Memory palace: the method of loci, and does it work?

The memory palace, or method of loci (Latin loci, “places”), is a technique for remembering lists: you imagine a route you know well, your home for instance, and at each spot along it you place, as a striking image, one of the things to be remembered; afterwards you only need to walk the route again in your mind to find them in order. Roman teachers of rhetoric described it more than two thousand years ago, and current studies say it works, above all for lists.¹²³ The previous article ended with a tree of forgetting touched before birth; this one opens a new section with the opposite, an art of not forgetting. I read the ancient sources in Latin.

What is the memory palace?

The clearest explanation is in the Rhetorica ad Herennium, a Latin handbook by an unknown author which Wikipedia dates to around 90 BCE.⁴ It distinguishes two memories, one “natural”, born with us, and one “artificial”, strengthened by method; and says the artificial memory “consists of places and images”. Places are things easy to remember, “such as a house, a space between columns, a corner, an arch”; images are figures of what one wants to remember. And the comparison that explains it all: “the places are very like wax tablets or papyrus, the images like the letters, the arrangement and disposition of the images like the writing, and the delivery like the reading.”² In other words: the route is the tablet, and what is placed on it is what gets written. The places stay; the images are wiped and replaced.

Where it comes from: Simonides and the banquet

Cicero, in On the Orator, from 55 BCE,⁴ tells the origin story that would be repeated for centuries. The Greek poet Simonides was dining in Thessaly at the house of one Scopas, who paid only half the fee for a poem because part of it praised the gods Castor and Pollux. Soon Simonides was told that two young men were waiting at the door; Simonides went out, found nobody, and at that moment the banqueting hall collapsed. The relatives could not recognise the bodies, and Simonides identified them by remembering “where each of them had been reclining”. From this, says Cicero, Simonides concluded that order is what most brings light to memory, and that one should use “places in place of wax, and images in place of letters”.¹

Just before, Cicero's speaker jokes about lacking the genius of Themistocles, who would have preferred an “art of forgetting” to one of memory.¹ A century and a half later, around 95 CE, Quintilian doubts the story: the accounts disagree on the place and on the owner of the house, and the part about the gods seems “fabulous”, because Simonides never mentions it, and would hardly have kept quiet about such glory. But Quintilian does not doubt the principle, which anyone can check: when we return to a place after a time, we not only recognise it but remember what we did there, the people, and even what we were thinking. “So the art, as in most cases, was born of experience.”⁵

The Roman rules

The Rhetorica ad Herennium gives very concrete rules, and nearly all are still used:²

• Places in order, so they can be walked forwards or backwards, “starting wherever we like”.
• Mark every fifth place: in the fifth, say, a golden hand; in the tenth, an acquaintance called Decimus.
• Quiet places: a deserted spot is better than a busy one, because the coming and going of people “confuses and weakens” the images.
• Places unlike each other, neither too large nor too small, neither too bright nor too dark, and about “thirty feet” apart.
• If there are not enough real places, invent them: thought “can embrace any region” and build places in it at will.

Above all, images that are remembered. The author starts from an observation: what we see every day, small and ordinary, we forget; what is “exceptionally base or honourable, unusual, great, unbelievable or ridiculous” we remember for a long time. No one marvels at sunrise, which happens daily, and everyone marvels at an eclipse. Hence the advice: images that do something (imagines agentes), of extreme beauty or ugliness, adorned with crowns or purple, stained with blood or mud, or comic.² And each person should make their own, because what strikes one person does not strike another.²

The handbook's example, written for a lawyer, is famous. To remember an accusation (that a man died by poison, that the motive was an inheritance and that there are many witnesses), one imagines in the first place the sick man in bed and, at the bedside, the defendant holding a cup in the right hand, tablets in the left and, on the fourth finger, a ram's testicles. The cup is the poison; the tablets, the will; and the testicles (testiculi), by the likeness of the word to testes, the witnesses.² An absurd and slightly obscene image, which is exactly what the handbook asks for.

Does the memory palace work?

Yes, and it has been measured. In 2003 a team led by Eleanor Maguire studied competitors in the World Memory Championships and found that their exceptional memory was not due to unusual intelligence or to structurally different brains: they used a spatial strategy, and while memorising activated regions such as the hippocampus, key to memory for places.⁶

In 2017 Martin Dresler and colleagues compared 23 of the world's best memory athletes with ordinary people. In a test of 72 words, the athletes recalled on average 70.8 after twenty minutes; the others, 39.9. Then they trained 51 volunteers with no experience: one group practised the method of loci for thirty minutes a day over forty days; another did a different, working-memory training; and another did nothing. The method-of-loci group improved far more than the other two, and the difference was still there four months later.³ One limit worth knowing: the 51 volunteers were all men, around 24 years old.

And it has a limit Quintilian already saw. For lists of things it works: “if many names of things heard in order have to be repeated”, one places “the table in the entrance hall, the lectern in the atrium”, and then walks through. But for learning a speech word for word it helps less: some words, such as conjunctions, cannot be turned into images, and having to look at a figure for every word breaks the flow. “We will teach simpler things,” Quintilian concludes: learn by parts.⁵

Try it: two lists, with and without a palace

This piece is a small experiment, with no timer and no saved scores. You memorise a list of ten words as you normally would and type the ones you remember. Then another list, but placing each word at a spot in a house and imagining a striking scene. At the end you see how many you recalled from each list.

A tip from the Rhetorica ad Herennium for the second list: make the scene do something, make it exaggerated or absurd, and make it your own.

What I could not read

I read in Latin the passages of Cicero (De oratore II.350-360), the Rhetorica ad Herennium (III.28-39) and Quintilian (Institutio oratoria XI.2.11-28). Of Maguire's study (2003) I read the abstract, and of Dresler's (2017), the author manuscript in PubMed Central, without the supplementary tables. I did not read Frances Yates, The Art of Memory (1966), the great study of the history of this technique, nor the Renaissance treatises (Giordano Bruno, Giulio Camillo), nor the treatise on mnemonics that, according to Wikipedia, the Jesuit Matteo Ricci published in Chinese in 1596.⁴ That stretch of the story is left for other articles. The “mind palace” of the BBC's Sherlock (2010) is, also according to Wikipedia, this same method.⁴

What we do with this

Anima Mundis is also made of places: frequencies, hours, a sky where each light is a voice. The art of memory reminds us that places put what is remembered in order, and that the everyday is forgotten while the unusual stays. The Observatory is our way of making sure what happened in each hour is not lost.