Humans can try to imagine the Umwelt of other organisms. Being a highly visual species ourselves, we buy smartphone apps that turn colorful images into those seen by people without color vision. We can walk around blindfolded to simulate the Umwelt of the vision-impaired in order to augment our empathy. My most memorable experience with an alien world, however, came from raising jackdaws, small members of the crow family. Two of them flew in and out of my window on the fourth floor of a student dorm, so I could watch their exploits from above. When they were young and inexperienced, I observed them, like any good parent, with great apprehension. We think of flight as something birds do naturally, but it is actually a skill that they have to learn. Landing is the hardest part, and I was always afraid they would crash into a moving car. I began to think like a bird, mapping the environment as if looking for the perfect landing spot, judging a distant object (a branch, a balcony) with this goal in mind. Upon achieving a safe landing, my birds would give happy “caw-caw” calls, after which I would call them to come back, and the whole process would start anew. Once they became expert flyers, I enjoyed their playful tumbling in the wind as if I were flying among them. I entered my birds’ Umwelt, even though imperfectly.
Whereas Uexküll wanted science to explore and map the Umwelten of various species, an idea that deeply inspired students of animal behavior known as ethologists, philosophers of the last century were rather pessimistic. When Thomas Nagel, in 1974, asked, “What is it like to be a bat?” he concluded that we would never know.3 We have no way of entering the subjective life of another species, he said. Nagel did not seek to know how a human would feel as a bat: he wanted to understand how a bat feels like a bat. This is indeed beyond our comprehension. The same wall between them and us was noted by the Austrian philosopher Ludwig Wittgenstein, when he famously declared, “If a lion could talk, we could not understand him.” Some scholars were offended, complaining that Wittgenstein had no idea of the subtleties of animal communication, but the crux of his aphorism was that since our own experiences are so unlike a lion’s, we would fail to understand the king of fauna even if he spoke our tongue. In fact, Wittgenstein’s reflections extended to people in strange cultures with whom we, even if we know their language, fail to “find our feet.”4 His point was our limited ability to enter the inner lives of others, whether they are foreign humans or different organisms.
Rather than tackle this intractable problem, I will focus on the world that animals live in, and how they navigate its complexity. Even though we can’t feel what they feel, we can still try to step outside our own narrow Umwelt and apply our imagination to theirs. In fact, Nagel could never have written his incisive reflections had he not heard of the echolocation of bats, which had been discovered only because scientists did try to imagine what it is like to be a bat and did in fact succeed. It is one of the triumphs of our species’ thinking outside its perceptual box.
As a student, I listened in amazement as Sven Dijkgraaf, the head of my department at the University of Utrecht, told the story of how, at about my age, he was one of only a handful of people in the world who was able to hear the faint clicks that accompany a bat’s ultrasonic vocalizations. The professor had extraordinary hearing. It had been known for more than a century that a blinded bat can still find its way around and safely land on walls and ceilings, whereas a deafened one cannot. A bat without hearing is like a human without sight. No one fully understood how this worked, and bats’ abilities were unhelpfully attributed to a “sixth sense.” Scientists don’t believe in extrasensory perception, however, and Dijkgraaf had to come up with an alternative explanation. Since he could detect a bat’s calls, and had noticed that the rate increased when bats encountered obstacles, he suggested that the calls help them traverse their environment. But there was always a tone of regret in his voice about the lack of recognition he had received as the discoverer of echolocation.
This honor had gone to Donald Griffin, and rightly so. Assisted by equipment that could detect sound waves above the 20 kHz range of human hearing, this American ethologist had conducted the ultimate experiments, which furthermore demonstrated that echolocation is more than just a collision warning system. Ultrasound serves to find and pursue prey, from large moths to little flies. Bats possess an astonishingly versatile hunting tool.
No wonder Griffin became an early champion of animal cognition—a term considered an oxymoron until well into the 1980s—because what else is cognition but information processing? Cognition is the mental transformation of sensory input into knowledge about the environment and the flexible application of this knowledge. While the term cognition refers to the process of doing this, intelligence refers more to the ability to do it successfully. The bat works with plenty of sensory input, even if it remains alien to us. Its auditory cortex evaluates sounds bouncing off objects, then uses this information to calculate its distance to the target as well as the target’s movement and speed. As if this weren’t complex enough, the bat also corrects for its own flight path and distinguishes the echoes of its own vocalizations from those of nearby bats: a form of self-recognition. When insects evolved hearing in order to evade bat detection, some bats responded with “stealth” vocalizations below the hearing level of their prey.
What we have here is a most sophisticated information-processing system backed by a specialized brain that turns echoes into precise perception. Griffin had followed in the footsteps of the pioneering experimentalist Karl von Frisch, who had discovered that honeybees use a waggle dance to communicate distant food locations. Von Frisch once said, “The life of the bee is like a magic well, the more you draw from it, the more there is to draw.”5 Griffin felt the same about echolocation, seeing this capacity as yet another inexhaustible source of mystery and wonder. He called it, too, a magic well.6
Since I work with chimpanzees, bonobos, and other primates, people usually don’t give me a hard time when I speak of cognition. After all, people are primates, too, and we process our surroundings in similar ways. With our stereoscopic vision, grasping hands, ability to climb and jump, and emotional communication via facial muscles, we inhabit the same Umwelt as other primates. Our children play on “monkey bars,” and we call imitation “aping,” precisely because we recognize these similarities. At the same time, we feel threatened by primates. We laugh hysterically at apes in movies and sitcoms, not because they are inherently funny—there are much funnier-looking animals, such as giraffes and ostriches—but because we like to keep our fellow primates at arm’s length. It is similar to how people in neighboring countries, who resemble each other most, joke about each other. The Dutch find nothing to laugh at in the Chinese or the Brazilians, but they relish a good joke about the Belgians.
But why stop at the primates when we are considering cognition? Every species deals flexibly with the environment and develops solutions to the problems it poses. Each one does it differently. We had better use the plural to refer to their capacities, therefore, and speak of intelligences and cognitions. This will help us avoid comparing cognition on a single scale modeled after Aristotle’s scala naturae, which runs from God, the angels, and humans at the top, downward to other mammals, birds, fish, insects, and mollusks at the bottom. Comparisons up and down this vast ladder have been a popular pastime of cognitive science, but I cannot think of a single profound insight it has yielded. All it has done is make us measure animals by human standards, thus ignoring the immense variation in organisms’ Umwelten. It seems highly unfair to ask if a squirrel can count to ten if counting is not really what a squirrel’s life is about. The squirrel is very good at retrieving hidden nuts, though, and some birds are absolute experts. The Clark’s nutcracker, in the fall, stores more than twenty thousand pine nuts, in hundreds of different locations distributed over many square miles; then in winter and spring it manages to recover the majority of them.7