In this post, we look at when and how you can reuse a memory palace or a peg list such as the number rhymes to memorize multiple sets of information. We will go through an example where using the same locations multiple times works like a charm and look at other situations where you should rather use a different room or peg list.
In the following, I will mostly talk about locations along a journey or in a room in a memory palace. However, the same applies also to peg lists like the number rhymes and the number shapes. I have written a post on the memory palace technique, also known as the method of loci, in case you are not yet familiar with it. At times, I will also refer to locations as loci. These two terms mean exactly the same: Loci is the plural of locus, the Latin origin of the word location.
The question of re-using a memory palace can refer to two very different cases. We will cover both of them.
- You have already used the locations in a room or along a journey to memorize a set of information for long-term use. Now you are wondering whether you can add a second set to the same loci or should rather use a different room or memory palace.
- You have used the locations for short-term memorization and hope to overwrite the information in these locations with new information.
Can you safely add an additional set of information to a room in which you have already stored information for long-term use?
The answer is Yes, if the new set of information belongs to a topic/context that can easily be distinguished from what has already been stored.
Let’s look at an example where I am doing this:
I have a room in which I have memorized the following 4 lists of information using the same loci:
- The 11 most important medical breakthroughs since 1840. This list is the result of a poll conducted by the medical journal BMJ.
- The 5 steps of the natural planning model (NPM). Apply the NPM when you want to plan a project (small or large), and you’ll know fast why you are doing something, what to do next, and when you should rethink your approach.
- The 10 cognitive distortions used in cognitive therapy, as described by David Burns in his book “Feeling Good.” They are very useful for identifying and changing common negative thinking habits that are often the cause of emotional distress.
- The names of the 12 months in Khmer (the language used in Cambodia).
Why did I memorize the lists in the first place?
The medical breakthroughs are part of my history education. Lists 2 and 3 are thinking tools that I want to have available at all times. Keeping procedures, checklists, and thinking guidelines in memory allows me to apply them at will and reflect on them. List 4 helps me to learn a foreign language.
How do I recall the information?
You may have noticed that these are 4 very different sets of information. To retrieve the first list, I probe my memory with “medical breakthroughs since 1840?” and then retrieve the list by mentally visiting the first 10 loci in my “storage” room, recalling the information as I go along. For the second list, I ask “5 steps of the NPM?” and retrieve the information from the first 5 loci. I proceed in the same way when retrieving the information from lists 3 and 4.
Generally speaking, first, I always clearly mentally establish the topic about which I want to retrieve information. This sets the stage. Then I mentally re-visit the loci and retrieve the mental images that contain the information.
You are probably wondering whether the lists interfere with each other.
Do I get images from a list different from the one I intended to access?
Well, I mostly get the correct information at my first retrieval attempt. Sometimes, I get an image (i.e., the information) from a different list, but because the topics are different, I know instinctively that the information doesn’t belong to the list I want to retrieve. I reject it, mentally go back to the locus, and my memory comes back with the correct information. This is how the mind works naturally anyway, even if you don’t use a memory palace or other type of mnemonic filing system.
In summary, I have no problems to retrieve all items from any of the 4 lists at will.
To convince yourself that this works, I suggest you try it yourself as an experiment.
If you find my lists 1-3 useful, use them. I assume that you are not learning the Cambodian language, so you may want to substitute a different list for the months in Khmer. It could be the months in a language you want to learn, or something completely different.
How did I memorize the lists?
I memorized all 4 lists in a room that had originally been designed with 10 loci. I memorized the lists on different days, just as I naturally came across the information.
Upon learning a list, I recalled the information a few times to strengthen the images for long-term use. Practicing recall (mentally revisiting the memorized information) is something you have to do to keep information you have learned, even if you use a memory palace or other mnemonic system.
The room didn’t have enough loci to accommodate lists 2 and 4. For list 2, I mentally linked the 11th item to the 10th item, and for list 4, I added two additional loci (furniture in the original room that hadn’t been part of my memory palace) on the fly.
In summary, if you have information that belongs to different topics, you can use the same loci for multiple sets of information. The topics serve as additional cues that allow you to clearly distinguish between the lists.
Progressive addition of items to a composite image can vastly reduce interference
In 1972, Gordon Bower and Judith Reitman ran an experiment in which they had students memorize 5 lists of 20 concrete nouns each, using a single mnemonic filing system with 20 pegs/loci. So the participants had to use each peg 5 times.
This is one of the few studies I know of that actually tested long-term memory retention of multiple lists as opposed to just measuring performance and interference effects on the same day.
The students were divided into three groups:
Group 1 used a number rhyme list with 20 pegs. Participants had to proceed through each list and memorize each item by forming an image where the item and the corresponding peg interacted. They used the same pegs for each of the 5 lists.
Group 2 used the same number rhyme list but employed a strategy Bower and Reitman called “progressive elaboration.” Group 2 memorized list 1 by attaching each item to its corresponding peg in the same manner as group 1. For each item in lists 2 to 5, the participants had to recall the scene already attached to the corresponding peg, and add the newly to be memorized item by forming a composite image. Let’s focus on item number 2 and see how that works (own example):
List 1, peg two – shoe: I imagine kicking a corn cob in football fashion with my massive boot.
