If I made you take the final exam for a class you studied a decade ago, would you pass?
The unfortunate truth is that, except for knowledge we actively use in daily life, much of what we learn is beyond our powers of recall. But that doesn’t mean it has been erased from our memories.
Why We Forget
Early theories of forgetting were based on decay. These theories assume unused memories fade with time like the yellowing of a photograph. The idea has some intuitive plausibility. Physical atrophy withers the body, so why not the delicate connections that store our thoughts?
Yet, the theory of decay is not the whole story. As psychologist Robert Bjork comments:
“Thorndike’s original law of disuse, of course, stands as one of the most thoroughly discredited of the various ‘laws’ psychologists have put forward over the years — which is a considerable distinction.”
Interference from other memories is another major factor in forgetting. Retrieving a memory is an active process. You need to search for a specific memory based on cues you have consciously accessible. As you acquire more memories, more and more of them become associated with familiar cues. It becomes harder and harder to retrieve any particular memory.
This may seem like a defect, but it’s actually a feature. Memory is only useful if we retrieve the right memories at the right times. Recalling the right memory requires both retrieving the correct option and suppressing all competing alternatives. Otherwise, our waking life would be a dreamlike flood of irrelevant and dissociated thoughts — hardly a sound basis to make intelligent decisions.
Forgetting Can Be Good for Learning
The adaptability of memory goes further. If a memory turns out to be surprisingly useful — i.e., we retrieve it despite barely remembering it and find it to be the answer we want — the memory becomes much easier to recall than if it was easy to retrieve.