Mirrors have long been a source of fascination, legend, and inspiration for writers. From Lewis Carroll’s Through the Looking-Glass to J.K. Rowling’s depiction of a young Harry Potter gazing longingly at his deceased parents in the Mirror of Erised, mirrors have occupied a powerful symbolic role in literature. However, their value is not limited to storytelling. In recent decades, mirrors have also become an important scientific tool for exploring a profound question: besides humans, can other animals recognize themselves in a mirror?
The Mirror Experiment
Today, science has made it clear that self-recognition is not necessarily exclusive to humans. Reaching this conclusion required numerous experiments, but one in particular proved so influential that it was replicated across many species: the mirror experiment developed by psychologist Gordon G. Gallup Jr.
Animals with sufficient visual acuity typically respond to their reflection as if it were another individual of the same species. Over time, however, some animals appear to learn that the image in the mirror corresponds to themselves. Gallup set out to test this hypothesis using two female chimpanzees with little prior exposure to reflective surfaces.
Each chimpanzee was placed in an isolated cage for two days. After this period, a mirror was introduced in front of the cage, and their behaviour was observed through a small hole in the wall. The mirror remained in place for eight days, resulting in a total exposure time of 80 hours (De Waal, 2018).
As the hours passed, the chimpanzees began to display increasingly complex behaviors in front of the mirror. They groomed parts of their bodies they could not normally see, removed food particles from their teeth using the mirror, picked their noses, and made exaggerated facial expressions. While intriguing, these behaviours were not yet considered conclusive evidence of self-recognition. As a result, Gallup decided to introduce a crucial modification to the experiment.
The Stain Test
On the tenth day, the chimpanzees were anesthetized with phencyclidine, and a red dye (Rhodamine B) was applied to one eyebrow and one ear. Once dry, the stains produced no olfactory or tactile cues that might allow the chimpanzees to detect them without visual assistance. The animals were then kept without access to the mirror for four hours while they ate and rehydrated. During this time, researchers observed whether they touched the stained areas. Afterward, the mirror was reintroduced.
The results were striking. When the chimpanzees saw themselves in the mirror, they repeatedly touched the stained areas on their faces while watching their reflection. They even examined their fingers afterward, as if checking whether the stain had transferred (it had not). These observations strongly suggested that the chimpanzees recognized the reflection as their own and understood that the face in the mirror belonged to them.
Unfortunately, when Gallup attempted to replicate the experiment with other species, the results were far less consistent.
Beyond Chimpanzees
Gallup extended the mirror test to other primates, including stump-tailed macaques (Macaca arctoides), rhesus macaques (Macaca mulatta), and crab-eating macaques (Macaca fascicularis). None of these species showed convincing evidence of self-recognition. Based on these findings, Gallup proposed that mirror self-recognition requires a high level of cognitive complexity.
He concluded: “Our data suggest that we have found qualitative psychological differences among primates, and that the capacity for self-recognition may not extend beyond humanas and the other great apes”
More recent experiments.
Although Gallup’s conclusion may seem pessimistic, it’s important to remember that his work was conducted in the early 1970s. Since then, the mirror test has been applied to a much wider range of species, often with surprising results. Elephants and dolphins, for example, have shown strong evidence of self-recognition.
More strikingly, psychologist Helmut Prior expanded the research beyond mammals. In Germany, he investigated wheter the common magpie (Pica pica), a bird species, could recognize itself in a mirror. Prior placed a small yellow stickes beneath the magpie’s peak- an area the bird could not see without a mirror. When presented with its reflection, the magpie persistenly scratched the marked area, even though the sticker was visible only in the mirrror. This behaviour suggested that the bird associated the reflection with its own body.
Conclusion.
From an evolutionary perspective, rigid distinctions between “conscious” and “non-conscious” species are increasignly difficult to defend. Every animal must possess some awareness of its own body in relation to its environment. As primatologist Frans de Waal aptly notes: “You wouldn’t want to be a monkey in a tree without awareness of how your body will affect the branch you intend to sit on”.
De Waal has also questioned Gallup’s conclusion that African great apes are intellectually superior to other primates simply because they pass the mirror test. Other primates, her argues, often use mirrors instrumentally rather than representationally. For example, if food can only be located using a mirror, many primates will readily use it as a tool.
Importantly, De Waal cautions against trating the mirror experiement as the sole indicator of self-awareness. While mirror self-recognition may reflect a form of self-identity, it is not the only pathway to understand animal consciusness. He famously compares self-awarenss to an onion stating: “Self-awareness develops layer by later- it does not suddenly appear at a particular age or in a single form”.
For this reason, tests such as the mirror or inkblot experiments should not be viewed as definitive proof of self-awareness, but rather as one of many approaches to studying the conscious self. To conclude, Gallup’s mirror test remains one of the most influential sutdies of the twentieth century in the field of animal cognition. In paved the way for decades of research and inspired countless studies across species and scientific disciplines. While it should not be regarded as the ultimate measure of animal consciousness, it continues to hold great intellectual and academic value. Ultimately, as De Waal suggests, the mirror test is best understood not as a final answer, but as one of many tools humans use in their ongoing effort to understand consciusness and self-awareness in non-human animals.
Sapiens Lara 