"I thought a little [while in the isolation tank], and then I stopped thinking altogether. … incredible how idleness of body leads to idleness of mind. After two days, I’d turned into an idiot. That’s the reason why, during a flight, astronauts are always kept busy."

Oriana Fallaci as quoted in Rocket Men: The Epic Story of the First Men on the Moon, by Craig Nelson, which cites 'Fallici, Oriana If the Sun Dies. New York. Atheneum, 1967', seen on http://www.johndcook.com/blog/2010/12/11/after-two-days-id-turned-into-an-idiot/