There’s a good reason to forget.

PennNeuroKnow gives those of us who tend to absent-mindedness hope, sharing research – and the story of a “super-rememberer” named Solomon Shereshevsky – that shows a certain level of forgetfulness is actually good for our brains … and the rest of us:

The effect of these forgetting mechanisms is that, in the average brain, only the adjustments associated with the most important or most rehearsed knowledge are retained. Knowledge that is seldom encountered or that does not seem relevant might cause some initial weak learning that is quickly undone by forgetting. In our berry example, the average brain would only be able to learn that there are certain core features (blue-colored and/or clustered) shared by many safe varieties. To a growing number of neuroscientists, the existence of these opposing learning and forgetting mechanisms and their effects suggest a possible source of super-human memory. Namely, one possibility is that the forgetting mechanisms of people like Shereshevsky are much weaker than that of the average brain.

However, imagine now that many of the berries you find were not in the guidebook. In this scenario, a perfect recollection of all the varieties of berries does not help. Rather, only those that learned the essential features shared by all safe varieties (blue-colored and/or clustered) would be able to determine whether each unknown variety is safe (Figure 1B). Thus, those that were forced to learn these essential features because they could not just memorize everything in the guidebook are much better off.

This exact scenario reflects a fundamental aspect of the world we live in – we are often required to make judgments about things we have not seen before. While these things might closely resemble other things we have experience with, it is often the case that no two things are exactly the same. By forcing us to learn the essential features and general trends that hold across a variety of similar, but different things (like all of the different types of berries that are safe to eat), a healthy balance between learning and forgetting allows us to make good judgments about things we have never seen before.

Since some species you previously associated with being safe are now unsafe and vice versa, you need to undo these now outdated associations and form the new correct ones. This process of undoing the original association and forming the opposite one is called reversal learning.

There are a bunch of primary sources at the link.