The one thing from this article which will stay with me forever is how different cultures view this optical illusion.
Now, most of us, myself included, will say that it looks like the arrow on the left is longer. In actuality the lines are the same length. It's commonly thought that if you show the above image to anyone they would agree that the line on the left seems larger, however this article claims that only people who live in a civilized community with walls and houses will view the lines as different lengths. When this optical illusion was shown to indigenous people, they said the lines were the straight length! This shows that the way our brains function, even on such a basic level such as sight, is very different dependent on our environment. We really are just sophisticated animals.