ILLUSTRATION BY EMMANUEL POLANCO
The idea for a tool to probe the basis of consciousness came to Gordon G. Gallup, Jr. while shaving. “It just occurred to me,” he says, “wouldn’t it be interesting to see if other creatures could recognize themselves in mirrors?”
Showing chimpanzees their reflections seemed like a fascinating little experiment when he first tried it in the summer of 1969. He didn’t imagine that this would become one of the most influential—and most controversial—tests in comparative psychology, ushering the mind into the realm of experimental science and foreshadowing questions on the depth of animal suffering. “It’s not the ability to recognize yourself in a mirror that is important,” he would come to believe. “It’s what that says about your ability to conceive of yourself in the first place.”
Gallup was a new professor at Tulane University in Louisiana, where he had access to the chimps and gorillas at what would later be known as the Tulane National Primate Research Center. The chimpanzees there had been caught as youngsters in Africa and shipped to America, where they were used mainly in biomedical research. By comparison, his experiment was far less invasive. He isolated two chimps in cages, and placed a mirror in each cage for eight hours at a time over 10 days. Through a hole in the wall, Gallup witnessed a shift in the chimps’ behavior. First they treated the reflection like it was another chimp, with a combination of social, sexual, and aggressive gestures. But over time, they started using it to explore their own bodies. “They’d use the mirror to look at the inside of their mouths, to make faces at the mirror, to inspect their genitals, to remove mucous from the corner of their eyes,” Gallup says.
Gallup was sure that the chimps had learned to recognize themselves in the mirror, but he didn’t trust that other researchers would be convinced by his descriptions. So he moved on to phase two of the experiment. He anesthetized the chimps, then painted one eyebrow ridge and the opposite ear tip with a red dye that the chimps wouldn’t be able to feel or smell. If they truly recognized themselves, he thought he knew what would happen: “It seemed pretty obvious that if I saw myself in a mirror with marks on my face, that I’d reach up and inspect those marks.”
That’s exactly what the chimps did. As far as Gallup was concerned, that was proof: “the first experimental demonstration of a self-concept in a subhuman form,” he wrote in the resulting 1970 report in Science. “It was just clear as day,” he remembers. “It didn’t require any statistics. There it was. Bingo.”
But the result that really blew Gallup’s mind came when he tested monkeys, and discovered that they did not do the same. The ability to recognize one’s reflection seemed not to be a matter of learning abilities, with some species being slower than others. It was an issue of higher intellectual capacity. Gallup had obtained the first good evidence that our closest relatives share with us a kind of self-awareness or even consciousness, to the exclusion of other animals. Here, finally, was an experimental handle on a topic that had been the subject of speculation for millennia: What is the nature of human consciousness?
Gallup wasn’t the first to come up with the notion that it might be significant if a person or animal recognizes itself in the mirror. He would only later learn that Charles Darwin had shown mirrors to orangutans, but they didn’t figure the mirror out, at least while he was watching. Darwin had also noted that, for their first few years, his children couldn’t recognize themselves in their reflections. In 1889, German researcher Wilhelm Preyer became the first to posit a connection between mirror self-recognition and an inner sense of self in people.
More than 50 years later, French psychoanalyst Jacques Lacan conceived of a childhood “mirror stage,” in which mirrors contribute to the formation of the ego. By 1972, developmental psychologists started using mark tests similar to Gallup’s to pin down the age at which children begin to recognize themselves in the mirror: 18 to 24 months.
Meanwhile Gallup, who moved to the University at Albany-SUNY, became interested in whether any non-primates could pass. In the early 1990s, he encouraged one of his Ph.D. students, Lori Marino, to explore the question. Working with Diana Reiss at Marine World Africa USA in California, Marino exposed two bottlenose dolphins at an aquarium to a mirror. Like the chimpanzees, the dolphins learned to use the mirror in a variety of ways, even “having sex in front of the mirror with each other, which we call our dolphin porno tapes,” Marino says. The three researchers published the results, saying they were “suggestive” of mirror self-recognition.
Still, they were missing the crucial mark test for another decade. The biggest hurdle was anatomical: The dolphins didn’t have hands to touch a mark. But Reiss and Marino, by then at the New York Aquarium, designed a modified test. When marked with black ink on various parts of their bodies, the dolphins flipped and wriggled in an attempt to see it, convincing the researchers and many others that they recognized themselves…