December 2017.


In addition to their ability to modify their colors, chameleons also have unusual powers of sight. Our human eyeballs are held in place by resting in deep sockets, which limit the movement of our eyes so that we cannot look behind us. But chameleon eyes are held in place with gigantic eyelids, an approach that allows chameleons to rotate their eyes to see further behind them.

At the same time, chameleons can move each eye separately. They can, in effect, be looking at two different things at once.

I find this wondrous, and difficult to imagine. I tried it this morning, staring at a chair but trying to imagine a different object in its place (a bottle of olive oil that I had seen in another part of the room). I could imagine combining the two things (a bottle of olive oil sitting on a chair), but I had difficulty holding two separate images in my mind (a bottle of olive oil in one corner of the room, the chair in the other, but both in my mind at the same time). Try it!

One of the articles I read described the chameleon using its sight to keep an eye on one object and then scan the scenery with the other. That seems even more difficult to me — not merely holding two images in awareness at the same time, but actually holding one image while searching the other image trying to find things hidden in it.

And there’s this too: chameleons can switch modes, going from moving and using two eyes independently, to seeing as humans do, using both eyes to focus on a single point. To us this is the default, the definition of how healthy sight works, but to them it’s just one option for viewing the world.