Answer:
You consider whether the behavior is atypical, dysfunctional, distressful, and/or deviant in order to assess whether it truly is a psychological disorder, such as obsessive-compulsive disorder.
Step-by-step explanation:
Psychological disorders refer to a combination of beliefs, thought patterns and behaviors that are clinically significant, and recurrently affect a person's social, emotional and occupational functioning. In this instance, if your brother's obsession with neatness is a problem and you are considering whether the behavior is atypical, dysfunctional, distressful, and/or deviant, you are likely checking if he has obsessive-compulsive disorder.
Obsessive-compulsive disorder (OCD) is a type of anxiety disorder when a person has chronically intrusive and uncontrollable thoughts (obsessions), that lead to compulsive behaviors such as obsession with neatness, cleaning one's room, etc.
Thus, if you are trying to decide if your brother's obsession with neatness is a problem, you are assessing whether it truly is a psychological disorder, such as obsessive-compulsive disorder.