visual illusion/pain?

[Ron Blue]

On 2 Nov 1995, Jan Vorbrueggen wrote:
> In article <Pine.3.89.9511010831.C11033-0100000 at lex.lccc.edu>
> rcb1 at LEX.LCCC.EDU (Ron Blue) writes:
> 
>    Does anyone know how I can get a copy of a visual illusion that causes
>    pain?  My understanding is that it looks like a circle with vertical lines
>    inside.
I was able to get the picture at 
http://cfa-www.harvard.edu/~perprbv/pain.html

I tried it out on 25 people. One out of six reported pain.  Two were
in a strong state of discomfort.  Also most reported subjective color.
Colors were blue, green, red, and orange.
Ron Blue