What are the motifs in What Hearts by Bruce Brooks?

Imagination is a recurring idea through the narrative. Asa has a great imagination. In the first story, Asa regales Dave with stories of his accomplishments in school and sports in such a fashion that it is clear to Dave that it is all lies. Later Asa believes that he goes on a roller coaster and stands up, flying free like a bird. Clearly these things are not true, but they make Asa feel better about himself and his situation.