Hi Michael, I just wanted to say thank you for your efforts to maintain and improve this website. I use it several times a year for my advanced physics majors. I use it when teaching my PHYS3190 Applied Optics and for PHYS3420 Data Acquisition and Analysis. It is a great way to drive home the point that what you think you see is not what you might actually measure. (Your security code is pretty hard to read though.)

Dear Yan Wong: Thank you for commenting. Your idea of placing the yellow spots on a separate depth layer is intriguing indeed. When I find the time, I'll explore it. Thanks, best, Michael.

Re: your motion induced blindness demo. I assumed that the brain erases the yellow spots because they are "overwritten" by the black space between the rotating blue crosses. When staring at the central point, the visual system may be inferring much of the peripheral information from the general background pattern, which then overwrites the presence of the yellow spots. In other words, the brain may be extrapolating the background pattern forwards in time, erasing previously observed features that aren't part of the pattern. I can thing of a few fun ways to test this: 1) Do the spots disappear if the scene is visualised in 3D and the yellow spots are in a radically different plane to the rotating background? I suspect they won't disappear so readily, because they are assumed not to be part of the background. 2) Do the spots disappear if instead of rotating in a constant direction, the background rotates back and forth, such that the yellow spots always occur between the same crosses? If they don't disappear, this should rule out the idea that the movement is contributing simply through adding noise to the background.

I love your website. I am going to be sending my friends here. Thank you.

Dear Dezmembrari: Interesting. Prompted by your observation, I've now tested it repeatedly -- for me there is no such tendency as you describe, though your description sounds plausible. Thanks for your feedback, best, Michael Bach

On the motion bounce illusion, I'd like to note that (for me at least) pressing the test button before pressing 1 also accomplishes a bounce. I assume it's because I'm primed to hear the sound again. If I press 1 again immediately after that though, we're back to the cross pattern.

I've been studying color history for some time. Thank you for all your effort. Your site has the best display of after image I've ever seen. No pun intended. Fabulous work!

Thank for your great website.

dear reading mind of michael bach.de I discovered UR web page in the bodleian library oxford researching the mind and finding richard m. restak's mind...the big questions... quite a fun trouvaille on a cold winter march day 2013 I am a female of 73+ on this planet made of illusions for sensationers... thanx with an invisible smile hewesufa www.printingeria.com

Dear Sohl: Thank you for your kind words, I'm glad you can use this. The security code is designed by my provider, and I'm glad it's not too easy, there was a time when I got >100 spams per day here. But it really is obnoxious, I agree. Best, Michael.