A lot of typing for a bad punchline

Behavioural scientists have recently discovered that all human beings possess one overriding obsession that guides all subsequent actions. The team have also found that these motivating factors can be divided into three distinct groups; the gastronomic (which the scientists graphically represented as a piece of pie); the narcotic (represented by a cigarette); and the erotic (represented by a gender-neutral human anus). Most astonishingly of all, it was revealed that this discovery had first been made in Ancient Greece (and since lost to the mists of time) where it was known as the 'Pie, Fag, or Arse Theorum'.