Did you know that forgetting is actually very useful?

Forgetting is part of our daily life. Maybe you walk into a room and forget why you went there — or someone greets you in the street and you can't remember their name.

Why do we forget things?‍

Is it simply a sign of memory problems, or are there benefits to it?
One of the earliest findings in this area showed that forgetting can occur simply because a person's average memory fades.
This was discovered by 19th century German psychologist Hermann Ebbinghaus, whose “forgetting curve” showed how most people quickly forget the details of new information but that it decreases over time. More recently, this has been replicated by neuroscientists.

The forgetting curve

However, forgetting can also serve functional purposes. Our brain is constantly bombarded with information. If we were to remember every detail, it would be increasingly difficult to retain the important information.

One of the ways we avoid this is by not paying enough attention in the first place. Nobel Prize winner Eric Kandel and a series of subsequent studies suggest that memories are formed when the connections (synapses) between cells in the brain (neurons) are strengthened.

Paying attention to something can strengthen those connections and retain that memory. This same mechanism allows us to forget all the irrelevant details we encounter every day. So while people show more signs of distraction as they get older and memory disorders like Alzheimer's disease are associated with attention disorders, we all need to be able to forget the unimportant details to create memories.

Dealing with new information

Retrieving a reminder can sometimes also cause it to change to process new information. Let's say you drive the same route to work every day. You probably have a strong memory of this route, where the underlying brain connections are strengthened with each ride.

But suppose one of your usual roads is closed on a Monday and there is a new route for the next three weeks. Your memory before the trip must be flexible enough to absorb this new information. One way the brain does this is by weakening some memory connections while strengthening new additional connections to remember the new route.

Have you ever reached the office and barely remember driving there?

It is clear that the inability to update our memories would have significant negative consequences. Think PTSD (post-traumatic stress disorder), where the inability to update or forget a traumatic memory means that someone is constantly triggered by memories in their environment.
From an evolutionary point of view, it is undoubtedly beneficial to forget old memories in response to new information. Our ancestors in hunter-gatherer society may have repeatedly visited a safe watering hole, only to one day discover a rival settlement or a bear with newborn cubs. Their brain had to be able to update the memory and label this place as unsafe. Failure to do so would have been a threat to their survival.

Reactivating reminders

Sometimes forgetting may not be the result of memory loss, but of changes in our ability to recall memories. Research with rodents has shown how forgotten memories can be remembered (or reactivated) by supporting the synaptic connections mentioned above.

Rodents were taught to associate something neutral (like the ringing of a bell) with something unpleasant (such as a mild shock to the foot). After a few repetitions, the rodents formed a “fear memory” where hearing the bell made them react as if they were expecting a shock. The researchers were able to isolate the neuronal connections that were activated by coupling the bell and the shock, in a part of the brain known as the amygdala.

They then wondered if artificially activating these neurons would make the rodents react as if they were expecting a shock, even without a bell and without a shock. They did this with a technique called optogenetic stimulation, which uses light and genetic engineering, and showed that it was indeed possible to activate (and then deactivate) such memories.

One way this may be relevant to people is via a type of temporary forgetting that may not be the result of memory loss. Back to the earlier example where you see someone on the street and you can't remember their name. Maybe you think you know the first letter and the name will come to mind in no time. This is known as the tip-of-the-tongue phenomenon.

When this phenomenon was first studied by American psychologists Roger Brown and David McNeill in the 1960s, they reported that people were able to identify aspects of the missing word better than would be expected by chance. This suggested that the information had not been completely forgotten.

One theory is that the phenomenon occurs as a result of weakened connections in memory between the words and their meanings, reflecting the difficulty in recalling the desired information.

Another possibility, however, is that the phenomenon could be a signal to the individual that the information has not been forgotten but is only temporarily inaccessible.

This could explain why it's more common as people get older and more knowledgeable, meaning their brain has to search through more information to remember something. The tip-of-the-tongue phenomenon may be a way in which the brain signals that the desired information has not been forgotten and that persistence can lead to successful recall.

In summary, we forget information for various reasons. Because we're not paying attention or because information fades over time. We can forget to update reminders. And sometimes, forgotten information is not permanently lost, but simply inaccessible. All of these forms of forgetting help our brain function efficiently and have supported our survival through the generations.

This is certainly not intended to minimize the negative consequences caused by people who become very forgetful (for example due to Alzheimer's disease). Nevertheless, forgetting has its evolutionary advantages. We just hope you found this article interesting enough to not soon forget the content.

By Prof. Dr. Sven Vanneste

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