Stephen replied to me off list about my post on this question. As I more carefully 
reread the information on that site I see that he is correct and the site only 
addresses stroboscopic conditions. I admit that I was distracted by thoughts of 
planning my new course in Human Sexuality. 

Here is a much better source for the answer to the question. 
http://www.pnas.org/cgi/reprint/93/8/3693.pdf This site has a paper that was published 
in the Proceedings for the National Academy of Sciences in 1996 by Purves, Paydarfar, 
& Andrews. It does contain the ideas that I had projected onto the other web page.

Here is the conclusion for that paper:

"The illusion of wheels or other radial patterns rotating backward
in continuous light, together with the perception of
supernumerary spokes, suggests that the human visual system
processes sequential episodes of information rather than a
continuous temporal flow. In addition to accounting for this
remarkable illusion, a strategy of vision that parses the world
in this way can explain why movies are so realistic (simply
because that is the way we normally see things) and how we
detect motion (by comparing the position of the same objects
in sequential episodes)."

I hope this one really does help.

Dennis

On 1 Apr 2004, Dennis Goff wrote:

> Tom,
> Take a look at
> http://www.newton.dep.anl.gov/askasci/gen01/gen01404.htm. Be sure to
> read both answers. The first answers indicates that the illusion won't
> happen under steady lighting. The second answer indicates how the
> illusion could happen under that condition. Hope it helps Dennis
> 


I've looked at the webpage you cited. But I don't see anything in the 
second answer which explains how the illusion can happen under steady 
lighting. Perhaps you're referring to the last sentence. But that 
sentence refers to a special case when two mesh screens are 
superimposed, and doesn't have anything to do with seeing the wagon 
wheel effect under steady illumination. Or did I miss something?

Regards

Stephen

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