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Given how easily we string the words animal and cognition together as if there were nothing to it—as if these words might even belong together!—it is hard to imagine the struggle we went through to reach this point. Some animals were considered good learners or hard-wired for clever solutions, but cognition was way too big a word for what they did. Even though for many people animal intelligence is self-evident, science never takes anything at face value. We want proof, which with regard to animal cognition has now become overwhelming—so much so, in fact, that we risk forgetting the immense resistance that we had to overcome. This is why I have paid ample attention to the history of our field. There were early pioneers, such as K?hler, Kohts, Tolman, and Yerkes, and a second generation, such as Menzel, Gallup, Beck, Shettleworth, Kummer, and Griffin. The third generation, to which I myself belong, includes so many evolutionary cognitivists that I am not going to list them here, but we too faced an uphill battle.

I can’t count the number of times I have been called naïve, romantic, soft, unscientific, anthropomorphic, anecdotal, or just a sloppy thinker for proposing that primates follow political strategies, reconcile after fights, empathize with others, or understand the social world around them. Based on a lifetime of firsthand experience, none of these claims seemed particularly audacious to me. So one can imagine what happened to scientists suggesting awareness, linguistic capacities, or logical reasoning. Every claim was picked apart and held up against the light of alternative theories, which invariably sounded simpler given that they derived from the behavior of pigeons and rats in the confines of a Skinner box.

They were not always so simple, though—accounts based on associative learning can get quite convoluted compared to ones that merely postulate an extra mental faculty—but in those days, learning was thought to explain everything. Except, of course, when it didn’t. In the latter case, we clearly hadn’t thought long and hard enough about the issue at hand or we had failed to conduct the right experiments. At times, the wall of skepticism seemed more ideological than scientific, a bit the way we biologists feel about creationists. However compelling the data we bring to the table, they never suffice. Things must be believed to be seen, as Willy Wonka sang, and entrenched disbelief is oddly immune to evidence. The “slayers” of the cognitive view were not open to it.

This epithet comes from the American zoologist Marc Bekoff and the philosopher Colin Allen who early on picked up Griffin’s torch for cognitive ethology. They divided attitudes toward animal cognition into three types: the slayers, the skeptics, and the proponents. When first writing about this in 1997, slayers were still abundant:

Slayers deny any possibility of success in cognitive ethology. In our analyses of their published statements, we have found that they sometimes conflate the difficulty of doing rigorous cognitive ethological investigations with the impossibility of doing so. Slayers also often ignore specific details of work by cognitive ethologists and frequently mount philosophically motivated objections to the possibility of learning anything about animal cognition. Slayers do not believe that cognitive ethological approaches can lead, and have led, to new and testable hypotheses. They often pick out the most difficult and least accessible phenomena to study (e.g. consciousness) and then conclude that because we can gain little detailed knowledge about this subject, we cannot do better in other areas. Slayers also appeal to parsimony in explanations of animal behavior, but they dismiss the possibility that cognitive explanations can be more parsimonious than noncognitive alternatives, and they deny the utility of cognitive hypotheses for directing empirical research.1

When Emil Menzel told me about the prominent professor—clearly a slayer—who tried to ambush him but ended up with his foot in his mouth, he added an interesting side note. The same professor publicly challenged young Menzel to tell him what capacities he could possibly hope to find in apes that were not also present in pigeons. In other words, why waste your time on those willful, hard-to-control apes if animal intelligence is essentially the same across the board?

While this was the prevailing attitude at the time, the field has come around to a much more evolutionary approach, which recognizes that every species has a different cognitive story to tell. Each organism has its own ecology and lifestyle, its own Umwelt, which dictates what it needs to know in order to make a living. There is not a single species that can stand model for all the others, most certainly not one with a brain as tiny as a pigeon’s. Pigeons are plenty intelligent, but size does matter. Brains are the most “expensive” organs around. They are true energy hogs, using twenty times more calories per unit than muscle tissue. Menzel could simply have countered that since ape brains are several hundred times heavier than those of pigeons and hence burn vastly more energy, it stands to reason that apes face greater cognitive challenges. Otherwise mother nature indulged in a shocking extravagance, something she is not known for. In the utilitarian view of biology, animals have the brains they need—nothing more, nothing less. Even within a species, the brain may change depending on how it is being used, such as the way song-related areas seasonally expand and contract in the songbird brain.2 Brains adapt to ecological requirements, as does cognition.

