Anyone who closely observes a sleeping human baby or adult, even a household
pet, can see eyes occasionally dart beneath closed lids.
Anyone can see that, but one would have to watch many sleepers closely
for hours to spot a pattern. No one reported doing that until 1953, when Eugene
Aserinsky, PhD, and Nathaniel Kleitman, PhD, of the University of Chicago,
published their landmark article, "Regularly occurring periods of eye motility,
and concomitant phenomena during sleep" (Science.
Lamberg L. Scientists Never Dreamed Finding Would Shape a Half-Century of Sleep Research. JAMA. 2003;290(20):2652-2654. doi:10.1001/jama.290.20.2652