Are We Smart Enough to Know How Smart Animals Are?(59)
The highest level of joint intentionality in the animal kingdom is perhaps achieved by killer whales. After spy-hopping to get a good look at a seal on an ice floe, several of them will line up and swim toward the floe at high speed in perfect unison. Their behavior creates a massive wave that washes the seal off the floe straight into some waiting mouths.
On land, lions, wolves, wild dogs, Harris’s hawks (teams of which control the pigeons at London’s Trafalgar Square), capuchin monkeys, and so on, exhibit plenty of tight teamwork, too. The Swiss primatologist Christopher Boesch has described how chimpanzees hunt colobus monkeys in Ivory Coast: some males act as drivers, while others take up distant positions high up in a tree as ambushers waiting for the monkey troop to escape in their direction through the canopy. Since these hunts take place in the dense jungle of Ta? National Park, and both the chimps and the monkeys are dispersed, it is hard to pinpoint what is going on in three-dimensional space, but it appears to involve role division and the anticipation of prey movement. The prey is captured by one of the ambushers, who potentially could quietly slink away with the meat but does exactly the opposite. During the hunt the chimps are silent, but as soon as a monkey is captured, they erupt in a pandemonium of hooting and screaming that draws everyone in, leading to a large cluster of males, females, and young jostling for position. I once stood under a tree (in a different forest) while this happened, and the deafening noise above me left little doubt about how highly chimps prize their meat. Sharing appears to favor hunters over latecomers—even the alpha male may go empty-handed if he failed to participate. The chimpanzees seem to recognize contributions to success. The communal feast that ensues is the only way to sustain this sort of cooperation, because why would anyone invest in a joint enterprise if not for the prospect of a joint payoff?40
These observations obviously contradict the view that chimpanzees, and other animals, lack joint action based on shared intentions. One can imagine the head butting between two scientists with such diametrically opposite views as Boesch and Tomasello, who have offices in the same building. Was their appointment as codirectors of the Max Planck Institute in Leipzig an experiment on how human collaboration fares in the face of disagreement? Given these divergent perspectives, let me return to the experiments that led Tomasello to his human uniqueness claim. After testing both children and apes on a cooperative pulling task, he concluded that only the children exhibit shared intentionality.
The question of comparability has come up before, however, and fortunately there are photographs of the respective setups.41 One shows two apes in separate cages, each with a little plastic table in front of him that he can pull closer with a rope. Oddly, the apes do not occupy a shared space, as in Crawford’s classical study. Their cages are not even adjacent: there is distance and two layers of mesh between them—a situation that hampers visibility and communication. Each ape focuses on its own end of the rope, seemingly unaware of what the other is up to. The photo of the children, in contrast, shows them sitting on the carpeting of a large room with no barriers between them. They, too, are using a pulling apparatus, but they sit side by side in full view of each other and are free to move around, touch each other, and talk. These different arrangements go a long way toward explaining why the children showed shared purpose, and the apes did not.
Had this comparison concerned two different species—rats and mice, say—we would never have accepted such dissimilar setups. If rats had been tested on a joint task while sitting side by side and mice while being kept apart, no sensible scientist would permit the conclusion that rats are smarter or more cooperative than mice. We’d demand the same procedure. Comparisons between children and apes get exceptional leeway, however, which is why studies keep perpetuating cognitive differences that, in my mind, are impossible to separate from methodological ones.
In view of the ongoing controversy, we decided to move away from pair-wise testing—whether separate or together—and develop a more naturalistic setup. I sometimes refer to it as our proof-in-the-pudding experiment, since we sought to determine once and for all how well chimps handle conflicting interests: what happens to cooperation in the face of competition? The only way to see which tendency prevails is to provide an opportunity for the chimpanzees to express both at the same time.
My student Malini Suchak came up with the right apparatus to test a colony of fifteen chimps at the Yerkes Field Station. Mounted on the fence of their outdoor enclosure was an apparatus that required very precise coordination to be moved closer to obtain rewards: either two or three individuals had to pull at exactly the same time at separate bars. To coordinate with two partners was harder than with only one, but the apes had no trouble either way. They were sitting spaced out but in full view of one another. Since the whole group was present, there were many possible partner configurations. The apes could decide who to work with while also being on the alert for competitors, such as dominant males or females, as well as freeloaders who might steal rewards without doing any work. They could freely exchange information and freely choose partners, but also freely compete. No large-scale experiment of this kind had ever been tried.
If it is true that chimps can’t overcome competition, the test should produce total chaos! The colony should descend into a bickering bunch of apes, fighting over rewards and chasing one another away from the test site. Competitiveness should kill all shared objectives. I knew chimps long enough, however, that I didn’t worry much about the outcome of this test; I had studied conflict resolution among them for decades. Despite their poor reputation, I had seen too many scenes of chimpanzees trying to keep the peace and reduce tensions to worry that they would all of a sudden abandon such efforts.