Bonobos, which along with chimpanzees are humans' closest living relatives, can be quick with a sympathetic hug and quick to recover from their own stressful events. And they have their mothers to thank for it.
That's the upshot of a new study of behavior among bonobos – primates that researchers have found to host remarkably humanlike abilities to empathize or to forgo aggression for cooperation in a society that gives females higher status than males.
In the past, studies of empathy and an ability to console others among bonobos have focused on who is giving and receiving comfort and under what circumstances, explains Frans de Waal, who heads the Living Links program at Emory University's Yerkes Primate National Research Center in Atlanta. The studies also have looked for parallels between bonobos and young children on these points.
But researchers had yet to explore the emotional traits among individual bonobos that are needed to develop empathy, explains Dr. de Waal, who was one of two Emory researchers conducting the study.
In human children, studies have indicated that orphans have a hard time keeping their emotions in check or bouncing back quickly from an emotional setback, compared with children raised by at least a mother, if not both parents. This study points to the same patterns in young bonobos.
Individuals who have a hard time regulating their emotions, "like orphans, for example,... are not capable of overcoming their own emotions in order to pay attention to the emotions of others," de Waal says.
The research was conducted by de Waal and Zanna Clay, a postdoctoral fellow at Emory and the lead author of the paper formally reporting the results in the current issue of the Proceedings of the National Academy of Sciences.
The duo initially aimed to study a wider array of behaviors among bonobos, including conflict resolution. Their subjects: bonobos at the Lola ya Bonobo sanctuary in the Democratic Republic of the Congo.
The sanctuary accepts animals that had been rescued from being turned into a bushmeat meal or sold as pets. Many of the bonobos in the study came to the sanctuary as orphans, although humans had served as temporary foster mothers for some. Others at the sanctuary were born there.
The researchers also were aware of studies conducted with human children who had been orphaned and their abilities to regulate their emotions. So they looked to see if the same patterns held with bonobos.
The bonobos included 13 adults, 11 adolescents, and 12 juveniles, some of which were orphans.
The researchers found that juveniles watching another bonobo endure a stressful event, such as aggression from another bonobo, were more likely to console the victim than were either adults or adolescents. Adults and adolescents were about equally likely to wrap an arm around a distressed bonobo. Among juveniles, those reared by mothers were three times more likely to console than were the orphaned juveniles, regardless of gender.
The team also precisely measured the time it took for a victim to get over the attack, de Waal says – based on how long an individual screamed, whether the individual resumed screaming once he or she had stopped initially, and how long it took for the individual to return to normal activities.
These primates displayed a wide range of responses.
Within two or three seconds, some aggrieved parties had gotten a grip and returned to normal activities, de Waal says, adding, "Other individuals keep screaming for three minutes" after enduring an attack.
"We found that the individuals who are the slowest to get out of their distress are the ones who have the least attention to the distress of others," he says. Also, they tended to be the orphans.
The same held true for the length of time young bonobos would play with each other. Individuals who had a mother's influence tended to play longer than those who did not, suggesting a higher level of social adjustment.
Many people still believe that animals are uninhibited in the way they express their emotions, de Waal says, "but all the inhibitions that we have in our emotional lives are present in chimpanzees and bonobos."
Indeed, a capacity for empathy and other emotions appears to be widely expressed in mammals – from rats to elephants to cats and dogs.