Just when you figured out “the dress,” a new visual riddle comes along

If you’re a fan of virtual treasure hunts, tricky visual puzzles, or brain teasers in general, you’ll love the mind-boggling image that Swiss photographer Tiziana Vergari posted on-line. It’s swept through the internet, bringing back memories of the white (?) dress that had everyone scratching their heads a few years ago.

Vergari originally posted the photo on Instagram as part of a hashtag project about identity. She asked simply, “How many girls do you see in this picture?” Except it isn’t so simple. The girls in the photo, however many, are dressed identically, look similar, have similar hairdos, and even have strangely similar facial expressions. If you stare at the photo for awhile, you might suspect that mirrors are in play. But that still doesn’t answer the question: how many girls? Mirrors or no mirrors, it’s a first-rate optical illusion.

To understand how optical illusions work, you need to consider exactly how you see things. First, light bounces off objects, then your eyes turn the light into electrical impulses that go to the part of your brain that processes visual information. Next, that part of the brain does its best to make sense of it all, producing a mental “image” that your mind can work with. Meanwhile, a huge amount of information is still streaming in from your eyes. Your brain can’t keep up with it all — imagine trying to gently sip water from a fire hose — and has to resort to “shortcuts” so it can focus on what seems to be important. By presenting a blend of the expected and unexpected, optical illusions exploit these shortcuts to fool your brain.

The video posted below has the answer to this particular conundrum. Let us know if you enjoyed puzzling over this astonishing image by dropping us a line in the Facebook comments. Be sure to like and share: it’ll fascinate your friends and maybe drive them up the wall, too.