With some help, the Boy can now sit. He casts his eyes here and there, his attention drawn to this sound or that motion, and his arms or legs are constantly in motion. It seems like it would be a good match for the hyper Girl.
They sit together, banging anything and everything, both delighted with the racket.
The difference comes later, when the Boy has a moment alone and sits silently, almost contemplatively, for a seemingly impossible length of time. The Girl wouldn’t last three seconds.