Social proximity and kinship have been shown to heavily influence our tendency to altruistic behavior. Evidence about group formation, the development of prosocial motivation during adolescence as well as on both endocrinological and psychological mechanisms involved in prosociality also highlight the likely inherently parochial character of human altruism. Meanwhile, other-regarding motivations can play a central role in vaccination behavior. It is not well-understood, however, what types of other-regard are involved, and what role they play.
In this study, I use a 2x2 factor survey experiment to investigate the differing effects of narrow (family-oriented) versus wide (purely altruistic) other-regard. I find that stimulating either of these types of other-regard leads to increases in vaccination propensity. However, the effects differ markedly between types of subjects: subjects in a settled family constellation display large effects of narrow, but not wide, other-regard, whereas others display the opposite. Wide other-regard therefore appears to be crowded out by narrow when humans enter pair-bonding. To maintain sufficient vaccination uptake, this distinction should be taken into consideration when designing messages to the public.