SoCal Code Camp

Although I don’t live in southern California, I often try to coordinate mini-vacations to coincide with SoCal Code Camp, an event organized by Woody Pewitt for the software development community. The event is essentially a mini-trade conference, without a lot of the noise and ceremony of the larger conferences. For two days, software developers take over a large portion of one of the universities in southern California to share information about technologies and techniques important to software developers.

Since the event is free, I like to contribute in some way for the generally excellent content that is made available to attendees. In my case, “paying rent” means presenting material. This year I presented material related to this blog – memory techniques. Software developers need to absorb and retain a ton of information, and most of that information becomes obsolete in just a few years. Being a software developer means constantly retraining oneself, constantly reading and learning. Therefore, I thought that a presentation about using your memory more effectively would be well received. I gave the same presentation last year, and I was stunned at how many people attended and how much positive feedback I got. More

Advanced Numbers: Memory System, Dominic System, and PAO

I’m finally getting close to completing my initial survey of memory techniques related to numbers. Yay! To that end, I now turn my attention to a couple of techniques that just don’t work for me. However, they may work for you, and people that participate in memory competitions swear by them, so I would be remiss if I didn’t at least point provide an overview.

The Major System

The Major System and the Dominic System both rely on relating phonetics with numbers. That is, they provide rules to relate numbers to sounds as an aid to memory. The basic process for remembering any number using these techniques is this:

  1. Break the number into two or three digit chunks.
  2. Apply rules to translate each chunk into consonants.
  3. Use the consonant sounds to make a word.
  4. Commit the word to memory. If required, use another memory technique to help remember long sequences.

To recall a number:

  1. Recall the word.
  2. Decode the word back to its original number.

That was probably less than helpful as a description. It will become clearer shortly.

The Major System uses a table to provide rules for translating each digit to consonant sound. Vowels are always ignored.

Digit Consonants
0 S, Z, or soft C
1 D or T
2 N
3 M
4 R
5 L
6 J, SH, soft CH, DG, ZH, or soft G
7 K, hard C, hard G, hard CH, Q or Qu
8 F or V
9 B or P


There is an excellent example in Wikipedia, which I’ll expand somewhat. Imagine you want to memorize the first digits of Pi, 3.1415927. Using the table above, 3=M; 1= T or D; 4=R; and so on.

3 1 4 1 5 9 2 7
M T or D R T or D L B or P N K, hard C, etc.


When memorizing these numbers, our task it to translate these sounds to words by adding vowels in between the consonant sounds. The Wikipedia examples suggests MeTeoR TaiL PiNK as a good solution, but I suspect that answer was far from obvious to most readers.

Most proponents of the Major System suggest sticking to nouns when encoding the digits. This makes sense, since our brains like remembering nouns, and it’s easier to apply other memory techniques such as the Memory Journey system if we stick to nouns.

When I try to encode the digits of Pi, I prefer to use two digit chunks, so I might end up with MaT RaT LaB kNacK.

The reason the Major System doesn’t work for me is that the process of going from number to consonant to word is too difficult and therefore slow, and the resulting nouns aren’t particularly interesting or memorable. Decoding from something like MeTeoR TaiL PiNK or MaT RaT LaB kNacK is just as tedious for me. Both the encoding and decoding process are vulnerable to ambiguity since many digits can be encoded as multiple consonant sounds.

Compare that to the Person Association technique. That technique requires the one-time pre-association of a person to each two digit combination (or three digit combination for the overly ambitious). Thus, instead of MaT RaT LaB kNacK, I might have a list of four famous people which I would then imagine in some silly or taboo scenes in order to lock in the memory.

There is no doubt the Major system is powerful and effective. However, for my purposes and the way my brain works, I don’t find it as useful as the Person Association technique. This is exactly why it’s important to develop a personal memory toolbox by learning those methods that work for you.

The Dominic System

The Dominic System is a bit more interesting to me, but even so I don’t use it. I tried it; I didn’t like it. The Dominic System uses an encoding scheme similar to the Major System. Instead of converting digits to numbers, the goal is to convert the digits to people and actions. The suggested encoding is:

Number Value
0 O
1 A
2 B
3 C
4 D
5 E
6 S
7 G
8 H
9 N


Notice that the Dominic System doesn’t shy away from vowels during the encoding, and there is no ambiguity; the mapping of digits to letters is one to one. Chunking of the series of digits to be memorized is always in pairs.

