"In psychology, tests of memory or attention will often use a second task to selectively block a particular mental process," Andrade said. "If that process is important for the main cognitive task, then performance will be impaired. My research shows that beneficial effects of secondary tasks, such as doodling, on concentration may offset the effects of selective blockade."
http://health.yahoo.com/news/healthday/takenotedoodlingcanhelpmemory.html
http://health.yahoo.com/news/healthday/takenotedoodlingcanhelpmemory.html
so afterall, all the scribbling is actually good!