Thesis defense

Environmental adversity and prosocial preferences, and a new methodology to increase the external validity of economic games

Niels Lettinga
Practical information
30 June 2021


Alex Cristia - École Normale Supérieure
Nicolas Claidière - CNRS Aix Marseille University
Alberto Acerbi - Brunel University
Coralie Chevallier - École Normale Supérieure


Humans trust others to do the right thing, we cooperate with others to our mutual benefit and we take part in collective actions to overcome complex problems. But we can also be selfish. Growing up or living in adverse environments seems to have an effect on cooperation. We tested whether environmental adversity is associated with decreased cooperation, and whether this effect is mediated by individuals’ life-history strategies. We indeed found evidence for these relationships, but only when cooperation was measured via self-reported questionnaires, not when it was measured with economic games.

A question emerges from these results concerning the accuracy of the methods used to measure people’s prosocial preferences. Specifically, why do economic games seem to lack external validity and how can this be improved. We proposed a new methodology of repeating economic games over time to decrease the variability in economic games decisions and subsequently increase their external validity.

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