Looking at photos of starving refugees or earthquake victims can trigger a visceral sense of empathy. But how, exactly, do we feel others’ agony as our own? A new study suggests that seeing others in pain engages some of the same neural pathways as when we ourselves are in pain. Moreover, both pain and empathy can be reduced by a placebo effect that acts on the same pathways as opioid painkillers, the researchers found.
“This study provides one of the most direct demonstrations to date that first-hand pain and pain empathy are functionally related,” says neurobiologist Bernadette Fitzgibbon of Monash University in Melbourne, Australia, who was not involved in the new research. “It’s very exciting.”
Previous studies have used functional magnetic resonance imaging (fMRI) scans to show that similar areas of the brain are activated when someone is in pain and when they see another person in pain. But overlaps on a brain scan don’t necessarily mean the two function through identical pathways—the shared brain areas could relate to attention or emotional arousal, among other things, rather than pain itself.
Social neuroscientist Claus Lamm and colleagues at the University of Vienna took a different approach to test whether pain and empathy are driven by the same pathways. The researchers first divided about 100 people into control or placebo groups. They gave the placebo group a pill they claimed to be an expensive, over-the-counter painkiller, when in fact it was inactive. This well-established placebo protocol is known to function similarly to opioid painkillers, while avoiding the drugs’ side effects.
Then, the team asked the participants to rate the amount of pain they felt from small electric shocks and gauge the pain they thought someone in an adjacent room felt from the same type of shocks. Those receiving the placebo pill reported less pain and rated other’s pain as lower than participants who received no pill at all. When the researchers watched the participants’ brains with fMRI, activation in brain areas that included both the empathy network and the pain network were dampened by the placebo, strengthening the idea—suggested by previous fMRI studies—that the two are driven by the same underlying processes in the brain.
Next, the team asked whether blocking the opioid pathway would restore empathy to normal levels. They repeated the experiment but gave some participants naltrexone, a drug that blocks the brain pathways through which opioid painkillers function. Those who took naltrexone no longer had the placebo-induced decrease in either pain or empathy, the researchers reported today in the Proceedings of the National Academy of Sciences. The result suggests that turning on the opioid pathways in the brain—as both placebo painkillers and true opioids do—can simultaneously dampen both pain and empathy.
“There’s still a lot of debate going on about whether empathy is really grounded in the same neural networks as pain,” says neuroscientist Christian Keysers of the Netherlands Institute for Neuroscience in Amsterdam. “But this study, by showing that both systems relate to the opioid system, certainly moves that debate forward.”
“It’s a really impressive study,” says neuroscientist Tor Wager of the University of Colorado, Boulder, citing the clever experimental setup. But the findings could be interpreted in multiple ways, he cautions. Because opioid pathways are involved in diverse processes in the brain that aren’t all directly related to pain, he says, “I didn’t come away with the impression that this definitively means that empathy and pain share fundamental processes.”
Lamm’s group next plans to study whether individual variations in opioid pathways in the brain affect empathy. “There are certainly variations in how we empathize,” Lamm says. “So we’d like to know whether that’s also rooted in differences in this pain mechanism.”