A writing instructor, my sister Angela recently told her high school students how doodling is important to their education. Write in your books! Draw along the margin! Mark them up! Underline, highlight, scribble!
I gave her a fist bump when she told me that. I'm a huge proponent of doodling. (Yep, I even signed the Doodle Manifesto.) The importance of doodling cannot be underestimated in the process of learning.
If you only have about five minutes, here's a quick fun TED talk about the history and importance of doodling from Sunni Brown, a leader in the Doodle Revolution: (If you'd rather look at images instead, you can see her slide deck from another talk, which hits the same important points.)
If you have some time, I highly recommend checking out the fantastic Doodle Revolution site. You'll get a glimpse of how people use doodles to process huge amounts of information, plan ideas, and make sense of the world around them. (You might spot a familiar name in the Showcase, too.)