Chimpanzees may comfort others in distress in ways very similar to how people do, according to what may be the largest study of consolation in animals by far. The new findings in our closest living relatives could help shed light on the roots of empathy in humans.

The spontaneous consolation of someone in distress with a hug, a pat on the back or other friendly display of physical contact has been studied in human children as a sign of sympathetic concern for others for decades. This kind of demonstrative empathy is often thought to be a large part of what sets humanity apart from other animals.

To better understand how empathy might have evolved in our lineage, animal behaviorist Teresa Romero of Emory University and her colleagues studied roughly 30 chimpanzees housed outdoors at the Yerkes National Primate Research Center. Over a span of eight years they documented cases where uninvolved bystanders offered comfort to recent victims of aggression. Whereas most studies on animal consolation typically involve looking into a few hundred cases of conflicts and their aftermaths, "ours is based on an analysis of about 3,000 cases," Romero says.

Although anecdotes about chimpanzees' empathy have been plentiful, empirical evidence was very limited until now, Romero explains. The large amount of data that she and her colleagues collected helped them detect various trends by observing when consolation was offered in the forms of grooming, embraces, gentle touches and kisses. For instance, females were significantly more consolatory overall than males were.

Empathetic roots
"These results are in line with the results obtained in humans," says primatologist and sociobiologist Elisabetta Palagi of the University of Pisa in Italy, who did not take part in this study. "This is an adaptive behavior that is probably based on the strong emotional links between the mother and her infant till the first stages of life. The capacity to understand, foresee and respond promptly to the necessities of a baby is extremely important for the fitness of the mother, so females' empathic behavior has probably been favored by natural selection."

Additionally, a similar pattern was seen in the highest-ranking males, who frequently offered consolation. This likely reflected the general pacifying function of these males in chimpanzee life, the researchers say. Another effect of social roles in consolation: low-ranking chimpanzees received solace roughly half as often as higher-ranked victims.

Similarly to humans, chimpanzees were more likely to console kin and those socially close to them than others—about two to three times more so—and they were significantly more supportive with those who had comforted them in the past. Also, consolation occurred roughly 50 percent more when aggressors ignored victims and no reconciliation had occurred between them. The researchers suggest that means bystanders offering solace were sensitive to the neglected victims' need for comfort.

Many mammals may be capable of basic forms of empathy. The point of this research is not so much that our closest living relatives display empathy, "but the possible level of empathy reached by chimpanzees," Romero says.

The human-animal connection
The consolation observed in chimps goes beyond merely basic empathy, Romero notes—if the apes only understood how others felt, they would be expected "to selfishly seek alleviation of their own distress, probably turning away from the victim." Rather, the distressed chimpanzees seem to experience concern born from sympathy, leading them to seek out and help others. "The underlying mechanism of consolation in chimpanzees may be similar to humans," Romero says. She and her colleagues Miguel Castellanos and Frans de Waal detailed their findings online June 14 in Proceedings of the National Academy of Sciences.

"This kind of study highlights the continuity between humans and animals, not only from a morphological, anatomical and physiological point of view, but also from a psychological and emotional point of view," Palagi says. "The human mind, like body, has evolved in continuity with other animals."

One challenge with calling such consolation sympathetic concern is that the researchers were measuring behaviors, not emotions per se, says developmental psychologist Carolyn Zahn-Waxler of the University of Wisconsin–Madison, who did not participate in this research. Future work could also investigate chimp vocalizations or even facial expressions to help overcome this issue, she notes. "Having visited the Yerkes Center firsthand, I myself have no doubts these behaviors the researchers are detailing are parallel to the first forms of comforting behaviors we see in human children," Zahn-Waxler adds.

Future research could also investigate more distant relatives of humans. "To date, there is no evidence that consolation is present in monkeys," Palagi says, "but we are working on an interesting [monkey] species, the gelada, in which females are extremely bonded. Preliminary data suggests that true consolation could be present in this species and, if the data are confirmed, will be a further important step in understanding the consolation mechanism and the cognitive scaffold at its basis."