At the end of the 19th century, a German psychologist named Hermann Ebbinghaus invented a method to study human memory using his own mind as the only resource. For hours, he memorized meaningless three-letter words called “trigrams,” each composed of a vowel between two consonants, for example DAX, REN or VAB. He discovered that he could only memorize sixty-four trigrams in each forty-five minute session before his mind gave out. His efforts revealed fundamental aspects of human memory, including the concept of the “forgetting curve,” which for the first time accounted for how quickly we forget information.
This story is collected by neuroscientist Charan Ranganath in his book
Why We Remember
(Peninsula), recently published in Spain. Ranganath is a pioneer in using functional magnetic resonance imaging (fMRI) to study how we remember past events. In his work, he addresses an essential and enigmatic question that Hermann Ebbinghaus already posed more than a century ago: “Much of what we experience today will be lost in less than a day. Because?".
Question:
In
Why We Remember
you argue that the brain is programmed to forget, what is the logic behind this evolutionary mechanism?
Answer:
Our brain is designed to form and store memories only of what it considers important. Generally, it creates episodic memories in situations that provoke surprise, curiosity, joy, desire, love, fear, anger or stress. These emotions trigger the release of certain chemicals in the brain, such as dopamine, norepinephrine, serotonin, and cortisol. These chemicals promote brain plasticity, a process that shapes neural circuits as we learn, which helps these memories persist over time.
Furthermore, memories tend to compete with each other. For example, we forget where we left our keys because we have put them in different places before. This competition between old and new memories can cause us to forget, a phenomenon known as “interference.”
Q:
Is it possible to overcome this “interference”?
A:
Yes. Sometimes memories we think are lost can come back if we have the right clues at the right time. Like when a song, a place or a scent takes us back to a moment in the past that revives those memories.
Q:
Like Proust's madeleine.
A:
Exactly.
Q:
Are there psychological or neurological benefits to remembering sad or traumatic events?
A:
There can be benefits to remembering painful events if we learn from them: sometimes you can learn from the mistakes you made in the past, and sometimes the lesson is that you are resilient and able to overcome adversity. And sometimes when we experience terrible events, we can later enjoy telling funny stories about how bad things were.
Q:
Is nostalgia necessarily negative?
A:
Nostalgia can be good, in the sense that remembering positive events can make us feel better in the present. Nostalgia is only bad when it distorts our view of the past and present. When we indulge in nostalgia, we often overlook the negative events that occurred or remember them in a more positive way. This can give the misleading impression that our lives were better before than they are today. And on a collective level, there are authoritarian leaders around the world who distort history and use nostalgia as a weapon to gain power and manipulate people. Therefore, nostalgia can be healthy, but we must be aware of the potential it has to become harmful.
When we are angry with someone, we have a natural bias to remember information that reinforces our negative feelings.
Q:
After a breakup, why is it common that it is initially difficult to remember the happy moments shared and we only remember the sad ones?
A:
Research shows that when we try to remember past events, we are biased toward finding memories that are congruent with how we feel and think in the present. Our emotions form a powerful part of our mental states, so when we are angry with someone, we have a natural bias to remember information that reinforces our negative feelings and we are less likely to remember happy moments.
Q:
Recent advances in neuroscience have revealed that it is possible to selectively “erase” traumatic memories in animal models. Based on these findings, what is your perspective on the ethical and practical implications of applying similar techniques in humans to treat disorders such as PTSD (Post Traumatic Stress Disorder)?
A:
It is not clear that the experiments in rats can be generalized to humans. A lab mouse remembering that she received an electric shock in a box is probably not comparable to the traumatic memories of a soldier who spent a year in combat or a girl who was repeatedly abused by her parents during her childhood. So I'm not surprised that results in neuroscience have been difficult to translate to PTSD treatment.
But if the barriers can be overcome, we need to think carefully about the goal. I don't think we should erase memories of negative events, even if they are quite traumatic. In my opinion, treatment should focus on changing the most distressing components of those memories, the parts that lead us to feel painful emotions every time we remember. We are seeing signs that psychedelic therapies for PTSD could have this effect, allowing people to remember traumatic memories without the severe pain, fear and shame.
Q:
Therefore, in your opinion, we should not try to erase memories that cause us pain.
A:
I would recommend that instead of getting rid of the memory, people focus on changing their perspective and questioning their beliefs about the event. Therefore, I advise sharing memories in the context of supportive and trusting relationships. Gaining outside perspectives, as in psychotherapy and support groups, gives us the opportunity to transform our memories, allowing us to view the past in a less distressing way.
Q:
Why do we sometimes forget what we were going to do when we entered a room or even why we are there?
