我们为什么会忘事？

大脑总是在忙着储存信息，但有时候，我们却很难回想起事情。你听说过 “门口效应” 吗？

How is your memory? Remembering things is an important function of our brain – if we can't recall how to do something, we can't survive. If you think about it, there is so much we have to remember – from where we left our car keys to how we walk. Maybe it's no surprise that sometimes we are forgetful.

Memory allows the brain to store and retrieve information when required. Our short-term memory can hold a small amount of information for a short time, while our long-term memory can hold an unlimited amount of information for a long time. Our memory is amazing, but why do we still forget things?

It's possible we don't always store information in our memory effectively, maybe because we are in a rush or we consider it irrelevant at the time. When we do store information, we often make connections with other things, which helps us recall it later. If you don't have these connections, then it can be easier to forget. Writing for the BBC's Science Focus magazine, Luis Villazon says "It is also possible that memories decay over time. As they have not been revisited, their biological 'trace' becomes weak." It's true that if you don't perform a task for a long period of time, it can be difficult to recall how to do it. This could be because, just like in a computer, our memory is full, or that our short-term memory is easier to access.

But sometimes even our short-term memory can let us down. Have you ever gone into a room to fetch something only to forget what you wanted when you got there? This is called ‘The Doorway Effect'. Writing for the BBC Future website, psychologist Tom Stafford explains that this "occurs because we change both the physical and mental environments, moving to a different room and thinking about different things." Put simply, we are metaphorically trying to spin too many plates at the same time.

So, if you have a mind like a sieve, it could be because you have too much on your mind. But we do need to keep our memory sharp by continually using it, especially as beyond our 50s our brains tend to shrink in volume and our memory begins to decline. That's when we're at more risk of getting Alzheimer's disease.

However, as Luis Villazon says, "Forgetting is not always a bad thing! It would waste cognitive resources if we remembered every detail of the world around us." That's something worth remembering!