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Article by Ron Keas

Cover one of your eyes and look across the street. Now open both eyes and look again. What happened?

Well, when one eye was covered, the world looked kind of flat, right? With both eyes, objects kind of jump out at you and are separated in space or depth.

That's what is called "binocular vision." (Binocular means "bi" = 2 and "ocular" the eyes, so "two-eyes", Vera). It is also called "stereoscopic" vision, and sometimes it is called "3D" (3D means Three-Dimensions, Height, Width and Depth - Vera). These days people talk about 3D pictures, but what they really mean is pictures that are drawn to look round or "rendered." Stereoscopic pictures REALLY look round the same way that real life does.

Not all animals can see in 3D. In order to see in 3D, both eyes need to be able to look forward. Some animals (especially birds like pigeons) have their eyes on the sides of their heads. Everything they see looks flat.

Could dinosaurs see in 3-D?   Paleontologists believe that most dinosaurs were not capable of seeing in 3-D. That is because their eyes are on the sides of their heads just like a pigeon.  The exceptions were probably the predatory dinosaurs: T. Rex, Deinonychus and the dromeosaurs. Their eyes were closer to the center of their heads.  They could look straight ahead!

A good way to determine if dinosaurs had 3-D vision would be to examine the skulls and see if the orbits (Another name for eye sockets, students. Nothing to do with John Glenn - Vera) were oriented such that both eyes could point forward at the same time. The stereoscopic vision of T. Rex would have been exaggerated by the distance between his eyes. In stereo photogrphy this is called "hyper stereo". It would have allowed him to perceive depth even at great distances. Human vision loses the illusion of depth after about 150 yards.

This photograph taken at the opening of Designing Dinosaurs (a totally awesome exhibit put on by Robert Walters and Tess Kissinger) shows a T. rex skull. Can you see both of the eyes staring right at you? Burrowing right into your brain? (heh heh). On the left the skeleton is covered with "flesh."  On the right the bones and muscles are visible!

3-D would have been a valuable tool for T. Rex when he was searching for prey. Dinosaurs without stereo vision relied mostly on movement to see their prey. T. Rex would have had the advantage of being able to see in depth. His prey would have stood out from the background, even if it were standing still.