The psychologist Naomi Eisenberger describes herself as a mutt of a scientist. Never quite fitting the mould of the fields she studied – psychobiology, health psychology, neuroscience – she took an unusual early interest in what you might call the emotional life of the brain. As a doctoral student at the University of California, Los Angeles (UCLA), Eisenberger found it curious that we often describe being rejected in terms of physical pain: ‘My heart was broken’, ‘I felt crushed’, ‘He hurt my feelings’, ‘It was like a slap in the face’. More than metaphors, these expressions seem to capture something essential about how we feel in a way that we can’t convey directly. And you’ll find similar ones not just in English but in languages all over the world. Eisenberger wondered why. Could there be a deeper connection between physical and emotional pain?
In a landmark experiment in 2003, Eisenberger and her colleagues had test subjects strapped with virtual-reality headsets. Peering through goggles, the participants could see their own hand and a ball, plus two cartoon characters – the avatars of fellow participants in another room. With the press of a button, each player could toss the ball to another player while the researchers measured their brain activity through fMRI scans. In the first round of CyberBall – as the game became known – the ball flew back and forth just as you’d expect, but pretty soon the players in the second room started making passes only to each other, completely ignoring the player in the first room. In reality, there were no other players: just a computer programmed to ‘reject’ each participant so that the scientists could see how exclusion – what they called ‘social pain’ – affects the brain.
Physical pain involves several brain regions, some of which detect its location, while others, such as the anterior insula (AI) and the dorsal anterior cingulate cortex (dACC), process the subjective experience, the unpleasantness, of pain. In fMRI scans of people playing CyberBall, Eisenberger’s team saw both the AI and the dACC light up in participants excluded from the game. Moreover, those who felt the most emotional distress also showed the most pain-related brain activity. In other words, being socially rejected triggered the same neural circuits that process physical injury, and translate it into the experience we call pain.
At the time, this was a radical idea – and it still is. It essentially suggests that the brain makes no distinction between a broken bone and an aching heart. Rejection, it tells us, actually hurts. For Eisenberger, this overlap between physical and social pain transcends scientific interest. ‘It reveals something to people that they probably already knew but maybe were afraid to believe,’ she told Edge magazine in 2014. ‘It’s not just in our head. It is in our head because it’s in our brain.’
Since the original CyberBall experiment, a number of studies have replicated and extended its results. Researchers have found, for example, that social rejection doesn’t have to be explicit to trigger the brain’s pain mechanism: just seeing a picture of your ex-partner or even a video of disapproving faces activates the same neural pathways as physical pain does. At one point, Eisenberger and her team posed a seemingly daft question: if physical and emotional pain are related, could a painkiller relieve heartache? In the study that followed, some participants took two daily doses of Tylenol (a common painkiller) for three weeks while others took a placebo, and each group recorded their day-to-day emotions in a diary. By the end of the experiment, the Tylenol group reported less distress and showed less brain activity in the pain regions after being rejected than the placebo group.
That’s not the end of emotional pain, of course, and you can surely do better than pop a pill each time the world snubs you. Still, the Tylenol study reveals something remarkable about rejection: that it can spill beyond our emotional lives and into our physical selves. In fact, in recent years social rejection has emerged as key to a number of discoveries across psychology, neuroscience, economics, evolutionary biology, epidemiology and genetics, forcing scientists to rethink what makes us sick or healthy, why some people live long while others die early, and how social inequalities affect our brains and bodies.
According to Eisenberger, the significance of social pain goes back to evolution. Throughout history, we depended on other people for survival: they nurtured us, helped to gather food and provide protection against predators and enemy tribes. Social relationships literally kept us alive. Perhaps, then, just like physical pain, the pain of rejection evolved as a signal of threat to our lives. And perhaps nature, taking a clever shortcut, simply ‘borrowed’ the existing mechanism for physical pain instead of creating a new one from scratch, which is how broken bones and broken hearts ended up so intimately interconnected in our brains.
What’s remarkable about this connection is how even trivial slights can ‘get under the skin’, as researchers put it. During CyberBall, being ignored by people you didn’t know and couldn’t even see was enough to trigger an ancient pain response designed to keep you alive. And simply watching videos of disapproving faces produced the same effect. But what about major blows to our need to belong? Intuitively, you’d expect that, the more significant the rejection, the stronger the ensuing pain – but this is not what researchers find. It turns out that something else happens too, when we get rejected – by spouses, bosses, peers, at work, at school, at home – and it can help us understand not only our struggle for acceptance but the often longing desperation that comes with it.