If you had a hard time seeing the error in these images, you’re not alone. In fact, for all the studying of the human form we humans do every day, we’re terrible at replicating and identifying the correct walking or running posture. Meltzoff’s study also looked into just how good people were at identifying correct and incorrect running posture. When participants were presented with a person walking, and asked to label which legs and arms were the right and the left, only 17 percent of them got it right. The other 83 percent marked the forward arm and leg as both being on the same side. In fact, they would have done just as well to guess randomly. And when participants were asked to pose in mid-run, only 14 percent of them picked the pose that actually reflected running. The other 86 percent froze with the same sided arm and leg moving forward.

When it comes to art, it’s possible that rather than being an error, the awkward, one sided lurch forward is an artistic choice. In Egyptian art, for example, artists followed strict rules about the position of the head and body. But as art evolved, and as accuracy of form become more and more important, it’s hard to imagine why someone like Da Vinci or Donatello would intentionally draw a person running in such an inaccurate pose. And modern “how to draw” guides are certainly not intentionally teaching someone the wrong posture.

But what about when it comes to our physical bodies? What's going on with the people who couldn't pose in the right running position? Jens Foell, a psychology researcher at Florida State University thinks it has to do with proprioception: the way we perceive the existence and placement of our body. “Even if you wake up in a dark room and can't feel anything on your skin, you'll still have some information about the arrangement of your limbs,” Foell says. “As such, it is a bona fide sense and is my second-favorite example to bring up whenever somebody perpetuates the 'only five senses' myth.”

Proprioception happens on multiple levels. There is information that the brain has built in about where arms and legs are (that information is why some people experience phantom limb pain after an amputation; their brains still thinks the limb is there). And there is also information coming in from the extremities. As you wiggle your fingers, your brain gets information coming in about what that feels like. How much of each of those two things—our internal map and our sensory input—make up proprioception is still a bit of a mystery, Foell says. But they’re both involved, and they both happen in the background of your perception when you’re asked to think about running position. “If you stretch out your hand to grab a pen, you're not thinking in terms of muscle tension, coordination of bones, increased blood flow to those muscles, and so on,” he says. The same goes for thinking about running.