1) Your child has uncontrollable outbursts that are more involved than a regular tantrum. He is not able to stop the behavior even if he gets what he wants. The response is so intense it is more like a fight/flight/freeze/shut down response (e.g. the feeling you might have if you found a spider or snake crawling on you).
2) Your child’s activity level is much different than his peers. This can be either much more active (can’t sit still, too rough with peers,) or very sluggish and it looks like “gravity is sucking him to the ground” (everyday tasks take forever, “spacey”).
3) Your child’s response to typical environmental stimuli is unusual such as sensory seeking (excessive spinning, crashing, staring at spinning objects, flicking lights on and off) or sensory avoiding (e.g. excessive reaction to certain noises, avoids lights, avoids hugs, extreme distress with hair and nail cutting).