Researchers Use A Computer Game To Test The Independent Eyes Of Chameleons


Chameleons are known for their ability to change color to blend in with their background to fool predators. But camouflaging isn't the only trick they have in their arsenal. Aside from their color-changing magic act, the lizards are also known for their huge protruding eyeballs that allow them to see 360-degrees around them.

While the top and bottom eyelids are close together, the lizard sees through a small hole left in between. But the most interesting aspect of their vision is that scientists previously believed their eyes moved independently from one another. With their wide field of vision, the chameleon is able to swivel each eye around in different directions, reducing the need to move it's body and give up its hiding spot.

However, researchers wanted to test this theory that because chameleons' eyes move independently from the other, they could then possibly see independently from one another, so they used a computer game as a way to test the chameleon's vision.

Professors Ehud Rivlin of the Technion-Israel Institute of Technology and Gadi Katzir of the University of Haifa developed a computer game that was meant to both frustrate the lizards yet test if their eyes really do work independently from each other.

The researchers showed their test subjects a double image of a small insect moving in opposite directions across the computer screen. The chameleon first focused on the virtual insect with one eye, as the other one looked around. However, when it wanted to pursue the snack, both eyes focused on the image the split-second before it shot out its tongue.

"There were a few seconds of indecision when the chameleons were deciding which target to shoot at," said Rivlin. "If the eyes were truly independent, one would not expect one eye to stay put and then have the other eye converge. But we found that once the chameleon made its decision about which target to fire on, it swiveled the second eye around to focus on the same simulated fly the first eye was locked on."

The study suggests that the second eye knows the direction of the right eye, which means the eyes aren't as independent from one another as previously thought. Instead, the left eye does know what the right eye is doing, engaging in what the researchers call "cross talk." This means that the chameleon's eyes get the right amount of depth perception to accurately devour its prey after the second eye locks in on the target that caught the first eye's attention.

With the ability to change colors and their bulging, seemingly wandering eyes, the researchers were able to demonstrate for the first time that chameleons can perform visual tracking both independently and with both eyes, as both eyes are aware of the other one's location.


Photo: Umberto Salvagnin | Flickr

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