A:
This happens because our memory is linked to the place, time and mental state in which we find ourselves, what we know as “context”. When this context changes, such as leaving a room or changing the topic in a conversation, an “event boundary” is created. This means that the brain stores memories differently before and after that change. For example, if you are in your bedroom and remember that you left your phone in the kitchen, when you leave the bedroom and walk to the kitchen, your context changes. So, when you get to the kitchen you need to remember why you went there, which means mentally crossing that event boundary and remembering what you were thinking in the bedroom.
By attempting to record every moment, we do not focus on any aspect of the experience in enough detail to form distinctive memories that we will retain.
Q:
In the digital age, we thoroughly document our lives with our mobile phones, does this have any impact on our natural ability to remember?
A:
Digital documentation can improve memory if used consistently with principles that help remember, but we often use it automatically, which impedes our natural ability to remember. We often focus on documenting at the expense of experimenting. For example, when people take photos for Instagram or record a concert with their phones, their attention is drawn to what is happening, but it takes them away from what is distinctive in the moment, the sights, sounds, smells and sensations that make them. make an experience unique and memorable. By attempting to record every moment, we do not focus on any aspect of the experience in enough detail to form distinctive memories that we will retain. So even if you look back at those photos and videos you've taken (and most of us don't), they won't evoke the same warmth or joy that they would have if you'd put away your phone and immersed yourself in the moment.
Q:
What would be the correct way to use technology?
A:
Thoughtfully taking photos or videos at opportune moments can orient us to what is interesting and distinctive around us. For example, my daughter likes to selectively photograph plants and flowers that catch her eye on our nature walks, allowing her to stop and fully absorb those aspects of the landscape in that moment. And later, if you take a moment to use those photos as cues to remember that event, you will find that the event becomes more memorable and easier to remember over and over again.
Q:
Compared to the storage and recall capabilities of digital memory, is human memory becoming obsolete? How do the two compare?
A:
They are very different. I often say that “my phone has photographic memory, but I don't, and that's okay.” Digital devices record every bit of information they receive, but the human brain records memories that prioritize the most novel, surprising, or emotionally significant parts of our experiences. The human brain has also evolved in a way that allows us to learn quickly, but also be flexible and quickly adjust our behavior when situations change. And these features help explain why powerful AI systems like ChatGPT, which have a massive carbon footprint and require enormous amounts of data, can't solve certain tasks that the human brain can do using barely enough energy to power a light bulb. .
Q:
What do you consider to be the main disadvantage or limitation of human memory?
A:
Working on computational models of the brain, I have learned that it is very difficult to judge a brain system as good or bad, or as having strengths or weaknesses. There is no way to design a brain optimally for every possible goal, just as there is no way to design a car that has perfect fuel economy, high speed, and the ability to carry a large amount of cargo. There are always trade-offs.
That said, I think our biggest limitation is the bias to remember events in a way that fits our beliefs. This bias gives us overconfidence in our abilities, leaves us open to prejudice, makes us vulnerable to misinformation, and deprives us of opportunities to learn from our mistakes.
Q:
Another limitation of human memory is the general absence of memories from the first years of life.
A:
It's true. Research indicates that during the first two years of life, a child has no episodic memories, known as “infantile amnesia.” In the next two years, a child may form episodic memories, but these are fragmented and blurred, and this is called “childhood amnesia.” During this period, the brain is reorganizing at a rapid rate. The hippocampus and prefrontal cortex, two areas crucial for episodic memory, are in very early stages of development. As a result, memories are being built on a foundation of sand that is constantly changing.
Q:
What are the recommendations to maintain good brain health and what factors can negatively affect it?
A:
There are many factors. The best advice I can give is that the mind, brain and body are all connected. Therefore, almost anything you can do to take care of your mental and physical health will be a good investment for brain health.
Some protective factors in this sense are a healthy diet, exercise, social interaction and sleep. Factors that can negatively affect brain health include common health problems such as diabetes and vascular diseases, chronic stress, insomnia, depression, alcohol abuse, infectious diseases such as long COVID, and even gum disease. Fortunately, unlike the United States, many people in Spain exercise regularly by walking and cycling, and follow a variant of the “Mediterranean diet,” which has been shown to be very effective in promoting brain health.
Q:
After so many years researching human memory, what do you think is the big question that still needs to be answered?
A:
This is the hardest question of all! I feel like each real discovery leads us to more questions we hadn't thought to ask before. The question I like to ask is: what is the best way to challenge my beliefs about how memory works? The biggest mysteries concern how we use memory in the real world: how we move from one place to another, how we understand what is happening in a basketball game or how we manage to follow what is happening during a stressful conversation. Humans seem to have this extraordinary ability to use the past to build an extraordinary understanding of how everything and everyone is connected. That ability, which allows us to draw a continuous line from the past to the present and the future, is what I want to understand.