The challenge sounds easy enough. You look at two images at a time during a 30 second challenge. There’s just one rule: choose the image that is larger in real life. The thing is…sometimes the image you’re looking at is larger in real life, but the image is smaller than the other object right next to it. This conflict - and what causes you to stop and say “What?” so many times - is caused by the fact that your brain - unknowing to you - is accessing a whole bunch of information about the objects you’re seeing - including their size. And when the information in your head conflicts with what you’re seeing…well, you’re stopped in your tracks for a second.

Try this little brain game and experience what it’s like when your working memory runs up against reality, and you’re left with your eyes crossed. Another great psychology app from Michael Britt and the web’s most popular academic psychology podcast, The Psych Files.