Another couple signs for the day:
You seem to catch onto the subtleties of humor and laugh at just about anything that you find amusing, whereas others would scratch their heads wondering, "What's so funny?"
When making discussion posts for class, your posts are usually the longest and so deeply reflective that your classmates don't respond back. They seem to think that you already know what you're doing.
When sitting in a textbook review group activity, and your group is chatting, you end up leafing through one of the group member's art history textbooks just to check out the artwork, and tune everyone else out, and you're wondering what the pieces of artwork mean, what do the images represent, what's the artists intentions, grasp onto symbolic concepts, and then your brain is off and running.
When you find the nearest computer terminal in the computer lab that is closest to the four walls/windows and out of view from everyone else.
When you have both a nerd side and artsy side.