Some species go further in that they understand mirror basics. Monkeys, for example, may not recognize themselves but are able to use the mirror as a tool. If you hide food that can be found only by using a mirror to look around a corner, the monkey will have no trouble reaching for it. Many a dog can do the same: holding up a cookie behind them while they watch you in a mirror makes them turn around. Curiously, it is specifically the relation with their own body, their own self in the mirror, that they fail to grasp. But even then, rhesus monkeys can be taught to do so. It requires adding a physical sensation. They need a mark that they can both see in the mirror and feel on their body, such as a laser light that irritates the skin or a cap fastened to their head. Instead of a traditional mark test, this is better described as a felt mark test. Only under these circumstances can monkeys learn to connect their reflection with their own body.14 This is obviously not the same as what apes do spontaneously relying on vision alone, but it does suggest that some of the underlying cognition is shared.
Even though capuchin monkeys fail the visual mark test, we decided to study them in a way that, surprisingly, no one had ever tried before. Our goal was to see if these monkeys truly mistake their reflection for a “stranger,” as is commonly implied. Capuchins were placed in front of a Plexiglas panel, behind which they faced either a member of their own group, a stranger of their species, or a mirror. It quickly became evident that the mirror was special. They treated their reflection quite differently from a real monkey. They didn’t need any time to decide what they saw, and reacted within seconds. They turned their backs to strangers, barely glancing at them, yet made prolonged eye contact with their own reflections as if thrilled to see themselves. They showed absolutely none of the timidity toward the mirror image that one would expect if they mistook it for a stranger. Mothers, for example, let their infants freely play in front of the mirror yet held them close in case of a stranger. But the monkeys also never inspected themselves in the mirror, the way apes do all the time, or the way Pepsi the elephant had done. They never opened their mouth to peek inside. Thus, while capuchins fail to recognize themselves, they also don’t mix up their reflection with someone else.
As a result, I have become a gradualist.15 There are many stages of mirror understanding, running all the way from utter confusion to a full appreciation of the specular image. These stages are also recognizable in human infants, which are curious about their mirror image well before passing the mark test. Self-awareness develops like an onion, building layer upon layer, rather than appearing out of the blue at a given age.16 For this reason, we should stop looking at the mark test as the litmus test of self-awareness. It is only one of many ways to find out about the conscious self.
Nevertheless, it remains fascinating how few species pass this test without a helping hand. After the Hominoids, spontaneous self-recognition was observed only in elephants and dolphins. When bottlenose dolphins at the New York Aquarium were marked by Diana Reiss and Lori Marino with painted dots, they would race from the spot where the marking took place to a mirror in another pool, at quite a distance, only to spin around seemingly to get a good look at themselves. The dolphins spent more time near the mirror checking out their bodies when they had been marked than without a visible mark.17
It was unavoidable that the mirror test would be tried on birds. While most species have thus far failed, we have one exception: the Eurasian magpie. It is an interesting species to put in front of a reflective surface. As a child, I learned never to leave small shiny objects, such as teaspoons, unattended outdoors as these raucous birds will steal anything they can put their beaks on. This folklore inspired a Rossini opera, La gazza ladra (The Thieving Magpie). Nowadays, this view has been replaced with a more ecologically sensitive one that depicts magpies as murderous robbers of the nests of innocent songbirds. Either way, they are considered black-and-white gangsters.
But no one has ever accused a magpie of being stupid. The bird belongs to the corvid family that has begun to challenge the cognitive supremacy of primates. The German psychologist Helmut Prior subjected magpies to a mirror test that was at least as well controlled as any conducted on apes and children. Placed on their black bib (throat feathers), the mark—a tiny yellow sticker—stood out but was visible only with help of the mirror. The birds were untrained, which is a critical difference with the highly coached pigeons employed long ago to discredit mirror research. Put in front of a mirror, the magpies kept scratching with their foot until the mark was gone. They never did the same amount of frantic scratching if there was no mirror to see themselves in, and they ignored a “sham” mark—a black sticker on their black bib. As a result, the self-recognition elite has now been expanded with its first feathered member. Others may follow.18
The next frontier will be to see if animals care about their mirror image to the point of embellishing themselves, the way we do with makeup, hair care, earrings, and the like. Does the mirror induce vanity? Would any species other than ours be prone to take selfies, if they could? This possibility was first hinted at by observations in the 1970s of a female orangutan at the Osnabrück Zoo, in Germany. Jürgen Lethmate and Gerti Dücker described Suma’s narcissistic ways:
Suma, an orangutan at a German zoo, loved to decorate herself in front of the mirror. Here she puts a leaf of lettuce onto her head like a hat.
She gathered salad and cabbage leaves, shook each leaf and piled them up. Eventually, she placed one leaf on her head and walked straight to the mirror with it. She sat down directly in front of it, contemplated her headcover in the mirror, straightened it a bit with her hand, squashed it with a fist, then put the leaf on her forehead and began to bob up and down. Later, Suma arrived holding a salad leaf in her hand at the bars [where the mirror stood] to lay it on her head once she could see herself in the mirror.19
The Mollusk Mind
As a biology student, my favorite textbook was Animals Without Backbones. It may seem an odd choice given my current interests, but I was awestruck by all the exotic life-forms that I had never heard about or could scarcely imagine, some of them so tiny that you needed a microscope to see them. The book went into great detail of all invertebrates—from protozoans and sponges to worms, mollusks, and insects—which together make up 97 percent of the animal kingdom.20 Whereas cognition research focuses almost entirely on the tiny vertebrate minority, it is not as if the rest doesn’t move, eat, mate, fight, and cooperate. Obviously, some invertebrates show more complex behavior than others, but they all need to pay attention to their surroundings and solve problems that present themselves. In the same way that almost all these animals have reproductive organs and digestive tracts, they can’t survive without a degree of cognition.
The brainiest of the bunch is the octopus, which is a soft-bodied cephalopod, or “head-footed” animal. This is an apt name, since their squishy bodies consist of a head that directly joins eight limbs, while the body (the mantle) is positioned behind the head. The cephalopods are an ancient class that arose well before there were land vertebrates around, but the group to which the octopus belongs is a fairly modern offshoot. We seem to have almost nothing in common with them, both anatomically and mentally. Yet they have been reported to open a pill bottle protected by a childproof cap. Since this requires the cap to be pushed down and twisted at the same time, it takes skill, intelligence, and persistence. Some public aquariums show off octopus intelligence by locking the animal in a glass jar that they close with a screw top. Like a true Houdini, the octopus takes less than a minute to grab the cover from within with its suckers and unscrew it so as to escape.