrase, that you handle as one item. A card that asks for a paragraph, a list of seven causes and two dates demands a lot at once. Smaller cards keep each answer within what you can handle. That is our practical advice built on the working-memory idea. The studies above did not test card sizes.

Before and after: five weak cards rewritten

Open questions fit a finding about recall and recognition. A meta-analysis reported that initial recall tests produced larger testing benefits than recognition tests (Rowland, 2014). A yes/no card, or a card with answer options, leans toward recognition.

Five rules to apply to every card

1. One idea per card. If the answer contains an 'and', consider two cards.
2. Ask a question, not a topic. A question tells you what to produce.
3. Prefer open questions to yes/no. Make yourself produce the answer.
4. Add just enough context. A subject tag such as 'Chemistry' removes ambiguity without giving the answer away.
5. Keep the answer short and checkable. You should be able to tell in seconds whether you were right.

None of the sources we read compares card styles, so these rules rest on the general principles cited above. Treat them as a starting point and adjust them to your own results. When a card does trip you up, checking the answer after you recall tells you what to fix.

A checklist for reviewing your own cards

• The card asks one question.
• It is not a yes/no question.
• I can tell right away whether my answer was correct.
• The context is clear, so the card means one thing.
• No wrong options sit next to the right answer.
• If I keep missing it, I will rewrite it instead of just repeating it.

Short cards also fit short sessions. Practice offers sessions of 10, 15 or 20 cards, and you can try a starter deck built for active recall. How many new cards to add each day is its own question, covered in how many new flashcards per day. For ways to use finished cards without a partner, see how to quiz yourself.

Common mistakes

• Copying whole textbook sentences onto cards. Pull out the one fact the sentence makes and ask for it.
• Writing answer options on the card. Multiple-choice testing can expose learners to wrong options that some of them then learn, and feedback reduced that effect (Butler and Roediger, 2008). Ask the open question and keep wrong options off the card.
• Flipping the card before trying to answer. Say or write your answer first, then flip and check it.
• Making a hundred cards in one evening. Every card comes back for review later. Start with a batch you can review in one short session.
• Never fixing a card you keep missing. The card may hold two ideas or lack context. Split it or add context, then keep reviewing it.

Frequently asked questions

How many words should a flashcard have?

None of the sources we read sets a number. A short question on the front and an answer you can say in a few seconds on the back is a good target. If the answer needs a paragraph, split the card.

Are yes/no flashcards bad?

They lean toward recognition rather than recall. You can answer them by guessing or by recognizing a familiar name, and initial recall tests gave larger testing benefits than recognition tests in one meta-analysis (Rowland, 2014). Our advice is to rewrite them as open questions.

What should I do with a card I keep missing?

Check the wording first. If it holds two ideas, split it. If it could mean several things, add context. If it is clear and you still miss it, keep it in rotation. In Practice a missed card goes back to box 1.

Where does the one-idea-per-card rule come from?

It is practical advice built on research into working-memory limits. Miller (1956) described about seven items and Cowan (2001) argued for about four chunks, and estimates differ by method. None of the sources we read tested card sizes directly.

Sources

We opened each source below before citing it. See Methodology and Sources for how we check them.

1. Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving Students' Learning With Effective Learning Techniques: Promising Directions From Cognitive and Educational Psychology. Psychological Science in the Public Interest, 14(1), 4-58. Open the source
2. Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63(2), 81-97. Open the source
3. Cowan, N. (2001). The magical number 4 in short-term memory: A reconsideration of mental storage capacity. Behavioral and Brain Sciences, 24(1), 87-114 (with open peer commentary to p. 185). Open the source
4. Rowland, C. A. (2014). The effect of testing versus restudy on retention: A meta-analytic review of the testing effect. Psychological Bulletin, 140(6), 1432-1463. Open the source
5. Butler, A. C., & Roediger, H. L. (2008). Feedback enhances the positive effects and reduces the negative effects of multiple-choice testing. Memory & Cognition, 36(3), 604-616. Open the source