Apples and Oranges

Why are my boys so different? My 4 year old never plays by himself. He always needs me to do somthing with him - play a game, play Wii, do a puzzle. I just don't understand the clinginess. Now the 1 year old can occupy himself for hours. He plays on the train table, he rolls trains on the floor, looks at books, he explores new toys and figures them out. He checks in every once in a while to make sure I'm still where I was before and to tell me what he's doing. "Thomas!" he'll walk over and exclaim to let me know he's playing with a Thomas train. It's so frustrating that the 4 year old can't seem to occupy himself. If I don't play with him, he'll veg in front of the TV. He needs to learn some lessons from the little guy.