How to remember what you read

Most nonfiction, most of the time, will be forgotten in weeks. A book you read a year ago, directly relevant to your present circumstances? Almost certainly worthless.

It doesn’t have to be this way.

I recently attended a book club where we re-read a book I’d read 4 years ago. You might expect this to be a great opportunity to refresh memories and recall long-forgotten concepts. It wasn’t; I got nothing from it because I remembered the key concepts from the book as though I’d read it yesterday.

This happened because I followed a specific learning process to extract and store useful knowledge based on spaced repetition learning.

The idea being spaced repetition is simple: most information that makes it into long term memory sticks for less than a week. But if you recall that fact before you forget it, your memory is solidified and will last longer — perhaps a few weeks. If you repeat the same process — recalling the fact before forgetting it — it gets stronger, and lasts longer. The delays in forgetting are exponential, so if you do this for 10 to 20 appropriately spaced repetitions, you’ll have cemented that knowledge for life. (More on Wikipedia.)

Visually, you can imagine this as a series of ‘forgetting curves’, where each curve shows the likelihood of remembering a fact after a certain number of repetitions:

This process greatly benefits from being automated in software that asks you questions that force you to recall the answers. There are several good options (e.g. Anki and Supermemo) that make this a snap. If you use them daily, they’ll ensure you remember the knowledge you wish to.

How do you apply this to non-fiction? It’s simple — as you read, identify the key takeaways and insights that you wish to permanently remember (highlighting on Kindle makes this particularly easy). After you’re done reading, go through those takeaways. For each one that still seems relevant, formulate a specific question (or series of questions) based on that insight. Tie these as closely as possible to how you might use this knowledge because the way it goes in is the way it will be remembered. Then put these into your spaced repetition software and let it do its thing.

For example, about 4 years ago, I wanted to teach myself some basic accounting; naturally, I picked up an introductory book. As I read the book, I constructed two kinds of questions:

• Factual knowledge
• Drills

For factual knowledge, I wrote questions like “What are the 4 categories of short-term liabilities on the balance sheet?” These questions ensured that I remember basic definitions of concepts.

Quotes — either full quotes, or with some words deleted — can be a pithy way to remember concepts.

For drills, I created scenarios where I’d have to apply the knowledge. I wrote questions like, “What effect does purchasing $20,000 worth of raw materials on credit have on the cash flow statement, the income statement, and the balance sheet?” These questions take you from knowing to doing — the reason you want to learn the material in the first place.

While I’m no accounting expert, I now have a pretty good understanding of the content of and differences between the cash flow statement, the income statement and the balance sheet and how assets flow across them. It still surprises me that I can keep this stuff straight without using it constantly.

If you want to play the long game, you need to make investments in the long term. While reading seems to be one of those investments, it’s an illusion — unless you use spaced repetition to turn your knowledge into a durable good.