What causes the phenomenon of childhood amnesia?
That's a classic example of a phenomenon known as childhood amnesia. Scientists have known about childhood amnesia for more than a century. But it's only in the past decade that they have begun to figure out when childhood memories start to fade and which early memories are most likely to survive.
For a long time, scientists thought that childhood amnesia occurs because the brain of young children simply can’t form lasting memories of specific events. In the 1980s, Patricia Bauer and other researchers began testing the memories of children as young as 9 months old, in some cases using gestures and objects instead of words.
What they found was that even as young as the second year of life, children had very vivid memories for specific events from the past. So, they began to wonder why as adults we have difficulty remembering this particular period of our lives.
At age 3, the children were all recorded speaking with a parent about recent events, like visiting an amusement park or a visit from a relative. Then as the kids got older, the researchers checked to see how much they remembered.
The findings of the study accurately reflect the phenomenon of childhood amnesia. Children as old as 7 years old could still recall more than 60 percent of those early events, while children who were 8 or 9 years old recalled less than 40 percent.
It's still not entirely clear why early memories are so fragile. But it probably has to do with the structures and circuits in the brain that store events for future recall, according to Professor Patricia Bauer.
When a child is younger than 4, those brain systems are still quite immature. This does not mean they do not work at all, but not as effectively as in later childhood and certainly in adulthood.