Forgetful person holding up a sign with a question mark

Here’s a Brain Fact You Won’t Forget

Actually, you might. But don't worry, culling old memories is actually a good thing: it helps us adapt and make better decisions.


It turns out that forgetting information is an essential function of the healthy brain.

It’s easy to understand why forgetfulness seems like a sign of a malfunctioning brain: if the brain is where memories are stored, then a near photographic memory sounds ideal. And under certain brain disorders, like dementia, this is indeed a worrying symptom. But in the right balance, selectively forgetting information helps people make smarter decisions.

Scientists at the University of Toronto and the Hospital for Sick Children have narrowed in on cell activities that actively help the brain erase memories.

“The real goal of memory is to optimize decision-making,” says co-author Blake Richards. “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.”

Previously, neuroscientists were more interested in the science of remembering than the science of forgetting. Framed this way, forgotten memories were considered a byproduct of being overwritten by new information, one of the main driving forces behind why most people lose the majority of their childhood memories.

But if the goal of having memories at all is to help us better understand the world around us, it makes sense that forgetting information helps reduce noise and clutter. Actively getting rid of irrelevant, conflicting, or outdated information helps people make smarter decisions based on their generalized experiences in life. Details of specific past events are not as helpful in predicting new experiences in changing environments.

For instance, co-author Paul Frankland published another study where mice were trained to find a hidden escape platform in a water maze. After enough sessions, mice selectively looked in the location where they knew the platform would be.

For a month after training, the mice were then either left to live in a normal cage, or in a cage with a running wheel. The extra exercise promotes formation of new connections in the brain that help the mice forget their spatial training in the maze.

As expected, the mice with the running wheels were less able to find the hidden platform again when later re-tested in the original maze.

But something interesting happened when Frankland moved the platform to a new location. The forgetful mice actually outperformed their peers in finding the new exit, as they were presented with a new situation that conflicted with their past experiences. The forgetful mice were more flexible to change.

The more sedentary mice, who remembered the first location better, were impaired when it came to learning the new location compared to their initial training. They were less able to adapt to conflicting information.

So the next time you forget the name of the person you just met, remember this: forgetting little details isn’t a glitch in your brain. It’s actively helping you form a clearer picture of your world.

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Karyn Ho is a science animator and engineer who thrives at the interface between science, engineering, medicine, and art. She earned her MScBMC (biomedical communications) and PhD (chemical engineering and biomedical engineering) at the University of Toronto. Karyn is passionate about using cutting edge discoveries to create dynamic stories as a way of supporting innovation, collaboration, education, and informed decision making. By translating knowledge into narratives, her vision is to captivate people, spark their curiosity, and motivate them to share what they learned.