Mnemonics and the memory palace: what they are for, what they cannot do, and the ones worth building

A mnemonic is a handle for something that has no logic of its own: a list in a fixed order, a set of names, a spelling. The handle can be a sentence whose first letters match the list, a rhyme, a picture, or a walk through your own home with one item placed at each stop, which is the memory palace. The research is clear on two points: these devices work for ordered lists, and they do nothing for understanding. Here are the four kinds, a palace built in ten minutes for a biology list, and the recall practice that has to follow.

What a mnemonic is, and what it is for

A mnemonic is a cue you build on purpose so that it leads you to the thing you need. The cue is easy to recall, and it is tied to something that is not.

The test for whether you need one is a single question: does this thing have an internal logic? If a rule explains the order, learn the rule, and the order comes free. If nothing explains it, you are holding a fact, and holding a fact is what a mnemonic is for. Memorize it or understand it is the sorting step on the memory-techniques page; this page assumes you have sorted and are looking at the pile marked "memorize".

Where that pile shows up in school: the levels of classification in biology, the order of steps in a cycle, a set of exceptions to a grammar rule, vocabulary in a language you are learning, the names and dates in a history unit, the first twenty elements. Each is a list with no reason in it that you could derive on the day.

Where mnemonics sit among the methods ranked by the evidence is on the study-methods hub: useful for one narrow job, and no substitute for recall practice on anything else.

The four kinds of mnemonic device

1. First-letter sentences and acronyms. The first letter of each word in a sentence stands for one item of the list, in order. The seven elements that exist as two-atom molecules at room conditions are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine: H, N, O, F, Cl, Br, I. A sentence of your own: "Hungry Newts Often Find Clams, Bread, Ice cream." It is slightly absurd, which is the point; you will picture the newts. Build it in two sentences' worth of effort: write the letters in order, then find words that make a picture. A sentence you wrote is easier to recall than one you were given, because you already did the work of making it mean something.

2. Rhymes and rhythm. A line with a beat holds an ordered list or a rule. The verse that lists the months with thirty days is the one everybody knows; a spelling rule set to a rhythm is another. Rhymes work because the beat and the rhyme constrain what the next word can be, so a half-remembered line often completes itself. Keep it short and exact.

3. The keyword method, for vocabulary. Take the new word, find a familiar word that sounds like part of it, and join the two with a picture. Atkinson and Raugh (1975) tested the method on students learning a 120-word Russian vocabulary and found that the students who used keywords learned the words better than the students who studied them without. Dunlosky and colleagues (2013) rate the keyword mnemonic low in their review of study techniques, not because it fails but because it serves one narrow job, vocabulary, and does nothing for anything else.

4. The memory palace. The method for a long ordered list, and the subject of the next section.

The memory palace (method of loci), built in ten minutes

The method of loci is the oldest study technique on this site. Orators in Greece and Rome used it to hold a speech in order, placing each part of the speech in a room of a building they knew and walking through the building as they spoke; Frances Yates traced its history in The Art of Memory (1966). "Loci" is Latin for places.

Five steps:

1. Choose a route you can walk with your eyes closed. Your own home: front door, hall, kitchen, stairs, landing, bathroom, bedroom, desk. The route must already be in your memory; a palace you have to build is two jobs.
2. Fix the stops in order. Eight to ten for a first list. Walk them once in your head before you place anything.
3. Turn each item into a picture that is odd or moving. A bland picture fades. A thing that is too big, the wrong colour, on fire or falling over stays.
4. Place one picture at each stop. The first item at the front door, the second in the hall, and so on.
5. Walk the route forwards, then backwards, then from the middle. If you can start at the bathroom and name the items on either side, the list is in.

Why it works: spatial memory is strong and it is ordered. You rarely forget which room comes after the kitchen in your own house, and the method borrows that order for a list that has none. Maguire and colleagues (2003) scanned people with exceptional memories and found ordinary brains using the regions that handle space and navigation; the memory-techniques page has the detail. Dresler and colleagues (2017) then trained ordinary adults in the method for six weeks, forty sessions of half an hour, and tested them on 72-word lists. The trained group recalled far more words than before and far more than two control groups, one of which had trained a different memory task, and the gain was still there months later. Ordinary brains, a learnable strategy.

Worked example: a palace for the Krebs cycle

A Grade 12 biology (SBI4U) student has to hold the eight intermediates of the Krebs cycle in order; it is idea 9 on the SBI4U course map. The list, from the course text: citrate, isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, oxaloacetate. No rule gives that order to a Grade 12 student on the day, so it is a palace job.

