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by Amelia Sanchez | DES MOINES – 2025/07/03 10:00:00
Bonobos, closely related to humans along with chimpanzees, exhibit increased optimism upon hearing laughter, according to new research. The study sheds light on the evolutionary connections between positive emotions in primates, including humans.
While laughter is often seen as a uniquely human trait linked to language and humor, great apes produce similar vocalizations during play, suggesting shared evolutionary origins. The study, published in Scientific Reports, indicates that laughter enhances positive emotions in bonobos, influencing their decision-making towards more positive expectations, similar to humans.
Sasha Winkler,a visiting research scholar at Indiana University Bloomington,and Erica Cartmill,professor of anthropology and cognitive science,collaborated with Isabelle Laumer from the Max Planck Institute of Animal Behavior and Heidi Lyn from the University of South Alabama on the study. Their findings demonstrate that great ape laughter may have cognitive and emotional effects comparable to those observed in humans.
Bonobos and cognitive Bias
The researchers employed a cognitive bias test, a method used in animal psychology to gauge mood by assessing whether subjects interpret uncertain situations positively or negatively. The test aimed to determine if hearing laughter would make bonobos more inclined to approach ambiguous stimuli, which is a behavioral sign of optimism.
According to Winkler, “We know that other apes, like chimpanzees, have contagious laughter during play. We were wondering if that behavior could be explained by positive emotions produced from the sound itself.”
“Studies like ours can definitely help to untangle the evolutionary building blocks of empathy, communication, and cooperation in humans.”
The study involved training bonobos to approach black boxes that consistently contained food rewards and avoid white boxes that were always empty. After exposing the bonobos to either bonobo laughter or a control sound, they were presented with gray boxes they had never encountered. The researchers found that bonobos, like humans and other animals in positive moods, were more optimistic and anticipated greater rewards when faced with ambiguous cues like the grey boxes.
Winkler explained,”Think of it like the rose-colored glasses effect. The bonobos were much more likely to approach the grey boxes after hearing laughter, treating them like the rewarded boxes, and indicating a more optimistic expectation of finding a treat.”
Evolutionary Roots of laughter
The study offers the first experimental evidence that great apes not only produce laughter but also undergo emotional changes upon hearing it, highlighting the deep evolutionary roots of the cognitive effects of positive vocalizations.
“The tendency to behave more optimistically after hearing laughter suggests that the sound alone induced a positive emotional state in bonobos,” Cartmill noted. “This is the first study of which we’re aware to measure a positive affect shift in non-human primates from a brief experimental intervention.”
Great apes, including bonobos, chimpanzees, gorillas, and orangutans, all produce vocalizations similar to human laughter during play. Acoustic analysis from previous research indicates that these vocalizations share an evolutionary origin with human laughter, suggesting that human laughter evolved from a sound made during play in a common ancestor of all great apes.
winkler stated, “Our results suggest that laughter in other apes shares not only phylogenetic and behavioral similarities with human laughter but also perhaps some of the same cognitive-emotional underpinnings.” She added, “This emotional contagion appears to have been present in the primate lineage long before the evolution of language.”
