The Dominic System

Two systems dominate number memorisation, and people who have learned one tend to be suspicious of the other. The Major System turns digits into consonant sounds and then into words: 42 is R-N, so 42 is rain. The Dominic System turns digits into letters and then into people's initials: 42 is D-B, so 42 is David Beckham (or David Bowie, or whoever D.B. is to you). Each person comes with a characteristic action, and a four-digit number becomes one person doing another person's action.

The system is named after Dominic O'Brien, who devised it in the late 1980s and used it to win the World Memory Championship eight times. It is the ancestor of the Person-Action-Object system that competitors now use for cards and long numbers, and it is still, for many people, the fastest route from "I can't remember phone numbers" to "I memorised a hundred digits of pi at the weekend."

This article explains the mapping, how to build your hundred people, how the person-action pairing works, and, since the question always comes up, how to choose between Dominic and Major.

The letter mapping

Ten digits, ten letters. Unlike the Major System, which maps to sounds and needs a paragraph of rules about soft and hard consonants, the Dominic mapping is a table you can learn in a minute.

Six to nine are the ones people stumble on for a day; after that the whole table is automatic. Notice what the mapping is not: it is not phonetic. The letter is the letter, so there are no arguments about whether "ph" counts as an F. This is the Dominic System's first advantage and, as we will see, the source of its main limitation.

From pairs to people

Every two-digit number from 00 to 99 becomes a pair of initials. 15 is A.E., 42 is D.B., 87 is H.G., 00 is O.O. For each pair, you choose one person, real or fictional, whose initials those are, and whom you can picture instantly. The classic examples from O'Brien's own list give the flavour: 15 is Albert Einstein, 07 is James Bond (the one deliberate cheat, because 007 is too good to waste), 40 is D.O., which O'Brien himself used for Dominic O'Brien, and 99 is N.N., which you will have to work at.

The rule for a good person is the rule for any mnemonic image, with one addition. They must be picturable, distinct from every other person on your list, and they must have an action you associate with them so strongly that you see the action the moment you see the face. Einstein writes on a blackboard. Bond fires a pistol. Bart Simpson (2-6, B.S.) rides a skateboard. Charlie Chaplin (3-3, C.C.) tips his bowler hat. Homer Simpson (8-6, H.S.) eats a doughnut. Without the action the person is only half a peg.

Where the initials fit nobody famous, you have three options. Use someone you know personally, which is often the strongest choice (your aunt Nora Nelson for 99 will outlast any celebrity). Use a fictional or generic figure whose initials fit (a Night Nurse for 99, an Opera Ogre for 00). Or bend the rule slightly and use a nickname or a single name whose first two letters fit (a person called Anna for 19, since 1 is A and 9 is N: A-N). The bent rule is common and harmless as long as you use it consistently.

The person-action pairing

Here is the part that makes the Dominic System more than an alphabetical peg list. A single person encodes two digits. But every person has an action, and the action can be borrowed. To encode a four-digit number, take the person from the first pair and the action from the second pair.

Take 1526. The first pair, 15, is Albert Einstein. The second pair, 26, is Bart Simpson, whose action is skateboarding. So 1526 is Albert Einstein riding a skateboard: one image, four digits, and the image is distinctive precisely because it is wrong. Einstein does not skate. Reverse it (2615) and you get Bart Simpson scribbling equations on a blackboard, which is a different picture, so order is preserved.

This is why the Dominic System became the basis for competitive number memorisation. With a hundred people and a hundred actions you have ten thousand distinct four-digit images and you had to learn only a hundred pairings. In a memory palace, each location holds one image, so a hundred-digit number needs twenty-five locations. Competitors later extended this with an object as well (person, action, object, six digits per image), which is the PAO system this dictionary teaches for cards.

Building your hundred

Do not try to do all hundred in a sitting. The people who abandon the Dominic System are almost always the ones who tried to fill the table in an evening and ended up with sixty names they could not picture.

Start with the pairs that come easily. Write out 00 to 99 as initials and fill in every pair that has an obvious person for you. Most people get thirty to forty on the first pass. Give each an action at the same time; a person without an action is not finished.

Drill those before adding more. Use the numbers practice on this site, set to two-digit groups, and work until any of your filled pairs produces its person in under a second. This usually takes two or three short sessions.

Fill the rest by category. For the stubborn pairs, go through categories: people you know, characters from books and films, sports, music, history, cartoons. Say the initials aloud; a name will often surface. For pairs that stay empty, use the bent rule (Anna for 19) and move on. A weak peg you drill beats a perfect peg you never chose.

Write it down and stop editing. The list is a tool, and the tool works because the same person always answers the same number. Change a person only when they have failed you three times in practice.

