Fairness decision-making in younger and older adults and associated neural indices.

OBJECTIVES: Previous literature using the mini-ultimatum game (the mini-UG) suggests that older adults consider outcomes more than others' intentions during fairness-related decision-making, whereas younger adults show the opposite pattern. Age-related declines in theory of mind (ToM) and executive functioning (EF) have been suggested as potential mechanisms underlying these age-related differences, but specific mechanisms remain unclear. The present work examines whether and how neural and behavioral factors known to be related to ToM and EF are associated with age-related differences in fairness processing. METHOD: Thirty-six younger (Mage = 21.19, SDage = 3.14) and 36 older (Mage = 72.08, SDage = 5.87) participants completed both magnetic resonance imaging (MRI) anatomical brain scans and the mini-UG alongside behavioral measures of ToM and EF outside of the scanner. Volumes and cortical thickness of ToM- and EF-related brain regions were extracted. Computational modeling of participant mini-UG decisions estimated individuals' tendencies to consider intention vs. outcome information. RESULTS: Older adults relied more on outcomes than intention information, whereas younger adults showed the opposite pattern. Structural brain indices and behavioral measures did not mediate age-related differences in decision-making. However, dmPFC volumes moderated the age differences in decision-making, and EF, but not ToM, was positively associated with intention-based (vs. outcome-based) decisions across age groups. DISCUSSION: These findings extend prior work on age differences in intention-based vs. outcome-based fairness consideration by showing that dmPFC volume may be one factor contributing to age differences in related decisions.