This is a very creepy effect called ” Flashed Face Distortion”. It makes an optical illusion. simply, when you put a cross between two faces they will appear grotesque. This discovery won the best illusion of the year contest of 2012 in the Vision Science Society.
According to cognitive scientist Matthew B. Thompson this discovery is “Like many interesting scientific discoveries, this one was an accident. Sean Murphy, an undergraduate student, was working alone in the lab on a set of faces for one of his experiments. He aligned a set of faces at the eyes and started to skim through them. After a few seconds, he noticed that some of the faces began to appear highly deformed and grotesque. He looked at the especially ugly faces individually, but each of them appeared normal or even attractive. We called it the “Flashed Face Distortion Effect” and wanted to share it with the world, so we put it on YouTube.The effect seems to depend on processing each face in light of the others. By aligning the faces at the eyes and presenting them quickly, it becomes much easier to compare them, so the differences between the faces are more extreme. If someone has a large jaw, it looks almost ogre-like. If they have an especially large forehead, then it looks particularly bulbous.”
So, watch the video below while focusing on the cross in the middle. Enjoy!