Someone else in same boat - my 2.5 year old has started doing this again - he has been through two phases of it before but stopped just as fast as he started. This time, it worries me enough to try and find out more about it. I have several theories - my initial one last year was that he had somehow not outgrown the infantile reflex, but as he has totally normal finger function and dexterity, this can't be the answer. Second was a theory that maybe his nerve endings hurt or something, but again, no sign of pain or distress when he does use his fingers to do things. Then I considered that maybe he was just experimenting, seeing what it was like. This was sort of borne out by the fact that at same time he sometimes switches to eating with his left hand even though he is right handed - I thought it was probably experimental, trying to see if he could make himself ambidextrous. He's a very bright (gifted) little boy, and excellent with numbers etc. I'd be curious to know if your two kids are bright too as that might be the solution - that they get bored and just try something new for a while until they lose interest. As I have been at such a loss to explain it, I confess my final theory was that if it wasn't something neurological, then maybe in some past life he was crippled with arthritis and he's sort of forgotten that he has fingers again. It is frustrating to watch. If anyone has any success in finding out anything about this behaviour, please let me know!