Children as young as three years of age are willing to share a prize equally with a peer, but only if both children previously collaborated in order to earn their reward.
Credit: MPI for Evolutionary Anthropology
Young chimpanzees eat their 'spoils' after a feeding. Even jointly gained resources are rarely shared by chimpanzees.
Credit: Felix Warneken
SYDNEY: Young children are more likely to share rewards equally with their peers if collaboration is involved than if they received an unexpected and unearned 'windfall'.
Adult humans produce most of their resources through collaborative efforts and try to distribute these equally, and now an international team of researchers have found that if very young children collaborated to produce the rewards, they would similarly divide these equally.
The researchers, led by Katharina Hamann from the Max Planck Institute for Evolutionary Anthropology in Germany, compared this behaviour to resource production and sharing amongst chimpanzees, one of humans' closest living relatives. While chimpanzees hunt as groups for food in the wild, they will usually only share under pressure of harassment.
"Evolutionarily, one can imagine that even when collaborative hunts became important, individual foraging was still possible and necessary; however, since the individual gain may not have been enough for even the individual him/herself, sharing was at least not obligatory," said Hamann of the study published in the current issue of Nature.
Equal division of the spoils
The study shows that children take note of whether collaboration was required to produce rewards such as toys. Pairs of two- and three-year-old children had to manipulate an apparatus to gain toys, either individually (with each child being able to move the apparatus independently) or as part of a collaborative effort.
Once this was done, they could retrieve the toys; however, one child would receive three toys - a windfall - and the other child would only retrieve one. The three-year-olds, and to some degree the two-year-olds, shared the toys more often after a collaboration, but less frequently after an individual effort or no work.
"The interdependence of actions in pursuing a joint goal in a collaborative scenario is highlighting the importance of the other child and that it 'deserves' a fair share of the rewards," Hamann said.
Passing the fruit around
A comparison of chimpanzee behaviour suggested that they did not share more often after collaboration. In a similar study by the same researchers, pairs of chimpanzees had to manipulate a board that held four pieces of fruit that were unevenly distributed, with one chimpanzee receiving two pieces and the other receiving one.
The chimpanzees were able to either claim the extra piece of fruit or actively choose to share. In most cases, the chimpanzee that only received one piece instantly tipped the board towards itself. In the remaining tests its partner, who had already received two pieces, claimed the fruit.
Different foraging habits
However, Frans de Waal from Emory University in the U.S. conducted a similar study with capuchins a decade ago, which demonstrated that monkeys share more with partners who have helped them get the food than when they obtained the food on their own. "In the wild (capuchins) sometimes hunt together just like chimpanzees and share the meat at the end."
De Waal said the complicated nature of the apparatus could have affected the results. "I think that chimpanzees are very hard to test and if the apparatus is too complex they don't understand that how it works."
Hamann said the researchers ensured that the chimpanzees understood the mechanism. "Overall, the chimpanzees participated successfully: They collaborated to obtain the food, and they shared from time to time. As capuchins are more distantly related to us, their evolution must have taken a different path, and different motivational-cognitive mechanisms are likely to be at work. More studies are necessary to shed light on this issue."
