Why does Mario ask Avril how to tell if somebody is sad?

Mario seems to have the best relationship with Avril of all of her sons, so it makes sense that he would go to her and ask a question he feels is insightful. His mother tells him that somebody who is sad will cry or seem distracted. Earlier on, Mario asked Hal if he thought their mother was sad when their father died and Hal says he does believe she was. It seems that Mario is worried about Hal and thinks he may be showing signs of depression.