Published on November 4, 2025 10:54 PM GMT
If you’re ever trying to find me at a meetup, the easiest way to spot me is to look for the guy with the bandana and the index cards. Gwern suggested that anything you explain three times you should just write a post about, which means I’m way overdue for an essay about the index cards.
I.
I have a bad memory.
More accurately, I have a bad memory relative to what you’d expect for someone otherwise intellectually capable. It’s not that I can’t remember anything, it’s that unless information happens to connect to one of my current obsessions, it just sort of slides out of my head after a short while. The best way I’ve found to describe it to other people is it’s kind of like if someone asks you to remember two or three phone numbers and just reads them all off without letting you write them down.
Sometime roughly around age sixteen, I started to regard this as an annoying flaw. I set out to fix it.
At the time I was, like many American schoolchildren, using flash cards for memorizing information I needed for classes. Since flash cards were the way I’d been learning a lot of things up until then, I assumed they were a good way to learn and just started adding information I cared about to flash cards.
Quotes I wanted to remember, names of classmates, phone numbers, what kind of flowers the cute senior girl liked the most, anything I wanted to keep in my head and was annoyed I kept forgetting[1], all of these started going on ruled index cards, 3.5 by 5 inches. The details of how I use them and what I care to try and remember have changed, but years later I still use them. Nowadays it's very common for me to pull out an index card in the middle of conversation with someone, jot down a few notes, and keep going.
The first thing I want to communicate is that you can decide to remember things. You don't have to forget.
II.
Why index cards, though?
You probably have a smart phone, possibly the one you're reading this on right now. You could type a note in it right now and it would be preserved in the digital record as long as you wanted, with perfect handwriting, searchable in an instant.
I prefer index cards for a few reasons. One is the social dynamic of taking notes in conversation is very different. If we're talking excitedly and I pull out my phone and start typing, that sends a very different signal than if I pull out a pen and paper and start writing. It's possible I'm doodling, but my attention can't have gone that far — I'm not on Twitter or Facebook.
Another is that pen and paper allow a lot of marks that are kind of awkward on smartphones. I routinely make quick sketches of what people look like, which is still hard to do on a phone. Over the years I've developed a lot of idiosyncratic shorthand symbols, things that mean to me "book recommendation" or "I told him that" or "add to my todo list" and the ability to invent my own symbology on the fly is handy. The physical layout of the card is useful; I can shade the corners of the cards to allow for easy sorting.
Why not a paper notebook? For one thing I was never sure what to do with a half full notebook. Do you carry around two for when you run out? Do you accept that you'll fill the current one up and be without? Do you get rid of it early and waste the space? With index cards I can swap out full cards and fill back up with fresh ones. I also like being able to spread them out on a table, then collapse them back into a stack and have them in my pocket. The pocket thing is great by the way, even small notebooks are surprisingly uncomfortable to sit on if they're in a back pocket. Plus, and I know this is a touch OCD of me, but it bugs me that I can't rely on getting exactly the same kind of notebook for years. If I ever really need a larger surface, a tiny bit of tape on the back can turn a dozen index cards into a mostly normal sized piece of paper.
The limited space is also surprisingly good. On a Google doc or Obsidian note, nothing stops me from continuing to type wall of text after wall of text but my own good sense. An index card is physically short on space, limited to about a paragraph of information. Ideas get summarized, and short summary connects to short summary with one card referencing another. The natural length of a note is about the length it's reasonable to actually try and memorize in one chunk.
Because that's the most important difference: I want to memorize this. It does me no good to have my partner's birthday written down on my phone if one day they ask "so, what's the plan for next weekend?" and that's their birthday weekend. I need that information to already be in my head. When I meet you for the third time, I want to recognize your face and be able to remember your spouse's name or what company you work for. By keeping my notes in index cards, there's low friction to start using them as flashcards.
Digital notes have the advantage of being backed up, but it's pretty quick and easy to take a picture of an index card with my phone. With recent advances in computer reading, I can turn a picture of an index card into a mostly searchable piece of text whenever I want. Notebooks have solid backs to make writing on them easier, but a stack of fifty index cards makes for a stable enough surface to write on with no trouble.
III.
So how do I use my index cards?
I use a modified version of the Leitner System, a form of spaced repetition, plus a review step that's a little like a journal. The basic idea is that I have a box divided into subsections, labeled with ascending numbers. (In my case, powers of two.) My modifications are mostly to make things easier for me, and me in particular, to manage the system without a lot of overhead.
At the end of every day, I go through all the notes I made that day. Most of them wind up getting thrown away since the information on them isn't worth remembering. My to-do list for the day won't matter to me in a year for example, or that bit of napkin math figuring out the tip. Others I'll rewrite, either because my handwriting was rushed and sloppy, or because on reflection I wrote three index cards about a topic but can condense it down to one card's worth I actually care about.
(As an aside, I like the function of making me come face to face with whether there was anything I learned today that I care about, so much so that I have a second habit of looking up one new vocabulary word if I haven't found at least one other thing worth remembering.)
Once I have the good versions of the cards, they go in the box. It's a shoebox, just the right size. Then I look at the section labeled 1. I read the prompt for that card, like "Abraham Lincoln" or "Family phone numbers" or what have you. I try and remember all the things that should be on that card, and then I look at what's written there. If I got it right, I move the card to the section labeled 2 and go the next card. If I got it wrong, I move it back a section- in this case it stays in section 1 since it can't go lower. Importantly cards can only move one section per day. Once I'm done with the section labeled 1, what happens next depends.
Every day, I do section 1. Every second day, I do section 2. Every fourth day, I do section 4. Remember, my sections are labeled in powers of two, so the gaps get larger and larger. When I'm traveling, often I just have a subsection of the stack to work through.
Sometimes as I'm reviewing a card I decide there's a better way to write the information on it, and I rewrite it and stick the new one into the stack, usually a section below where the original was.
And to answer the inevitable question: the highest section I've got in the box is the 2048, which contains cards I would only see after five years. I've got some that should be in 4096 somewhere, but I'm less organized about them at that point and that's a separate box that's basically just for long term storage.
IV.
You know what else is cool about index cards? They're a physical object I almost always have with me, where I don't care what happens to them.
I also write a lot of things I don't try to remember forever. Every morning I make a quick todo list that I add to as I go along the day. I jot down notes for math. If I ask for directions at the front desk, I'll write down what they tell me.
I can write my email on an index card and hand it to someone and not worry about getting it back. If I don't like the way I wrote a card, I throw it away and write another. If I realize I want a deck of cards but forgot to bring one, I can just write "A♠", "2♠", "3♠" and so on. I can fold them into origami cranes if I'm bored. Sure, sure, you might think, those are all reasonable things to do with paper. But carrying around completely disposable paper has been good practice for a kind of lateral thinking.
I've wedged a few folded index cards under the short leg of a wobbling chair. I've folded a card into a little box to trap a spider and move it. Twisted into a cone and with the bottom folded up, an index card will last long enough as a cup to have a drink or two. I've used a bunch of index cards as impromptu oven mitts — it ruined the top layer of cards, but who cares, they cost pennies to replace.
I recommend you try it. It'll cost a buck fifty to get a hundred cards and a couple pens[2] and you just have to carry them around in a pocket for a while and use them when the need arises. Maybe it doesn't work and you forget about it after a couple days.
Or maybe it works, and you remember what you care about for decades.
- ^
I was sixteen. The most important thing was the flowers.
- ^
Here's the ones I use and my favourite pens, though that's a bulk link to buy a lot of them at once.
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