Revealing the reasons why people often forget childhood memories

Illustration: Sohu

The study, published in the journal Science on March 20, followed 26 babies between the ages of 4.2 and 24.9 months. The babies were divided into two groups: one group under 12 months old and the other group between 12 and 24 months old.

In the experiment, the babies were placed in an fMRI machine to monitor their reactions as they viewed a series of special images, each of which appeared for about two seconds. Scientists focused on observing activity in the hippocampus, the area of ​​the brain responsible for memory, emotion, and the autonomic nervous system.

“The hippocampus is a structure deep in the brain that cannot be seen with conventional methods. So we developed a new approach to perform memory experiments on children in an MRI machine… Previously, these types of studies were mainly conducted while the children were sleeping because infants move frequently, have difficulty following instructions, and have short attention spans,” Dr. Nick Turk-Browne, a professor of psychology at Yale University and the study’s lead author, said in an email.

Dr. Simona Ghetti, a psychologist at the University of California, Davis, who studies memory development in children, said previous studies have shown that infants are able to encode memories. But what is unique about this study is that it has established a link between memory encoding and hippocampal activity. Note that Ms. Ghetti was not involved in the study.

In the experiment, after a period of time, the babies were shown two images side by side, including one familiar image and one new image. To determine the level of image recognition, scientists tracked the babies' eye movements to assess which image held their attention longer.

If your baby's eyes focus more on the familiar shape, it shows that he has the ability to remember. Conversely, if he has no clear preference between the two shapes, it may show that his memory is not fully developed.

“Eye movements are a tool that has been used in hundreds of studies of memory and categorization in infants. Infants naturally gravitate toward things they find interesting, and researchers have exploited this trait to understand how memory works,” Ghetti said by email.

Illustration: K.sina

Analysis of hippocampal activity

After collecting the data, the team analyzed the fMRI scans from the children who looked longer at the familiar images and compared them to a group that had no clear preference. Trials were excluded if the children were not focused on the screen or had excessive movements, such as blinking too much, during the scan.

The results showed that the ability to encode memories varied across age groups. In the older group, the hippocampus showed higher activity when encoding information. In addition, only the group over 12 months old showed activation in the orbitofrontal cortex, an area involved in decision-making about memory and recognition.

“In adults, we tend to remember information that is important and directly related to our own experiences,” said Lila Davachi, PhD, a professor of psychology at Columbia University. Although she was not involved in the study, she noted: “What is remarkable about this study is that it demonstrates that at a very early age, the hippocampus of infants is involved in memory encoding, even when the images are not particularly meaningful to the child.”

The reason why children over 12 months old are better at encoding memories is not yet clearly understood. However, scientists hypothesize that this change may be related to major changes in brain development.

“The infant brain undergoes many important changes during early life, including cognitive, language, motor and biological development. In particular, the hippocampus develops at a rapid rate during this period,” explains Dr. Turk-Browne.

Turk-Browne's team is now looking further into why early memories can't be retrieved later. He hypothesizes that in infancy, the brain isn't developed enough to provide precise "search keywords," making it difficult to recall memories in adulthood. How memories are encoded may depend on a child's early experiences.

The significance of the newborn stage for parents

Dr. Ghetti encourages parents to consider the importance of infancy for their children, even though children cannot recall these experiences as adults.

At this age, children take in a large amount of information, including the ability to learn language by associating sounds with meaning. In addition, children also begin to form expectations about family members and explore the world around them, including the characteristics of objects.

Parents can observe this process when they notice their children responding to songs or stories that are repeated over and over again. According to Dr. Davachi, this not only helps children remember, but also makes their responses more natural as they grow older.

“Repeated interactive activities help strengthen the bond between parent and child,” shares Ms. Davachi.

In Ghetti's view, although early memories cannot be recalled as adults, experiences during this period still have a profound impact on a child's cognitive and emotional development.

“This reminds parents that infancy is not a time of empty nesting. Babies are absorbing a lot of knowledge, and allowing them to observe and explore can play an important role in developing their learning skills later on,” she added.

Thanh Mai (according to CNN)