How do mnemonics work?

Try to commit the following letters to memory: C E O H B O P H D N A S A.

I can make it easier by grouping those letters: CEO, PHD and NASA. I could make it easier still if I told you, “The CEO of HBO has a PhD in Physics and once worked in NASA.”

Mnemonics are incredibly efficient ways to remember large pieces of unrelated information. While we often marvel at their efficacy, how do they actually work?

People of normal intelligence have four to seven slots in their working memory. Each of those slots can hold one piece of information. This is why we copy down phone numbers or bank account numbers 4 to 7 digits at a time. However, if I told you to remember the sentence, “A little boy with brown eyes set fire to your house”, you are likely to remember it more easily than my phone number, although my phone number has 11 digits and this sentence has 41 letters.

Our brains do this using a trick called chunking. Numerical digits are abstract and unrelated. Therefore, each digit occupies one slot in our working memory. The same goes for different letters that are not arranged in a particular order. But for things already known to us, CEO’s and juvenile arsonists for instance, our brains can do a little compression trick. “CEO”, “PHD” and “NASA” would occupy only 3 slots in our working memory, whereas the image of a little boy burning your house down requires just one slot. If our memory is an email message which has slots for 4 attachments, creating a chunk is analogous to zipping several files and using up only one out of those four slots. Memory champions everywhere have built a formidable repository of these chunks and have trained their minds to remember things.

This leads to two implications. If we have a bad memory – for people’s names or memorizing abbreviations – it merely means that we haven’t trained our brain to chunk yet. It’s simply a matter of practice – of linking unknown things to concepts you already know.

More interestingly, the more neural chunks we have in our brain, the more we can use them to remember other things. Knowing about CEOs, PhDs and NASA helps you learn an entirely new fact that combines these things. That is why being an expert in one field lends itself to translating this expertise across several other related fields.

Inspiration: Sense of Style

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