Triadic balance in the brain: Seeking brain evidence for Heider’s structural balance theory

Structural balance theory is a foundational theory of social network research. Despite enduring interest in seeking network evidence for the theory, the fundamental question of why people care about structural (im)balance has received relatively little attention. The original answer to the question, dating back to Heider’s work six decades ago, is that structural imbalance causes a person to experience cognitive dissonance and sentimental disturbance. In this paper, we used a state-of-the-art neuroimaging technique to test the argument. Our study shows that individuals’ psychological states, evidenced by the activation of brain areas, are different when they are situated in unbalanced rather than balanced triads. More specifically, the differences in the brain activation between triadic imbalance and balance were found in brain regions known for processing cognitive dissonance, as discovered by previous research. Our study provides novel brain evidence in support of Heider’s original account for the psychological and biological foundations of structural balance theory in the formation of social networks.