Social distancing has emerged as one of the most effective weapons against the spread of COVID-19. Yet social distancing, like any medicine, has side-effects: we’re probably all feeling a little lonelier and more isolated. New research [note: this is a pre-print and has not yet been peer-reviewed] by scientists at MIT and the Salk Institute for Biological Studies sheds light on the effects of mandatory social isolation on brain function.

Humans are a social species, and social interaction is inherently rewarding for us. The parts of our brains that are responsible for motivating us to go out and obtain rewards react to social interaction just like they do to receiving food or money. Interestingly, these parts of our brains react in anticipation of a future reward, and the magnitude of that reaction reflects how much reward we’re expecting. Scientists have found that the strength of your brain's reaction to a reward reflections how much you crave it. But is this also true for social rewards? 

The scientists behind this new research spent over three years working to answer this question in humans. They recruited 40 participants into their study, and each participant was subject to three trials: one control condition, one in which they fasted for 10 hours, and one in which they sat alone in a room with no one to talk to (and no internet or social media) for 10 hours. Participants then had their brains scanned while they completed a task where they were shown images of food and social scenes – the very things they might be craving. This allowed the researchers to compare the effects of severe hunger with the effects of social isolation. 

They found that, just as the brain over-reacted to pictures of food when the participants were hungry, it also over-reacted to pictures of social scenes when they were isolated. The hungrier or lonelier the participant felt, the larger the reaction. The size of the effect of fasting and isolation were also very similar, suggesting that when they were isolated, the participants craved social interaction just as much as they craved food when they were fasting.

This work helps to cement social interaction as an important and primary reward that all people need. Our brains are craving social interaction when we’re isolated, just like they would crave food if we were extremely hungry. What we don’t know, and one important direction for future research, is how much social interaction is sufficient, and how much of this craving social media is able to satisfy.