I had a older friend who had only one good eye. He would – automatically – “bob” his head before reaching out to contact something like a proffered hand, to “scan” for a 3-D location… And, he was unaware that he did this. When shown a video of the action, he was astonished! Perhaps pigeons also employ this method to locate, given their “side-mounted” eyes? And, one has to wonder, are they aware of this, or do they really care…?
I know you are going to get people coming in here with differing opinions, but the truth is, they like it.
From the column:
This does not make sense. Pigeons are smarter than cows? How come cows and pigs can function with parallax shifts, but pigeons can’t? Unexplained. Furthermore, how do pigeons fly, if parallax shifts are so much trouble? Do they bob their heads when they fly?
The forward motion of the pigeon provides a parallax shift… no need to bob in flight.
The bobbing is also mating/challenging behavior perhaps?
Martin S’s screed being virtually unreadable, I refer the reader to this article (Warning: PDF):
Back in the late seventies, Barrie J. Frost, a visual neuroscientist at Queens University in Kingston, Ontario, put pigeons on a tiny treadmill. They walked, but they didn’t move relative to their environment-and they stopped bobbing.
*Pigeons *on a treadmill?
This is some kind if sick doper in-joke, isn’t it?
Or the latest from the Game Room, how many Cecil columns can be referenced in a single question.
And, Gregor, if the parallax shift is provided with the forward momentum of flight, why is it an issue with the forward momentum of walking?
It’s really simple, there is a string that connects the pigeon’s head, and its legs.
I’m not clicking that, it could be a shrimp roll and I heard enough Rick Astley in the 80’s.
Besides, youtube makes my PC go paralytic. … Maybe headbobbing would help.
I actually came into this thread just to suggest putting pigeons on a treadmill, but apparently I was 30 years too late.
For another one-eyed data point, I’ve only had one good eye since birth. I do not ‘bob’ for location or for scanning. I have checked with Mrs. Petro and she agrees and has never seen me do this. I believe since my good eye is still forward facing, I compensate by other means.
Since an old, old SD classic has been revived, I’m reviving my response:
They’re F. Scott Fitzgerald fans and they don’t have any hair?
More than reducing motion parallax, the head-bobbing reflex of the pigeon will also reduce retinal slip. Retinal slip is the motion of the image of the world on the retina when the eyes move relative to the surrounding.
A bad eye stabilization will mean a lot of retinal slip which does not only reduce visual acuity (which is, anyway, not really high in pigeons. However, try to shake a book in front of your eyes and to read it on the same time) but also decrease visual motion perception (which is quite usefull for detecting predators). In brief, it is much easier to detect something moving in the middle of a stable image than to analyse a moving image and look for something that moves differently.
Notice that virtually all vertebrate species have an gaze stabilization system (the eye move to compensate head motion) known as vestibulo-ocular reflex. This reflex will work during head rotation (which doesn’t cause parallax), indicating that its primary purpose is to minimize retinal flow.
Maybe the pigeons are bass players.