The Closest Relatives to Humans Also Prefer a Glass That's Half Full

Humans aren't the only ones that like positivity. It turns out that apes also prefer a glass that's half full. Scientists have discovered that chimpanzees and bonobos are susceptible to "glass half empty" thinking.

People are known to rate a burger as more tasty when it is described as "75 percent lean" than when it is described as "25 percent fat," even though it's the same thing. In addition, people are more willing to recommend a medical procedure when it has a 50 percent success rate than when they are told it has a 50 percent chance of failure.

Now, though, researchers have found that humans aren't the only ones influenced by this type of presentation. The researchers presented 23 chimps and 17 bonobos with a choice between two snacks: a handful of nuts and some fruit. In one series of experiments, the fruit was framed positively-by offering one piece of fruit with a 50 percent change of a surprise bonus piece.  In another experiment, the apes were offered two pieces of fruit for the fruit option, but if the fruit was chosen then the apes had a chance of being shortchanged and only receiving one.

In this case, the researchers found that when the fruit was framed positively, the apes were more likely to choose it. When it was framed negatively, the apes were less likely to choose it and instead preferred the nuts. In addition, the preference for the positive option was especially strong in males.

"People tend to prefer something more when you accentuate its positive attributes than when you highlight its negative attributes, even when the options are equal," said Christopher Krupenye, one of the researchers, in a news release. "Historically, researchers thought these kinds of biases must be a product of human culture, or the way we're socialized, or our experience with financial markets. But the fact that chimps and bonobos, our closest living primate relatives, exhibit the same biases suggests they're deeply rooted in our biology."

The findings are published in the journal Biology Letters.

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).