How putting 3D glasses on a praying mantis could lead to better robot vision

praying mantis
A praying mantis wearing 3D glasses. Credit: Newcastle University

(Image credit: Newcastle University)

It may look like this little insect is about to watch the latest blockbuster at the cinema, but its stylish headwear is actually part of a groundbreaking experiment in praying mantis vision.

In the early 1980’s, Professor Samuel Rossel was the first to prove that the praying mantis had 3D, or binocular, vision, just as humans do. When we look at an object, our brain uses the slightly different views captured by the right and left eye to calculate how far away it is, helping us to perceive depth. At the time, this was assumed to be something only mammals with forward-facing eyes could do, but Rossel proved that even though the praying mantises had evolved independently from humans, they could do it too.

He found this out by placing prisms in front of a mantis’ eyes, a very basic experiment that has now being given a much-needed upgrade. A team of researchers at Newcastle University has created an insect cinema, complete with special 3D glasses for the insect audience.

“We knew that the praying mantis was the only insect that had stereo vision, but we wanted to see what the mechanisms of that stereo vision were,” said Dr Vivek Nityananda, a sensory biologist who worked on the project. “We actually tried out several different ways of presenting 3D images to praying mantises, but we weren’t particularly successful at getting them to work. Then we hit upon this idea of actually trying to fit 3D glasses onto the insects.”

The glasses in question are similar to the ‘old school’ ones we used to use in the cinema, however, because praying mantises can’t see red light very well, blue and green filters were used instead of blue and red. They fixed these glasses onto the mantis using a mixture of beeswax and resin. Vivek explained; “We put a small drop on the forehead of the mantis, just between the eyes, then inserted the glasses and allowed it to solidify to hold them in place. It took a while. It was a learning curve but I became quite skilled at it.”

Once the glasses were in place, the team then showed the mantis videos of simulated bugs moving around, with the screen positioned just beyond their reach. When they were shown 2D footage, the mantis did not react, but when the 3D footage was played, they struck out at it, believing the bug was within their grasp. This proved that the mantis could perceive the distance between them and their prey, and so must have stereo vision just like us. You can watch a clip of the experiment below…

The reason why the mantis has evolved this 3D vision is still not known, but Vivek thinks it’s important for how they hunt their prey. “The praying mantis has a very particular hunting strategy, in that it sits really still and waits for prey to pass by,” explains Vivek. “Then, only when the prey is at a particular distance from it, does it reach out with what’s called a predatory strike. If it strikes and misses, then it is giving away its position, so it is important for it to know the distance of its prey without moving.”

With their experiment a success, the team now hopes to learn more about how the mantis’ brain puts together the views from its left and right eye and sees the world. To do this, they are hoping to create a computer algorithm.

Dr Jenny Read, Professor of Vision Science and leader of the study, explains; “In my ideal world I’d have a little computer programme that you could feed video streams representing the left eye image and right eye image of the mantis, then the output would be what the mantis actually sees. The programme would be a little model of part of the mantis brain. We currently have Dr Ronny Rosner in the lab recording from individual nerve cells within the mantis brain. It’s very fine, delicate work because these are tiny fibers that are less than a micron across and he’s got a glass electrode in there. But by doing this he can actually see these computations happening within the mantis brain.”

If they manage to create this algorithm, it could be implemented in robots to give them better depth perception. “Insects are absolutely incredible,” explains Jenny. “Their brain is less than the size of a pin head, yet they perform incredibly well. They totally wipe the floor with current robotics. If we could get a fraction of their performance into our current robots we would still be doing extremely well.”

Discover more about the praying mantis vision study, and why animals have evolved the vision they have, in Explorer: Eyes Wide Open on National Geographic Channel. The episode, which airs on Monday 29th February at 8pm, will also explore the amazing things our eyes can do, and why they are often so pitiful in comparison to other animals.

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