How does Alain Robbe-Grillet use imagery in The Replacement?

The narrative weaves together three separate scenes. The first involves a schoolboy who is standing by a tree, peering intently at something in the branches. He repeatedly tries to reach a branch that seems within his grasp. After failing to grasp it, he lowers his arm, appears to give up, and continues to stare at something in the leaves. He then returns to the foot of the tree and resumes the same position he took at the beginning of the story. The narrator describes the position of the boy's body as he peers up at the branches. He holds a book satchel in one hand while the other hand is obscured, probably because he is using it to balance himself against the tree. His face is pressed to the tree and turned in such a way that it would not be visible to an observer. The boy scrutin