When I visit the zoo, I always dedicate a prolonged block of time to staring at our hairy cousins, the great apes. My zoo-going companions — adults and children alike — invariably echo my fascination, their faces close to the enclosure window and their eyes alight. How can we not be transfixed by these hirsute, screeching beings that remind us, in somewhat uncomfortable ways, of ourselves? Frequently on such a visit, one of those nonhuman Hominidae will stare back at me with curiosity. Moments like this make it hard not to wonder what they think of us.
The family Hominidae, often referred to as the great apes, consists of gorillas, chimpanzees, orangutans and bonobos. And, of course, one extant species of humans. Decades of research regarding primate cognition tell us that the other members of our ancestral family are highly intelligent. But are they self-aware? Are they aware that others have minds? When they look at me, do they wonder what I’m thinking?
If you give a 1-year-old human child a mirror, they might try to eat it. Maybe they’ll crawl behind your leg in fear. They certainly won’t recognize themselves. Self-recognition by humans in mirrors doesn’t occur until the child is at least one and a half years old (and, in many cases, until the child is much older).
At that point, the child begins to show signs of understanding that the image they see reflected back at them is, in fact, themselves and not another human child. They will make faces, test out body movements, inspect their nostrils — everything you’d consider familiar in to your own mirror routine.
How can we not be transfixed by these hirsute, screeching beings that remind us, in somewhat uncomfortable ways, of ourselves?
In March 1838 — a little more than 20 years before he released “On the Origin of Species” — Charles Darwin saw his first ape. Her name was Jenny, and she was an orangutan who lived in the London Zoo. Her keepers dressed her in tunics and taught her to eat her food from a spoon. Darwin was fascinated when he observed Jenny pass a mirror and appear to recognize herself. In his notebook, he later wrote that she seemed “astonished beyond measure” at her own reflection.
Almost 150 years later, psychologist Gordon Gallup Jr. put Darwin’s intuition of Jenny’s mirror reaction to the test with a group of four preadolescent chimpanzees. After placing each chimpanzee in a room by itself, Gallup and his team put a full-length mirror in the room with the chimpanzee.
At first, the chimpanzees indicated that they felt threatened by their own images by making aggressive gestures at their respective mirrors. Eventually, however, the chimpanzees’ behavior changed. They slowly began to use their reflections for self-directed behaviors, such as picking their noses and grooming the parts of their bodies they could not see without the mirror. They also seemed to enjoy blowing bubbles at their reflections.
In the next round of his investigation, Gallup anesthetized the chimpanzees and painted a red mark on their eyebrow and above their left ear. Upon drying, the mark had no tactile cues that would cause the chimp to sense its presence, and yet, in every case, when the chimpanzees woke up and were given a mirror to look into, their hands went to the mark on their face.
Many of the chimps inspected their fingers after touching the marks and adjusted their bodies to better view the mark in the mirror. Gallup’s mirror self-recognition, or MSR, test has become a foundational technique for attempting to assess self-awareness in other species. Chimpanzees, orangutans, bonobos and gorillas all pass.
For some, this evidence is not compelling. University of Louisiana at Lafayette biology professor Daniel Povinelli suggests that perhaps animals that pass the MSR test view their reflection as some external entity that they are able to control with their own movements. Yet at least one other study suggests that beyond having awareness of themselves, primates also formulate theories of mind for individuals they know to be distinct from themselves.
In 2016, Kyoto University professor Satoshi Hirata dressed up in a furry ape costume and performed a game of guess-where-the-ball-is with his colleague Fumihiro Kano. All in the name of science, of course.
Hirata and Kano carefully planned this endeavor, filmed it and showed it to a waiting primate audience.
Yet at least one other study suggests that beyond having awareness of themselves, primates also formulate theories of mind for individuals they know to be distinct from themselves.
In the film, Hirata in his ape costume grabs a stone from Kano and hides it under the left of two boxes. After watching this happen, Kano leaves, and Hirata moves the stone to the right box. Kano then returns to retrieve the stone. As this film plays, eye-tracking software recorded what the apes were looking at as they watched.
