Most people see a blur when they dive underwater, but a group of youngsters in Southeast Asia, who belong to a seminomadic, seafaring tribe called the Moken, can discern small objects on the sea floor. Swedish scientists, who have studied these children, reckon this heightened ability highlights human adaptability to diverse environments.
"The ... Moken of Southeast Asia are a shy people," explains Anna Gislén of Lund University, Sweden. "But, the kids were happy to participate in our experiments, thinking it was just a game." Gislén and colleagues measured visual acuity of Moken and European children using increasingly finer-striped patterns underwater. "When the kids can no longer see the pattern, we have their resolution limit." The Moken children were twice as adept as European children at the test, she says.
Underwater, the Moken children's pupils constrict, rather than dilate, consequently sharpening the image that hits the retina, Gislén reports (A. ...
