One of the surest ways to prove your courage to all the other kids at the slumber party was to march into a dimly lit room (it was almost always a bathroom, for some reason), stare at your face in the mirror, and repeat the words Bloody Mary 13 times. According to legend, a woman would suddenly appear in the mirror and scratch your face off—or perhaps even kill you. Different iterations of this game exist around the world; in one, the mysterious mirror woman goes by Mary Worth or Kathy, and in another, the devil himself makes an appearance.
Of course, no ghosts or demons ever actually appeared, but that didn't stop you from running out of the bathroom screaming, convinced that you saw a twisted or bloodied face looking back. Even as adults, our minds sometimes play tricks on us. We may get spooked after thinking we see something in the mirror while getting ready for work or brushing our teeth, even though we are rational beings and understand that nothing is there.
There's a perfectly logical explanation for this. The longer you stare in a mirror, the more likely you are to start seeing things that aren't there—even if you haven't been forewarned that something ghastly will appear. This is partly due to a phenomenon called the Troxler effect. When you stare at the same object for a prolonged period of time, there comes a point when your brain adapts or gets used to unchanging stimuli. As a result, your neurons cancel the information out, and the image often appears blurry, faded, or distorted until you blink or look around.
Likewise, if you gaze into your own eyes in front of a mirror, your whole face will start to look strange if you look long enough. You can try this optical illusion out for yourself—no mirror needed.
Stare at the plus sign in the center of the image below for seven or eight seconds:
Did the colorful blotches fade to gray? This is just one of the many ways your brain can trick you and distort your vision. It's actually an important coping mechanism, though. As Live Science wrote, “If you couldn't ignore the steady hum of your computer monitor, the constant smell of your own body odor or the nose jutting out in front of your face, you'd never be able to focus on the important things—like whether your boss is standing right behind you.”
Another part of the phenomenon is the recently described “strange face in the mirror” illusion. Italian psychologist Giovanni Caputo conducted an experiment in 2010 in which people were asked to enter a dimly lit room and look at their reflection in the mirror for 10 minutes. Afterwards, they were asked to report what they saw. Of the 50 test subjects, 66 percent reported seeing “huge deformations” of their face, and 48 percent also saw “fantastical and monstrous beings.” Others described seeing the face of a parent (some of whom were deceased), the face of an animal, or the face of an old woman or child.
Humans in general have a remarkable ability to see faces in everyday objects—from clouds to trees to pieces of toast—so it makes sense that dim lighting and visual tricks would cause people to see another face of some kind. In addition, when an image is distorted, your brain draws from past experiences and expectations to fill in the gaps. Hence the dead relatives.
Interestingly, the same effect “can also be obtained during eye-to-eye gazing between two individuals,” Caputo tells Mental Floss. In fact, this “inter-subjective gazing” produced an even higher number of “strange faces” seen by test subjects, according to another experiment conducted by Caputo in 2013.
So we've ruled out the presence of mirror monsters, but what about Bloody Mary? The origin of this particular mirror game would seem to be related to “Bloody” Mary I, who served as queen of England in the 16th century—but folklorists are unconvinced.
That the figure goes by multiple names—such as Mary Worth, Mary Worthington, Mary Lou, etc.—suggests against a real person as the inspiration. Psychoanalysts have proposed that the game has to do with young girls and the onset of menstruation. Others have noted earlier analogues of the game, including a Robert Burns poem where he explained that if you “[t]ake a candle, and go alone to a looking glass; eat an apple before it; and some traditions say, you should comb your hair all the time,” you'll see over your shoulder the face of the person you'll marry (and some psychoanalysts have even proposed an importance of the homophone Mary/marry). But as far as we know, no one has ever actually appeared in a mirror to confirm what—or who—Bloody Mary is about.
A version of this story originally ran in 2018; it has been updated for 2021.