What: While I still feel that “dot’s that won’t quit” is a better name, this illusion is actually called the scintillating grid illusion which was discovered by Elke Lingelbach in 1994, although it also falls into the category of Hermann Grid Illusion [1] (I don’t have this one built yet, but will in future!) The effect is simple and strong, you’ll see dark dots appearing in the intersection circles when they aren’t there!

How To: You can customize the colors and achieve varying degrees of this effect, for example, they work when flipped and you will see light dots. You can adjust the colors and sizes and see exactly which contrasting sets it works with. For me, a very small size is still extremely effective, absolutely no chance of counting those dots.

Explain it: It seems like there is some discourse currently as to what exactly is causing the effect previous understanding was that your receptive fields were miscalculating the light and dark colors. However, those smart folk at MIT are suggesting something different. I’m no authority and struggle to gain any understanding of any explanation but feel free to go down the rabbit hole [2]. All in all, I think we’re still in limbo as to the exact reason (using your brain to study your brain is hard!)

Cites and Extras:

• [1] A paper on the effect.
• [2] Some debate about as to how/why this works at all
• The wiki for grid illusions has the Hermann Grid, which is a similar effect but comes on a little less strong.
• While this effect that I’ve renamed “dots that will quit” is not exactly related, I consider it a cousin, since the dots dissapear rather than appear!

I've researched these optical illusions in my spare time but am clearly not any kind of expert and my explainations are pretty smooth brained, if you find something mis-cited, earlier examples, or general mistakes please new let me know via toymaker@toms.toys, be kind!