Peripheral vision is the way we look at stuff without knowing we are looking. The centre of my gaze was all on the computer screen, and all of its information was received in the fovea, the cone-heavy part of the eye that deals with all the stuff that’s dead in front. So far as I was concerned, that was all I could see.
I was writing a complex piece about South African sport for The Spectator, but I was also looking out of the window to my left, through what happens to be my dominant eye. Looking without knowing I was looking — until movement caused me to turn my head sharply.
Peripheral vision is divided into three zones, near, mid and far. Far peripheral vision can stretch back 110 degrees. It’s all rods in this part of the eye, which means that sensitivity to colour and shape and detail is pretty low. What’s left is movement.
I turned my head because I had seen without knowing I had seen a stoat. He had been at 90 degrees to my gaze: a flicker of movement and I turned my head to give him the benefit of my full two-eyed vision. As I did so he vanished into the tangled vegetation in front of the dike, but at least he had the consideration to show me his black tail-tip, telling me he was no weasel. I returned to my struggle with the quota system – and a few minutes later I found myself turning again as the stoat returned, this time at about 20 degrees behind square, at the extreme, range of my far peripheral vision.
I gave him my full attention, picking up colour and shape and detail from my stereoscopic front-on vision, enhancing this by means of the excellent optical equipment I usually have to hand, my binoculars. And as I watched the stoat did a weird thing.
He flung himself onto his back and then got up again, the whole process taking no more than half a second. He jumped about eagerly, and then leapt, twisted in the air and landed flat on his back. He briefly squirmed and then was effortlessly on four paws again, pausing for a good look around — peripheral vision is important to him in a place full of predators bigger than him and capable of dropping out of the sky — and then he twisted and rolled once again. After that he vanished, this time not to show again: reminding me I had 1100 words to write before lunch.
What was he up to? Was he washing in the heavy dew? Did he have the most unbearable itch? Was there something more seriously amiss? He looked a whorseon mad fellow as he leapt and twisted and squirmed, but when I held his black eye with my own through the lenses of my bins, I could read nothing but the fearful intensity of the day’s struggle.