Staring in a dimly lit mirror too long can distort your perception of your face.

Original photo by EyeEm Mobile GmbH/ iStock

Man staring at his reflection in a dimly lit mirror

You may have grown up testing your nerve in front of the mirror by chanting in the dark to see if any spirits would appear. And while this may not summon ghosts, it turns out it can summon illusions. Staring into a dimly lit mirror for an extended period of time can distort your perception of your own face, making it appear to warp, blur, or even morph into someone — or something — else.

This phenomenon, dubbed the “strange-face-in-the-mirror illusion,” was first described in a 2010 study by Italian psychologist Giovanni Caputo. Subjects were placed in a room lit by a 25-watt lamp behind them with a mirror about a foot in front of them. They typically began to perceive the illusion after less than a minute, and after 10 minutes of gazing, many reported eerie changes.

More than 60% of participants saw “huge deformations” to their own faces, while others saw someone else entirely in their reflection, such as an old woman or a child. Almost 20% described seeing animal faces such as a cat, pig, or lion, and almost half experienced distorted perceptions of monstrous beings.

Ancient mirrors were made of volcanic glass.

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Obsidian, a volcanic glass, has been polished into mirrors since at least as early as 8000 to 6000 BCE in the Anatolian peninsula (modern-day Turkey).

The effect may seem frightening, but it isn’t supernatural — it’s neurological. When the brain is deprived of dynamic visual input, it quickly starts to adapt. Think of the optical illusions you’ve likely tried: In the lilac chaser, for example, a ring of lilac dots seems to vanish and a green dot appears in their place. This happens because of a process called the Troxler effect, in which staring at a fixed point can make surrounding details fade.

At the same time, because our brains are wired to search for faces, the experiment can also result in subjects seeing the faces of their own parents or other loved ones staring back.

Interestingly, this kind of illusion isn’t limited to mirrors. Caputo found in another study that staring into someone else’s eyes in dim light can trigger similar — or in some cases, even more dramatic — hallucinatory experiences. Many participants saw facial deformities and monsters, but they also reported that colors seemed muted, the volume of surrounding sounds noticeably increased or decreased, time felt stretched, and they felt spacey and dazed.

Numbers Don't Lie

Light-sensitive cells known as rods and cones in a human eye

~126 million

Year the first Magic Eye optical illusion book was published in North America

1993

Hours Thomas Edison’s 1879 light bulb lasted

~14

Distance (in light-years) to the Andromeda Galaxy, the farthest object visible to the unaided eye

2.5 million

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The ability to see millions more colors than the average person is known as ______.

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The ability to see millions more colors than the average person is known as tetrachromacy.

Those tiny specks in your vision are shadows inside your eyes.

The tiny dots that occasionally drift through your vision may seem to be specks of dust in the atmosphere, but those eye floaters, as they’re called, are actually shadows cast on your retina. They’re caused by clumps of collagen fibers floating around inside the gel-like vitreous body between the lens and retina.

When light passes through the eye, those tiny clumps block or scatter it slightly, creating the little shapes you see. The clumps also move as your eyes move, darting across your field of vision, and they’re more visible against bright backgrounds such as a clear sky or a white wall.