© Joseph HeinrichJoseph Heinrich conducts behavioural economics experiments in the countryside of southern Chile
The Ultimatum Game works like this: You are given $100 and asked to share it with someone else. You can offer that person any amount and if he accepts the offer, you each get to keep your share. If he rejects your offer, you both walk away empty-handed.
How much would you offer? If it's close to half the loot, you're a typical North American. Studies show educated Americans will make an average offer of $48, whether in the interest of fairness or in the knowledge that too low an offer to their counterpart could be rejected as unfair. If you're on the other side of the table, you're likely to reject offers right up to $40.
It seems most of humanity would play the game differently. Joseph Henrich of the University of British Columbia took the Ultimatum Game into the Peruvian Amazon as part of his work on understanding human co-operation in the mid-1990s and found that the Machiguenga considered the idea of offering half your money downright weird - and rejecting an insultingly low offer even weirder.
"I was inclined to believe that rejection in the Ultimatum Game would be widespread. With the Machiguenga, they felt rejecting was absurd, which is really what economists think about rejection," Dr. Henrich says. "It's completely irrational to turn down free money. Why would you do that?"
