Are We Smart Enough to Know How Smart Animals Are?(42)

At this point, you may wonder why perspective taking was ever declared uniquely human. For this, we need to look at a series of ingenious experiments in the 1990s in which chimpanzees could gain information about concealed food either from an experimenter who had witnessed the hiding process or from another one who had been put in the corner with a bucket over his head. Obviously, they should ignore the second experimenter, who had no idea, and follow the directions of the first. They made no distinction, however. Or an ape could beg for cookies from an experimenter sitting out of reach with a blindfold over his eyes. Would the chimps understand that there was no point stretching out an open hand to someone who cannot see them? After a great variety of such tests, the conclusion was that chimpanzees fail to understand the knowledge that others have and don’t even realize that knowing requires seeing. It was a most peculiar conclusion, given that the main researcher himself relates how playful apes put buckets or blankets over their heads and walk around until they bump into each other. When he himself put things over his head, however, he immediately became the target of play attacks by these apes, who exploited his obscured vision.25 They knew he couldn’t see them and tried to catch him by surprise.

I knew a couple of juvenile male chimps who loved to throw rocks at us, practicing their impressive long-range aim, invariably doing so as soon as I moved my camera to my eye, which made me lose visual contact. Such behavior alone tells us that apes know something about the vision of others and that tests with blindfolds must therefore be missing something. But as happens so often among experimentalists, behavior in the testing room was given priority over real-life observations. As a result, human exceptionalism was loudly proclaimed, most dramatically by concluding that apes do not possess “anything remotely resembling a ToM.”26

This conclusion was warmly greeted and is still being broadcast today even though it has not held up to scrutiny. At my home institution, the Yerkes Primate Center, David Leavens and Bill Hopkins conducted tests in which they placed a banana outside a chimpanzee enclosure where humans regularly walked by. Would the chimps draw attention to get people to hand them the fruit? Would they distinguish between people who could see them and those who could not? If so, this would suggest that they grasped another individual’s visual perspective. The chimps did, because they’d give visual signals to people who looked in their direction, but they’d vocalize and bang on metal if people failed to notice them. They even pointed at the banana to clarify their wishes. One chimpanzee, afraid to be misunderstood, pointed first with her hand at the banana and then with a finger at her own mouth.27

Intentional signaling is not limited to captive apes, as became clear when scientists put a fake snake on the path of wild chimpanzees. Recording the apes’ alarm calls in a Ugandan forest, they found that calling is not just a reflection of fear, because the chimps vocalize regardless of whether the snake is near or far. It is rather a warning intended for others: they call more when others are present, especially friends who have failed to notice the serpent. Callers look back and forth between nearby chimps and the danger, calling more to companions who are na?ve about it than to those who already know. Callers thus specifically inform those who lack knowledge, likely because they realize how knowing requires seeing.28

A critical test of this connection was conducted by Brian Hare, then a student here at the Yerkes Primate Center. Brian wanted to know if apes exploit information about another’s visual input. A low-ranking individual was enticed to pick up food in front of a high-ranking one. This is a tricky thing to do, and most subordinates shy away from the confrontation. They were offered a choice between pieces of food that the dominant individual had seen being hidden and pieces hidden without him knowing. The subordinate, on the other hand, had watched it all. In an open competition, like an Easter egg hunt, the safest bet for the subordinate would be to pick only those food items that the dominant had no clue about. This is exactly what they did, showing that they understood that if the dominant had not seen the hiding process, he couldn’t know.29 Brian’s study threw the question of animal ToM wide open again. In an unexpected twist, one capuchin monkey at the University of Kyoto and several macaques at a Dutch research center recently passed similar tasks.30 This is why the whole notion that visual perspective taking is limited to our species is now in the trash bin. Each of the above experiments in and of itself may not be entirely watertight, but taken together they come down on the side of perspective-taking abilities in other species.

It is a testimony to Menzel’s pioneering work that we keep hiding food or snakes, and pitting guessers against knowers. It remains the classical paradigm to assess these capacities both in humans and in other species. Perhaps most telling is an experiment by Menzel’s son Charles. Like his father, Charlie Menzel is a deep thinker, unsatisfied with easy tests or simple answers. At the Language Research Center here in Atlanta, he’d let a female chimp named Panzee watch while he hid food in the pine forest around her outdoor enclosure. Charlie would dig a small hole in the ground to put a bag of M&Ms into it, or place a candy bar in the bushes. Panzee would follow the process from behind bars. Since she could not go where Charlie was, she would need human help to eventually get the hidden food. Sometimes Charlie would hide it after all other people had gone for the day. This meant Panzee could not communicate with anybody about what she knew until the next morning. When the caretakers arrived, they were unaware of the experiment. Panzee first had to get their attention, then provide information to someone who had no clue as to what she was “talking” about.