We have also met a second type of slayer, though, and they have been even harder to deal with since they don’t share an interest in animal behavior. All they care about is humanity’s position in the cosmos, which science has been undercutting since the days of Copernicus. Their struggle has become rather hopeless, though, because if there is one overall trend in our field, it is that the wall between human and animal cognition has begun to resemble a Swiss Gruyère full of holes. Time after time we have demonstrated capacities in animals that were thought to set our species apart. Proponents of human uniqueness face the possibility that they have either grossly overestimated the complexity of what humans do or underestimated the capacities of other species.

Neither possibility is a pleasant thought, because their deeper problem is evolutionary continuity. They can’t stand the notion of humans as modified apes. Like Alfred Russel Wallace, they feel that evolution must have skipped the human head. Although this view is currently on its way out in psychology, which under the sway of neuroscience is edging ever closer to the natural sciences, it is still prevalent in the humanities and most of the social sciences. Typical is a recent reaction by the American anthropologist Jonathan Marks to the overwhelming evidence that animals pick up habits from one another, hence show cultural variability: “Labeling ape behavior as ‘culture’ simply means you have to find another word for what humans do.”3

How much more refreshing was David Hume, the Scottish philosopher who held animals in such high esteem that he wrote that “no truth appears to me more evident than that beasts are endow’d with thought and reason as well as men.” In line with my position throughout this book, Hume summarized his view in the following principle:

’Tis from the resemblance of the external actions of animals to those we ourselves perform, that we judge their internal likewise to resemble ours; and the same principle of reasoning, carry’d one step farther, will make us conclude that since our internal actions resemble each other, the causes, from which they are deriv’d, must also be resembling. When any hypothesis, therefore, is advanc’d to explain a mental operation, which is common to men and beasts, we must apply the same hypothesis to both.4

Formulated in 1739, more than a century before Darwin’s theory saw the light, Hume’s Touchstone offers a perfect starting point for evolutionary cognition. The most parsimonious assumption we can make about behavioral and cognitive similarities between related species is that they reflect shared mental processes. Continuity ought to be the default position for at least all mammals, and perhaps also birds and other vertebrates.

When this view finally gained the upper hand about twenty years ago, supportive evidence poured in from all sides. It was not just the primates anymore but also the canines, corvids, elephants, dolphins, parrots, and so on. The stream of discoveries became unstoppable, featured in the media on a weekly basis to the point that The Onion felt like spoofing the trend in an article claiming that dolphins are not nearly as smart on land as they are in the ocean.5 Joking aside, this was a valid point related to the species-appropriate testing that is one of our field’s main challenges. The public got used to a great variety of claims, including news stories and blogs about animals liberally sprinkled with terms like thinking, sentience, and rational.

Some of it was hype, but many reports presented serious peer-reviewed studies based on years of painstaking research. As a result, evolutionary cognition began to gain standing and attract a growing influx of students ready to cut their teeth on a promising topic. Students like nothing better than a new area where fresh ideas matter. Nowadays many scientists studying animal behavior proudly put the word cognitive in statements about their research, and scientific journals add this trendy term to their names, realizing that it attracts more readers than any other in behavioral biology. The cognitive view has won.

But an assumption is still only an assumption. It doesn’t absolve us from working hard on the issues at hand, which is to determine at what cognitive level a given species operates and how this suits its ecology and lifestyle. What are its cognitive strengths, and how do these relate to survival? It all goes back to the kittiwake story: some species need to recognize their young and others just don’t. The first will pay attention to individual identities, while the second can safely ignore them. Or recall how Garcia’s nauseated rats broke the rules of operant conditioning, as if to drive home the point that remembering toxic food is a magnitude more important than knowing which bar delivers pellets. Animals learn what they need to learn and have specialized ways of sifting through the massive information around them. They actively seek, collect, and store information. They are often incredibly good at one particular task, such as caching and remembering food items or fooling predators, whereas some species are endowed with the brainpower to tackle a wide array of problems.

