Are We Smart Enough to Know How Smart Animals Are? (14 page)

Inspired by an Aesop fable, crows have been tested to see if they will throw stones into a tube filled with water to bring floating rewards within reach. They do.

The Ancient Greek poet Aesop may have had an inkling of these talents given his fable
The Crow and the Pitcher
. “A Crow, half-dead with thirst,” so the fabulist went, “came upon a Pitcher.” There wasn’t enough water in the pitcher for the crow to be able to drink it. He tried to reach in with his beak, but the water level was too low. “Then a thought came to him,” as Aesop put it, “and he took a pebble and dropped it into the Pitcher.” Many more pebbles followed until the water had risen enough for a drink. It seems an unlikely feat, but it has now been replicated in the lab. The first was an experiment on rooks, a corvid that in the wild does not use any tools. The rooks were presented with a vertical water-filled tube with a floating mealworm just out of reach. The water level would have to be raised if the rook were to reach the delicacy. The same experiment was carried out with New Caledonian crows, known as real tool experts. True to the dictum that necessity is the mother of invention, and confirming Aesop’s story several millennia later, both crow species successfully solved the floating worm puzzle by using pebbles to raise the water level in the tube.
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Let me add some caution, though, because it is unclear how insightful this solution was. For one thing, all the birds had been pretrained using a slightly different task. They had received ample rewards for plunging stones into a tube. Moreover, while they were facing the tube with the mealworm, stones had been conveniently placed right next to it. The experimental setup strongly suggested the solution, therefore. Imagine that Köhler had taught his chimps to stack boxes! We would never have heard of him, as it would have undermined any claims of insight. In the course of testing, the crows did learn that large stones work better than small ones, and that there is no point dropping stones into a pipe filled with sawdust. Rather than working these answers out in their minds, however, it may have been a matter of fast learning. Perhaps they noticed that adding stones to water brought the mealworm closer, which led them to persist.
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When we recently presented our chimpanzees with a floating peanut task, a female named Liza solved it right away, adding water to a plastic tube. After some vigorous but ineffective kicking and shaking of the tube, Liza abruptly turned around, went to the drinker to fill her mouth, and returned to the tube to add water. She made several more trips to the drinker before she got the peanut at the right level to reach it with her fingers. Other chimps were less successful, but one female tried to pee into the tube! She had the right idea even though the execution was flawed. I have known Liza all her life and am sure that this problem was brand new to her.

Our experiment was inspired by a floating peanut task conducted on a large number of orangutans and chimpanzees, a subset of which cracked the puzzle at first sight.
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This is especially remarkable, since—unlike the crows—the apes had no pretraining; nor did they find any tools nearby. Rather, they must have conjured the effectiveness of water in their heads before going out of their way to collect it. Water doesn’t even look like a tool. How hard this task is became clear from tests on children, many of which never found the solution. Only 58 percent of eight-year-olds came up with it, and only 8 percent of four-year-olds. Most children frantically try to reach the prize with their fingers, then give up.
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These studies have set up a friendly rivalry between primate chauvinists and corvid aficionados. I sometimes teasingly accuse the latter of “ape envy,” because in every publication they draw a contrast with the primates, saying the corvids are either doing better or at least equally well. Calling their birds “feathered apes,” they make outrageous claims such as “The only credible evidence of technological evolution in nonhumans to date comes from New Caledonian crows.”
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Primatologists, on the other hand, wonder how generalizable corvid tool skills are, and if “feathered monkeys” isn’t a better moniker for the birds. Are crows one-trick ponies, like the clam-smashing otters or the Egyptian vultures that throw rocks at ostrich eggs? Or do they have the intelligence to take on a broad array of problems?
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This issue is far from settled, because even though ape intelligence has been studied for over a century, corvid tool studies have come up only in the last decade.

An intriguing new entry is the use of metatools by New Caledonian crows. A crow is presented with a piece of meat that it can retrieve only by using a long stick, but this stick is behind bars wide enough for the crow’s beak but not its head. The crow is unable to reach the tool. In a nearby box, however, lies a short stick suitable for retrieving the long one. To solve this problem, the right order is to pick up the short stick, use it to fetch the long one, and then apply the latter stick for the meat. The crow needs to understand that tools can be used on nonfood objects and to take steps in the right order. Alex Taylor and coworkers used wild New Caledonian crows on Maré Island, placed temporarily in an aviary. They tested seven crows, all of which managed metatool use; three followed the right sequence on the first attempt.
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Presently, Taylor is trying out tasks with even more steps, and the crows are keeping up with the challenge. This is most impressive, and considerably better than monkeys, which have trouble with stepwise tasks.

Given the evolutionary gulf between primates and corvids, and the many ancestral species of mammals and birds in between that don’t use tools, we are dealing with a typical example of convergent evolution. Independently, both taxonomic groups must have faced a need for complex manipulations of items in their environment, or other challenges that stimulated brain growth, which led them to evolve strikingly similar cognitive skills.
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The arrival of corvids on the scene illustrates how discoveries of mental life ripple across the animal kingdom, a process best summarized by what I’ll call my cognitive ripple rule:
Every cognitive capacity that we discover is going to be older and more widespread than initially thought
. This is rapidly becoming one of the best-supported tenets of evolutionary cognition.

