Best forgotten? How the brain needs to filter memory to stay fit

The brain as a filter

The brain receives information, interprets it, and selectively stores some of it for future retrieval. In this sense, the brain can be thought of as a filter. Why, though, does it retain some things and not others?

The process of memory formation and memorising involves several fundamental stages, beginning with the sensory record.

The brain gathers information from the environment through auditory and visual signals. As it does, attention becomes crucial to forming short-term memories.

Have you ever been looking for your mobile phone, only to realise that you were already holding it in your other hand while talking to a friend? If so, it is probably because your attention was absent during the sensory record stage.

Consequently, the information (in this case, the phone's location) does not progress to the next phase: forming short-term memory.

Short-term memory serves as a temporary storage unit. Yet, without repetition, the information might still slip away.

This is where working memory steps in, holding onto information for processing before transferring it to long-term memory, where it stabilises indefinitely.

Not all information you encounter—like what you learned in science class at school—makes it into long-term memory. In fact, most get cast off.

This is the aspect of memory that scientists most want to understand. How come so much of what we hear and see fade away?

How to forget

During the Industrial Revolution of the late 19th century, German psychologist Hermann Ebbinghaus dedicated himself to studying and researching memory and forgetfulness.

Recognising the value of subjective experience, he undertook an experiment. He compiled 169 lists of meaningless passages in which each syllable comprised three letters and committed them to memory.  

He then sought to test his retention by relearning these lists after intervals ranging from 21 minutes to 31 days. Ebbinghaus observed a rapid rate of forgetting immediately after memorising the lists for the first time.

However, over time, the rate of forgetting slowed down. The 'forgetfulness curve' was born. He showed that the rate of forgetting information follows a logarithmic pattern rather than a linear one.

In his experiments, Ebbinghaus hit upon another intriguing concept: unconscious knowledge.

When he revisited the passages five or six years later, he found that he could recall them more strongly than his counterparts who were memorising them for the first time. They had, it seemed, lodged in his unconscious.

Decay and interference

Research proposes two theories of forgetfulness: the theory of decay and the theory of interference.

The theory of decay suggests that memory declines if a particular memory is not reinforced through repetition. The theory of interference suggests that new information entering the brain may replace or disrupt older information.

Despite being seen as annoying or problematic, forgetfulness is an essential process that serves a purpose in the formation and functioning of memory.

Until the 1950s, neuroscientists commonly believed that forgetfulness indicated a defect in the brain's nerves. Later research debunked this. We now know that forgetting makes memory flexible.

The brain helps refine decision-making by selectively ignoring irrelevant and outdated information. This strategic forgetting makes decision-making more manageable due to the vast amount of information and memories. Simultaneously, the retention of valuable information remains a priority.

Use in decision-making

Forgetfulness got a better reputation after neuroscientist Dr Paul Frankland and his team revealed in studies from 2017 that it serves crucial functions.

Forgetting helps prevent excessive rumination on past events, limits the influence of outdated information on memory-driven decision-making, and enhances memory flexibility.

This suggests that memory's primary objective is not merely to transfer information across time but rather to optimise the decision-making process.

Memory aims to improve decision-making by retaining what is significant while discarding the rest. These findings were published in the journal Neuron in January 2017.

Speaking to Al Majalla, Frankland said forgetfulness may be beneficial in two ways.

"First, the loss of detailed memory enables individuals to focus on the broader picture rather than getting lost in specific details," he said.

"Second, it allows us to ignore outdated information. Of course, this won't be useful if nothing changes in our local environment, where everything's fixed.

"But in the real world, things change all the time. What used to be useful to remember at one point may become less important over time."

Facilitating this 'big picture' thinking could be a crucial factor powering people's intelligence like Einstein.

It may be why Napoleon Bonaparte forgave André-Marie Ampère, a French physicist, mathematician, and founder of the science of classical electromagnetism.

Ampère was invited to dine with the emperor. He accepted, then forgot all about it. The general laughed it off – he knew the scientist's reputation for forgetfulness and assumed he had better things to think about.

Wandering minds

The Greek philosopher Thales of Miletus was so engrossed in stargazing that he fell into a well, so the story goes. It is one of the earliest reminders that forgetting or wandering is not indicative of foolishness.

Forgetfulness points to the inherent complexity of scientists' minds: a cacophony of ideas needing organisation. Within this mindful storm, an idea that fundamentally alters human thinking or our understanding of the world may emerge.

A study featured in the journal Neuropsychologia in August 2017 supports the idea that individuals prone to mental wandering or daydreaming tend to possess higher intelligence and creativity.

A wandering mind is not inattentive; rather, it is directed toward internal thoughts unrelated to the task at hand.

As attention plays a crucial role in transferring information from the sensory record to the short-term memory stage, encrypting and preserving memories becomes challenging in this mental state.

Ampère was a brilliant scientist whose discoveries impact our lives today. His name, which was one of only several to be engraved in the Eiffel Tower, is today given to the unit of measurement for electric current – the amp.

In the course of his musings, he mistook chalk for sugar, and once collided with a tree in the college courtyard, before offering it apologies as if it were a fellow human.

He was in such a rush to write a new solution down that he did so on the door of a carriage, thinking it was a lecture board.

Isaac Newton, another genius, would become so engrossed in thought during meals that he would forget to eat his food, which went cold in front of him.

Inhibiting the fluff

Forgetting does not necessarily indicate a flaw or a gap in the cognitive process. It reflects an effort to prioritise and focus on the more important things.

Einstein summed it up thus: "Never memorise what you can look up in books." When asked for his phone number, he would go to the phone book to get it.

He exemplified the idea of not burdening one's mind with information readily available externally. He reserved mental space for more critical matters.

Dr Ronald Davis, a neurology professor at Scripps in Florida, says forgetting is a common aspect of everyone's daily lives, irrespective of their intelligence.

Heightened forgetfulness can be boiled down to one's preoccupation with other life matters, crises, or stress. Geniuses often concentrate on what they deem most important, forgetting the rest.

According to Davis, intelligent individuals—whether consciously or unconsciously—choose to remember what is significant to them and intentionally forget the trivial.

As such, the brain may activate "inhibitor" circuits that prevent the retention of unimportant information.

Our brains host an impressive 100 billion neurons, the nerve cells that send messages all over the body. What if our memories retained every detail of our lives, both positive and negative?

Davis says this would be a disaster. It would result in us becoming prisoners of our memories.

This makes sense. Soviet neuroscientist Alexander Luria once described a patient with an exceptionally strong and detailed memory as "disabled", because of the difficulties this caused.

It underscores the vital role of forgetting as a necessary and fundamental component of a healthy memory system. Not everything needs to be remembered.

Having said that, it does help to remember where you live, and how to get back there.