When I was a boy we lived close to a pond that had a thriving population of frogs. I used to go down to the pond, and when I popped my head over the bank all of the frogs would jump into the water, or if they were in the water with their heads
and eyes visible they would duck into the water. But if I sat down, within maybe 15 minutes the frogs would re-emerge, even though I was right beside the bank. Why didn’t the frogs see me? If I moved they would immediately disappear.
I think that they only see movement, not the static background. Very efficient for catching bugs.
My theory is that lizards also see in the same way. Hold still and they don’t see you. We have lizards in our back yard.
I observe them as they move about, and see that they often bob their heads up and down. Why do they do that? Is it because they need movement to see and they get movement relative to themselves by bobbing their heads?
Many birds walk in
what seems to be a strange way. They take a step without moving their heads and then move their heads forward, and repeat this body movement, then head movement. Chickens walk this way, doves and pigeons move this way. Is it because they
need movement to see, and they create movement this way? They create movement by moving their heads and then analyze the picture formed when they hold their heads still as the step forward.
The small brains of these amphibians, reptiles
and birds are more efficient if they don’t continuously process the entire background scene, they only see what moves. Theory only. No proof.