You have probably tried it before – getting a trivia question in a quiz that you know your brain has the answer to. You just can’t find it. You say that it’s right on the tip of your tongue, but at some point the other players stop believing you.
You have probably also tried to read a great amount of material for a test where you had to show your knowledge. Most of the material you spent so many hours studying has now been archived in the infinite library of oblivion. On the other hand, you can probably remember phone numbers for friends and family from back when everyone spoke on landline phones. That’s a lot of years ago and you don’t need those numbers anymore – yet, they are still etched into your memory.