There is considerable preparation work required. Each pair of digits needs to be permanently associated with a person whose initials match the value to be remembered. For example, in our Pi exercise, the first two digits 3 and 1 are encoded as C and A. Thus, we need to know a famous or significant person whose initials are C and A. This can be quite a challenge at times. It took me a few minutes before I came up with the name of Chester Arthur. It’s debatable how many people think the 21st president of the United States still counts as famous or significant. I don’t mean to demean the memory of the 21st president, but I honestly don’t remember what he looks like, which makes making a mental image to aid memory somewhat challenging.

So, to continue our Pi exercise, 3.1415927 turns into CA DA EN BG. We need to translate these initials into people, preferably using a pre-memorized list of person associations. Perhaps we get something like:

CA Chester Arthur

DA Dan Aykroyd

EN Eugene Nowak

BG Bill Gates


You may be wondering who Eugene Nowak is. I have no idea. It took a couple of minutes of searching the web for me to find someone whose initials are EN, and Dr. Eugene Nowak was at the top of my search results. He’s a surgeon. I think.

Again, this reveals what I consider one of the weaknesses of the Dominic System. In order to use it, you must have pre-memorized a list of people for each possible two digit combination. Therefore it takes as much work as the Person Association technique, but without the freedom to choose people who are personally significant to you.

But wait – it gets better. For each person, you must also remember an associated action. This makes the Dominic System even harder, but this extra step is also where the power comes from. Using the Dominic System, you can encode four digits in a single image instead of the Person Association’s two digits per image.

Our Pi example should be chunked into two groups of two pairs:

31 41 and 59 27

This becomes:

Chester Arthur/Dan Aykroyd and Eugene Nowak/Bill Gates

But we aren’t done yet. Now we keep the first person in our head, but use a pre-memorized action associated with the second person.

To explain: Our pre-memorized list might look like:

27 = Bill Gates writing code on a computer

31 = Chester Arthur vetoing a bill

41 = Dan Aykroyd dancing in the Blues Brothers

59 = Eugene Nowak performing surgery


The mental image we build combines the person of the first pair of digits doing the action of the second pair of digits. Thus, we remember:

31 41 = Chester Arthur telling a joke

59 27 = Eugene Nowak writing code on a computer


As you can see, each scene encodes four digits, which is very powerful and potentially very fast for remembering large sequences of digits.

The PAO System

The PAO system is just like the Dominic System, but it extends the fun by allowing six digits to be encoded per image.

PAO is Person-Action-Object. The Dominic System could also be called the Person-Action system. It requires pre-memorizing a person and action for each possible two digit combination. PAO does this one better by requiring the pre-memorization of a person, action, and associated object for each possible two digit combination.

For our Pi example, we would have to pre-memorize something like:

Digits Person Action Object
27 Bill Gates Writing code On a computer
31 Chester Arthur vetoing A bill
41 Dan Aykroyd Telling jokes To an audience
59 Eugene Nowak Performing surgery On a patient


We chunk the number to be memorized six digits at a time as three pairs:

31 41 59

And we build a scene to remember by using the person of the first pair, the action of the second pair, and the object of the third pair:

Chester Arthur telling jokes to a patient.

Typically most people would then place that constructed scene at the first loci of a Memory Journey.


It should be obvious that these are advanced techniques for those very serious about being able to memorize long sequences of digits with ease. They all require significant investment in pre-memorization work.

Personally, I don’t have a lot of interest in party tricks or memory competitions. However, if I did want to memorize the first 10000 digits of Pi, the Dominic or PAO system is the way I would choose.

The guy who came up with the Dominic system is Dominic O’Brien. If you have an interest in getting really good at remembering a series of digits, you might want to show some love to the guy that came up with the system by buying one of his books.


I made a comment in a previous post that sparked a discussion at work. I made the remark that I recommend afternoon naps as a memory aid. Don’t believe me?

I used to think that the secret for good health was actually pretty simple: eat a reasonable and varied diet, exercise, and get a good night’s sleep.

