(this is a section from something I sent my son today--I think I spelled one of the words wrong):
Do you know, I think of you all the time, and I don't ever forget things we've done. It's a little bit easier for adults to remember some things than kids when kids are really little, like when they're babies or just 1 or 2 years old. Babies are learning so many new things every minute, that their brains have to keep some of the memories but not all of them. A babies brain, like your brain when you were a baby, and my brain, is sort of like thinking of a road you make in the dirt. You know how you can make roads in the dirt for your trucks and cars and things? Well, as you know, to make a new road, you are pushing some of the dirt to different places. Sometimes in front, or to the sides, and some of it stays in the road and gets patted down. So that is how a baby's brain is, when it is learning so many new and important things...inside of your brain are little parts that work to store your memories. You know how you put your clothes into dresser drawers or put your toys away to take them out later? That is how your brain works, to put memories into storage places inside of your brain. And inside of the storage places, are lots of teeny tiny parts that all work together and they are "cells" and "neurons" and "dendrytes" and then there are lots of good chemicals and blood and oxygen (air) that all work to keep these parts healthy. So these teeny parts are like little particles of dirt, and when your brain is making new "roads" to the storage places to keep your memories and ideas and things you've learned, when you're a baby, there are SO many new roads, and there is so much dirt (if we pretend dirt is standing in for a particle that keeps your memories), that some of this dirt gets pushed to the side, or out of the way and then some of your memories get patted down and you use those ones all the time.
So this is why we don't always remember every single thing that we think or that happens to us, or even things we learned, or where we put our toys, and people's names and things. And for people when they are babies, they hardly remember being a baby at all, because most of the memories get pushed to the side or out of the way. Then you get older, and your brain isn't making as many new roads, as fast, even though it makes lots of roads every single day, and so it's just a little bit easier for us to remember things we want to remember later.
This is why even if you don't remember everything about you and me when you were a baby, because your brain was working so hard all the time, I remember things about you and and me because I am a grown up and my brain is working a little slower so I have more time to remember things. So Oliver, I can tell you about many things you did when you were a baby, and things you said and what you liked.
Now that I don't get to see you, I have to guess and hear from other people about you. But you are old enough now that it is a teeny bit easier to remember things I tell you or send to you.
Maybe next time I will tell you a little bit more about what these parts are that are inside of your brain that help you to think and me to think!