Our brains shield us from the idea of our own deaths, making us unable to grasp our own mortality, according to a new study.
On one level, everybody knows that they are going to die, said study lead author Yair Dor-Ziderman, who was a doctoral student at the Bar Ilan University in Israel at the time of the study. But Dor-Ziderman and his team hypothesized that when it comes to our own deaths, there's something in our brains that simply can't understand "the idea of ending, of nothing, of complete annihilation."
Their research was an attempt to reconcile the brain's way of learning with the universality of death. The brain is kind of a "prediction machine," Dor-Ziderman, who is currently a postdoctoral researcher at the Interdisciplinary Center Herzliya in Israel, told Live Science. The brain uses old information to predict what might happen in similar scenarios in the future, which is an important tool for survival, Dor-Ziderman said.
It's also true that everyone who ever lives will die, so it would make sense that your brain should be able to "predict" that you, too, will die someday.
But it doesn't seem to work that way. To see why not, the researchers in the new study recruited 24 people and observed how their brains' prediction mechanisms operated when facing their own deaths.
Dor-Ziderman and his team looked at a special signal in the brain that represented "surprise." This signal indicates that the brain is learning patterns and making predictions based on them. For instance, if you show a person three pictures of oranges but then show them a picture of an apple, the person's brain will give off a "surprise" signal, because the brain had already learned the pattern and was predicting it would see an orange.
In this study, the team showed volunteers pictures of faces — either the volunteer's own or that of a stranger — paired with either negative words or words related to death, such as "grave." The researchers simultaneously measured viewers' brain activity using magnetoencephalography, which measures magnetic fields created by the electrical activity of brain cells.
After learning to associate a given face with words of death, the participants were then shown a different face. As the researchers predicted, when participants were shown this "deviant" image, their brains showed the telltale surprise signal, indicating that they had learned to connect the concept of death with a specific stranger's face and were surprised when a new one appeared.
But in a second test, the participants were shown an image of themselves next to a death word. When they were then shown the deviant picture of a different face, their brain activity did not show a surprise signal. In other words, the brain's prediction mechanism broke down when it came to a person associating death with themselves, the researchers said.
Death is all around us, yet when it comes to our own deaths, we are not updating our prediction to assimilate that reality, Dor-Ziderman said. It's unclear what evolutionary purpose this breakdown serves.
But at one point in time, humans made a huge leap forward as they evolved from apes; they developed a theory of mind and, at that point, became very aware they would die, Dor-Ziderman said.
But according to theorists, awareness of death would decrease the likelihood of reproducing, because humans would be so fearful of death that they would not take the risks needed to find a mate, he said. So "in order for us to develop this unique ability [to have a theory of mind], we also had to … develop this ability to deny reality, particularly death."
But while most people may have an underlying fear of dying, some highly trained meditators have supposedly eliminated the fear of death. Dor-Ziderman and his team are now bringing those mediators to the lab. "We want to see if this is true," he said.
The new study's findings will be published next month in the journal NeuroImage.
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Originally published on Live Science.
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Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.