How the perceived cost of prosocial action inspires observers to contribute

Conventional wisdom suggests that people are less likely to help when doing so involves a high cost. However, through five experiments, this work demonstrates that when a donor's prosocial action is perceived as costlier, observers are more likely to follow the donor and engage in the same prosocial behaviour (Study 1a, N = 154; Study 1b, N = 127). The effect cannot be attributed to observers’ original preferences for costly prosocial action itself (Study 2; N = 401). Rather, it occurs because when the prosocial action is costlier, observers are more likely to perceive the donor as more intrinsically motived, which, in turn, enhances the desirability of the prosocial action, leading to a higher likelihood that the observers would engage in the same action (Study 3; N = 250). We further show that this effect is attenuated when the donor clearly demonstrates her/his extrinsic motivation (Study 4; N = 149).