The Buddha Rat

"Is it possible to see absolutely nothing? Or do you always see something, even if it is nothing more than a blur or the insides of your own eyelids?

"This question has been well investigated. In the 1930s, a psychologist named Wolfgang Metzer designed an experiment to show that if you have nothing to look at, your eyes will stop functioning. Metzer put volunteers in rooms that were lit very carefully so there was no shadow and no gradients from light to dark. The walls were polished, so it was impossible to tell how far away they were. After a few minutes in an environment like that, the volunteers reported 'gray clouds' and darkness descending over their visual field. Some experienced an intense fear and felt as though they were going blind. Others were sure that dim shapes were drifting by, and they tried to reach out and grab them. Later it was found that if the room is illuminated with a bright color, within a few minutes it will seem to turn dull gray. Even a bright red or green will seem to turn dull gray. "