How old is your earliest memory? Why can't you remember anything before that?

When you were a child, you chewed your feet, ate your boogers, got kissed by a group of aunts until your face was covered with lipstick, and peed on your second uncle... When your family reminisced about your embarrassing childhood, you were the only one with a "confused" expression. Although it's not a glorious thing, why do you forget so many things? Especially before the age of 2 or 3 , you have no impression at all, as if you have never experienced it.

Early studies have suggested that anyone who cannot clearly recall details of childhood memories suffers from " childhood amnesia." Xue Song, secretary general of the Cognitive Neuroscience Committee of the Jiangsu Psychological Society and lecturer at the School of Psychology of Nanjing Normal University, said that childhood amnesia means that when people recall events from their childhood, they are completely unable to recall any clear and complete details.

This phenomenon was first proposed by Sigmund Freud, a famous psychologist and founder of psychoanalysis more than 100 years ago . He believed that our brain did not forget these things, but stored these early memories in a place in the brain, which is what we call the subconscious.

However, with the development of cognitive neuroscience, the "immature brain" theory has gradually replaced Freud's psychoanalytic theory and become the mainstream .

Researchers from the Department of Psychology at City College, University of London conducted a test in which they asked more than 6,000 people about their earliest childhood memories. 60% of them remembered when they were 3.24 years old (3 to 4 years old), which is also the time when we develop intelligence and form memories from a physiological point of view. Another 39% of people claimed to remember some stories before the age of two, and even 893 people said they still remembered fragments before the age of one, which can be said to be an astonishing number. For example, these people would say that they seemed to remember the story of "the first time walking" and "wanting to tell my mother that I was hungry before speaking".

Researchers at Memorial University of Newfoundland in Canada also published a paper titled "What is your earliest memory?" The study showed that, on average, the earliest memory people can recall can be traced back to 2 and a half years old. This is the conclusion drawn by researchers after a 21-year study of existing data . Hawking, the world's most famous "ALS patient", said that his earliest memory was when he was 2 and a half years old. At that time, he was crying loudly in the nursery. The children around him were playing with toys, but he didn't want to join in because he was scared. This shows that children from about 3 years old to preschool age have memories, so why do most people have no impression of things before 2 and a half years old? Doesn't the brain have memory function at this time?

There is a mysterious place between the thalamus and the medial temporal lobe of our brain - the hippocampus . It is part of the limbic system and is mainly responsible for the storage, conversion and orientation of short-term memory . If the memory content is repeatedly mentioned in a short period of time, the hippocampus will transfer the information to the cerebral cortex to form long-term memory. If the information stored in the hippocampus is not used or repeated in time, it will be gradually forgotten.

The hippocampus has limited capacity, and the hippocampus in the brain is constantly growing new neurons. As new neurons multiply in large numbers, old neurons will be squeezed aside or even directly replaced, and the long-term memory circuit that was originally strung together will no longer exist . So we have memories when we were young, but because the hippocampus is not mature enough, these memories are eliminated with the shedding of nerve cells. However, this process is very important. New cells are used to store new memories and help us learn how to learn.

For adults, normal memory is encoded, recorded, and stored deep in the brain in the form of language. Children under the age of 3 cannot speak and do not have complete language expression. The memory form stored deep in the brain is basically infant language. After children gradually learn to speak and express themselves correctly, the form of language expression changes, and the form of memory will also change accordingly. Therefore, it is difficult to retrieve memories from infancy through existing memory forms.

Some people say: " I still have some impressions of my childhood memories. Whenever my parents talk about it, I feel that it really happened ." Generally, this kind of hazy memory seems to exist vaguely. Professor Martin Conway of the Department of Psychology at City College, University of London said that if your earliest memory occurred before you were 2 years old, it may be fictional .

Childhood memories are easily influenced by the outside world, and these memories may be generated after seeing photos or hearing other people's memories . For example, when your mother first told you about your childhood, she mentioned an item. You don't remember doing that thing, but you have seen the item mentioned by your mother when she told you about it. The real memory fragments around you are combined with your mother's narration, and they are shattered and reprocessed in your mind, thus becoming your own "memories".

Although it is difficult to recall things from childhood, some particularly impressive things can still be vaguely remembered , such as the time when your parents beat you the hardest. This is because when things are too profound, self-consciousness will associate with surrounding things, such as the look of your father losing his temper, the stick, etc., forming a solid long-term memory. Therefore, children who are good at associative memory can remember more things.