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

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.

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.

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.

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.