Then I read Sara Mednick’s book Take a Nap! Change Your Life. Now I think the secret to good health is to eat a reasonable and varied diet, exercise, get a good night’s sleep and an afternoon nap. The author, Dr. Sara Mednick, is a research scientist at the Salk institute in La Jolla, California. Her resume is filled with names like Harvard. The book is based on her research and on the research of scientists she collaborates with. In the book, Dr. Mednick points out that nearly all mammals nap. The fact that people in the United States don’t nap is driven by culture, not biology. Your body wants to nap. Your brain wants to nap. More

What About Supplements?

No shortcuts!

One of the questions that I get asked when I talk about memory has to do with what I think about using supplements to improve memory. My answer usually comes through gritted teeth.

I don’t think that the idea that there is some food supplement, vitamin, or herb that will make your memory better is particularly interesting or useful. I think it represents a desire to pop a pill and get “magic” benefits without having to put in any effort.

The analogy I like to use is that worrying about what supplements you can take to have a better memory is a lot like asking what protein shake you should take in order to have a great body without going to the gym and exercising. It just doesn’t work that way. More

Using Association to Remember Numbers

There are lots of techniques that can be used to remember numbers, and they all have their trade-offs. Today’s post is about the Number Association system.

I find the Number Association system most applicable to remembering shorter sequences of digits. It also seems works best for people that are “concrete” thinkers or describe themselves as hands-on or kinesthetic learners.

The Number Association system is somewhat similar to the Number Rhyme system. In the Number Rhyme system, digits are converted to concrete objects using a simple rhyming scheme. In the Number Association system, digits are converted to concrete objects based on the thing associated with the digit. If you are looking for a technique to help remember short sequences of digits I suggest learning either the Number Rhyme system or the Number Association system, but not both. More

Remember Numbers With Rhymes

The Number Rhyme system is one of the easiest ways to remember short sequences of numbers. It requires almost no preparation, unlike most of the other techniques for remembering numbers. I find it useful for things like ATM PINs.

For example, suppose you decide to change your primary checking account PIN. PINs are almost always four digits. Most interesting in this case is the fact that a few weeks’ of use will wipe out any need for artificial memory tricks. What’s really needed is a simple technique to get through the couple of weeks between when you get the new PIN and when frequent use makes the memory naturally permanent. The Number Rhyme system may be just the trick.

A few key concepts are worth a brief review. First, numbers are too abstract to be easily memorized. Therefore all memory techniques for numbers rely on converting abstract numbers into something concrete. More

Moonwalking With Einstein by Joshua Foer

Moonwalking with Einstein: The Art and Science of Remembering Everything by Joshua Foer is the first book on memory that I read. Here is a link to an extended article by the author. The NY Times article is so extensive that I don’t feel the need to provide much of a review. You’ll get a good sense of what the book is all about by reading the article. Instead, I want to share some observations I have had since finishing the book.

The book is extremely well written and entertaining, and makes an excellent introduction to the world of the memory athlete. However, first and foremost it is a story, and as such falls a bit short in terms of being instructive about memory techniques. This is more than made up for by More

A Survey of Memory Techniques For Numbers

Remembering anything abstract is a problem. Numbers are no exception. Despite that, there are a number of well documented ways to remember numbers. There are also a number of poorly documented ways to remember numbers which take a little more work. Let’s see if we can add some clarity.

The basics of all of the memory schemes that focus on numbers is the same – convert the number into something concrete and remember the associated concrete thing. Alas, this means that the person that wants to be able to easily memorize numbers is going to have to do considerable preparation work and practice.

As an aside, it turns out that playing cards are basically numbers. Most of the memory tricks that work for numbers work just as well for cards. With a little creativity, learning how to remember a series of digits leads to being able to remember the order of cards in a deck. More

The Memory Coin

Penny (or whatever) for your memories?

I love this memory technique.

I like it for a couple of reasons – I found it described in Mary Carruthers’ utterly brilliant book The Book of Memory: A Study of Memory in Medieval Culture, which is about the history and practice of memory training and techniques in the middle ages. Although she described it, she never really gave it a name – at least not a simple name like “Method of Loci”. Therefore I took the liberty of naming it myself. I’ve also taken a few liberties with the methodology to make it more useful for the way my brain works.

Second, and more importantly, More