Sean Murphy was looking at sets of faces for one of his experiments when he observed something really freaky. Skimming fairly rapidly through pictures of two faces side-by-side, Murphy started noticing that some of the people he had pictures of had grotesque and deformed faces. But when he looked at the pictures again, this time individually, they all looked normal.

Murphy, who undoubtedly possesses a strong stomach and an unbelievable resistance to nightmares, decided to look into the illusion further with the help of his colleagues Jason Tangen and Matthew Thompson. The three called it the “Flashed Face Distortion Effect”. Watch the video below and follow the instructions to make your brain creep you out.

Scary huh? Although Murphy, Tangen and Thompson have yet to fully explain the illusion, it seems as if it happens because we’re only given a short period of time to examine the pictures. For some reason our brains want to differentiate the two faces that we’re seeing, and to do so under the time constraint it ends up exaggerating the features of each face. For me it’s the slanted, evil eyes that creep me out the most.

[via Matthew Thompson’s website & Perception via Videosift]