Is that color gray or green? Could depend on how recently you slept
Here's an interesting nugget from SLEEP 2010, the annual sleep-research meeting taking place this week in San Antonio: Sleep affects color perception.
Scientists at the University of Houston ran visual tests on five people just before they went to sleep or right after they woke up (after a snooze of nearly eight hours, on average). When the subjects had been awake for a while, they classed "gray" as having a greenish tint. When they woke up, gray was gray again.
What the -- ?
"Our tentative conclusion is that wakefulness causes color classification to drift away from neutrality and sleep restores it back," the authors say in their research presentation abstract. This doesn't, of course, explain why it happens. (Perhaps it has something to do with the functioning of the rods and cones of the retina?)
SLEEP 2010 meeting is put on by the Associated Professional Sleep Societies. Here's a link to all the abstracts of the meeting presentations.