Frans de Waal: Moral behavior in animals

By Lambert Strether of Corrente.

Some of us became aware of primatologist Frans de Waal back in 2008 through his concept of inequity aversion:

[W]e did a study in which capuchin monkeys received either a grape or a piece of cucumber for a simple task.

If both monkeys got the same reward, there never was a problem. Grapes are by far preferred (as real primates, like us, they go for sugar content), but even if both received cucumber, they’d perform the task many times in a row.

However, if they received different rewards, the one who got the short end of the stick would begin to waver in its responses, and very soon start a rebellion by either refusing to perform the task or refusing to eat the cucumber.