"Western, Educated, Industrialized, Rich and Democratic (WEIRD) societies"
The main point of the paper is very important. People in these kinds of societies are different, and it is not right to generalize their traits to all humans:
Here, our review of the comparative database from across the behavioral sciences suggests both that there is substantial variability in experimental results across populations and that WEIRD subjects are particularly unusual compared with the rest of the species—frequent outliers. The domains reviewed include visual perception, fairness, cooperation, spatial reasoning, categorization and inferential induction, moral reasoning, reasoning styles, self-concepts and related motivations, and the heritability of IQ. The findings suggest that members of WEIRD societies, including young children, are among the least representative populations one could find for generalizing about humans.
One notable thing from the paper is that, when playing the Ultimatum Game, people in WEIRD societies are far more 'fair' than people in primitive societies. Americans were much more likely to split money evenly than people in other societies. This is not the only study to show that, contrary to what many people claim, being in a free-market society tends to foster a sense of fairness. The authors speculate:
It may be that what behavioral economists have been measuring among undergraduates in such games is a specific set of social norms, culturally evolved for dealing with money and strangers, that have emerged since the origins of agriculture and the rise of complex societies.