By Alex Fradera

We all differ in how much empathic brain activity we experience in response to witnessing somebody else in pain. For instance, hospital physicians, who are regularly exposed to other people’s suffering, tend to show a dampened response – perhaps a pragmatic necessity to cope in the job, and might along the way explain the blasé gallows humour seen in the profession. If these differences are found within a job, perhaps they also occur within a lifestyle choice, such as one that involves playing with and consenting to painful activities, such as bondage, discipline, dominance, submission, sadism, and masochism, typically abbreviated to BDSM.

As they report in Neuropsychologia, Siyang Luo at Sun Yat-Sen University and Xiao Zhang at Jinan University explored this issue by first running a preliminary online study on a Chinese BDSM web forum, finding that across genders and BDSM roles, female submissives showed the clearest differences from controls in terms of their having a diminished response to other people’s pain and lower scores on aspects of an empathy questionnaire. (Female doms didn’t show a reliably different response to pain, and male BDSM practitioners barely differed from controls.)

Next, Luo and Zhang invited 32 of these female submissive practitioners together with 32 female controls, into their lab, where they measured their electrical brain activity with EEG (electroencephalography) while they viewed images of faces with either neutral or painful expressions. The self-identified submissive participants found painful expressions less unpleasant and intense than controls, and when the images were framed in a BDSM context, they also found them more enjoyable and arousing, loosely replicating what was suggested by the online experiment.

The EEG data showed that an early negative spike in brain activity in the frontal lobes (called N1) was larger for the controls when they saw painful versus neutral stimuli, and more so when the participant found the images particularly unpleasant. But for the submissives, the N1 was similar in both cases. Past research has implicated N1 in registering threatening information, such as that denoted in a fearful face, so this could suggest that the submissives were seeing less threat, understandable given submissive practices that willingly incorporate pain.

Meanwhile, a positive spike in brain activity, also in the frontal lobes (called P2), which is usually associated both with pain and emotion processing, was flattened in submissive participants when they viewed generic pain – again suggesting less empathic response. However, when seeing BDSM-related images, their P2 was actually larger than controls, and this correlated with their subjective arousal ratings, suggesting that the brain response was capturing their interest in pain rather than distress. A third brainwave signal, also associated with emotion processing (the “LPP” in the parietal lobe), also showed an attenuation in the submissive group, corroborating the case for a weakening of empathic response.

Luo and Zhang also measured their participants’ day-to-day empathy, in terms of how they related to other people. Again, the submissive group had significantly lower empathy scores than controls, centred on lower reported ability to take different perspectives – e.g. “I find it difficult to see things from the other guy’s point of view.”

This study is limited to one subgroup of people who practice BDSM, and doesn’t implicate the wider field. The fact that the effects were initially discovered for women, not men, may reflect the fact that men tend to be less empathic to begin with. And the online study’s identification of submissive practitioners, rather than dominant ones, as having lower than normal empathy and an atypical response to pain, could reflect that this is the subset of people who willingly expose themselves to pain experience, which could be densensitising, or because this group is made up of individuals started out less sensitised.

This last issue is a point to emphasise – because we don’t know whether the kind of person drawn to submissive practices is different from the norm, the study doesn’t show that practicing BDSM causes any changes in empathy. But that the differences could be produced by the practice is certainly conceptually possible, both from the general principles of brain plasticity and from more specific insights from pain science. Working in a pain management service over this summer has left me in no doubt that our relationship with pain is shaped by psychological factors, and can change over time. More research will be needed to tell if this is the case here.

If submissive practices were causing empathic changes, would this matter? On the one hand, our neural empathic responses don’t dictate our moral capacities – we don’t assume that emergency ward doctors are less caring than stockbrokers, even if they are less sensitised to someone suffering from an injury. Some even argue that being tethered to reactive empathy is a moral state we would do well to forego. On the other hand, as we covered here at the Digest recently, there is evidence linking neural empathic responses to even very concrete altruistic decisions like donating a kidney to a stranger. Also, if the lower trait empathy scores among the BDSM practitioners were the product of their sexual practices, this would arguably be worth reflecting on, as it could have potential consequences for the quality of their relationships.

—Empathy in female submissive BDSM practitioners

Alex Fradera (@alexfradera) is Staff Writer at BPS Research Digest