It's more like tenacity of thought. (Gifted, much?)

He just can't seem to get off the "hamster wheel" of his obsession until he reaches a conclusion that is satisfactory. We've (DH and I) learned that if we don't reach resolution on a subject before bedtime, DS will bring it up again then and will not calm to go to sleep. I'm a bit embarrassed to admit to slipping him a half a Melatonin tablet in dinner when it's REALLY bad.