Cognition may even push physical evolution in a particular direction, such as the reliance of New Caledonian crows on tools crafted out of leaves and twigs. These crows have straighter bills than other corvids and also more forward-facing eyes. The bill shape helps them get a stable grip on their tools, whereas binocular vision lets them peer deeply into the crevices from which they extract caterpillars.6 Cognition is not merely a product of an animal’s senses, anatomy, and brainpower, therefore, but the relation also works the other way around. Physical features adapt to an animal’s cognitive specializations. The human hand may be another example, having evolved its fully opposable thumbs and remarkable versatility to suit our reliance on refined tools, from stone axes to the modern smartphones. This is why evolutionary cognition is such a perfect label for our field, because only evolutionary theory can make sense of survival, ecology, anatomy, and cognition all at once. Instead of searching for a general theory that covers all cognition on the planet, it treats every species as a case study. Of course, some cognitive principles are common to all organisms, but we don’t seek to downplay variation between species with lifestyles, ecologies, and Umwelten as different as, say, a dolphin and a dingo or a macaw and a monkey. Each one faces its own specific cognitive challenges.

Once comparative psychologists began to appreciate that every species is special, and that learning is dictated by biology, they gradually began to enter the fold of evolutionary cognition. Their discipline greatly contributed to it through its long history of carefully controlled experiments and its many scientists with cognitive leanings. Even though these pioneers worked mostly under the radar and were forced to publish in second-tier journals, they described “higher mental processes” that they felt excluded learning.7 Given the absolute hegemony of behaviorism at the time, it made sense to define cognition in opposition to learning, but this always strikes me as a mistake. This dichotomy is as false as the one that pits nature against nurture. The reason we rarely talk about instincts anymore is that nothing is purely genetic: the environment always plays a role. In the same way, pure cognition is a figment of the imagination. Where would cognition be without learning? Some sort of information gathering is always part of it. Even K?hler’s apes, which heralded the study of animal cognition, had previous experience with boxes and sticks. Rather than looking at the cognitive revolution as a blow to learning theory, therefore, it is more like a marriage. The relationship has had its ups and downs, but in the end, learning theory will survive within the framework of evolutionary cognition. In fact, it will be an essential part of it.

The same holds for ethology. Its ideas about behavioral evolution are far from dead. They live on in many areas of science together with the ethological method. Systematic description and observation of behavior are at the core of all animal fieldwork as well as studies of child behavior, mother-infant interactions, nonverbal communication, and so on. The study of human emotions treats facial expressions as fixed action patterns while relying on the ethological method to measure them. For this reason, I don’t look at the current flowering of evolutionary cognition as a break with the past but rather as a moment in time when forces and approaches that have been around for a century or longer have won the upper hand. We finally have the breathing room to discuss the marvelous ways in which animals gather and organize information. And while the slayers of the cognitive view are a dying breed, we obviously still have the other two categories around—the skeptics and proponents—both of whom are essential. As a proponent myself, I do appreciate my more skeptical colleagues. They keep us on our toes and force us to design clever experiments to answer their questions. So long as progress is our shared goal, this is exactly how science ought to work.

Even though the study of animal cognition is often portrayed as an attempt to find out “what they think,” that is not really what it is all about. We’re not after private states and experiences, although it would be great if one day we could know more about them. For the moment, our goal is more modest: we wish to pinpoint proposed mental processes by measuring observable outcomes. In this sense, our field is no different from other scientific endeavors, from evolutionary biology to physics. Science always starts with a hypothesis, followed by the testing of its predictions. If animals plan ahead, they should retain tools that they will need later on. If they understand cause-effect relations, they should avoid the trap in the trap-tube the first time they encounter it. If they know what others know, they should vary their behavior depending on what they have seen others pay attention to. If they have political talents, they should treat the friends of their rivals with circumspection. Having discussed dozens of such predictions, and the experiments and observations they have inspired, the pattern of research is obvious. Generally, the more lines of evidence converge in support of a given mental faculty, the stronger it stands. If planning for the future is evident in everyday behavior, in tests with delayed tool use, as well as in untrained food caching and foraging choices, we are in pretty good shape to claim that at least some species have this capacity.

