Biased beliefs affect real-world decisions, including political solutions to societal challenges. One crucial example is environmental policy: people tend to underestimate the incentive effect of Pigouvian policies. Addressing biased beliefs at scale is then paramount. In the days leading up to...

We show in a public goods experiment on three continents that conditional cooperation is a universal behavioral regularity. Yet, the number of conditional cooperators and the extent of conditional cooperation are much higher in the U.S.A. than anywhere else.

The 1998 Kyoto protocol signalled a new earnestness of international intent toward addressing the perceived risk of climate change. Kyoto demands that developed nations turn their economies so as to hit differentiated, sub-1990 level carbon emission targets within the next decade or so. But when...