He's a tinkerer.  He keeps a junk box or two or three in the closet of his bedroom.  Recently he pulled out his dad's small screw driver set and his own screw driver set and tore apart this broken digital camera.  He looked, analyzed and mentally cataloged each piece trying to determine what it's function was.  In order to truly have the knack though I think he would have needed to put it all back together and made it work.  All kidding aside, he really does have a bent towards how things work and his mind just intuitively picks up on how it all goes together. One day John was in the car driving back from who knows where with Job and he asked how kinetic energy worked with heat transfer of molecules.  John said that he talked for almost two hours about it and Job just drank it all in.