a matter of perspective
Here are some optical illusions, which Chelsey was kind enough to e-mail me.
Which is the top? Which is the bottom?
Look at the chart and say the color, not the word. (Your right brain tries to say the color, but your left brain insists on reading the word.)
And is it a duck? Or is it a rabbit?
Believe it or not, I've actually known people over in the philosophy department who seriously worry about this duck-rabbit... It has something to do with a philosopher named Wittgenstein...