But still I often feel that we are too obsessed with the pinnacles of cognition, such as theory of mind, self-awareness, language, and so on, as if making grandiose claims about these is all that matters. It is time for our field to move away from interspecific bragging contests (my crows are smarter than your monkeys) and the black-and-white thinking it engenders. What if theory of mind rests not on one big capacity but on an entire set of smaller ones? What if self-awareness comes in gradations? Skeptics often urge us to break down larger mental concepts by asking what exactly we mean. If we mean less than we claim, they wonder why we don’t use a more reduced, down-to-earth description of the phenomenon.

I have to agree. We should start focusing on the processes behind higher capacities. They often rest on a wide range of cognitive mechanisms, some of which may be shared by many species, while others may be fairly restricted. We went through all this in the discussion of social reciprocity, which was initially conceived as animals remembering specific favors in order to repay them. Many scientists were unwilling to assume that monkeys, let alone rats, kept tabs on every social interaction. We now realize that this is not a requirement for tit-for-tat, and that not only animals, but also humans often exchange favors on a more basic, automated level related to long-term social ties. We help our buddies, and our buddies help us, but we aren’t necessarily counting.8 Ironically, the study of animal cognition not only raises the esteem in which we hold other species, but also teaches us not to overestimate our own mental complexity.

We urgently need a bottom-up view that focuses on the building blocks of cognition.9 This approach will also need to include the emotions—a topic I have barely touched upon but that is close to my heart and is in equal need of attention. Breaking down mental capacities into all of these components may lead to less spectacular headlines, but our theories will be more realistic and informative as a result. It will also require a greater involvement of neuroscience. At the moment, its role is rather limited. Neuroscience may tell us where things happen in the brain, but this hardly helps us formulate new theories or design insightful tests. But while the most interesting work in evolutionary cognition is still mostly behavioral, I am sure this is going to change. Neuroscience has thus far only scratched the surface. In the coming decades, it will inevitably become less descriptive and more theoretically relevant to our discipline. In time, a book such as the present one will have a huge amount of neuroscience in it, explaining which brain mechanisms are responsible for the behavior observed.

This will be an excellent way to test the continuity assumption, since homologous cognitive processes imply shared neural mechanisms. Such evidence is already accumulating for face recognition in monkeys and humans, the processing of rewards, the role of the hippocampus in memory and of mirror neurons in imitation. The more evidence for shared neural mechanisms we find, the stronger the argument for homology and continuity will become. And conversely, if two species engage different neural circuits to achieve similar outcomes, the continuity stance will need to be abandoned in favor of one based on convergent evolution. The latter is quite powerful, too, having produced face recognition in both primates and wasps, for example, or flexible tool use in both primates and corvids.

The study of animal behavior is among the oldest of human endeavors. As hunter-gatherers, our ancestors needed intimate knowledge of flora and fauna, including the habits of their prey. Hunters exercise minimal control: they anticipate the moves of animals and are impressed by their cunning if they escape. They also need to watch their back for species that prey on them. The human-animal relationship was rather egalitarian during this time. A more practical knowledge became necessary when our ancestors took up agriculture and began to domesticate animals for food and muscle power. Animals became dependent on us and subservient to our will. Instead of anticipating their moves, we began to dictate them, while our holy books spoke of our dominion over nature. Both of these radically different attitudes—the hunter’s and the farmer’s—are recognizable in the study of animal cognition today. Sometimes we watch what animals do of their own accord, while at other times we put them in situations where they can do little else besides what we want them to do.

With the rise of a less anthropocentric orientation, however, the second approach may be on the decline, or at least add significant degrees of freedom. Animals should be given a chance to express their natural behavior. We are developing a greater interest in their variable lifestyles. Our challenge is to think more like them, so that we open our minds to their specific circumstances and goals and observe and understand them on their own terms. We are returning to our hunting ways, albeit more in the way that a wildlife photographer relies on the hunting instinct: not to kill but to reveal. Nowadays experiments often revolve around natural behavior, from courtship and foraging to prosocial attitudes. We seek ecological validity in our studies and follow the advice of Uexküll, Lorenz, and Imanishi, who encouraged human empathy as a way to understand other species. True empathy is not self-focused but other-oriented. Instead of making humanity the measure of all things, we need to evaluate other species by what they are. In doing so, I am sure we will discover many magic wells, including some as yet beyond our imagination.

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