Jesus Christ on toast? Brain scan explains how facial pareidolia happens

One afternoon in 1994, Diana Duyser, a jewelry designer from Florida, experienced an epiphany in her kitchen. The message came through a grilled cheese sandwich. “I went to take a bite out of it, and then I saw this lady looking back at me,” she told the Chicago Tribune newspaper. The burns on the surface of the bread drew a recognizable silhouette. It was the Virgin Mary. “I was in a state of shock,” she said then. Instead of finishing her snack, Duyser put it in a plastic bag and told her story first to local journalists, then the national press, and over the years, to the international media. A decade later, with the uncorrupted sandwich turned into a pop icon, she auctioned it off on eBay, where she received $28,000 for it. The sale made it quite clear that Ms. Duyser was a marketing genius, but also that she was not the only one to see a human (or divine) face on a slice of bread.

Not so long ago when this happened people built hermitages, sold relics, or told stories of ghosts or aliens. But in recent years, science has begun to understand the complicated neural process by which people believe they see faces everywhere. The phenomenon is called facial pareidolia and a few days ago, research published in the Proceedings of the National Academy of Sciences (PNAS) journal analyzed how and where it occurs in the brain. Studying it can open the door to understanding autism spectrum disorders, schizophrenia, and Parkinson’s.

“This study uses an electroencephalogram and is in line with recent research,” explains neuropsychologist Saul Martínez-Horta in a telephone conversation. “For some time now we have had the ability to segment in milliseconds what, when, and where activity occurs in our brain, and we are beginning to understand the entire sequence of processes that accompanies perception.”

In the case of pareidolia, the sequence would be as follows: when we see a human face, or something that vaguely resembles it, a “dialogue” takes place between different areas in our brain. There are the areas that deal with visual stimuli, and there are the areas of memory, which fill in the gaps in what we are seeing with what “we are probably seeing.” And finally, an area called the facial fusiform gyrus plays a critical role in the early stages of recognizing faces, but not any other visual stimulus. “That is, a different area of the brain begins to process faces, and it processes them earlier,” says Martínez-Horta.

How to recognize Elvis

In human perception we are not constantly analyzing the external world. What we see around us is usually an anticipation; we perceive what seems most likely to the brain. “When you see Elvis, you are not recognizing all the elements that make up Elvis’s face, but your brain already has a typical representation of his face: it knows his face,” says the expert. This avoids the brain investing a huge amount of resources reading all the information that comes to it. “The brain accesses memories banks in which we store pieces and fragments that resemble what we are seeing. And at this point, something is already starting to tell your visual system, hey, this could be Elvis.”

But what happens when we see Elvis in a pot of McDonald’s ketchup? The dialogue that occurs between different areas of our brain sometimes works like the game of broken telephone, and erroneous information is sent from one area to another. There is no face, but we believe we see it. “The fact that pareidolia happens, especially with faces that we know very well, is explained because we store their meaning in memory,” explains Martínez-Horta. And because, in some way, we are programmed to see human faces. We are obsessed with them.

Susana Martínez-Conde, a neurologist at the State University of New York, measures this obsession in her laboratory. “Exposing participants to all types of images, we analyze their eye movements, and we have seen that we spend much more time examining faces than other objects,” she confirms in a telephone conversation. At an evolutionary level, this makes sense, “because being social animals, it is important to recognize if the face we are seeing is that of a friend, a family member, a neighbor, or an enemy.” In fact, it is a common trait with other social mammals, such as monkeys, which also suffer from pareidolia.

Pareidolias say more about the people we see than what we see. Our way of understanding the world is reflected in optical illusions. And there is an overwhelming tendency to see men’s faces. In a study published in PNAS, it was found that 80% of the participants had a male bias when giving a gender to faces. On toast, on potatoes, or on walls, we see men’s faces everywhere. There is a tendency to perceive illusory faces as masculine rather than feminine, by a ratio of four to one. Only 3% of participants had a female bias.

This hallucination reflects the brain’s broader tendency to find meaning where there is none. “To artificially organize disordered components into a coherent perception. Because it is not a phenomenon that exists in the world, but rather we construct it, so that our subjective perception does not correspond to objective reality,” says Martínez-Conde.

The same thing happens with sounds, when we believe that someone has said our name. Or with psychophonies or hidden messages in audio tracks. “The information is disorganized, but since we are wired to recognize words and give them meaning, we tend to find words where there are none,” explains the expert. Perception is more construction and simulation than exact reconstruction of reality.

But after perceiving this supposed face, our brain reevaluates what we are seeing. Unless religious or esoteric beliefs come into play, we understand that it is a hallucination or an optical illusion. As long as there is no type of illness. “We study the phenomenon of pareidolia a lot in the context of neurodegenerative diseases, especially Parkinson’s,” explains Martínez-Horta. A 2021 study claimed that more than 47% of Parkinson’s patients had experienced this type of optical illusion. “Before patients have more complex and grotesque hallucinations, they begin to see faces everywhere,” confirms the expert. But the subsequent process of understanding that they are not real does not occur here, so pareidolia is integrated as part of reality.

Understanding this phenomenon can help to better understand neurodegenerative diseases, and explain how we perceive the world around us. Having located the part of the brain responsible for this phenomenon, it not only confirms that the toast is not Jesus Christ, but it can help us understand ourselves better. “Pareidolia tells us very well,” Martínez-Horta summarizes. “The fact that we have no control over what we are seeing is an example of how we often perceive the world.”

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