Ok, He/she understands that Catherine. Why not enlighten the person with a guess based on the information given? Else, the person probably would have not asked that qustion on a forum such as this. In the end they all need to be seen by a professional to get any solid relliable answers, right?
My best guess would be that you have just developed a strong association between your drawing and the activity of listening. You may have put importance on listening to your teachers or parents ,but you also enjoyed doodling. Maybe these people did not mind that you draw during instruction as long as you could show you were paying attention. You may have become skilled at this to the point of needing one action(drawing) to ellicite another(paying attention). If your interested in how this might work, look into "Pavlov's Dogs" and "classical conditioning" I hope that left you with at least something to think about.(if the post isnt too old).