The world does not talk to an animal through its nerves any more than the world sends photocopies of objects through the nerves, or simulacra, or eidola, or images. The analogy with language is even worse, if anything, than the analogy with images, for animals do not have language and yet they certainly perceive the world around them. The flowing sea of energy in which an animal is immersed has certain invariants of structure that specify the environment. When the system has picked up the facts that are relevant, then the animal has perceived. And this activity of visual attention is not located in the brain but depends on a continuous input-output process that tends toward an optimal state.
Perception is based on invariants that specify the environment.
The information in light consists of these invariants, whether the light comes from all around or only from a display. The invariants do not resemble what they specify and they do not say what they specify. These invariants, I said, were formless , meaning that they are not triangles or squares or circles or anything of that sort. We pick them up whenever we walk around a solid object, or whenever the object turns. The perspective change but the invariants do not.