How did an average-IQ undergraduate manage to be able to instantly remember seven random phone numbers?
Cambridge neuroscientist Daniel Bor explains the process in The Ravenous Brain. The student had average-memory capacity when he became who was the subject of a simple psychological experiment. Researchers would read to him a set of random numbers; his job was to repeat it back to him. If he got it right, the next test would be a digit longer; wrong and it would be shorter. He did this for an hour a day, four days a week, over two years.
He got up to seven numbers in a given sequence (a telling figure, as psych nerds know). Then he, quite understandably, got bored, and started to push his limit. As Maria Popova writes in the Atlantic:
By the end, some 20 months later, he was able to say back a sequence that was 80 digits long—or, as Bor puts it, "if seven friends in turn rapidly told him their phone numbers, he could calmly wait until the last digit was spoken and then, from memory, key all seven friends' numbers into his phone's contact list without error.
So how did he do it? He turned the numbers into something that mattered to him. He loved to run track, so he started to see number groups as running times: 3492 became 3 minutes and 49.2 seconds, near the world-record time for running a mile.
"In other words," Bors says, "he was using his memory for well-known number sequences in athletics to prop up his working memory ... he rapidly more than doubled his working memory capacity to nearly 20 digits."
What this clever experiment subject had run into was a memory strategy called chunking, where you compress the info you're being tasked with—like a random handful of numbers read to you by some psych researcher—into a more consumable and easier to remember set, like the world records that you happen to be acquainted with. In this way, something chaotically foreign can be turned into a familiar order.
When you're chunking, you're recognizing a pattern of information in order to store it later. Here's how to do it:
Use mnemonic devices: Do you remember how "My Very Energetic Mother Just Served Us Nine Pizzas"? That's because it's a popular mnemonic device to remember the order of the planets. And an awesome example of the chunk.
Find ready to use similarities: Turn unfamiliar numbers into familiar ones. Remember how our experiment subject turned 3492 into a track time?
Impose order: Random numbers (8675309) are hard to remember, but phone numbers can become unforgettable (867-5309). Why? Because you turn seven unwieldy items into two more handleable things.
Hat tip: Lifehacker
[Correction: An earlier version of this post used 'pneumonic' in place of 'mnemonic,' which was rightfully called out by commenters.]