Indiana University:

While laughter is often considered uniquely human, tied to language and sense of humor, all great apes produce remarkably similar vocalizations during play that share evolutionary origins with human laughter.

In a new study, an international team led by two Indiana University researchers has discovered that bonobos, our closest living relatives along with chimpanzees, tend to be more optimistic after hearing the laughter of their fellow apes—and these findings have implications for understanding the evolution of positive emotions in primates, including humans.

The study, titled “Bonobos tend to behave optimistically after hearing laughter” and recently published in Scientific Reports, reveals that laughter seems to enhance positive emotions in bonobos, just like in humans, and influence their decision-making to expect more positive outcomes.

This research is the first to demonstrate that great ape laughter may have cognitive and emotional effects similar to those seen in humans. Sasha Winkler, a Visiting Research Scholar in the Cognitive Science Program in the College of Arts and Sciences at Indiana University Bloomington, and Erica Cartmill, Professor of Anthropology and Cognitive Science in the College, authored the study with collaborators Isabelle Laumer from the Max Planck Institute of Animal Behavior in Germany and Heidi Lyn from the University of South Alabama.

In the study, the researchers conducted a cognitive bias test—a method in animal psychology that assesses mood by seeing whether subjects interpret uncertain situations more positively or negatively—to determine if hearing laughter would make bonobos more likely to approach ambiguous stimuli, a behavioral indicator of optimism.

“We know that other apes, like chimpanzees, have contagious laughter during play,” said Dr. Winkler, the lead author of the study. “We were wondering if that behavior could be explained by positive emotions produced from the sound itself.” [Continue reading…]