Hold a pencil in front of you and look at it with one or the other eye closed: it appears to shift a little.
That's the key to three-dimensional vision (scientifically called stereopsis): each eye has a slightly different angle of view, then our brains "figure out which bit of the left eye's image corresponds to the same point in space as a given bit of the right eye's image," explains Jenny Read, Professor of Vision Science at the University of Newcastle.
It might seem mundane, but it's a remarkable feat. So much so that humans and other vertebrates devote quite some brain space to that, where complicated processing algorithms work their magic to bestow upon us the marvel of depth perception.
Dr. Read's team...