I was just thinking about my childhood days when I saw it. All the theories has a possibilities. And indeed, "Memories are the most beautiful pictures, out minds can paint and nothing ever can erase them."
Personally, I can remember some of my kiddy scenarios when I was three. With the additional of my photos took by my parents, I love reminiscing the past. <3
Yes, three is about the usual age that most people can remember. After that, memories do seem to become clearer. Thanks for reading!