Interesting experiment. Seem to remember reading somewhere that the childhood memories often return in later life too. Might be an interesting follow up!
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Most adults don't have any memories from before they were age 3 or 4. That's certainly true for me. My earliest memories that I can accurately place in time come from when I was 3, just before Return of the Jedi came out. I'm pretty sure that my earliest memory is watching the Death Star explode on TV, followed closely by memories of a vicious preschool playground debate over whether or not Darth Vader was actually Luke's father. (I got that one wrong. I totally thought he was lying.)
But a Canadian study suggests that this limit to how far back grown ups can remember doesn't apply to kids. A group of 100 children, between the ages of 4 and 13, were asked to describe their earliest memories. After verifying events with parents, researchers found that the youngest kids could recall things that happened when they were as young as 18 months old.
But, when the same kids were brought back two years later, those memories had faded. Their earliest memories were now different, later events. And the kids couldn't recall their previous early memories even with prompting. The researchers are speculating that our brains may encode memories in different ways during the first few years of life than they do later on.
Via Mark Changizi