Rationally, the "smart" response would be to take any offer, no matter how low, but participants routinely reject offers lower than $10 or $20, said Manfred Milinski, an evolutionary biologist at the Max Planck Institute for Evolutionary Biology in Germany, who was not involved in the study. Most people offer around $40 to their partners and in some countries, people offer more than half of the money to partners, Milinski told LiveScience.
Selfish apes But past studies of the ultimatum game in chimpanzees (with raisins) had suggested our closest living relatives were "rational maximizers" who would accept even the stingiest offering without getting ruffled. They even accepted zero-raisin offers without even a squawk. That suggested their main goal - getting more tasty raisins - overrode any meager sense of fairness they may have had.
Those studies, however, instantly started a new round of the game if the apes accepted, but made them wait a full minute after rejecting the offer, raising the possibility that the apes realized it was more fruitful to accept quickly to get more raisins, rather than rejecting low-ball offers.