In this extraordinary adaptation strategy, Thailand’s Moken sea gypsies can see twice as clearly underwater by controlling the size of their pupils. What was generally considered an automatic reflex for the rest of us is now thought to be something that any child under 5 could learn how to do.
From a study called Superior Underwater Vision in a Human Population of Sea Gypsies by Dr. Anna Gislén:
The Moken may learn to do this due to their extensive use of their eyes in water, where accommodation and concurrent pupil constriction is necessary for them to see the items they gather for food. It should then be possible for all humans to learn to see better underwater. But because sea gypsies have lived by and off the sea for thousands of years, evolution may also have favored those who had intrinsically better underwater accommodative powers. The ability to see well underwater could have become a genetic trait. Another possible explanation is that accommodation underwater is a side effect of the diving response; the parasympathetic nerves that control this reflex also control pupil constriction.
Read more at National Geographic.
In the archives: more swimming and these extreme eye closeups.
Why does the full moon look larger when it’s near the horizon than when it’s high up in the sky? For generations, astronomers, psychologists, brain researchers, and many others have hypothesized about this effect, and yet there still doesn’t seem to be a definitive answer.
In this TED Ed, Andrew Vanden Heuvel explains The Moon Illusion, and the theories behind our perception of our moon’s size in the sky.
Previously on this intriguing topic: The Moon Illusion with ASAP Science.
"Wow the moon looks huge tonight!" We’ve all said it, but is the moon ever larger or closer at the horizon? (No, it’s not.) Is it some visual magnification by the atmosphere? (Nope, evidently that’s not why either.)
The answer(?): evidently our brains are playing tricks on us when we see a huge moon. The perception of the moon’s size is influenced by what’s surrounding it. (Or is it?)
Created by Mitchell Moffit and Gregory Brown, this ASAP Science video, The Moon Illusion explains why the moon looks larger near the horizon. There’s also more information here and here.