Andy Clark has done a piece that is really worth reading in the Stone, a New York Times forum for contemporary philosophers. (And, check out the video below):
Might the miserly use of neural resources be one of the essential keys to understanding how brains make sense of the world? Some recent work in computational and cognitive neuroscience suggests that it is indeed the frugal use of our native neural capacity (the inventive use of restricted “neural bandwidth,” if you will) that explains how brains like ours so elegantly make sense of noisy and ambiguous sensory input. That same story suggests, intriguingly, that perception, understanding and imagination, which we might intuitively consider to be three distinct chunks of our mental machinery, are inextricably tied together as simultaneous results of a single underlying strategy known as “predictive coding.” This strategy saves on bandwidth using (who would have guessed it?) one of the many technical wheezes that enable us to economically store and transmit pictures, sounds and videos using formats such as JPEG and MP3.
...perception may best be seen as what has sometimes been described as a process of “controlled hallucination” ...in which we (or rather, various parts of our brains) try to predict what is out there, using the incoming signal more as a means of tuning and nuancing the predictions rather than as a rich (and bandwidth-costly) encoding of the state of the world.
The basic effect hereabouts is neatly illustrated by a simple but striking demonstration (used by the neuroscientist Richard Gregory back in the 1970’s to make this very point) known as “the hollow face illusion.” This is a well-known illusion in which an ordinary face mask viewed from the back can appear strikingly convex. That is, it looks (from the back) to be shaped like a real face, with the nose sticking outward rather than having a concave nose cavity. Just about any hollow face mask will produce some version of this powerful illusion, and there are many examples on the Web, like this one: