What emotion is associated with 7-2521's laughter?

I think it is the emotion of freedom. He laughs as he realizes that he can either stay lying down or rise and do whatever he wishes. He thinks he is not making any sense, but his body rises and spins around until his hands swing him into a tree, as he celebrates his own strength. When the branch snaps, he falls back onto the moss, and he begins to roll in the moss and laugh.