Hirata and Kano wanted to know where their ape audience anticipated Kano would look for the stone first. Remarkably, the eye-tracking software revealed that the apes stared at the left-most box — the first box where Hirata hid the stone — when Kano returned, indicating that the apes understood that this is where Kano would believe the stone to be, even though they had watched the stone get moved to the right-most box.
Kano argued that this was evidence that apes held theories of mind, or the ability to attribute mental states to themselves and others.
Critics responded with skepticism: Who’s to say the apes weren’t just looking at the last place Kano saw his stolen stone? That’s nothing more than the demonstration of an associative ability and offers no evidence that apes form theories of mind.
In response to this skepticism, Kano redesigned his experiment. In a new video, the same scenario played out. This time, however, instead of leaving the room, the actor being robbed stood behind a seemingly opaque barrier. Prior to showtime, half of the ape audience was shown the same opaque barrier. The other half were shown a barrier that looked similar but was actually made of see-through mesh.
The apes who were shown the opaque barrier prior to watching the film focused their attention on the first box when the actor looked for the stone, indicating that they reasoned the actor was looking through the same barrier and thus could not see where the stone was actually moved. The apes who were shown the see-through barrier prior to the film screening looked more frequently at the second box, indicating that they knew the actor could see where the stone was moved.
And then there’s Kanzi the bonobo. Kanzi was born Oct. 28, 1980 in the Yerkes Field Station at Emory University before he was moved at a young age to the Language Research Center at Georgia State University. As an infant, Kanzi joined his adoptive bonobo mother, Matata, to sessions during which researchers were making efforts to teach her language through keyboard lexigrams.
Matata was uninterested and slow on the uptake, but Kanzi, who had received no direct language lessons from researchers, surprised everyone by demonstrating that he could competently use the lexigram.
Kanzi has become somewhat of a legend, besting toddler humans in comprehension quizzes and learning how to make stone flakes using the Oldowan, a tool used by our human ancestors in the Stone Age. Bonobos have different vocal tracts than humans, so hoping for a witty vocal repartee from Kanzi might be asking for too much. Yet his caretakers and researchers report that every time Kanzi communicates with humans using graphic symbols, he also produces vocalization.
“Kanzi, An Ape of Genius” is a short documentary that offers some extraordinary footage of Kanzi seeming to understand entire conversations between him and his trainer Susan Savage-Rumbaugh during a camping excursion. He follows requests to pull Savage-Rumbaugh’s lighter out of her pocket and start a fire to cook dinner, find sticks to roast marshmallows and stir their dinner as it cooks.
Savage-Rumbaugh co-authored a book that was published in 1996 titled “Kanzi: The Ape at the Brink of the Human Mind,” which documents her experiences with the bonobo. In it, she questions whether our reluctance to grant that the great apes — and every other animal, for that matter — might have consciousness is because we are afraid of losing the control that we have over the planet.
“Man’s ability to exploit the planet, to take of its resources as he needs, and to usurp entire forests and all living creatures therein, rests upon the unwritten assumption that the chasm between himself and all other creatures is impassable.” — Susan Savage-Rumbaugh
“With the man/animal boundary so deep a part of the Western psyche, it is little wonder that many resist its dismantling on both a logical and emotional level, and with great confusion manifest between the two,” Savage-Rumbaugh writes. “Man’s ability to exploit the planet, to take of its resources as he needs, and to usurp entire forests and all living creatures therein, rests upon the unwritten assumption that the chasm between himself and all other creatures is impassable.”
The body of research indicating that animals think and feel complicated things continues to grow. Monkeys can count. Elephants have rituals for their dead. Rats choose saving a drowning companion over receiving a tasty treat.
Luckily, the tools provided to us by science enable us to keep being surprised. Maybe one day I’ll learn the answer to whether that ape staring back at me is thinking about me like I’m thinking about it. Or maybe one day science will tell me that’s not the most interesting question to be asking about our distant cousins in the first place.
Contact Katherine Blesie at [email protected].