“”Emotions are known to influence a wide range of cognitive functions, such as memory, attention and decision -making“, reminds AFP Sasha Winkler, co-author of the study published Thursday in Scientific Reports.
But positive emotions are less well studied than negative affects such as fear, which “have obvious behavioral correlates, such as immobilization or leak, easy to observe and measure“, notes the researcher in evolutionary anthropology at Duke University (United States), according to whom this research bias is also explained by the”reluctance to attribute emotions to animals“.
Laughter is thus traditionally considered to be the characteristic of man. However, there are many similarities between it and the signals issued by other animals during the game.
The big apes produce vocalizations resembling laughter when they are tickled or during sudden games, just like human children.
These vocalizations share a common evolving origin with human laughter and scientists believe that they are used to reduce the risk that the game is interpreted as an assault.
They could be the vector of an emotional contagion, a process by which emotional signals emitted by an individual trigger similar states in others.
To verify the influence of laughter, the authors of the study conducted an experience with bonobos of the Center for Studies and Conservation Ape Cognition and Conservation Initiative to monks (United States).
Empathy
This required training for two to four months. “”One of the main difficulties was that bonobos only participated if they wanted to: they had the choice to voluntarily separate from their group to participate in the sessions in another room“, Says Ms. Winkler.
Mali, a 14 -year -old bonobo female, and Teco, Nyota and Kanzi, three males of 12, 24 and 41, first familiar with a black box containing food and an empty white box.
The researchers led them to repel the white, which did not contain a reward. Before adding randomly three boxes of ambiguous colors, ranging from light gray to dark gray, which contained food only in half of the cases.
During some tests, they released bonobos laughter records, while others were accompanied by a wind noise, serving as control.
Bonobos approached the black box in 93% of cases and the white box in only 1%.
When confronted with gray boxes, they approached dark boxes more frequently than clear boxes. But they were three times more likely to go and check the gray boxes when they heard laughter.
“”They tended to behave more optimistic“, summarize the authors.
These results support the theory that communicative signals have “evolved mainly to modify the behavior of receivers by influencing their emotional states, rather than to transmit precise information“, Ms. Winkler advances.
“”That the simple fact of hearing a laugh, without any visual or social context, can influence decision -making in bonobos shows how large these emotional effects can be“, She adds.
Emotional contagion is considered an essential component of empathy, which plays a role “important in the evolution of prosocial behavior, allowing large -scale cooperation that is observed in human societies“Continues the anthropologist.
“”Understanding when our common ancestors with other great apes have developed these aspects of empathy has important implications to better understand our own sociability“She says.