A laugh puts us in a good mood, even if it is someone else’s. In fact, there is something intrinsically contagious in the expressions of joy, and it seems that we are not the only ones to think so. Even our closest relatives, the great monkeys, are in fact led to experiment with positive emotions when they feel a conspecific laughing, so much so that they become more optimistic and behave more confident than usual. It is the result of a study published in Scientific Reports by two researchers from the University of Indiana.
The research involved some specimens of Bonobo, our closer cousins who – like chimpanzees – share with our species 98 percent of their genome. Like the other great monkeys, these animals emit characteristic sounds during the game and friendly interactions, which closely remember the laughter of our species, albeit in a less complex and articulated version. In short, it cannot be said – that they have our own sense of humor, but the Bonobo also laugh when they have fun in the company.
Is this why the authors of the study have wondered: also these monkeys find the joy of a conspecific contagious? To find out, they used a method known as “Cognitive Bias Test”, an experimental approach used in the research of animal psychology to evaluate the mood of the subjects, based on the fact that they consider some situations more or less positively.
The effect of a laugh
In the experiment, the researchers used two boxes. A black, in which the Bonobo have been trained the presence of food. And a white one, in which a culinary reward was never present during the training phase. Animals were therefore made to hear a sound: a laugh by another bonobo, or a neutral control noise. And therefore a gray box was presented, intermediate color between the two used during the training phase: the propensity to open it was interpreted as optimism, a positive mood that pushes to believe that inside all in all there is excellent chances of finding food. Conversely, if the animals did not open the gray box to win was obviously their natural reluctance, the habit of imagining the presence of food only inside the black boxes.
Well, what results did they get? After repeating the experiment a number of times, the researchers confirmed that by hearing the laughter of a conspecific, the Bonobo tend to open the gray box more often in search of a reward. “The tendency to behave more optimisticly after hearing a laugh suggests that the sound is enough to induce a positive emotional state in the Bonobo,” explains Erica Cartmiill, professor of anthropology and cognitive sciences of the University of Indiana, and co -author of the research. “As far as we know, this is the first study in which we managed to measure a change in mood in positive in non -human primates following a rapid experimental intervention”.
The results suggest that like human beings, even great monkeys let themselves be infected by the emotions of the other specimens of their own species. Something that in the past was believed to be the prerogative only of our species, and which represents a fundamental aspect of the ability to understand the emotions of others and put themselves in their shoes, that is, of what we call empathy. A capacity that perhaps – let the results of the new research hypothesize – has evolved well before our species evolved.
“Our results suggest that laughs in other great monkeys shares not only phylogenetic and behavioral characteristics with the human one, but perhaps also some of the same cognitive and emotional foundations”, concludes Sasha Winkler, researcher of the University of Indiana who collaborated in the study. “This emotional contagion seems to have been present in the descent line of primates long before the evolution of language”.