Optical illusions have a way of driving people crazy. No matter how much you try to avoid being “tricked,” your brain often interprets things in unexpected ways. One illusion now confusing the entire internet shows six girls sitting on a couch—yet only five pairs of legs are visible. How is that possible? According to the Queensland Brain Institute, an optical illusion happens “when our brain and eyes try to speak to each other in simple language but the interpretation gets mixed up.”