Experimenting with Social Norms, edited by Jean Ensminger and Joseph Henrich, compiles and synthesizes a rich combination of experimental and ethnographic findings from an international team of anthropologists and economists aimed at investigating the tensions between cooperation and self-interest across diverse human societies. How do societies manage to solve problems collectively, enticing individuals to forego their own narrow short-term economic interests in a way that benefits the whole group, and fosters mutually beneficial exchange? And furthermore, how does the decision to subordinate one’s self-interests for the larger group—or what Ensminger and Henrich call prosocial behavior—vary among different societies based on locally acquired social norms and motivations?

Using experimental economics games, this team examined levels of fairness, cooperation, and norms for punishing those who violate expectations of equality across a diverse swath of societies, from hunter-gatherers in Tanzania to a small town in rural Missouri. The researchers employed the following games to assess each group’s level of prosociality:

Dictator Game
Two players from the same community, interacting anonymously, are given a sum of money equivalent to one day’s wages to split. Player 1, assigned to be the “dictator,” decides how to allocate the money between the two players. Both players receive the actual amounts of money that Player 1 “dictates.” In Europe and the U.S. a fifty-fifty split is considered a “fair” outcome.

Ultimatum Game
This version of the dictator game adds an ultimatum: Though Player 1 decides how to allocate the money, Player 2 may reject the offer—in which case, neither party receives anything. The behavior of Player 1 in this scenario has elements of both fairness and strategy, while the behavior of Player 2 in this game captures the price that people are willing to pay to punish Player 1 for what they perceive to be an unfair offer. The willingness to punish an anonymous partner for unfairness, at a personal monetary cost, can be interpreted as prosocial behavior because this punishment may alter Player 1’s future interactions with other group members.

Third-Party Punishment Game
In this experiment, two people play the Dictator Game with the addition of a third anonymous player— endowed with an amount of money equivalent to half the amount given to the first two players—who has the option of using any part of his or her money to punish Player 1 for making an unfair offer to Player 2. Unlike the Ultimatum Game, in the Third-Party Punishment Game, the person paying a price to do the punishing is not the injured party.

The recent swell of media attention around French economist Thomas Piketty’s new book, Capital in the Twenty-First Century, has propelled it to the New York Times’ bestseller list and the #1 spot on Amazon. An ambitious examination of income inequality, Piketty’s work illuminates the mechanisms that allow wealth to concentrate in the top 1% of society. He argues that when the rate of return on existing capital exceeds the rate of economic growth, the wealth of the rich will accumulate faster than that of the rest of society, exacerbating inequality and heralding in a new Gilded Age.

Though Piketty’s book has been the subject of a robust discussion between journalists and pundits, how does it stack up before a Nobel Prize winning economist? In his review of the book for The New Republic, Robert Solow—the 1987 winner of the Nobel Prize in Economics and the Russell Sage Foundation’s Robert S. Merton Scholar—says that Piketty’s theory on inequality is right. Calling Piketty’s paradigm the “rich-get-richer dynamic,” Solow describes the book as a “new and powerful contribution to an old topic.” Piketty’s theory, Solow further notes, also portends that not only will the rich get richer across the board, but inherited wealth in society will increase faster than that of recently earned (and therefore more merit-based) fortunes.