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Author Topic: How is peripheral vision better at spotting moving objects?  (Read 8632 times)

Bill

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Bill asked the Naked Scientists:
   
I was laying in bed last night and staring at the ceiling fan. You know the way that looks. You can't see a single blade of the fan, but just a spinning blur.

I noticed that when I quickly looked in another direction to focus, for a split second I would see a freeze-frame of the fan. I mean, just for an instant, a very clear and still image of individuals fan blades flashed at me. As though they were taken with a high speed camera.

I thought that was pretty cool, it made me wonder how our perception worked. On some level, even when the fan is spinning, we can see individual blades. But we can't perceive them, except for a brief second by using this trick.

What's going on here? How does shifting my gaze cause an instant of perfectly focused perception?

What do you think?


 

Offline chris

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How is peripheral vision better at spotting moving objects?
« Reply #1 on: 11/09/2009 12:23:28 »
That's a very good answer and there's not much I can add with the exception of pointing out that the retina is wired slightly differently for peripheral vision compared with central (high acuity) vision.

The peripheral retina uses a different class of ganglion cells whose job it is to transmit information from the light-sensitive rods and cones (photoreceptors) to the thalamus and brainstem for relay to the brain's visual and motor areas.

In the periphery the ganglion cells collect signals from a much larger clutch of photoreceptors and are of the "Y" class, which transmit that information very rapidly - making peripheral vision extremely fast, but with poor spatial localisation.

Chris
 

Offline Geezer

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How is peripheral vision better at spotting moving objects?
« Reply #2 on: 11/09/2009 20:17:13 »
Just for info: You can take advantage of this phenomenon in Astronomy. For example, Andromeda is difficult to see, even with binoculars, but if you use your peripheral vision, you can capture an image of it on your retina.
 

Offline Geezer

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How is peripheral vision better at spotting moving objects?
« Reply #3 on: 12/09/2009 00:41:24 »
Easy. Just look to the side, not straight in front. Works with, or without, binoculars or telescopes. Try it. You might be surprised. It's a well known technique. I'll try to dig up an authoritative reference.
 

Offline RD

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How is peripheral vision better at spotting moving objects?
« Reply #4 on: 12/09/2009 00:56:24 »
Just look to the side, not straight in front ... It's a well known technique.
I'll try to dig up an authoritative reference.


Is wikipedia "an authoritative reference" ? ... http://en.wikipedia.org/wiki/Averted_vision


Re: original question.

The existence of Akinetopsia is strong evidence that perception of motion is a property of the brain, not the eye.
« Last Edit: 12/09/2009 01:51:20 by RD »
 

Offline Geezer

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How is peripheral vision better at spotting moving objects?
« Reply #5 on: 12/09/2009 02:27:02 »
Just look to the side, not straight in front ... It's a well known technique.
I'll try to dig up an authoritative reference.


Is wikipedia "an authoritative reference" ? ... http://en.wikipedia.org/wiki/Averted_vision


Re: original question.

The existence of Akinetopsia is strong evidence that perception of motion is a property of the brain, not the eye.

In this case, authoritative enough for me! Thanks RD.

BTW, my optician told me I was Presbyterian. I told him to mind his own blinking business.
« Last Edit: 12/09/2009 03:07:09 by Geezer »
 

Offline RD

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How is peripheral vision better at spotting moving objects?
« Reply #6 on: 12/09/2009 03:16:26 »
The original fan observation may be due higher flicker fusion threshold in the more sensitive rod cells which predominate in peripheral vision ...

Quote
the rod cells of the human eye have a faster response time than the cone cells,
 so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision.
http://en.wikipedia.org/wiki/Flicker_fusion_threshold
 

Offline RD

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How is peripheral vision better at spotting moving objects?
« Reply #7 on: 12/09/2009 03:39:07 »
BTW, my optician told me I was Presbyterian. I told him to mind his own blinking business.

My optician told me I display the signs of crucifixion: he says I'm a stigmatic.
« Last Edit: 12/09/2009 03:43:33 by RD »
 

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How is peripheral vision better at spotting moving objects?
« Reply #7 on: 12/09/2009 03:39:07 »

 

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