Choices Make Chimps Emotional
May 30, 2013

Apes Get Emotional When Faced With Choices

[ Watch the Video: Bonobo Decision-Making ]

Michael Harper for — Your Universe Online

In the Stanford University Marshmallow Experiment, children are given a simple choice: Eat one marshmallow now or wait a few minutes and get two marshmallows. The results are chock full of cute kids agonizing over their decision to wait for two marshmallows. Some of them even pantomime eating the one marshmallow, and one even sniffs it just to get a flavor of the treat.

Stanford University had more than cute kids in mind when they created this experiment in the 1960s. They also wanted to understand how well humans handled delayed gratification.

Alexandra Rosati from Yale University and Brian Hare from Duke University have studied the same effects on chimpanzees and Bonobo monkeys in Africa, observing the emotional responses of these animals to understand how they make their decisions.

"Psychologists and economists have found that emotions play a critical role in shaping how humans make complex decisions, such as decisions about saving or investing money. But it was not known if these processes are shared with other animals when they make decisions about their important resources–such as food,” said Rosati in a recent statement.

In a modified version of the Stanford University Marshmallow Experiment, Hare and Rosati created two experiments meant to measure the emotional reaction of bonobos and chimps when faced with a game of chance.

In the first experiment, the animals were given the choice to eat one piece of food now or three pieces of food later. The researchers slid a table with the options near the cage and if the animal chose the three pieces of food, they slid the table away for a moment. In an accompanying video (listed above), the bonobo begins to scratch himself and reach through the bars of the cage towards the pieces of food. According to Hare and Rosati, these are emotional responses in the animals. The researchers also found that both bonobos and chimps displayed some kind of emotional response after making their choice, either pouting because they had to wait for their food or lamenting their choice of instant gratification.

In another experiment, Hare and Rosati let the animals choose a better tasting treat, but they may have been given a less than favorable treat if their gamble did not pay off. In this experiment, some of the animals even tried to change their minds in the middle of the test once they were given the unsavory treat. Those animals which won the gamble, however, were understandably pleased with their choice.

The bonobos and the chimpanzees responded in species-specific ways, and some of them responded according to their own particular idiom.

While Hare and Rosati feel further research needs to be conducted to understand if these emotional responses can affect the animal´s choices, they did say their experiment proved that apes do express emotion when they´re faced with choices. This also adds to the long and ongoing list of similarities between humans and primates.

Their research is published in the journal PLoS ONE.