Like other brain systems, memory wasn’t designed; it evolved to solve adaptive problems in the environment. What we think of as memory is actually several biologically and cognitively distinct systems. Only some things that you experience get stored in memory. This is because one of the evolutionary functions of memory is to abstract out regularities from the world, to generalize. That generalization allows us to use objects like toilets and pens—you can use a new toilet, or a new pen, without special training because functionally, it is the same as other toilets or pens you’ve used.