The route is the student's own home, eight stops. One odd picture each:

1. Front door: citrate. A giant lemon wedged in the doorframe, so you have to squeeze past it.
2. Hall: isocitrate. The same lemon, but now cut in half and stuck to the mirror, so you see it twice ("iso", the same).
3. Kitchen: α-ketoglutarate. A kettle (keto) boiling over with glue (glutarate) on the stove.
4. Stairs: succinyl-CoA. Someone sucking a lollipop shaped like a coat hook (CoA) on the bottom step.
5. Landing: succinate. The same lollipop, dropped and stuck to the carpet, hook gone.
6. Bathroom: fumarate. Fumes pouring out of the bath.
7. Bedroom: malate. A mallet lying on the pillow.
8. Desk: oxaloacetate. An ox with an acetate sheet over its head, standing on the desk.

Ten minutes to build, three walks to set. The pictures are not clever; they are odd, and odd is what holds.

Then the honest half. The palace holds the order and nothing else. Everything a question could ask beyond "name them in order" is understanding, and understanding is learned another way: by redrawing the cycle from memory and checking it against the course text. From that text, the carbon counts around the cycle are 6, 6, 5, 4, 4, 4, 4, 4: two carbons leave as CO₂, one at the step from isocitrate to α-ketoglutarate and one at the step from α-ketoglutarate to succinyl-CoA. NADH is made at those two steps and at malate to oxaloacetate; FADH₂ at succinate to fumarate; and the one GTP (or ATP) at succinyl-CoA to succinate, giving the net per acetyl-CoA of 2 CO₂, 3 NADH, 1 FADH₂ and 1 GTP. None of that is in the palace. It comes from redrawing the cycle from memory with the counts on the arrows, then checking.

The second night's recall. The eight names in order, from the walk: 8 of 8. The carbon counts from memory, one per intermediate: 6 of 8, with the two 4s after succinyl-CoA written as a 5 and a 3. The order was a palace job and the palace did it; the counts were an understanding job, and two are left to fix.

What mnemonics cannot do

They do not explain. The sentence about the newts tells you which elements are diatomic; it does not tell you why those seven and not sulfur.

They do not transfer. A palace for the Krebs cycle helps with nothing else in the unit.

They can be recalled without the list they stand for. Every student has produced an acronym in an exam and then stared at a letter they could not expand. The device is a cue, not the knowledge.

They take time to build, so a list of three does not need one. If you can hold it by saying it twice, say it twice.

The rule that follows from all four is the one the memory-techniques page states: a mnemonic is scaffolding, and it must be followed by recall of the real list.

The recall that follows: from the device to the knowledge

Roediger and Karpicke (2006) showed that students who tested themselves on a passage remembered more a week later than students who reread it. The same holds for a list behind a mnemonic: the device is the first retrieval cue, and the practice is what makes the list yours.

• Tonight: say the device, then write the real list with everything covered, then mark it. Write the real list covered and mark it: the marking rules are there.
• Tomorrow: try the list without the device first. Reach for the device only when you stall.
• In a week: the list cold, no device, no walk. The spacing schedule says why a week.

The device is dropped when the list comes without it. That is the point at which a mnemonic has done its job and can be forgotten. Chapter 1 of the free playbook is this recall step on one page.

The mistakes

• A mnemonic for something with a rule. If the order can be derived, derive it; the mnemonic is more work and breaks when the question changes shape.
• A borrowed sentence you cannot picture. Build your own.
• Bland pictures. They must be odd or moving. A lemon in a bowl is forgotten; a lemon wedged in the door is not.
• A palace route you do not actually know. The route has to be free; if you have to think about which room is next, the method is carrying two loads.
• Never testing the real list. The device recalled perfectly and the list not at all is the most common failure, and it only shows up in the exam.
• Building devices as a way of avoiding problems. In a maths or physics course, a rhyme for a formula is a way of not practising it; a procedure is a worked example, and the example is where the time goes.

The method on one page

• Need one? Only if the thing has no internal logic and more than three items.
• Four kinds: first-letter sentences and acronyms, rhymes, the keyword method for vocabulary, the memory palace for long ordered lists.
• The palace in five steps: a route you know, eight to ten stops, odd pictures, one per stop, walk it forwards, backwards and from the middle.
• The device holds order; understanding is learned by redrawing and checking.
• Recall schedule: tonight with the device, tomorrow without it first, in a week cold. Drop the device when the list comes alone.

Where YSR Studies does the bookkeeping

On paper, you keep the list, cover it, and remember when the week is up. In YSR Studies a card's answer stays on the server until you have tried it, so the list is recalled before it is shown; the schedule is FSRS at a desired retention of 0.9, which brings the list back cold at about the right gap; the course map shows each idea as Learned, Shaky or Not shown yet; and notes and cards export as the .apkg deck format and Markdown. Five free hours every month.