As humans, we like to think we're the only species capable of using others to get what we want. New research shows that chimpanzees, in the right circumstances, are also capable of social manipulation, highlighting a previously unknown cognitive capacity in our ape relatives.
Social animals are equipped with an assortment of cognitive tricks to help them deal with others, some good and some not so good. Wolves and dolphins, for example, participate in cooperative hunting, in which they work together to round up prey.
Various species of monkeys, birds, and rodents issue alarm signals, alerting other members of a group to an incoming threat. Some of these social skills can be used for nefarious or deceptive ends, such as male chickens who make a false food call to female chickens as a lure for sex.
But there are very few examples in which social animals physically use their cohorts as a means to an end, that is, when an individual uses another member of their in-group like a tool to achieve a desired goal.
Of course, humans excel at "social tool use" as this behaviour is known. Our large brains and unique cognitive capacities, say geneticists Sergey Gavrilets and Aaron Vose, "evolved via intense social competition in which social competitors developed increasingly sophisticated 'Machiavellian' strategies as a means to achieve higher social and reproductive success." It's our conniving, manipulative brains, according to this theory, that contributes to human nature and partly explains our evolutionary success.
But as a new paper published this month in the Journal of Comparative Psychology reveals, humans don't hold a monopoly on social tool use. A team of researchers from the University of St. Andrews, the University of Leipzig, and the Max Planck Institute for Psycholinguistics, have uncovered the faint glimmerings of Machiavellian intelligence in the brains of chimpanzees.
The researchers, led by Manon Schweinfurth of the School of Psychology and Neuroscience at St. Andrews, studied a group of semi-wild chimpanzees at the Chimfunshi field site in Zambia, which is one of the largest chimpanzee sanctuaries in the world. Going into the project, however, the scientists were actually expecting to observe instances of chimpanzee cooperation, but instead and quite unexpectedly, a lone adult male chimp changed the entire complexion of the experiment, and by consequence, the very nature of the study.
For the experiment, Schweinfurth and her colleagues presented a group of chimpanzees with a rather challenging apparatus consisting of a fruit juice fountain and a pair of buttons that released the juice. Frustratingly for the chimps, however, the fountain and the buttons were located 3m apart, which meant a single individual couldn't both press the buttons and satisfy their thirst at the same time. So, to get at the desired fruit juice, another individual was required.
It proved to be a frustrating predicament — except for a 24-year-old adult male chimpanzee named Bobby. This resourceful chimp quickly grasped the concept of social tool use, employing other members of his group — namely three younger members of the troop — to push the buttons while he reaped the rewards at the fountain. But this was no quid pro quo arrangement; Bobby did not return the favour.
Indeed, as the researchers pointed out in the study, this was an example of manipulation and not cooperation:
Bobby displayed several behaviours aimed at enticing the juveniles to press a pair of buttons that activated a juice fountain located 3 m away from them. His behaviour varied in the level of control over the juveniles. First, he actively recruited them by rolling or dragging them towards the buttons. In those situations, the juveniles seldom had the chance to escape and were under Bobby's almost full control and in constant contact.
Next, Bobby pushed the juveniles in the direction of the buttons. Because the buttons and the fountain were 3 meters apart, he had to release them to drink from the fountain. Hence, his control was limited, and the juveniles could decide whether to press the buttons or to escape. In the case of escaping, however, the social tool user successfully retrieved them in almost half of the cases, suggesting some form of control.
When these strategies failed, Bobby resorted to stereotypical chimpanzee begging behaviour, which included the blowing of raspberries with his mouth and reaching out with his arms. Incredibly, this lone adult male used other chimpanzees more than 100 hundred times to gain access to the juice.
For Schweinfurth, the most surprising aspect of the study, aside from the unprecedented observation of social tool use among chimps, was that the manipulated chimps didn't try to escape or avoid Bobby.
"They live in really large enclosures and could easily hide there," Schweinfurth told Gizmodo. "In addition, they could have sought help from other adults, which they commonly did in other situations. So, why did they let another individual use them? We think this might be explained by increased play behaviour of the user [Bobby] with his social tools [the juvenile chimps], which is highly rewarding to youngsters. Probably, the youngsters faced a trade-off between rewarding play and being used as a tool from time to time."
The researchers say it's now the "biggest data set" of social tool use recorded among nonhuman animals. Bobby's repeated use of other individuals as social tools is a complex behaviour, and potentially indicative of Machiavellian intelligence.
"It is really interesting that nonhuman animals use others repeatedly for their benefit," said Schweinfurth. "It is well known from humans, but we were not sure whether other animals are able to do this. Especially manipulating or using others repeatedly requires the actor to make sure that the tools do not avoid him, so that the actor can repeatedly use or manipulate them. A skill that is important for example in many political situations."
In terms of limitations, it's important to point out that only one individual, Bobby, was observed to exhibit this behaviour. It's possible that Bobby is an outlier in terms of his intelligence, or he had some previous experience with humans that somehow influenced his behaviour. Future observations of social tool use in other apes in different contexts would be good to corroborate these findings. Still, it's surprising that Bobby used a strategy that, for him, was spectacularly successful.
"This suggests that chimps can use others, but it is probably not the default strategy in dealing with others," explained Schweinfurth.
So yes, some chimpanzees, like some humans, are just manipulative arseholes.