A starter list: 00 to 19

To show what a finished section of the list looks like, here are twenty people for the first two rows. They are suggestions. Replace any of them the moment a better person occurs to you, and notice how the awkward pairs (05, 01) are solved with generic figures or the bent rule rather than left empty.

Two things to notice. Every action is physical and different from every other action in the table; "firing an arrow", "firing a pistol", "firing a tommy gun" and "shooting a rifle" are close enough that a stricter list would separate them further (make Capone smashing a barrel instead). And the people vary in era, gender and silhouette, which is what keeps Oliver Hardy and Oliver Cromwell from merging into one man in a hat.

Drill this table with the numbers practice until any two-digit number from 00 to 19 gives you the person and the action without a pause. Then fill the next row.

Encoding cards

The Dominic System was designed for numbers, but O'Brien used the same people for playing cards, and it is worth knowing how, because it is the bridge to the PAO system. Each card is given a two-digit code: the number cards take their value as the first digit and the suit as the second (clubs 1, diamonds 2, hearts 3, spades 4, for instance), so the six of hearts is 63 and becomes S.C., whoever your S.C. is. Court cards get their own people (a king of hearts might be your own father). A deck then becomes 52 people, and, using the person-action trick, 26 images of one person doing another's action, which fits in a modest palace. Most competitors now prefer a dedicated card list with a person, action and object per card, which this dictionary provides as a starter deck, but the Dominic route is a perfectly good way in if you already have your hundred.

Dominic versus Major

This is the question everyone asks, and the honest answer is that both work, that the difference is smaller than partisans on either side claim, and that the choice depends on what you are memorising.

The Dominic System's strength is compression: four digits per image with only a hundred pegs. Its weakness is that it only runs in one direction. You can turn 42 into David Beckham, but you cannot look at a word and read a number out of it, because the letters have nothing to do with the sounds of ordinary words. The Major System is two-way: any word you see (a shop sign, a surname) can be decoded into digits, which makes it far better for opportunistic use and for numbers embedded in facts, dates, and prices. This is also why a dictionary like this one is built on Major: the chart can list a peg for every number and let you swap any of them, because there are always more words.

A common and sensible compromise is to use Major pegs for everyday numbers and short strings, and to build a Dominic or PAO list for serious training, where a fixed image per four or six digits and a palace to put them in is the whole game.

A worked example: a phone number

Suppose you want 0117 2664 (a made-up British number). Pairs: 01, 17, 26, 64. In Dominic initials: O.A., A.G., B.S., S.D. Say your list has 01 as an Olympic Athlete (sprinting out of the blocks), 17 as Alan Grant (the palaeontologist from Jurassic Park, brushing dust from a fossil), 26 as Bart Simpson (skateboarding), and 64 as Sherlock Holmes... except Holmes is S.H., so 64 is S.D.: Snoop Dogg, say, rapping into a microphone.

Four-digit images: 0117 is an Olympic sprinter brushing dust from a fossil. 2664 is Bart Simpson rapping into a microphone. Two images; put the first on your front door and the second on the hall table, and the number is in. Rehearse it once tonight and once tomorrow and it will still be there in a month, which is longer than you will remember the number by repetition.

Common problems

Two people with the same action. If both 15 and 71 "write", then 1571 and 7115 look the same. Every action must be unique across the hundred. Go through the list and resolve duplicates before you start drilling.

People who are too similar. Two bald men in suits will merge. As you fill the list, keep a rough eye on variety of gender, era, size, and colour.

Actions that do not involve the person's body. "Thinking" is not an action. An action must be visible and preferably noisy: kicking, juggling, pouring, drilling. Cerebral people get physical actions (Einstein scribbles, he does not theorise).

Confusing 6 and 7. S and G are the two letters with no obvious digit link, and they are the pair most often swapped. A private cue helps: six has a snaky S shape in its lower curve, and a 7 with a crossbar looks like a G.

Where to go from here

If you have read this far and want to try it, do not start with the list. Start with ten people, for the pairs 01 to 10, give each an action, and memorise a ten-digit number tonight. Then decide whether the person-action move suits you. If it does, the pi journey on this site supports Major, three-digit Major, and PAO encodings and will take you from ten digits to a hundred and beyond with a review schedule attached. If it does not, the Major System and its chart are waiting, and the skill you practised (a number becoming a picture in under a second) transfers entirely.

Dominic O'Brien's own view, repeated in every book he wrote, is that the system is a scaffold for imagination rather than a substitute for it. The letters get you to a person. Everything that makes the person memorable, the action, the setting, the absurdity of Einstein kicking, is yours to supply, and it is the supplying that does the remembering.