How to memorize things fast, and keep them

Why memorizing feels hard

You can only hold a few things in mind at once. George Miller's famous “seven, plus or minus two” from 1956 was more a rough estimate than a measured limit; a 2001 review by Nelson Cowan brought the evidence together and put the real limit of working memory at about four chunks. Try to take in a page of new terms in one go and most of it never makes it past that bottleneck.

The way around it is to move information into long-term memory, which has no practical limit, and to package it into bigger chunks so each slot holds more. Every technique below does one or both.

1. Test yourself instead of rereading

Recalling an answer strengthens memory far more than seeing it again. In Henry Roediger and Jeffrey Karpicke's 2006 experiment, students who read a passage once and then practised recalling it three times remembered 61% of it a week later; students who read it four times remembered 40%.

Cover the answer, say it, then check. Flashcards are the simplest way to do this at scale. More on active recall, and on how it compares with other methods in the study techniques, ranked.

2. Space it out

Three short sessions on different days beat one long session. Each time you come back as a memory starts to fade, recalling it makes it last longer. In a 2009 flashcard study by Nate Kornell, spacing beat massing for 90% of the learners, although most of them believed massing had worked better.

A spaced repetition app times this per fact. If your exam is close, see cramming vs spaced repetition for how to space even in a week.

3. Make it meaningful

Isolated facts are hard to keep; connected ones are easy. Ask why something is true, link it to what you already know, and look for the pattern behind a list. A drug's side effects make more sense, and stick better, once you know its mechanism. A legal rule is easier to remember once you know the problem it solves.

Producing an answer yourself also beats reading it. In 1978 Norman Slamecka and Peter Graf showed that words people generated themselves, from a cue, were remembered better than the same words simply read. Write cards in your own words, and explain an idea before you look up the explanation.

4. Chunk it

Chunking means grouping items into meaningful units, so four slots of working memory hold four groups instead of four items. A phone number is three chunks, not ten digits. The cranial nerves are easier as sensory, motor and mixed. Vocabulary is easier in phrases than as single words.

Taken far enough, chunking looks like a superpower. In a study published in 1980, Anders Ericsson, William Chase and Steve Faloon trained a student, known as S.F., for more than 230 hours. His digit span grew from 7 digits to 79. He was a keen runner and recoded strings of digits as running times, so each chunk carried several digits. What grew was a skill with digits, built on chunks, not a better memory in general.

For languages, see how to memorize vocabulary.

5. Use pictures

People remember pictures remarkably well. In a classic 1967 study, Roger Shepard showed people around 600 pictures one after another, then tested whether they could pick out the ones they'd seen: they recognised almost all of them, and did better than with words or sentences. Pairing words with images (what Allan Paivio's dual coding theory describes) gives a memory two routes back.

• Draw the diagram from memory, then compare it with the original.
• Hide the labels on a figure and name each one (image occlusion).
• Turn a process into a simple flowchart you can redraw.
• Use a picture instead of a translation for concrete vocabulary.

6. Use places: the method of loci

The method of loci, or memory palace, is how most memory champions memorize decks of cards and long lists. You pick a route you know well, such as the rooms of your home, and place a vivid image of each item at a point along it. To recall the list, you walk the route in your mind.

1. Choose a familiar route with 10 to 20 distinct stops, always in the same order.
2. Turn each item into a vivid, odd image: big, moving, funny or absurd.
3. Place one image at each stop, interacting with the place.
4. Walk the route once in your mind to recall the list, then check.
5. Review it the next day and a few days later, as with any memory.

It can be learned. In a 2017 study led by Martin Dresler, people with ordinary memories trained the method of loci for 30 minutes a day over 40 days. Their score in memorizing random words in five minutes rose from about 17 to about 42, and their brain networks shifted towards those of 23 of the world's best memory athletes. It's best for ordered lists and sequences; for understanding, combine it with the techniques above.

7. Mnemonics for ordered lists

Acronyms and sentences are great for lists you must reproduce in order. A classic for the twelve cranial nerves: “Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Such Heaven”: olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory, hypoglossal.

Mnemonics are a hook, not understanding. Pair them with cards that ask what each item does. The keyword method for foreign words, which Richard Atkinson and Michael Raugh tested on Russian vocabulary in the 1970s, works but tends to fade faster than plain recall practice, so keep it for the few items that won't stick.

8. Sleep on it

Sleep after learning helps stabilise new memories, as Susanne Diekelmann and Jan Born describe in their 2010 review. A review in the evening and a quick check in the morning is a strong pair.

Sleep before learning matters too. In a 2007 study by Seung-Schik Yoo, Matthew Walker and colleagues, people who had missed a night's sleep remembered markedly less of what they learned the next day than people who had slept. An all-nighter undoes much of the work.

A 30-minute session to memorize something new

1. 5 minutes: read the material once to understand it, and split it into small facts or questions.
2. 10 minutes: test yourself on every question, checking each answer. Put the misses in a pile.
3. 5 minutes: a break. Walk, stretch, don't look at it.
4. 5 minutes: test the whole set again, misses first.
5. 5 minutes: the blank page. Write down everything you remember, then check what's missing.
6. Tomorrow: test it again, then let the gaps grow: a few days, a week, a month.

How fast can you really memorize?

Faster than you'd think for a day, and slower than you'd hope for a year. Getting through a hundred new facts in an afternoon is possible; keeping them means reviewing each one several times over the following weeks. In our simulation of a year of spaced repetition, each new card cost about ten reviews in its first year, half of them in its first month.

So the sustainable speed is set by your daily review time, not by how fast you can read. Ten to thirty new cards a day suits most students alongside their other work; before an exam you can go faster for a while, as long as you plan for the reviews that follow.

What to avoid

• Rereading and highlighting as your main method: they feel productive and do little.
• Copying notes out neatly instead of testing yourself.
• Learning a hundred new facts in one sitting and never seeing them again.
• Dropping cards the moment you get them right once. In a 2008 study by Nate Kornell and Robert Bjork, letting students drop flashcards they thought they knew had small but consistently negative effects on learning.
• Memorizing something you haven't checked: you'll remember the mistake just as well.

That last point is why FlashCardz quotes the line and page every card comes from: when an answer looks wrong, one tap shows you the source. See how it works.