The first evidence for animal culture came from sweet-potato-washing Japanese macaques on Koshima Island. Initially, the washing tradition spread among same-aged peers, but nowadays it is propagated transgenerationally, from mother to offspring.
Like the scientist who gave us the mirror-anesthesia hypothesis, the one who wrote an entire article debunking the Koshima discovery was a nonprimatologist who, moreover, never bothered to set foot on Koshima or check his ideas with the fieldworkers who had camped for decades on the island. Again, I can’t help but wonder about the mismatch between conviction and expertise. Perhaps this attitude is a leftover of the mistaken belief that if you know enough about rats and pigeons, you know everything there is to know about animal cognition. It prompts me to propose the following know-thy-animal rule: Anyone who wishes to stress an alternative claim about an animal’s cognitive capacities either needs to familiarize him-or herself with the species in question or make a genuine effort to back his or her counterclaim with data. Thus, while I admire Pfungst’s work with Clever Hans and its eye-opening conclusions, I have great trouble with armchair speculations devoid of any attempt to check their validity. Given how seriously the field of evolutionary cognition takes variation between species, it is time to respect the special expertise of those who have devoted a lifetime getting to know one of them.
The Thaw
One morning at Burgers’ Zoo, we showed the chimpanzees a crate full of grapefruits. The colony was in the building where it spends the night, which adjoins a large island, where it spends the day. The apes seemed interested enough watching us carry the crate through a door onto the island. When we returned to the building with an empty crate, however, pandemonium broke out. As soon as they saw that the fruits were gone, twenty-five apes burst out hooting and hollering in a most festive mood, slapping one another’s backs. I have never seen animals so excited about absent food. They must have inferred that grapefruits cannot vanish, hence must have remained on the island onto which the colony would soon be released. This kind of reasoning does not fall into any simple category of trial-and-error learning, especially since it was the first time we followed this procedure. The grapefruit experiment was a one-time event to study responses to cached food.
One of the first tests of inferential reasoning was conducted by American psychologists David and Ann Premack, who presented Sadie, a chimpanzee, with two boxes. They placed an apple in one and a banana in the other. After a few minutes of distraction, Sadie saw one of the experimenters munching on either an apple or a banana. This experimenter then left, and Sadie was released to inspect the boxes. She faced an interesting dilemma, since she had not seen how the experimenter had gotten his fruit. Invariably, Sadie would go to the box with the fruit that the experimenter had not eaten. The Premacks ruled out gradual learning, because Sadie made this choice on the very first trial as well as all subsequent ones. She seemed to have reached two conclusions. First, that the eating experimenter had removed his fruit from one of the two boxes, even if she had not actually seen him do so. And second, that this meant that the other box must still hold the other fruit. The Premacks note that most animals don’t make any such assumptions: they just see an experimenter consume fruit, that’s all. Chimpanzees, in contrast, try to figure out the order of events, looking for logic, filling in the blanks.36
Years later the Spanish primatologist Josep Call presented apes with two covered cups. They had learned that only one would be baited with grapes. If Call removed the tops and let them look inside the cups, the apes chose the one with grapes. Next, he kept the cups covered and shook first one, then the other. Only the cup with grapes made noise, which was the one they preferred. This was not too surprising. But making things harder, Call would sometimes shake only the empty cup, which made no noise. In this case, the apes would still pick the other one, thus operating on the basis of exclusion. From the absence of sound, they guessed where the grapes must be. Perhaps we are not impressed by this either, as we take such inferences for granted, but it is not all that obvious. Dogs, for example, flunk this task. Apes are special in that they seek logical connections based on how they believe the world works.37
Here it gets interesting, because aren’t we supposed to go for the simplest possible explanation? If large-brained animals, such as apes, try to get at the logic behind events, could this be the simplest level at which they operate?38 It reminds me of Morgan’s provision to his canon, according to which we are allowed more complex premises in the case of more intelligent species. We most certainly apply this rule to ourselves. We always try to figure things out, applying our reasoning powers to everything around us. We go so far as to invent causes if we can’t find any, leading to weird superstitions and supernatural beliefs, such as sports fans wearing the same T-shirt over and over for luck, and disasters being blamed on the hand of God. We are so logic-driven that we can’t stand the absence of it.
Evidently, the word simple is not as simple as it sounds. It means different things in relation to different species, which complicates the eternal battle between skeptics and cognitivists. In addition, we often get tangled up in semantics that aren’t worth the heat they generate. One scientist will argue that monkeys understand the danger posed by leopards, whereas another will say that monkeys have merely learned from experience that leopards sometimes kill members of their species. Both statements are really not that different, even though the first uses the language of understanding, and the second of learning. With the decline of behaviorism, debates on these issues have fortunately grown less fiery. By attributing all behavior under the sun to a single learning mechanism, behaviorism set up its own downfall. Its dogmatic overreach made it more like a religion than a scientific approach. Ethologists loved to slam it, saying that instead of domesticating white rats in order to make them suitable to a particular testing paradigm, behaviorists should have done the opposite. They should have invented paradigms that fit “real” animals.