(Image source: Science)

BY STEVEN SPARKMAN

ANCHOR JIM FLINK

Who would have thought blurry vision could be a superpower? It turns out the jumping spider, one of nature’s best jumpers, has a trick for measuring distance that’s unique in the animal world.

For decades, scientists have wondered how the spider manages its precise jumps. After all, it has to judge distance perfectly if it wants to catch prey. But the more they studied the spider’s eyes, the more of a mystery it became. (Video source: National Geographic)

That’s because there are lots of ways animals judge distance, and spiders use none of them. Humans compare the different images from our two eyes. Chameleons continually refocus their eyes to gauge distance. Some insects bob their heads side to side to see how the image changes.

But the jumping spider uses the same blurry vision that sends humans to the optometrist. Discover Magazine explains.

“[To] gauge how far away their targets are, they use special retinas that produce sharp images and out-of-focus ones at the same time. … The amount of blur depends on an object’s distance from the spider’s eye. The closer it is, the more out of focus it is...”

To test their idea, scientists played a little red-light-green-light with the spiders. By studying the spider’s eye, they found the blurry image responded mostly to the green wavelengths of light. So they put the spiders in a cage with some fruit flies and watched them work.

When the spiders had plenty of green light to work with, they gauged their jumps perfectly. But when the researchers turned on red lights, leaving out the green, the spiders’ jumps kept coming up short. (Video source: Science)

So far, jumping spiders are the only animal to use “depth defocus” as their main rangefinder. But it’s not a completely foreign idea. Popular Photography explains -- you’ve seen this before.

“Humans already do this to a certain extent -- when you see an out of focus area in a photograph, you automatically understand that it's a different distance from the area in focus. The jumping spider's version is just this turned up to 11.”

Oddly enough, engineers have already thought of depth defocus as a way for robots to gauge distance. Now thanks to the jumping spider, they might be able to take a few hints from nature’s playbook.