Summary: Using transcranial magnetic stimulation to suppress excitability in the dorsolateral prefrontal cortex enhanced prosocial behaviors.
HSE University researchers have found that if cortical excitability is suppressed, the conflict between self-interest and prosocial motivations is resolved in favor of the latter—but only in cases when this conflict is really present.
The paper, titled “The Role of the Prefrontal Cortex in Prosocial and Self-Maximization Motivations: An rTMS study,” was published in Scientific Reports.
Many theories of economic behavior ignore the existence of prosocial motivation in humans. It is believed that people pursue exclusively selfish interests and are not interested in making decisions that are also beneficial to others. However, neuroscientific research proves that this is not the case.
For example, when interacting with a stranger, it is more profitable for an individual to allocate resources in whatever manner allows them to gain as much as possible. But people are more likely to share equally, even when there is no punishment for selfishness. That is how our desire for cooperation and justice works, which is probably inherent.
Researchers know that the right dorsolateral prefrontal cortex is involved in choosing between self-interest and prosocial motivation. But it is still not entirely clear what exact behavior is triggered by the activation of this area. In some studies, suppression of the region’s activity led to prosocial behavior, while in others it resulted in an active pursuit of selfish interests. In some cases, it produced no effect at all.
In order to specify the role of the dorsolateral prefrontal cortex in such situations, HSE University researchers carried out an experiment with the use of transcranial magnetic stimulation (TMS), which suppresses the excitability of the stimulated area of brain.
A total of 46 participants aged 18 to 27 were split into two groups. The first group received dorsolateral prefrontal cortex stimulation for five to seven minutes, while the second group received stimulation of the brain areas responsible for visual perception. The participants then played two economic games in a row—a dictator game and a generosity game.
In the dictator game, a participant playing the dictator shares a certain amount of resources between themselves and a partner. The partner is only capable of accepting the dictator’s offer. In the generosity game, one participant also decides on how much to give to their partner. However, the amount of resources they get themselves is fixed and does not depend on the other player’s share.
The researchers found that suppressing the excitability of the dorsolateral prefrontal cortex made participants of the dictator game give more to their partner compared to those whose visual cortex was stimulated. No such effect was observed in the generosity game: participants shared in about the same manner regardless of the type of stimulation.
“These results may prove that the dorsolateral prefrontal cortex is involved only if the participant experiences a conflict between self-interest and prosocial motivation, while its suppression leads to the resolution of this conflict in favor of other people’s interests. That’s why the stimulation of this area only impacts behavior when the game motivates this conflict,” said Oksana Zinchenko, research fellow at the International Laboratory of Social Neurobiology and co-author of the paper.
“In the generosity game, there was no conflict between self-interest and prosocial motivation, since the participant’s personal profit did not depend on their generosity towards their partner. In the dictator game, this conflict is more apparent.”
About this behavioral neuroscience research news
Author: Press Office Source: HSE Contact: Press Office – HSE Image: The image is credited to HSE
The Role of the Prefrontal Cortex in Prosocial and Self-Maximization Motivations: An rTMS study
More than a decade of neuroimaging and brain stimulation studies point to a crucial role for the right dorsolateral prefrontal cortex (rDLPFC) in prosocial behavior. The intuitive prosociality model postulates that the rDLPFC controls intuitive prosocial behavior, whereas the reflective model assumes that the rDLPFC controls selfish impulses during prosocial behavior.
The intuitive prosociality model implies that the transient disruption of the rDLPFC should increase voluntary transfers in both dictator and generosity games. In contrast, the reflective model suggests that the transient disruption of the rDLPFC should decrease transfers in the dictator game, without affecting voluntary transfers in the generosity game, in which selfish motives are minimized.
The aim of this paper was to compare predictions of the intuitive and reflective models using the classic dictator game and generosity game and continuous theta burst stimulation (cTBS). In this study, two groups of healthy participants (dictators) received either cTBS over the rDLPFC or right extrastriate visual areas. As shown by the results, the transient disruption of the rDLPFC significantly promoted prosocial motives in the dictator game only, particularly in the trials with the lowest dictator’s costs.
These findings partially support the notion that the rDLPFC controls intuitive prosocial behavior.