Now! Think back immediately to what you had for lunch the day before yesterday!

Now! Right now! Think back to what you had for lunch the day before yesterday.

…

If you can’t remember it right away, then… congratulations!

Wait, why congratulations?

In daily life, we often feel frustrated because we forget information, and we fantasize about how great it would be if we could remember everything we saw! Why did we evolve a brain capable of complex reasoning, but not a stronger memory?

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01

Forgetting may also be our "superpower"

In fact, we should be grateful that we have the ability to forget, because forgetting can reduce the cognitive load brought by memory and make cognition more efficient . This is a beneficial side effect of the efficient operation of a cognitive system with limited capabilities.

Perhaps we can get some clues from a few examples:

Solomon Shereshevskii is a journalist who has a "coveted" photographic memory. He can memorize long lists of numbers with ease, but he can't find a pattern in them. His mind is filled with isolated facts, but he can't deduce some common patterns to organize them, which makes him unable to understand metaphors, similes, poetry, or even more complex sentences.

Dominic O'Brien, the world memory master, is a globally recognized memory genius. With his own memory method, he has defended the World Memory Championship 8 times. He also broke the Guinness World Record by accurately memorizing the order of a total of 54 decks of cards (2,808 cards) (only 8 cards were wrong).

Dominic O'Brien (Photo credit: Worldkings.org)

But his reading comprehension ability is much lower than that of ordinary people. When reading, every word seems to jump out of the book. He has to point to the words one by one, otherwise it is difficult to read. When listening to the class, he has a hard time concentrating and will be distracted involuntarily...

This is actually the dilemma facing artificial intelligence today: it is difficult to abstract and generalize. Perhaps it is because we sacrificed part of our memory that we have unique inductive and abstract thinking.

However, "improving memory" is still the goal we have been pursuing. So what types of memory do we have? And what tips can help us remember things?

02

Classification of memory types: long-term memory and short-term memory

Memory capacity refers to the amount of information that can be maintained at the same time. If the memory capacity is exceeded, the information will be lost. In order to explore the limits of human memory capacity, scientists have made unremitting efforts, which also gave us a more intuitive understanding of memory: our memory can be divided into short-term memory and long-term memory according to the time scale.

Short-term memory usually only lasts a few seconds, and the memory capacity is very limited. The average person has around 4. But for example, the neighbor of Ma Dongmei in "Charlotte's Troubles" can only remember two words in "Ma Dongmei", so his short-term memory capacity is 2.

Image source: Screenshot from the movie "Charlotte's Troubles"

If a piece of information is memorized repeatedly, it can be converted into long-term memory . The capacity of long-term memory is much larger than that of short-term memory. The knowledge and skills we have acquired and past experiences all belong to long-term memory. Although it may also be forgotten, there is no obvious capacity limit for long-term memory - it can accompany us until the end of our lives.

The process of converting short-term memory into long-term memory, and short-term memory will be forgotten if it is not reinforced through repetition (Image source: adapted from opentextbc.ca)

03

What if you forget? Let your brain guess!

In some memory experiments, even if the subjects did not remember the target, they still completed the task more accurately than if they had relied on random guessing. Further analysis found that the subjects were able to infer the option with the highest probability based on their past experience, which improved their accuracy.

This strategy is called the " availability heuristic ." The heuristic study of human decision-making was originally proposed by Herbert A. Simon and developed by psychologists Amos Tversky and Daniel Kahneman.

Heuristics uses a practical approach or self-discovery to solve problems in any way that is not guaranteed to be optimal, perfect, logical, or reasonable, but can solve problems quickly.

The premise of heuristics is to recognize limited rationality and seek satisfactory solutions instead of optimal solutions. For example, given a novel, the subjects are asked to recall which of the words starting with k and the words where k is the third letter is more common. Most people think that the words starting with k are more common, but in fact the latter are twice as many as the former. This is because it is easier to remember words starting with k than words where k is the third letter.

In short, your memory produces a biased sample of information. Heuristics are often mental shortcuts that reduce the cognitive load that comes with making a decision .

04

If you want to improve your memory, try this method

Of course, memory can be improved through training. One of the more famous mnemonics is called the " memory palace ."

First, imagine a familiar and detailed scene in your mind, such as the street where you live, and then associate the objects you want to remember with their locations in the scene.

For example, if you want to memorize a string of words: bread, chair, stone, car, textbook, glass, spoon, desk lamp, flowers, sword... you can put them on a street you are familiar with: there is a big piece of bread at the corner of the street; there is a chair at the entrance of the kindergarten at the corner; there is a stone at the bus stop...

To remember these words, you just need to imagine that you are walking down a familiar street and encounter these objects on the way... The power of the memory palace lies in that once you bind the objects to the spatial locations, even if you mess up the order of the objects, you can still restore them based on the corresponding spatial locations in your memory. Therefore, to build a memory palace, the key is to choose eye-catching visual images to represent the objects .

The process of building a memory palace (Image source: adapted from ChessBase)

The principles of the memory palace need to be studied in depth. Some people have proposed a possible explanation from an evolutionary perspective: the neurons that allow us to remember things originate from the position cells used for spatial navigation, and it may be more natural to remember information by linking it with location.

However, the memory palace also requires long-term practice, and maintaining these memories also requires the brain's cognitive resources.

In the Internet age, we cannot and do not need to remember all the knowledge and everything we see and hear. After all, the Internet can help us check information at any time, but we cannot rely entirely on the Internet and not exercise our memory.

Author: Xu Da, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences

References:

[1]Ma, WJ, Husain, M., Bays, PM Changing the concept of working memory. Nat. Neurosci. 2014.

[2]Sims, CR, Jacobs, RA, & Knill, DC An ideal observer analysis of visual working memory. Psychological Review 2012.

[3]Daniel Kahneman. Thinking, Fast and Slow. Farrar, Straus and Giroux.

[4]György Buzsáki. The Brain from Inside Out. Oxford University Press.

[5]Rodrigo Quian Quiroga. The Forgetting Machine. BenBella Books, Inc. Dallas, TX.

This article is produced by Science Popularization China, supervised by the Computer Network Information Center of the Chinese Academy of Sciences, and produced by Xu Da

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