Dr. Tanner's behavior can seem extremely erratic, bordering on neurotic and psychotic at times, depending on the situations in which he's encountered. At times, he can appear non-sensical and rambling, spouting figures and information about seemingly random subjects. At other times, he will be quite lucid, ably demonstrating his keen intellect, sharp wit, and even charm. Very few understand the mechanisms that determine just which Tanner they will encounter at any given time, and this has caused Tanner to have very strained relationships with other people over the years, personally and professionally.