Pareidolia: Why Your Brain Sees Faces in Outlets, Clouds and Toast

A wall outlet stares at you in surprise. A cloud has a nose. And in 2004 a Florida woman sold a grilled cheese sandwich for $28,000 because she saw the Virgin Mary in it. None of this is strange: it is your brain doing exactly what it was built to do.

It’s called pareidolia. Two holes and a line are enough.

Your brain doesn’t wait for evidence. It puts the face there first and asks questions later.

What is pareidolia, and where does the word come from?

Pareidolia is the perception of a meaningful pattern in something that contains none.

By far the most common version is the face.

The German psychiatrist Karl Ludwig Kahlbaum coined the term (Pareidolie) in 1866, from the Greek para (“beside”, “instead of”) and eidolon (“image”).

The usual suspects:

• Outlets, faucets and backpacks with startled expressions.
• Clouds with human or animal profiles.
• Car grilles that seem to grin or scowl.
• Marks on toast, damp stains on a wall, the surface of the Moon.

The most famous case belongs to Diane Duyser.

By her account, she had taken a bite of a grilled cheese sandwich ten years earlier and saw a face looking back.

In November 2004 she auctioned it on eBay, and an online casino paid $28,000 for it.

What William James noticed in 1890

William James never uses the word “pareidolia” in The Principles of Psychology (1890).

But his chapter on the perception of “things” describes the mechanism with remarkable precision.

His thesis fits in one line:

we see, as always, the most probable object.

William James, The Principles of Psychology

For James, perceiving isn’t photographing. It’s completing.

Sensation supplies a few strokes, and the mind fills in the rest from what it already knows.

His examples are almost domestic:

• A sportsman shooting woodcock, a case James borrows from Romanes, sees a bird of the right size and color fly up through the foliage. He fires. It was a thrush: his mind had supplied everything else.
• “Twenty times a day the lover,” James writes, will think he sees his beloved’s bonnet ahead of him in the street.
• James himself, waiting in Boston for a car to Cambridge, read “Mount Auburn” “most distinctly” on a signboard that actually said “North Avenue.”

Then there is what he called the proof-reader’s illusion.

Fluent readers of novels and newspapers, he argued, don’t check every letter:

“More than half of the words come out of their mind, and hardly half from the printed page.”

Pareidolia is that same completion machine, pointed at faces.

A nun in Venice and a terrier that sounded like a flood

In Venice, in the winter of 1858, a Professor Hyatt saw a nun’s head in a wimple beside his bed.

It was moonlight filtering through lace curtains.

Hearing plays the same tricks:

• James once heard what he took for the distant roar of a flood. It was the breathing of a little Scotch terrier asleep on the floor.
• The philosopher Thomas Reid, frightened in bed, thought someone was knocking and opened the door more than once. It was his own heartbeat.
• A chorus of “barking dogs” turned out, as the zoologist Van Beneden explained, to be toads.

The most revealing detail is about the dog.

Once James knew what the sound was, he “could not then hear it” the way he had heard it a moment before.

When the mind switches hypotheses, perception switches with it.

The same goes for the face in the outlet: once seen, it’s hard to unsee.

What happens in the brain when you see a face in an object?

More than a century later, neuroscience put a stopwatch and a scanner on James’s intuition.

• Hadjikhani and colleagues (2009), using magnetoencephalography, found that face-like objects activate the ventral fusiform cortex, a face-selective region, at about 165 milliseconds. That’s nearly the same time and place as a real face. Ordinary objects produced no such response.
• Liu and colleagues (2014) showed people pure visual noise after telling them half the images contained faces or letters. They reported seeing faces 34% of the time. When they “saw” one, the right fusiform face area lit up, and frontal regions appeared to push expectation down into visual cortex. The paper was titled “Seeing Jesus in toast,” and it won the 2014 Ig Nobel Prize in Neuroscience.
• Wardle and colleagues (2020), combining fMRI and magnetoencephalography, found that illusory faces are at first represented more like real faces than like matched objects; by around 250 milliseconds, that representation shifts and they are treated as ordinary objects.

The brain sounds the “face!” alarm first and corrects itself afterwards.

All of this happens on roughly the timescale of what your brain decides in a fifth of a second, well before any conscious judgment, much like when your brain responds to a click before you know what it is.

Why do most faces in objects look male?

In experiments with 3,815 adults, Wardle and colleagues (2022) found that illusory faces aren’t neutral.

People assign them an age, an emotion and a gender.

And there is a strong bias to see them as male, at a ratio of roughly four to one.

The type of object didn’t explain it, and neither did its visual features.

The authors’ reading: without features typically associated with femaleness, the mind falls back on a default category.

Another “most probable object” in the Jamesian sense.

The mind also completes with its own social habits.

Better one face too many than one too few

The most common explanation is evolutionary, and it remains a hypothesis.

For a social animal, missing a real face (a predator, a rival, someone approaching) costs far more than mistaking a rock for one.

The face detector works like a smoke alarm tuned to go off even for burnt toast.

Sometimes it’s a nuisance, but it rarely lets a fire slip by.

One finding points that way: we aren’t alone.

Taubert and colleagues (2017) showed that rhesus monkeys look longer at photos of objects with “faces” than at similar objects, and scan the “eyes” and “mouth” the way they would a real face.

What James got right, and what he couldn’t have known

James got the essentials right:

• That perceiving is inferring: the mind contributes more than it receives.
• That once a stimulus is reinterpreted, it is hard to perceive it the old way.

What he couldn’t have known:

• That the brain has a region specialized for faces, and that pareidolia triggers it within about 165 milliseconds.
• That the error isn’t slow reasoning but an early detection that gets corrected later.

The same urge to find someone where no one is shows up in another psychology classic: how a Ouija board works, and who is really moving the planchette.

Sources

• James, W. (1890). The Principles of Psychology. Henry Holt and Company.
• Hadjikhani, N., Kveraga, K., Naik, P., & Ahlfors, S. P. (2009). Early (M170) activation of face-specific cortex by face-like objects. NeuroReport, 20(4), 403-407. https://doi.org/10.1097/WNR.0b013e328325a8e1
• Liu, J., Li, J., Feng, L., Li, L., Tian, J., & Lee, K. (2014). Seeing Jesus in toast: Neural and behavioral correlates of face pareidolia. Cortex, 53, 60-77. https://doi.org/10.1016/j.cortex.2014.01.013
• Taubert, J., Wardle, S. G., Flessert, M., Leopold, D. A., & Ungerleider, L. G. (2017). Face pareidolia in the rhesus monkey. Current Biology, 27(16), 2505-2509. https://doi.org/10.1016/j.cub.2017.06.075
• Wardle, S. G., Taubert, J., Teichmann, L., & Baker, C. I. (2020). Rapid and dynamic processing of face pareidolia in the human brain. Nature Communications, 11, 4518. https://doi.org/10.1038/s41467-020-18325-8
• Wardle, S. G., Paranjape, S., Taubert, J., & Baker, C. I. (2022). Illusory faces are more likely to be perceived as male than female. Proceedings of the National Academy of Sciences, 119(5), e2117413119. https://doi.org/10.1073/pnas.2117413119