The trade-off between cooperation and intention-based fairness

Groups frequently ostracise members who are unable, rather than unwilling, to contribute to collective efforts, despite many people viewing such exclusions as fundamentally unfair. Across two experiments (N=520), we demonstrate that this apparent contradiction arises because, under ambiguity, when individuals cannot distinguish between intentional free-riding and genuine inability, groups face a dilemma: be tolerant and risk cooperation breaking down, or be intolerant and risk ostracising individuals who are unable to contribute and, arguably, deserve help. We show that depending on the economic costs of tolerance, groups adopt different strategies to address this dilemma. They either act in line with intention-based fairness ideals but risk cooperation decline or they adopt a more rigid stance and ostracize non-contributing group members, even when they know that these group members were unable to contribute. Our findings can elucidate why groups often act intolerantly towards vulnerable members, despite widespread norms endorsing intention-based fairness.