It used to be thought that only primates have stereo vision but this has been refuted, asstudies have now led to the conclusion that “s tereopsis has evolved independently at least four times: in mammals, birds, amphibians and insects.” But not all mammals, or other types animals have stereo vision. Humans can make qualitative depth judgements based on the position of these monocularly occluded regions.”

Natural scenes typically contain many such occluded regions, which by definition have no corresponding match in the other eye. “If you hold a finger in front of your face and close first one eye then the other, you notice that the finger occludes different parts of the background in the two eyes. This is called lack of correspondence and takes a lot of brainpower. Thus, our eyes, spaced about six inches apart, provide slightly different information to our brains which then uses that disparity to calculate and perceive depth. The exact definition of stereopsis is “the ability to gain information about the 3D structure of visual scenes by comparing information collected separately and simultaneously from different lines of sight to the same region of space.” Other animals, humans being a prime example, can triangulate using the third method which is called stereopsis. Some animals appear to only be able to use triangulation when an object moves or when their own eyes move. As for triangulation, it can occur by (a) stationary eye(s) observing moving objects, (b) by moving eyes observing stationary objects or (c) by eyes spaced apart transmitting slightly different scenes to the brain. Triangulation: this provides depth cues by comparing views of an object from different locations.Īnimals use a combination of the three methods to perceive depth and distance.Perspective: The image of an object changes in size as the object approaches or recedes relative to an observer.This conveys depth perception via shading – light creates shadows provides cues about depth. There are three main ways this is accomplished: Sighted animals, including humans, see in 2D and use various depth cues to convert what they see into 3D perception.

Predator vs prey ears