Inequity aversion in old age: An outcome bias in older adults’ socio-economic decisions

Little is known about how healthy aging affects decision making. Here we studied how the social economic decisions of younger (19–39 years) and older (75–100 years) adults depend on the intentions of agents and the outcomes of their actions. Participants played the role of a responder (R) in an Ultimatum Game. A proposer (P) offered them a specific division of lottery tickets, which they could either accept or reject. Crucially, in each trial they were told that P was constrained to choose between two divisions of lottery tickets, resulting sometimes in an intended unfair offer and others in an unintended unfair offer. In the critical intended unfair offer, P kept 8 tickets and offered 2 to R, but he could have chosen a fair 5P/5R split. In the critical unintended unfair offer, P kept 8 tickets and offered 2 to R, but the alternative involved the same 8P/2R split. The unintended unfair offer was rejected by most of older adults (67 %), but only by a minority of younger adults (28 %). In general, older adults were less affected than younger adults by contextual constraints relevant to inferring P's intentions. These findings suggest that aging brings about an outcome bias in social economic decision making.