The advantage of using two eyes to see the world around us has long been associated with our capacity to see in 3-D. Now, Rensselaer Polytechnic Institute scientist Mark Changizi has uncovered an eye-opening advantage to binocular vision: our ability to see through things. An assistant professor of cognitive science at Rensselaer, Changizi noted that while animals with forward-facing eyes lose the ability to see what's behind
them, they gain X-ray vision, maximizing their ability to see in leafy environments like forests.
Changizi studied 319 species across 17 mammalian orders and discovered that eye position depends on two variables: the clutter, or lack thereof in an animal's environment, and the animal's body size relative to the objects creating the clutter. He discovered that animals in non-cluttered environments - which he described as "non-leafy" surroundings - tended to have sideways-facing eyes. In cluttered environments - which Changizi defined as leafy surroundings where the cluttering objects are smaller than the separation between an animal's eyes - animals tend to have a wide field of binocular vision, and thus forward-facing eyes.
Changizi said human eyes have evolved to be forward facing, but we now live in a non-cluttered environment where we might actually benefit more from sideways-facing eyes.
