I suggest that we view the results described in this article as indicating that humans frequently act like monkeys, not vice versa. Further, what is being measured as fairness may better be seen as the basis for envy and greed. It is not surprising that monkeys have the ability to display these tendencies, but they are not the epitome of what makes us human.

Phil von Voigtlander
Northport, Mich.

I don’t see how the experiment demonstrates a sense of fairness in monkeys. The monkey rejecting the cucumbers could have been thinking, in effect, not “I should get a grape because she did,” but “I should get a grape because they’re available and I prefer them.” If monkeys shown grapes and cucumbers but given only grapes reacted less vigorously when they didn’t see another monkey getting grapes, that would be more convincing.

Henry Jones
Baton Rouge, La.

Researcher Sarah Brosnan says that monkeys tested without partners displayed greed for grapes but grew more likely to exchange their tokens for cucumbers by the end of their sessions. In contrast, in the test with an over-rewarded partner, the monkeys grew less likely to make that exchange. Brosnan interprets this as signaling that a monkey becomes more upset about an inferior reward when its partner receives the better one .–S. Milius