Piotr Wozniak, the author of SuperMemo, published a document titled "20 rules to structure knowledge" in 1999. I read this sentence and realized that I made my flash cards in the wrong ways. The way to make the questions were not appropriate. Here are some excerpts to explain.

In 20 rules, I think the most important rule is "Rule 4: Sticking to minimum information principle." It says we should make the questions as simple as possible. Simple cards are easy to remember, and adjustment of the review interval works effectively. For example, when you remember only a part of the answer, you review it at short intervals including the part you already remembered. When you remember almost correctly, but there is a slight difference, you worry about whether you consider it as a correct answer or an incorrect answer. Those phenomena happen because the question on the card is not simple enough.

Let's see a concrete example. For example, you want to remember what country are the Benelux countries. You may create a question card as follows. This question is a bad example.

Front: What countries are the Benelux countries?

Back: Belgium, Netherlands, and Luxembourg.

Let's break up the same content into three simple questions, for example:

1 Front: Benelux countries are Be... , Nederland, and Luxembourg

1 Back: Belgium]

2 Front: Benelux countries are Belgium, Ne... , and Luxembourg

2 Back: Nederland

3 Front: Benelux countries are Belgium, Nederland, and Lux...

3 Back: Luxembourg

Instead of requesting all three answers, I fixed the order of answers and split the original question into three fill-in-the-blank questions. In this question making, I use "Rule 9: Do not try to memorize an unordered set," "Rule 10: Do not try to remember the sequence of multiple things," and "Rule 5: The fill-in-the-blank question is easy to remember." The fill-in-the-blank question is called "cloze."

We cannot use this way of making questions with paper flashcards. If the order of questions is fixed, the answer of the second and the third question appears in the first question. However, when the software shuffles the order of questions, the problem which comes out first changes every review. If there is a question which is hard to memorize, only the question is reviewed more frequently, and your memory improves efficiently.

It is also a good option to paste map images of the three countries of Benelux on the flash card. It is "Rule 6: Use Images".

*25 In a learning software Anki, which I introduce later, we can create multiple cards from one sentence by specifying multiple places to fill in. Anki adjusts the timing of question so that those cards are not shown on the same day.