Just in time for Halloween, an extremely unsettling dysmorphic video has surfaced on r/blackmagicfuckery, a subreddit dedicated to the inexplicable. Stare at the video long enough, and the undoctored photos of notably beautiful celebrities start to look more and more grotesque, as if they were wax statues melting in the heat. It’s scary stuff, but the only black magic happening is in the twisted pathways of the human brain.

The video is a freaky concoction dreamed up several years ago by Sean C. Murphy, who at the time was an undergraduate student in Australia working with Matthew Thompson, Ph.D., who is now a lecturer in cognition at Murdoch University. As the story goes, Murphy was quickly flipping through some images of faces for another project when he noticed that their faces seems to be bending and contorting in strange ways. Murphy and Thompson were both were so taken by the phenomenon that they both published a paper about it in Perception and put a sample video up on YouTube, where it has been messing with people for nearly eight years.

At the time, the researchers didn’t propose a complete scientific explanation for the phenomenon, which the team called the “flashed face distortion effect.” But they did put forth one idea, suggesting that this illusion has something to do with a cognitive phenomenon known as a “visual aftereffect.” It’s the idea that the brain is a bit slow in processing visual information, so it tends to get hung up on parsing the image it saw a few seconds ago, even if there’s a new one in its place.

We experience visual aftereffects all the time. For example, if you stare at a curved line for a long enough time and then look at a straight one, the straight line will, only momentarily, appear to be curved in the opposite direction.

visual aftereffects
Stare at the left red line for 30 seconds and then the right. You'll notice that the straight lines should look like they're bending in the opposite direction. 

While this effect is normally demonstrated with lines or colors, there’s evidence that this occurs with faces too. Thompson’s paper references a 1999 study in which viewers stared at one distorted face for up to 60 seconds and then observed a new one, only to discover that the new face often had opposite distortions, and even characteristics:

“In the basic paradigm, participants study a single artificially distorted face for a few seconds to several minutes followed by an unaltered face that now appears distorted in the opposite direction to the adapting face,” Thompson writes. “Adaptation to a distorted face that is fat, happy, contracted, male, etc, causes neutral faces to appear thin, sad, expanded, female, etc.”

As you watch the video, the features of the faces that appear in the periphery of the central cross are constantly changing, and the brain struggles to process these new facial stimuli. With every new face, the brain may still be trying to grapple with the image seen moments before, resulting in strange “visual aftereffect” distortions in the new image.

Still, Thompson’s theory isn’t bulletproof. These images are moving quickly, so the jury is out on whether the faces actually linger long enough to produce this brain-scrambling effect. Whatever the case, the phenomenon is a question of neuroscience, not black magic — though some fuckery is certainly involved.