In this activity, students learn that two eyes are better than one, especially when it comes to depth perception.
Humans have two eyes located side-by-side in the front of their heads, unlike some animals, such as horses and deer. Thanks to their close side-by-side positioning in humans, each eye takes a view of the same area from a slightly different angle. The two eye views have plenty in common, but each eye picks up visual information that the other does not.
Each eye captures its own view and the two separate images are sent on to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture. The mind combines the two images by matching up the similarities and adding in the small differences. The combined image is more than the sum of its parts – it is a three-dimensional stereo picture.
Stereoscopic vision, is used for the visual ability of creatures with forward facing eyes. The word "stereo" comes from the Greek word "stereos" which means firm or solid.
With stereoscopic vision you see an object as solid in three spatial dimensions, width, height and depth. The ability to see the depth dimension means that we can observe where objects are in relation to our own bodies with much greater precision.
Depth perception is the ability to judge objects that are nearer or farther than others. Depth perception is very important, especially when objects are moving toward or away from us in the depth dimension. When you have to cross the road and you see a car coming, you have to decide whether it is far enough away so you have time to cross, or whether it is too close and you should wait.