I AM a professional doodler. Self-taught, of course. A true blue doodler is always self-taught.
Self-taught doodlers almost always start their training in the classroom and so, many teachers are quite unconciously the inspiration of the bulk of doodlers. The next time you start thinking morosely of Puan So-and-So as the most boring History teacher that ever lived, just reposition her as the Muse of Doodles.
The Macmillan English Dictionary for Advanced Learners defines doodle as (noun) "a pattern or picture you draw when you are bored or thinking about other things" and (verb) "to draw patterns and pictures because you are bored or thinking of other things".
Truly inspired doodling requires you to be in quite specific states of mind: "Not-quite-comatosed" and "away-with-the-fairies" are conditions that produce some of the very best doodles. Every doodler specialises in different patterns and shapes. I favour squares, wavy lines and concentric circles. Many years of doodling have evolved my speciality patterns and shapes into recognisable forms so that I now also seem to be quite competent drawer of elephants, pigs, flowers, cars and houses.