If you place your thumb in front of you and then look at it with your left eye and then the right eye, what you will notice is that the thumb is “moving” in relation to the objects behind it. This phenomenon is what helps the human brain see depth and thus perceive which object is in front and [Page 2694]which one behind. It is called binocular vision, and the displacement of your thumb is called parallax. The larger the parallax, the further our thumb is from the objects behind it. What we actually perceive is the parallax, and through this we see and appreciate depth. However, it would be wrong to think that all human depth perception comes from the parallax. There are many ...