Brain imaging study uncovers new details about the neurobiology of trusting one’s neighbors

New research suggests that the salience network of the brain is associated with our sense of trust in our neighbors. The study, published in Psychiatry Research: Neuroimaging, found brain volumes in three specific regions were associated with interpersonal trust.

“Trust has always been an interesting and intangible topic in the world of neuroscience. Although there are multiple studies examining the neurobiology behind trust either through neuroimaging and/or brain analyses, there is still a great deal we do not know about the formation of trust despite it playing such an integral role in basic human interactions,” said study author Mohona Sadhu, a psychiatry resident at the University of Texas Southwestern Medical Center.

“Furthermore, investigations between specific brain regions and trust of neighbors have not, to our knowledge, ever been studied before in a large diverse multi-ethnic population. Given how important building trust among neighbors is in order to develop a sense of community, foster social cohesion, and create a safe environment leading to cooperation for survival, exploration of brain regions associated with fostering neighbor trust may lead to better understanding of human behaviors.”

The researchers examined data from 1,527 participants in the Dallas Heart Study, a multiethnic population-based study that has collected extensive information from individuals in Dallas County.

The new research specifically examined participants who had undergone brain imaging at the University of Texas Southwestern Medical Center and had responded to a questionnaire about neighbor trust.

“Three brain regions were determined to have a statistically significant relationship with neighbor trust,” Sadhu told PsyPost. “Right caudal anterior cingulate cortex thickness and left caudate volume were inversely correlated with neighbor trust while left amygdala volume was positively correlated with neighbor trust.”

“Given that anterior cingulate cortex, caudate, and amygdala are all integral parts of the salience network, the results of the study suggest that the salience network, the network responsible for detecting and filtering emotional and sensory stimuli resulting in complex human behaviors, may play a role in the formation of interpersonal trust.”

“Furthermore, higher level of education, older age, and non-African American race (i.e. Caucasian and Hispanic) were also shown to have a positive relationship with neighbor trust. Thus, the take away may be that both the salience network and population demographics play a role in the formation of neighbor trust,” Sadhu said.

The study — like all research — includes some limitations.

“Due to limitations of the data available in the DHS, not all brain regions included a cortical thickness measure. Therefore, our results and conclusions about cortical thickness can only be made with regard to those specific regions and not universally about cortical thickness,” Sadhu explained.

“Additionally, due limitations in the original study design by DHS, which included a seven year gap between the questionnaire and MR scan, the possibility of structural brain changes affecting the various regions along with the effects of aging is also a limitation. Although the effects of aging may have led to variation in the results, the time lapse between the individuals was uniform and consistent with an average of 6.8 years.”

“A question yet to be answered is what role does social environment and/or life experiences play in relation to neural circuitry changes that may also influence the formation of interpersonal trust. The answer could reflect differences between genetic and environmental effects on interpersonal trust formation. This study, however, was not able to answer that question,” Sadhu told PsyPost.

Despite the new findings, there is still much to learn about how the structure and function of the human brain is related to social decision-making.

“A defining characteristic of humans is the ability to trust and cooperate with genetically unrelated strangers. While this study provided new insight into the brain regions associated with trust of neighbors, there are still many unanswered questions regarding the development of interpersonal trust and the role both genetics and social environment play,” Sadhu added.

“Given the importance of trust in neighbors resulting in the creation of beneficial communities and overall improved health, additional future studies are needed in order to continue to better understand the driving forces both socially and neurobiologically behind these social systems.”

The study, “Relationship between trust in neighbors and regional brain volumes in a population-based study“, was authored by Mohona Sadhu, Theresa de Freitas Nicholson, Rogelio Garcia, Susana Lampley, Marian Rain, Andrew Fritz, Bayan Jalalizadeh, Erin Van Enkevort, Jayme Palka, and E. Sherwood Brown.