The CGI special effects in the new Planet of the Apes movie are impressive, especially all the work that was done to make “Caesar” – the leader of the rebellious apes - look so real.  I recently read a blog post by science writer Faye Flam for the Philadelphia Inquirer, where she pointed to the reason why Caesar looks so “human” to us: the CGI guys gave Caesar whites in his eyes.

Real chimps don’t have whites in their eyes, which makes it hard for us, and for other chimps, to tell which way they’re looking.  But here’s the coolest part: humans are the only primates that do have whites in their eyes.  According to this story in The New York Times, human eyes probably evolved in a way to help us cooperate with each other – after all, humans have the most complex social networks of all creatures on the earth, and our eyes let us communicate non-verbally with each other.  In fact, a person will instinctively follow your eyes if you shift them, even if you don’t move your head.  A chimp, however, will be much more likely to follow your glance only if you move your whole head.

I’m probably not the first person to do this, but here’s a picture of the original Caesar from the movie, and the same picture with the whites of the eyes darkened like a real chimp using Photoshop.  I think it makes a huge difference.

Caesar from the movie (left), and Caesar with no whites in his eyes (right). Notice that his pupils haven't changed, but it's a lot harder to see which way he's looking. Original image from Twentieth Century Fox/allmovies.com