A study in PLOS Biology reports that synchronizing activity between frontal and parietal brain regions using noninvasive electrical stimulation slightly increased participants’ willingness to share money in a standard economics task, including in choices that reduced their own payoff.
A research team led by Jie Hu of East China Normal University in China, working with colleagues at the University of Zurich in Switzerland, reported evidence that increasing coordination between two brain regions can nudge people toward more generous choices.
In experiments described in a February 10 paper in the open-access journal PLOS Biology, 44 participants completed 540 decisions in a Dictator Game. Across rounds, participants chose how to divide varying amounts of money with another person, and the options could leave them with either more or less money than their partner.
While participants made these decisions, the researchers used transcranial alternating current stimulation (tACS) aimed at frontal and parietal brain areas. The stimulation was designed to entrain neural rhythms at either a gamma frequency (reported in the paper as 72 Hz) or an alpha frequency (reported as 12 Hz), with a sham condition used for comparison.
The researchers found that strengthening gamma-band synchrony between the targeted regions produced a modest increase in altruistic choices compared with alpha-frequency stimulation and sham. In the paper’s analyses, the effect appeared mainly in situations of “disadvantageous inequality,” when the decision options tended to put the participant at a relative disadvantage compared with the partner.
Using computational modeling, the authors reported that gamma-frequency stimulation shifted how participants evaluated the options, increasing the weight placed on the other person’s outcome when deciding how to split the money.
The study did not directly record brain activity during stimulation. The authors said future work combining stimulation with methods such as electroencephalography (EEG) could help confirm how the intervention changes neural signals.
Coauthor Christian Ruff said, “We identified a pattern of communication between brain regions that is tied to altruistic choices. This improves our basic understanding of how the brain supports social decisions, and it sets the stage for future research on cooperation -- especially in situations where success depends on people working together.”
Hu added, “What’s new here is evidence of cause and effect: when we altered communication in a specific brain network using targeted, non-invasive stimulation, people’s sharing decisions changed in a consistent way -- shifting how they balanced their own interests against others’.”
Coauthor Marius Moisa said the team was surprised by the behavioral shift: “We were struck by how boosting coordination between two brain areas led to more altruistic choices. When we increased synchrony between frontal and parietal regions, participants were more likely to help others, even when it came at a personal cost.”
The findings add to evidence linking coordinated activity in frontal and parietal brain networks to social decision-making, though the reported behavioral change was small and measured in a controlled laboratory task.
