Here’s a fun game: Take your friends to a parking lot, blindfold them, and tell them to try to walk in a straight line. It’s basically guaranteed that you’ll get to watch them fail miserably and bump into parked cars, says German scientist Jan Souman. He tried the same thing last year, only in the Sahara Desert, on a beach, and elsewhere, and concluded that humans are incapable of walking in a straight line without visual reference points.
Scientists have been trying similar experiments since the 1920s, always with the same results, reports NPR. Humans simply can’t walk, swim, or even drive without visual help. And no one has any idea why. Souman says he’s ruled out a bunch of theories—like the idea that maybe one leg is simply longer than the other, or that one side of the brain dominates the other. He’s working on a multi-causal theory, but for now scientists, like the blindfolded, are going in circles. (Read more mystery stories.)