Tiny glasses reveal praying mantises have a different kind of 3D vision
According to the Jurassic Park movies, the T-Rex's vision was based on movement, so it couldn't see you if you stood perfectly still. That advice won't help you at all in the unlikely event that you ever find yourself hunted by a real Rex, but it turns out it might actually save your life in the equally-unlikely event that your hunter is a giant praying mantis. By putting tiny 3D glasses on the bugs, researchers at Newcastle University have found that praying mantises possess a unique, previously unknown type of vision.
Humans, like many other animals, have stereoscopic vision – our two eyes see the world from slightly different perspectives, and our brains instinctively know how to stitch those images together to get a sense of depth. Praying mantises are the only insects known to see in 3D, so the Newcastle researchers wanted to test how close their vision is to our own.
They did so by making tiny 3D glasses for the bugs. Like those you might wear to see a 3D movie, these glasses are designed so that each eye sees slightly different things on a 2D screen, allowing the image to pop out in three dimensions.
The researchers put the mantises into an "insect 3D cinema," treating them to a movie of some prey buzzing around. The illusion was convincing enough that the bugs kept lunging for the virtual food. So far, praying mantis vision sounds like it works on the same principle as that of human's.
But the bugs fared differently under other circumstances. As you might remember from the old red-and-blue 3D anaglyph images in magazines, humans can stereoscopically see still images just fine. But it turns out that praying mantises can't – if something's not moving, the bugs aren't interested.
Mantis vision, it seems, is based on movement, which suits the carnivorous bugs just fine. Their prey will usually be moving, so there's no need for them to focus on the details of the image, just where the image is changing at any given time.
"This is a completely new form of 3D vision as it is based on change over time instead of static images," says Vivek Nityananda, co-author of the study. "In mantises it is probably designed to answer the question 'is there prey at the right distance for me to catch?'"
Particularly interesting is just how far the mantises can push this focus. Apparently, they care so little about the details of the image that when each eye is shown completely different images, they can still pick out which parts are changing over time. The bugs even managed to outperform humans at this test.
This strange discovery could have robotic applications. Autonomous vehicles, drones and robots often rely on depth-sensing to navigate, and much of the time these algorithms are based on human perception, which can be pretty complicated. Mimicking the mantis' form of 3D vision could be a much simpler way to achieve the same effect.
"Many robots use stereo vision to help them navigate, but this is usually based on complex human stereo," says Ghaith Tarawneh, co-author of the study. "Since insect brains are so tiny, their form of stereo vision can't require much computer processing. This means it could find useful applications in low-power autonomous robots."
The research was published in the journal Current Biology. The team describes the work in the video below.
Source: Newcastle University