IE started exhibiting some "off" behaviors around the time he turned 2 1/2 or 3. He lost eye contact. He started spinning in circles. He had not really talked before, but then began speaking like a 30 year old. He would do repetitive things and become very angry if he was prevented from doing them. He was no longer quiet and laid back. He now had tantrums out of the blue that could last for hours. Much of the time it was hard to figure out where it was coming from. If anyone barely touched him he would yell "Ouch" at the top of his lungs. However, he would crash into people and things with surprising force. He would contort his body into strange positions that most people would find very uncomfortable and stay that way. He would beat his head against floors and walls when he was mad. Everything around him was too "bumpy". "itchy", "soft", "hard", etc (any of a slew of adjectives or adverbs).
It was around this time we found out he was not just starring at books - he could read them!
We had him evaluated and it turns out he has something called Sensory Processing Disorder. He also may be on the Autism spectrum somewhere. We are awaiting an appointment with a psychologist to determine the extent of his "problems". While we wait, he is in Occupational Therapy.
When I found out his diagnosis I purchased a book from Amazon called The Out of Sync Child. It is a wonderful book that has really helped me to begin to understand what it might feel like to be him. It talks about how people with the disorder interpret (or fail to interpret) their surroundings. I highly recommend it to any one who knows a child with this disorder. I also recommend it to anyone who works with children at all. It can really help you to understand that child that always seems just a little "off".
This book also has a companion book, The Out of Sync Child Has Fun. I would also recommend it for the same reasons as above. It takes the first book a step further. The first book does an excellent job of describing the disorder via the use of case studies. This book shows you things you can do to help the children. I think "normal" children would also enjoy many of the games!