My kids will often ask me about what I was like at their age. It might be about how fast I swam a couple of length freestyle, it could be what music I was into, or when I went on a particular holiday I mentioned in passing. Of course, as I didn’t keep a diary as a child, these questions are almost impossible to answer. I simply can’t remember how old I was when certain things happened.

Over and above that, though, there’s some things that I’ve just completely forgotten. I only realise this when I see, hear, or perhaps smell something that reminds me of a thing that my conscious mind had chosen to leave behind. It’s particularly true of experiences from when we are very young. This phenomenon is known as ‘childhood amnesia’, as an article in Nautilus explains:

On average, people’s memories stretch no farther than age three and a half. Everything before then is a dark abyss. “This is a phenomenon of longstanding focus,” says Patricia Bauer of Emory University, a leading expert on memory development. “It demands our attention because it’s a paradox: Very young children show evidence of memory for events in their lives, yet as adults we have relatively few of these memories.”

In the last few years, scientists have finally started to unravel precisely what is happening in the brain around the time that we forsake recollection of our earliest years. “What we are adding to the story now is the biological basis,” says Paul Frankland, a neuroscientist at the Hospital for Sick Children in Toronto. This new science suggests that as a necessary part of the passage into adulthood, the brain must let go of much of our childhood.

Interestingly, our seven year-old daughter is on the cusp of this forgetting. She’s slowly forgetting things that she had no problem recalling even last year, and has to be prompted by photographs of the event or experience.

One experiment after another revealed that the memories of children 3 and younger do in fact persist, albeit with limitations. At 6 months of age, infants’ memories last for at least a day; at 9 months, for a month; by age 2, for a year. And in a landmark 1991 study, researchers discovered that four-and-a-half-year-olds could recall detailed memories from a trip to Disney World 18 months prior. Around age 6, however, children begin to forget many of these earliest memories. In a 2005 experiment by Bauer and her colleagues, five-and-a-half-year-olds remembered more than 80 percent of experiences they had at age 3, whereas seven-and-a-half-year-olds remembered less than 40 percent.
It's fascinating, and also true of later experiences, although to a lesser extent. Our brains conceal some of our memories by rewiring our brain. This is all part of growing up.
This restructuring of memory circuits means that, while some of our childhood memories are truly gone, others persist in a scrambled, refracted way. Studies have shown that people can retrieve at least some childhood memories by responding to specific prompts—dredging up the earliest recollection associated with the word “milk,” for example—or by imagining a house, school, or specific location tied to a certain age and allowing the relevant memories to bubble up on their own.
So we shouldn't worry too much about remembering childhood experiences in high-fidelity. After all, it's important to be able to tell new stories to both ourselves and other people, casting prior experiences in a new light.

Source: Nautilus