Old ideas that REM sleep deprivation led to insanity have been convincingly disproved…
Now I hope this second part was not funded by government money:
…although studies show that depriving someone of sleep, for example by prodding him or her awake repeatedly, can definitely cause irritability…
What else did I learn?
Body size appears to be a major determinant in the amount of sleep that a species needs. In general, the larger the animal, the less sleep it requires. Data suggest that one of the functions of sleep is to repair damage to brain cells. The higher metabolic rates of small animals lead to increased cellular injury and may, consequently, require more time for repair.
Opossums sleep eighteen hours a day, elephants three.
From the November issue of Scientific American, the article, “Why We Sleep,” is not yet on-line.