In A Study In Scarlet, Doctor Watson was astonished to learn that Sherlock Holmes did not profess to know whether the sun revolved around the earth, or the earth revolved around the sun. Holmes, unembarrassed by his unfamiliarity with basic astronomy, responded to Watson with a famous analogy:
“I consider that a man’s brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.”
I thought about Holmes’ notion when I ran across this article about the relationship of intelligence and forgetfulness. It reports on a study that concludes that forgetfulness is important to “intelligent decision-making in dynamic, noisy environments.” As one of the researchers explained, the study demonstrates that “[t]he real goal of memory is to optimize decision-making. It’s important that the brain forgets irrelevant details and instead focuses on the stuff that’s going to help make decisions in the real world.”
Intelligent brains therefore are quick to jettison memory of irrelevant or unnecessary information–which might be things like the names of people you haven’t seen in months, the details of a conversation that happened some time ago, or whether the sun revolves around the earth–to ensure there is space for relevant information that will actually be needed in your daily decision-making. And here’s some good news for those of us who have been around for a while: the study indicates that older brains forget accumulated older information in order to make room for newer information. So those “senior moments” aren’t a sign of approaching mental feebleness, they are just your brain efficiently sifting through the pile of debris and trying to get the limited space in your mental attic in order.
So Sherlock Holmes was right, and the study confirms the ultimate accuracy of his analysis of the human brain as like an attic with limited storage space. Of course, being Holmes, he probably wouldn’t read about the study in the first place.