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So you’ve discovered that everyone really is hanging out without you, and now you feel awful and weird. Social rejection is an incredibly powerful feeling — powerful enough to mess with your nervous system, causing your heart rate to slow down when the cold truth hits you, according to research published in 2010.

A team of scientists in Amsterdam recruited about two dozen undergrads for their study, bringing them into their lab one by one and wiring them up to an electrocardiogram, which would track each person’s heart rate. About two weeks before this, the students had been asked to submit a photo of themselves; their pictures, the researchers said, would be passed along to students at another university, who would use the images to make a snap judgment about whether they liked the person pictured. This was a little lie; no one outside the lab ever saw their photos.

While the study volunteers were in the lab, they saw a total of 120 photographs of students at a different university — supposedly, these were the ones who’d already seen and judged their own images, lied the researchers. When each person’s face flashed on the screen, the participants were to answer yes or no to a simple yet terrifying question: Do you think this person liked you? They were given a moment to respond, and then the “answer” was revealed (in reality, this was a random reply generated by a computer program).

While they were anticipating the answer — Did this person like me or not? — their heart rate dropped. Their heartbeat fell further, and took longer to return to normal, when they were blindsided by the rejection — if they’d guessed that the person had liked them, and then learned they’d guessed wrong.

So it’s not just that we’re emotionally or mentally sensitive to feeling disliked; we’re physically sensitive to rejection, too. Heart rate is controlled by the parasympathetic nervous system, which is involved with the regulation of biological processes we don’t have much direct control over, like digestion or sexual arousal. It’s not exactly clear why feeling unpopular seems to result in a slower heart rate, but the study authors say it could help to trigger a “neural alarm system,” alerting us that we maybe don’t belong where we thought we did. It’s not the most satisfying answer, and, clearly, more work needs to be done to explain the point of this apparent heartbeat slowdown. Still, in a study published earlier this year, this same team of researchers were able to replicate their findings in a group especially vulnerable to feeling unpopular: teenage girls.