How to remember what you read

Why you forget most of what you read

Forgetting is not a sign that you read badly. It is how memory works. In 1885 the psychologist Hermann Ebbinghaus measured how quickly he forgot material he had just learned, and found that most of it was gone within days unless he went back to it. This pattern is now called the forgetting curve.

Books make it worse in two ways. First, you read a lot of ideas in a row, so each one gets very little attention. Second, finishing a book feels like an achievement, so you move on to the next one and never come back to the first.

The good news: memory researchers know quite precisely what slows the forgetting curve down. Two techniques stand out.

What actually works (and what doesn't)

In 2013, a team of cognitive psychologists led by John Dunlosky reviewed hundreds of studies on ten popular study techniques. Only two were rated high utility:

• Practice testing (also called retrieval practice): trying to recall information from memory, for example by answering questions about it.
• Distributed practice (also called spaced repetition): spreading that recall over time instead of cramming it into one session.

Highlighting and rereading, the two things most readers do, were rated low utility. They make the text feel familiar, and that familiarity is easy to mistake for knowing it.

How big is the difference? In a well-known 2008 study published in Science, Jeffrey Karpicke and Henry Roediger had students learn word pairs. Students who kept testing themselves recalled about 80% a week later. Students who kept studying instead, once they had recalled a pair, remembered only 33 to 36%. Same time spent, very different results.

A 6-step method to remember any book

1. Read with a question in mind. Before you start, write down why you are reading this book or what you hope to get from it. You will notice and keep what answers that question.
2. Stop at the end of each chapter and write from memory. Close the book and write three to five lines about what you just read, without looking. This is retrieval practice, and it is the single most important step.
3. Put it in your own words and connect it. Rewrite each idea as you would explain it to a friend, and link it to something you already know or have experienced. Ideas with connections are much easier to recall.
4. Turn the key ideas into questions. "What is the two-minute rule?" works better than a summary, because a question forces you to retrieve the answer instead of just recognizing it.
5. Review on a schedule. Answer your questions about a day later, then after a few days, a week, two to three weeks and once a month. Each review can take less than a minute per idea.
6. Use the ideas. Explain them in a conversation, apply one to your week, or write a short post about the book. Using an idea is the strongest form of practice there is.

Steps 2 and 6 are where the learning happens. Steps 4 and 5 are what keep it from fading. They are also the steps most people skip, because writing questions and tracking review dates by hand is tedious.

A reading notes template you can copy

Use this after each chapter or at the end of a book. It takes five minutes and covers steps 1 to 4.

Book:
Chapter / section:
Why I'm reading it:

In one sentence, this chapter says:

3 ideas, in my own words (from memory):
1.
2.
3.

This connects to (something I know or experienced):

One thing I'll try this week:

Questions to test myself later:
-
-
-

What this looks like in Prismo

Prismo is the app I built to do steps 2 to 5 without the busywork. You write a few lines in your own words, or dictate them. Prismo pulls out the ideas worth keeping, files them under the right topic, writes questions from them and schedules your reviews with spaced repetition. Here is an example from a note on Atomic Habits:

You see what Prismo found and untick anything you don't want, and you can edit any topic later. The questions come back at longer intervals each time you get them right.

Common mistakes to avoid

• Copying quotes instead of thinking. A page of highlights you never revisit is a graveyard, not a memory. Keep a favorite quote if you like, but write the idea in your own words too.
• Writing too much. Five lines you will actually review beat five pages you won't. Pick the ideas you would want to remember in a year.
• Reviewing only when you feel like it. Memory fades on a schedule, so reviews need one too. A daily five-minute habit beats an occasional long session.
• Testing yourself with the answer in view. If you can see the answer, you are recognizing, not recalling. Cover it, answer, then check.

Sources

• Ebbinghaus, H. (1885). Über das Gedächtnis (Memory: A Contribution to Experimental Psychology).
• Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving students' learning with effective learning techniques. Psychological Science in the Public Interest, 14(1), 4–58.
• Karpicke, J. D., & Roediger, H. L. (2008). The critical importance of retrieval for learning. Science, 319(5865), 966–968.