A study on human interactions and motivations suggests altruistic behavior is associated with stronger connections between two parts of the brain. Moreover, the same study found that connections between one of those brain regions and a third region influence the reasons why people choose to act in ways that benefit others. The work may lead to answers on what makes someone selfish or generous.
In Science, Dr. Grit Hein of the University of Zurich reported that their study matched participants with two partners. These were designed to induce empathy and reciprocity in the participants. Conditions were manipulated to induce positive feelings for one partner (either empathy or reciprocity), while the other served as a control. In half the cases, the participants witnessed their non-control partner suffer an electric shock (empathy), while in the other half the non-control sacrificed money to save the participant from receiving a shock (reciprocity).
Participants then allocated money between themselves and their partners. Not surprisingly, the controls got less money than the people with whom the participants had formed a bond. Empathy and reciprocity produced similar overall responses, although selfish people proved more motivated by empathy than reciprocity to act more altruistically than they would without prompting. People who were already pro-social proved more influenced by reciprocity.
Hein used a functional magnetic resonance imaging (fMRI) scanner to see which parts of the participants' brains lit up and the intensity of the connections between them. The team “found marked differences between empathy-based and reciprocity-based decisions,” said Hein in a statement.
Selfish individuals showed low connectivity between the anterior cingulate cortex (ACC) and the anterior insula (AI) when deciding, compared to generous ones. When people were motivated by reciprocity, there was strong connectivity between the AI and the ventral striatum (VS), but these areas were, if anything, slightly less connected when empathy was guiding decisions, as compared to acting towards the control.
The team's work may offer a way to learn more about people's motivations. Observing signals between regions could tell us why people have chosen a particular action – at least in the lab. “The impact of the motives on the interplay between different brain regions was so fundamentally different that it could be used to classify the motive of a person with high accuracy,” Hein said.
A larger question is what causes the ACC-AI connectivity associated with kindness. Is it genetic or learned, for example? “To answer this, long-term studies are needed that investigate the development of neural connectivities over the life span and under different social circumstances,” Hein told IFLScience.
“I hope that we will be able to do these kind of studies in the future. For now, our results show that neural connectivities that are relevant for social behaviors (such as the connectivity between the anterior insula and the cingulate cortex) are altered by particular social experiences. For example, in the case of selfish people these connectivities increase after experiencing empathy with another person. I think that these results speak against a strictly genetic determination.”
IFLScience recently covered another of Hein's papers, which suggested it is surprisingly easy to develop empathy towards people previously regarded as unworthy of it, perhaps because that connectivity is induced.