The researchers worked with 23 chimps and 15 bonobos in two ape sanctuaries in the Republic of Congo. Alexandra Rosati designed two games to play with the apes, which were rescued orphans of the of the bushmeat trade, and therefore "as close as we can come to wild animals without actually being in the wild."
The first game delayed gratification by letting the apes choose a smaller food reward immediately or larger reward they have to wait for. The second game involved choosing between a known "safe" option and a "risky option."
The safe option was six peanuts under a bowl. The risky option was a bowl that contained either a delicious banana, or a dull piece of lettuce or cucumber.
Many apes became upset when they had to wait or when they took a risk and lost. The very tantrum-like responses ranged from "pout moans" and "screams" to scratching and banging on the bars of the enclosure.
"Some of the reactions look similar to a kid [shouting] 'no, I wanted it!'," said Dr. Rosati. The results, published in the journal PLoS One, show that feelings of frustration and regret are not unique to humans.
Reseachers also found that the chimps were more willing to take risks, and more patient than the bonobos. "These differences might be reflected in differences in how the apes choose to forage in the wild," said Rosati. "This might be why chimpanzees are more likely to engage in risky strategies like hunting."