It feels so intuitive: whenever you’re hurt and in pain, being helped by a familiar face must surely be the quickest and most effective method to become pain-free. After all, don’t we all identify with and trust someone familiar more than a total stranger?

To find out if this is indeed the case, the researchers conducted a controlled lab experiment in which participants were divided into two groups and were administered pain on the back of their hand. In one group, the pain was treated by a person from a similar social and cultural background while in the other treatment was provided by someone from a different background. The researchers meanwhile measured how the pain relief treatment changed neural pain responses and how each participant subjectively judged his or her own level of pain.

Treatment by stranger more efficient

The findings revealed that although both groups showed similarly strong responses to pain initially, there was a marked difference in treatment response. ‘The participants in the group who were treated by a person who they considered a stranger, rated their pain less intense than the other group’, says Dr Jan Engelmann, associate professor of Neuroeconomics at the UvA and one of the authors of the study. ‘This effect was not only limited to subjective pain experience – we also saw a similar reduction of the pain-related activation in the corresponding brain regions.’

Pain-relieving effect

The study shows that these reductions in pain perception and pain-related neural activations in Anterior Insula are related to Pavlovian learning about pain relief. ‘Our findings might be surprising at first glance and they do not call into question previous results showing pain relief in the presence of familiar individuals’, says Engelmann. ‘Instead, they underline the importance of learning about pain relief. Such pain relief learning was greatest for participants that were treated by a stranger with a different cultural background: because they had initially low expectations about the outgroup, they had the opportunity to learn and update these expectations while they experienced the stranger repeatedly helping them. When such helping is more surprising or unexpected, social learning mechanisms lead to larger levels of pain relief, both at the neural and the behavioral level.’

Publication details

Hein, G., Engelmann, J.B., & Tobler, P.N. Pain relief provided by an outgroup member enhances analgesia. Proceedings of the Royal Society of London B: Biological Sciences. http://dx.doi.org/10.1098/rspb.2018.0501.