As a case in point, we now have evidence of tool use outside mammals and birds. Primates and corvids may well show the most sophisticated use of technology, but what to think of partially submerged crocodiles and alligators balancing large sticks on their snouts? Crocodilians do so especially in pools and swamps near rookeries during the nesting season, when herons and other wading birds are in desperate need of sticks and twigs. You can imagine the scene: a heron lands on a log in the water from which it wants to pick up an attractive branch, but suddenly the log comes to life and grabs the bird. Perhaps crocs initially learn that birds land on them when branches float nearby and then extend this association by making sure to be near branches when herons are nesting. From there, it may be a small step to cover oneself with objects that attract birds. The problem with this idea, however, is that there are actually very few free-floating branches and twigs around. There is too much demand for them. Is it possible that the crocs—which the scientists lament are historically taken to be “lethargic, stupid, and boring”—bring their stick-lures with them from far away? This would be another spectacular cognitive ripple, one that extends deliberate tool use to the reptiles.
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The final example, which may again stretch the definition of a tool, concerns the veined octopus in the seas around Indonesia. Here we are dealing with an invertebrate: a mollusk! It has been seen collecting coconut shells. Since octopuses are a favorite food of many predators, camouflage is one of their main goals in life. Initially, the coconut shells yield no benefit, however, because they have to be transported, which only draws unwanted attention. Stretching its arms into rigid limbs, the octopus tiptoes over the sea floor while holding its prize in some of its other arms. Awkwardly walking to a safe lair, it can then use the shells to hide underneath.
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A mollusk collecting tools for future protection, however simple, goes to show how far we have come since the days when technology was thought to be the defining characteristic of our species.

4
TALK TO ME

Speak and I shall baptize thee!

—French Bishop to a chimpanzee, early 1700s
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W
e associate research in the natural habitat with sacrifice and bravery, since fieldworkers must tackle the unpleasant and dangerous creatures of the tropical rainforest, from bloodsucking leeches to predators and snakes. By contrast, students of captive animals are thought to have it easy. But we sometimes forget how much courage it takes to defend one’s ideas in the face of staunch opposition. Most of the time this occurs just among academics, which is disagreeable rather than hazardous, but Nadia Kohts faced lethal risks. Her full name was Nadezhda Nikolaevna Ladygina-Kohts, and she lived and worked early last century in the shadow of the Kremlin. Under the sinister influence of the would-be geneticist Trofim Lysenko, Joseph Stalin had many a brilliant Russian biologist either shot or sent to the Gulag for thinking the wrong thoughts. Lysenko believed that plants and animals pass on traits gained during their lifetime. The names of those who disagreed with him became unmentionable, and entire research institutes were closed down.

It was in this oppressive climate that Kohts, with her husband Alexander Fiodorovich Kohts—founding director of Moscow’s State Darwin Museum—set out to study ape facial expressions, inspired by
The Expression of the Emotions in Man and Animals
by that bourgeois Englishman, Charles Darwin. Lysenko was distinctly ambivalent about Darwin’s theory, some of which he labeled “reactionary.” Staying out of trouble became a major preoccupation of the Kohtses, who hid documents and data among their taxidermy collection in the museum basement. They wisely put a large statue of the French biologist Jean-Baptiste Lamarck—famous proponent of the inheritance of acquired characteristics—at the museum entrance.

Kohts published in French, German, and most of all her native Russian. She wrote seven books, of which only one was translated into English, long after its appearance in 1935. The English version of
Infant Chimpanzee and Human Child
, edited by me, appeared in 2002. The book compares the emotional life and intelligence of a young chimpanzee, Joni, with that of Kohts’s little son, Roody. Kohts studied Joni’s reactions to pictures of chimpanzees and other animals, and to his own mirror image. Even though Joni was probably too young to recognize himself, Kohts describes how he would entertain himself in front of his reflection by pulling weird faces and sticking out his tongue.
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Kohts is little known compared to Wolfgang Köhler, who conducted his groundbreaking ape research from 1912 through 1920. I wonder what she knew about it while working in Moscow from 1913 until Joni’s premature death in 1916. While Köhler is widely recognized as a pioneer of evolutionary cognition, pictures of Kohts’s work leave little doubt that she was on exactly the same track. One of the museum’s glass cases features Joni’s mounted body surrounded by ladders and tools, including sticks that fit into each other. Was Kohts overlooked by science due to her gender? Or was it her language?

I learned about her from the writings of Robert Yerkes, who came to Moscow to discuss her projects through an interpreter. In his books, Yerkes described Kohts’s work with the greatest admiration. There is a good chance, for example, that Kohts invented the matching-to-sample (MTS) paradigm, a staple of modern cognitive neuroscience. MTS is nowadays being applied to both humans and animals in countless laboratories. Kohts would hold up an object for Joni, then hide it among other objects in a sack and let him feel around to find the first one. The test involved two modalities—vision and touch—demanding that Joni make a choice based on his memory of the previously seen model.