Vicki Bruce, Patrick R. Green, Mark A. Georgeson
physiology, psychology and ecology
We call this ability perception, and it in turn requires that an animal be sensitive to at least one form of energy that can provide information about the environment.
The form of energy that can provide information about distinguishing inanimate from animate surroundings or when large distances are involved, is Light.
The spatial and temporal pattern of light converging on a point, provides information about the structure of the environment and events occurring in it.
The speed of light ensures that, in effect, events in the environment are represented in the optic array instantaneously.