In A Nutshell
When we learn new facts, we aren’t forced to “delete” old ones. That’s because our brains don’t work like hard drives or bookshelves. In fact, the memory space in our ol’ noggins is so large, that we can’t possibly hope to fill it within our lifetimes. It’s effectively unlimited. The brain is also not as broad a storage unit as a hard drive, as it has different ways of storing memories that help prioritize what’s important and what isn’t (and is unable to delete things at will).
The Whole Bushel
“ ’You appear to be astonished,’ he said, smiling at my expression of surprise. ‘Now that I do know it I shall do my best to forget it.’ ”
It’s perhaps one of the most famous interactions in the Sherlock Holmes franchise: Dr. John Watson, having just explained to Holmes that the Earth revolves around the Sun, is rebuffed by Holmes, who declares that it isn’t important.
Featured in A Study in Scarlet, by Sir Arthur Conan Doyle, Holmes declares that the human brain has a limited amount of space, like an attic, and shouldn’t be crowded with impractical facts. It’s an interesting idea, but it’s totally untrue.
The human brain is very different from an attic, or bookshelf, or, for a more modern analogy, a hard drive. Memories are not stored in a single place but are reconstructed from various areas in the brain. This enables the brain, more or less, to store an unlimited amount of information for an indefinite period of time. During the course of one lifetime, it would be impossible to fill the memory space of the human brain. Some have estimated that the brain is somewhere close to a million gigabytes.
Different types of memory include sensory memory, short-term memory, and long-term memory. When something has been moved into long-term memory, your brain will be more effective at remembering it. For example, you’d obviously be better at reciting a poem you’ve memorized instead of one you’ve just read.
What about the crowds of impractical facts? The brain has automatic mechanisms for prioritizing what’s important and what isn’t. The answer to the math question you solved on the third day of eighth grade probably wouldn’t be too easy to recall. Your first kiss, on the other hand, can probably be remembered instantly.
It’s impossible to delete a memory at will, but sometimes memories can be completely forgotten. Complete photographic memory is a bit of a myth, though there are people who have extreme recall abilities. But your brain prioritizes things for a reason: People with eidetic memory can have difficulty making it through a day because of all the information they have to sift through.