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Ape Aid: Chimps share altruistic capacity with people
Bruce Bower
Many researchers have asserted that only people will assist strangers without receiving anything in return, sometimes at great personal cost. However, a new study suggests that chimpanzees also belong to the Good Samaritan club, as do children as young as 18 months of age.
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MAY I HELP YOU? New experiments indicate that chimpanzees aid strangers, regardless of personal gain, much as people, including very young children, do. |
Without any prospect of immediate benefit, chimps helped both people and other chimps that they didn't know, and the 18-month-olds spontaneously assisted adults they'd never seen before, say psychologist Felix Warneken of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues.
The roots of human altruism reach back roughly 6 million years to a common ancestor of people and chimps, the researchers propose in the July PLoS Biology.
"Learning and experience are involved in altruistic helping, but our claim is that there is a predisposition [in chimps and people] to develop such behavior without explicit training," Warneken says.
His team conducted three experiments with adult chimps living on an island sanctuary in Uganda and two experiments with 18-month-old German children. In the chimp version of the first experiment, 36 animals watched one at a time from a barred enclosure as an experimenter in an adjacent room—who had had virtually no prior contacts with the animals—reached through the bars for a stick on the other side. The stick was within reach of only the observing chimp.
Most chimps snatched the stick and gave it to the experimenter, whether or not the experimenter offered a piece of banana as a reward. No assistance came if the experimenter didn't first reach in vain for the stick.
A similar trial with 36 youngsters yielded comparable altruistic behavior, regardless of whether the experimenter offered toys as a reward.
The second round of experiments included 18 chimps and 22 infants who had helped at least once in the first experiment.
The chimps still retrieved a stick for an experimenter, although they now had to climb a 2.5-meter-high platform to reach the item. The children navigated barriers and hurdles to get a pencil for an experimenter. No reward was offered in either case.
The third experiment tested nine chimps' willingness to aid other chimps that they neither knew nor were related to. One chimp watched another in a separate room try to enter an adjacent space through a chained door in order to obtain food. Only the observing chimp could remove a peg in its enclosure to release the chain, allowing the other chimp to nab a snack.
All but one observing chimp did just that in numerous trials.
"These are wonderful experiments and present a real challenge to previous findings," remarks anthropologist Joan B. Silk of the University of California, Los Angeles. Silk and other investigators have reported that chimps don't give food rewards to their comrades, even at no cost to the potential donor.
Chimps may help others who fail to achieve observable goals, as in the new experiments, Warneken suggests. Further studies need to compare individuals' reactions to different types of cooperative tasks, Silk says.
The results "come as no surprise to any field worker who has spent lots of time close to wild chimpanzees," comments anthropologist William C. McGrew of the University of Cambridge in England.
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