Strange-face illusion

How it works

The illusion was tested by Giovanni Caputo, an Italian psychologist, in 2010¹. He sat 50 people in front of a mirror in a room lit by a single dim lamp behind them¹. Each person stared at their own reflected eyes for 10 minutes¹.

The results were strong. About 66% of the people saw their face deform¹. 28% saw an unknown person¹. 48% saw a fantastic or monstrous being¹. Others saw an animal face, a parent’s face, or an old person¹. Many said the new face seemed to have its own emotions and to look back at them.

The most likely explanation combines two known effects. The first is Troxler fading. When you hold your gaze on one point, the parts of the image away from that point fade and lose detail¹. In a dim mirror, your face is low contrast, so it fades fast. The second is pareidolia, the brain’s habit of finding faces in patchy or noisy input². As parts of your face fade, the brain fills the gaps with a new face. The result is a stranger.

The effect goes away as soon as you move your eyes or turn up the light. It is not a sign of anything wrong.

Try it

Some people find this unsettling. Stop if you do not like it.

1. Sit about 40 centimetres from a mirror in a dim room. One small lamp behind you is enough. You should just be able to see your face.
2. Stare at your own reflected eyes. Do not look away and do not blink more than you have to.
3. Keep going for 5 to 10 minutes.
4. Watch your face fade, shift, and change. When it is enough, look away or turn on the light.

History and culture

Mirror-gazing in dim light appears in old folk traditions and in games such as “Bloody Mary”². The same fading and filling-in probably explains many reports of faces appearing in dark mirrors.