Older Adults Show Altered Default Mode and Executive Control Network Connectivity during Fairness Decisions

bioRxiv, August 2025

40894566

Dominic S. Fareri, Yi Yang, Rita M. Ludwig, James B. Wyngaarden, Derrick Dwamena, Katherine Hackett, Tania Giovannetti, David V. Smith

The ability to navigate diverse social contexts, such as interacting with different individuals, is crucial across the lifespan and has implications for fraud susceptibility. However, the neural mechanisms supporting social decisions in older adults within varied social contexts remain largely unknown. This study investigated how age and partner similarity modulate neural activation and network connectivity during fairness-related decision making and whether individual differences in behavioral sensitivity to fairness norm violations correlate with neural activities. Younger (18-35) and older (65-80) adults underwent fMRI while playing an ultimatum game with ostensible partners of a similar or dissimilar age. We used regression to model choice behavior and whole-brain fMRI analyses to examine functional activation and connectivity of the Default Mode (DMN) and Executive Control (ECN) networks. Behaviorally, choices did not differ by age, partner similarity, or their interactions. In contrast, neuroimaging revealed interactions between age, partner similarity, and individual sensitivity to norm violation. Younger adults exhibited positive DMN-anterior cingulate connectivity when interacting with a similar-aged partner, whereas older adults showed a negative connectivity. Furthermore, younger adults demonstrated a negative correlation between their sensitivity to norm violation and the partner-identity effect in ECN-medial prefrontal cortex connectivity, whereas older adults showed a positive correlation. Our findings indicate a brain-behavior dissociation where different neural mechanisms support similar behavioral outcomes across age groups. These opposing patterns of neural responses suggest age-related functional reorganizations, which may represent compensatory strategies that enable older adults to preserve behaviors similar to that of their younger counterparts.