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Most people cannot remember the first few years of their lives, a phenomenon called childhood amnesia. Why are events from infancy not stored in memory?
What’s the trend?
Scientists are regularly looking for new techniques and ways to study the human brain, which is still fraught with many mysteries. Studying this organ is not only interesting, but also useful – discoveries make it possible, among other things, to find ways to treat various diseases.
Read The original article is available on the Scientific American website.
Can babies form memories?
Despite the vast differences in detail, early memories have a few things in common: most of them are autobiographical or relate to significant events in a person’s life. As a rule, these memories originate no earlier than 2-3 years. But research shows that even babies can form memories, but they are different from what a person remembers later in life. During the first few days of life, newborns may remember the face of the mother and distinguish it from the face of a stranger. After a few months, babies can already demonstrate that they remember many familiar faces by smiling at the people they see most often.
Actually there are many different kinds of memories besides autobiographical ones. There are also semantic memories, or memories of facts, such as the names of different varieties of apples or the capitals of countries. Procedural memories, that is, how to perform an action, such as opening the front door or driving a car.
research, conducted in the laboratory of psychologist Carolyn Rovey-Collier in the 1980s and 1990s showed that infants can form some of the above memories from a very young age. Of course, they cannot say exactly what they remember. Therefore, the key point in the Rovi-Collier study was to develop a method that responds to the rapidly changing body and ability of infants to assess their memories over a long period of time.
The essence of the method was that the researchers put babies between the ages of 2 and 6 months in a crib, over which a mobile hung. The scientists measured how hard the child kicked to get an idea of their natural tendency to move their legs. They then tied a rope from the child’s leg to the end of the mobile, so that whenever the child kicked, the mobile moved. The babies quickly realized that they were in control – they liked to see the mobile move, and therefore they kicked their legs more often than before the rope was tied to their leg. In this way, infants have demonstrated that they understand the relationship between their actions and the changes in space that they lead to.
For children aged 6 to 18 months, a similar experiment was used. But instead of a crib, the baby sat on his parents’ lap, his hands on the lever that moves the toy train along the rails. At first, the lever did not work, and the experimenters measured how hard the child pressed on it. Then they turned on the lever. Then every time the baby pressed it, the train moved along the rails. The infants again quickly mastered the game and pressed the lever that set the toy in motion much more often.
What does this have to do with memory?
After teaching the infants one of these methods for several days, Rovi-Collier tested how well they remembered the sequence of actions. When the babies returned to the lab some time later, the researchers simply showed them the mobile or train and watched to see if they kept kicking and pulling the lever.
Using this method, Rovi-Collier and her colleagues found that if 6-month-old infants were exercised for one minute, they could remember the event a day later. The older the babies were, the more they remembered. The psychologist also discovered that babies can help remember events longer if you train them for a longer time and give reminders – for example, by showing them that the mobile moves on its own for a while.
Why are early memories limited?
If babies can form memories in their first months of life, why don’t adults remember events from a very early stage of life? It is still unclear whether infantile amnesia occurs because children are unable to form autobiographical memories, or whether we simply do not have the ability to retrieve them. No one knows for sure what’s going on, but scientists have a few guesses.
One is that autobiographical memories require self-respect or self-awareness. You must be able to think about your behavior in terms of how it relates to other people. Researchers have tested this ability in the past with a mirror recognition task called «ruddy dough”.
To do this, they put a stain on the child’s nose with red lipstick or rouge. The researchers then placed the baby in front of a mirror. In the experiment, babies under 18 months simply smiled at the cute baby in the reflection, showing no sign of recognizing themselves or the red mark. Between 18 and 24 months, babies touch their noses, even when embarrassed. This suggests that they associate the red dot in the mirror with their own face – that is, they already have some self-esteem.
Another possible explanation for childhood amnesia is that because babies do not language until about the second year of life, they are unable to compose a story about their own life that they could remember later. In addition, the hippocampus, the region of the brain that is responsible for memory, is not fully developed during infancy.
Scientists continue to investigate how each of these factors contributes to our being unable to remember much or little of our lives until the age of two.