Duke research: Chimps and bonobos both get emotional when life serves up bummers

Los Angeles TimesJune 30, 2013 

Brian Hare is an evolutionary anthropologist at Duke University. (Duke University photo)

DUKE UNIVERSITY

Ever let out a groan, bang your fist or scratch your head in frustration when life didn’t go your way?

Well, the same holds true for our closest living animal relative, the chimpanzee. In a study published last month in the journal PLOS One, researchers concluded that chimps and bonobos both get emotional when life serves up bummers.

A three-minute wait for food, or a surprise helping of boring old lettuce instead of delicious banana slices can inspire an epic tantrum of moans, screams, body scratching and hand banging, according to Duke University researchers.

Although most adult humans are able to regulate their emotions when faced with delays or disappointment, researchers say the basis of those feelings is rooted in our evolutionary past and played a fundamental role in the development of human decision-making.

Understanding what angers apes can provide insights into our own mental processes, according to the study authors, evolutionary anthropologists Brian Hare and Alexandra Rosati.

“Emotions play an important role in human choice processes,” they wrote.

To see how disappointment and frustration played into the animals’ decision-making, study authors devised a series of experiments in which 23 chimpanzees and 15 bonobos were faced with various food-related dilemmas.

In some cases, the apes were offered two choices of food – one of which might consist of a single slice of papaya, while the second choice had a greater number of slices.

In order to obtain the larger, preferred portion, however, the test subjects had to wait up to three minutes.

Those apes who wanted to play it safe went for the first choice, while risk takers opted for the concealed treat.

If the gamble paid off and the test subject received a large helping of their favorite fruit, there was little fuss. But if their wager resulted in a less desirable item such as cucumbers or lettuce, they threw a fit, or tried to switch their choice at the last minute. (The experiments were conducted in separate ape sanctuaries in central Africa; apes who showed no interest in playing the games were allowed to drop out of the study.)

Chimps were much more willing to wait for food, and were much more likely to assume risk. The bonobos were less patient and more likely to go with the safe choice.

Chimps chose a risky reward about 65 percent of the time, while bonobos went for the mystery treat only about 40 percent of the time.

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