List 2, peg two – shoe: (Now I want to remember the horse.) I recall two – shoe: “Aah,” I was kicking the cob in football fashion. I missed the goal and instead hit a big checkered horse on the head.
List 3, peg two – shoe: I again recall the scene: I kicked the corn cob with my boot and hit the horse. A police officer gives me a ticket for kicking cobs on public roads.
I continue in the same fashion for lists 4 and 5, and add items to my previously imagined scene.
Group 3 also used progressive elaboration, but attached the items to loci in a pre-memorized memory palace.
Immediately after memorizing all 5 lists and again one week later, the participants had to recall all items of all lists in order.
Groups 2 and 3, who had used progressive elaboration, vastly outperformed group 1. After one week, group 1, that is, subjects who had memorized the 5 lists by just re-using the same number rhyme pegs and forming single images had forgotten almost 70% of the list items (compared to the immediate recall test directly after learning).
Both progressive elaboration groups fared much better: Group 2 (number rhymes) had forgotten only 25% and group 3 (memory palace technique) only 24%.
I tried this experiment myself with 4 lists of randomly chosen concrete nouns and also experienced significant interference effects when using single images. It became very difficult to keep the lists apart. I was able to recall most of the items, but often could not remember which list an item belonged to.
This comes to no surprise since the lists were all made up of random concrete nouns, instead of belonging to different, clearly discernible topics. Naturally, I would not have tried to memorize this type of information by attaching multiple single images to the same loci, but it is interesting to experience the interference effects yourself.
If you want to memorize random lists, progressively adding items to what you have already attached to your loci is a good strategy (provided you are not trying to optimize recall speed).
For lists of different topics, the topic serves as an additional cue and primes your brain for what you want to recall. You should have no problems to keep the lists apart. In this case, there is no need for progressive elaboration.
Erasing information you have memorized for short-term use
Memory athletes who take part in memory competitions keep several journeys to memorize decks of cards. Their objective is to memorize the order of 52 playing cards as fast as they can. They then recall the cards by mentally retrieving them from their loci and subsequently have no further use for the information. When they memorize a new deck, they do not like “shadow images” from previous memorization exercises intruding into their current set of cards. They also have no clear contextual cues or different topics that would allow them to distinguish between two different decks of cards. So they rotate between different journeys and give the ones they have recently used a rest to let the information “decay.” This allows them to reuse the loci after a day or two, or at worst a few days if they don’t revisit them and practice recalling the information.
If you want to practice card, number, or word memorization, I suggest you prepare multiple journeys, so that you can give each journey some rest before reusing it.
Other short-term information
For other short-term information, such as to-do lists, shopping lists, or lists to capture ideas when it is inconvenient to write them down (e.g., you are in the shower), it depends. I use the number rhymes to capture ideas and to-do items temporarily and transfer the items to written lists when it is convenient. Then I reuse my number rhyme pegs. If I need additional temporary storage locations or want to memorize a shopping list, I enlist the help of the number shapes.
Should you want to keep all temporary information in your memory, instead of in your smartphone/computer, you need to devise a different system. For a weekly to-do-list, you could, for example, prepare two journeys and alternate between them, giving old information a week to be “forgotten.”
So for temporary storage, instead of trying to actively “erase” information, I would just alternate between a few journeys, rooms, or peg lists.
You can use the same memory palace or peg list multiple times to store information about different topics. Tell yourself clearly what topic you are going to memorize before “storing” information. Do the same before you start recalling information. Recall the information from time to time to keep it.
Recall speed can suffer though if you attach too many items to one location. For practical purposes, I would limit myself to 4 or so items per location.
Progressive elaboration is an effective strategy to keep lists apart if they can’t be easily distinguished by their topic.
If you intend to memorize a lot of information for a topic, give it its own location, room, or even memory palace.
For practicing memory sports and short-term memorization, keep multiple journeys / peg lists and alternate between them.
How and when are you reusing your memory palace locations or pegs? I’d be most happy to get your comment on this.
- Image credits:
- St.Petersburg Palace, by Dashadee via Pixabay.com
- Misc Mental Memory, by Glitch via Openclipart.org
- Bower, Gordon H., and Judith S. Reitman. “Mnemonic Elaboration in Multilist Learning.” Journal of Verbal Learning and Verbal Behavior 11, no. 4 (1972): 478–485.
- De Beni, Rossana, and Cesare Cornoldi. “Does the Repeated Use of Loci Create Interference?” Perceptual and Motor Skills 67, no. 2 (October 1, 1988): 415–18. doi:10.2466/pms.1918.104.22.1685.
- Massen, Cristina, and Bianca Vaterrodt-Plünnecke. “The Role of Proactive Interference in Mnemonic Techniques.” Memory 14, no. 2 (February 1, 2006): 189–96. doi:10.1080/09658210544000042.