My daughter is 3 now and has been friends with a little boy, same age, since birth. The two go to nursery school together full time and we share a carpool with his family. When things are good they are so cute together - totally inseparable, so polite and very loving. When things are not so good - they either turn into a tornado of screaming, throwing things, running maniacally from one activity to the next - out-of-control running down streets together away from panicking parents etc. OR they start provoking each other and it ends it physical violence and tears.
I have tried to observe the behavioral pattern in each of them that leads to this, so that I can better understand and redirect them from chaos. One observation is that the boy seems to have a great deal of trouble with coordination - falls constantly and if you hold his hand, seems very "loose", like he will fall right over if you don't hold him up. He falls off the curb nearly every time when we are crossing the street.
Yesterday, I had the opportunity to watch the two of them by myself for the first time, for several hours and observed some things that further fleshed out this observation. He walks in a room and goes directly to an object, any object, what ever it is - and grabs it and often throws it HARD on the ground. This generally upsets my daughter and she starts to block him and say "mine" about the objects he's about to grab, then he snatches to object and she looses control - sometimes hitting or scratching him, pushing, yelling etc. (this I have been working on - one on one with her...)
I really see it in the way that he enters a space and starts to explore it - as if he perceives no boundaries of what is appropriate to touch and in what
way to touch (fragile, hard, soft, etc). He often falls on the ground, gets tripped up in his own legs, like he's made of rubber - he flings open doors without care that they will slam, he even broke right through our screen door - without opening it. Just walked right through the middle of the screen bending it backwards, just like nothing happened kept going - running in and out of the screen continually as I was scrambling to close the glass door. oh yeah, if there is glass - he will bang on it incessantly.
And for quite some time I have noticed his strange relationship with animals. He seems to like them, but all he can do when he walks up to them is hit or bang or shriek at them. I've noticed his parents have a routine time-out for him when he hits their dog. Some of these behaviors seem deliberate but I can't help thinking that it's part of a pattern, that he doesn't know how to behave otherwise. Maybe now he has learned what kind of response he will get from adults, so he hurts things with compulsion, but I just find it hard to believe that a three year old with very little stress would behave this way out of malice.
I edited a video a year ago about the parents of children with special needs and I heard about sensory integration disorder. I found this website and did the check list, because I want to understand my little girl's "best friend", and hopefully ease the conflicts in their budding relationship. I don't know some of the more personal things on the list about eating, hearing, touch, but it was helpful with the section on Vestibular Disorder and Proprioceptive Dysfunction. I know from experience that growing up very close to someone with a disorder, that is not addressed, effects the friend just as much as the person who has it.