If we have established that the silhouette does not change direction, and the only difference is in our perception, what actually causes this effect? Was it determined in the link alluded to further upthread?
Well I showed the OP’s link to the folks at work, and they were all mighty impressed (except for one person whose computer played the animation abnormally slowly so they didn’t get the full effect). No doubt they will forward the link to others in turn, and soon we will all be slaves of the Frodis.
Hah, the return of LSD 
Just want to offer my opinion as somebody … well … um … experienced:cool: to those of you who might have never tried LSD but wondered: The visual effect caused by the OP link is very very very similar to how you see while tripping. Only you get a whole lot more of it. LSD can do a bit more than that too, of course. That’s just the most common visual part.
I remember chewing on that in college in the '80s.
Some of the friends I was with got sick and threw up, I felt queasy but never did hurl.
But, yeah, about the same only weirder and it lasted longer.
Until God told me to stop.
I think I was annoying Him.
Yup, I’ll confirm that. Add in intense colours, distortion of images, and heightened sound awareness, and you are getting close to the real LSD deal.
Here’s the previous thread on the spinning dancer:
The circles are trippy, I saw the gorilla, and the girl moves clockwise for me.
And she has a nice rack. That is all.
The dancer moves clockwise for me, and it’s only with a great deal of concentration that I can see her move the other way. Once I did it, it got easier to switch back and forth, but I’m almost motion-sick with the effort. I must be very “right-brained!”
My 13 year old daughter at first sight saw it both ways–I don’t think she really believed me when I told her that the clip doesn’t change in any way. To her, the dancer spun one way, then spun the other–she really thought at first that it was animated that way. She had a hard time believing that I never saw it change at all!
Note that the previous thread fairly thoroughly debunked the notion that one’s perception of the spinning dancer has anything to do with “right-brained” or "left-brained"ness. (Indeed, the whole idea of literal “right-brained” and "left-brained"ness is sort of bunk to begin with)
I know we are not in GQ, but is “sort of bunk” a new technical term?
Of course everybody knows that it has to do with what side of the equator you’re on.