Authors Drew Pinsky and S. Mark Young, a professor of entertainment business at the University of Southern California have studied celebrities and the general population by administering a widely used screening tool called the Narcissistic Personality Inventory (NPI), which is included in The Mirror Effect.

The book advises answering the 40 questions below in a single sitting, without asking for help or clarification. It notes, “There’s no such thing as a good or bad result on this test. Scoring high on the narcissism inventory, or high on any of the component categories, doesn’t mean you have a disorder, or that you’re a good or bad person.”