There Are 12 Black Dots In This Image And You Will Never See Them All At Once

Look at this image. You will see black dots pop up at various intersections. You might see a few of them at once. You will almost certainly not see all 12 at once, thanks to our eyes being relatively bad at peripheral vision, thanks to a phenomenon called lateral inhibition. Instead, you'll see the dot in the center of your vision, along with some of the adjacent dots.  

If you can see all 12 dots at once, you should go ahead and put that on your resumé. 

[Akiyoshi Kitaoka via The Verge] ​