Keeping it for yourself or your sister? Experimental evidence on birth order effects on resource distribution between kin and non-kin

Florence Lespiau (1) , Astrid Hopfensitz (2) , Gwenaël Kaminski (3, 4)

1 APSY-V - Laboratoire Activités Physiques et Sportives et processus PSYchologiques : recherches sur les Vulnérabilités / Université de Nîmes
2 TSE-R - Toulouse School of Economics
3 CLLE-LTC - Cognition, Langues, Langage, Ergonomie
4 IUF - Institut universitaire de France

Birth order supposedly influences individuals' cooperative attitudes: firstborns are more family-oriented and favor their kin, while laterborns are more likely to turn to non-kin. However little direct experimental evidence exists concerning costly resource sharing between full siblings. The present study investigates sharing decisions with respect to a monetary resource by full sisters when either: (i) interacting with an unknown individual or (ii) their sister. A total of 112 sisters from 56 different families participated in an economic experiment regarding the distribution of an actual monetary reward. In line with kin selection theory, the results showed that participants favor their sister over strangers. Additionally, firstborns invested more costly resources in their sister (than laterborns) while they knew that the latter did not.

Mots clés: Resource allocation; Decision-making; Equality; Siblings

Domaines: Sciences cognitives

Florence Lespiau, Astrid Hopfensitz, Gwenaël Kaminski. Keeping it for yourself or your sister? Experimental evidence on birth order effects on resource distribution between kin and non-kin. Journal of Economic Psychology, 2021, 82, ⟨10.1016/j.joep.2020.102335⟩. ⟨hal-03130344⟩