I am in the middle of a series of signage articles on Slate. The first article in the series, The Secret Language of Signs, is worth reading and got me thinking in a number of different directions.
One road it sent me down was the idea that we are always looking for signs that reinforce our feelings of exceptionalism, be they political, professional or personal. Being special seems to be a psychological imperative.
In the learning and development world, we go so far as to grant post-graduate degrees in instructional design, incorporating ideas from graphics, psychology, organizational behavior, adult learning theory and various bits of technology research and development, among other specialty areas.