Why Hunger and Loneliness Activate the Same Part of the Brain

The Covid-19 pandemic has made the world feel lonelier than ever as people have been shut away in their homes, aching to gather with their loved ones again. This instinct to evade loneliness is deeply engrained in our brains, and a new study published in the journal Nature Neuroscience suggests that our longing for social interaction elicits a similar neurological response to a hungry person craving food, reports Ali Pattillo for Inverse.

Livia Tomova, a cognitive neuroscientist at the Massachusetts Institute of Technology, and her collaborators conducted a study in which they had a test group of 40 people fast for ten hours. At the end of the day, the hungry subjects were shown images of pizza and chocolate cake while receiving a brain scan, reports Bethany Brookshire for Science News.

In a second round of experimentation, the subjects were barred from social interaction—no in person or virtual human contact—for ten hours. Afterward, they were shown images of people gathering and playing sports as the team scanned their brains. The scans revealed that the same part of their brains perked up in response to both food and social gatherings, reports Science News.

In both situations, the neurons in the midbrain's substantia nigra and ventral tegmental area flared up in response to the images. The midbrain is known as the "motivation center," and it produces dopamine, a chemical associated with reward, reports Inverse.

The participants also reported how they felt through the experience. After a day of fasting, they noted that they were uncomfortable and had intense food cravings. After social isolation, they felt lonely and unhappy and yearned for interactions, reports Natalie Parletta for Cosmos magazine.

"[This study] provides empirical support for the idea that loneliness acts as a signal—just like hunger—that signals to an individual that something is lacking and that it needs to take action to repair that," Tomova tells Inverse. As such, the study suggests that social interaction isn't just comforting or fun, but it's a human need. Logically, when we're isolated, human brains seek to remedy feelings of loneliness.

Given the current state of the world, it's "important to pay attention to this social dimension of the current crisis," Tomova tells Cosmos. The world was already facing a "loneliness epidemic" as people report feeling increasingly lonelier, and the Covid-19 pandemic has exacerbated that.

"If already one day of being alone makes our brains respond as if we had been fasted for the whole day, it suggests that our brains are very sensitive to the experience of being alone," Tomova says. "Previous research has shown that when chosen intentionally, solitude can have positive effects on wellbeing. However, currently people have little choice about whether to isolate or not and while some people might not mind as much, others might suffer from feeling disconnected with others."

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Rasha Aridi is a science journalist based in Richmond, Virginia. She has written for Science magazine and Science News for Students. You can find her portfolio at rashaaridi.com.