… who’s the most self-aware of them all?

by Ayanthi Bhattacharya

After a particularly soporific botany class on a hot Delhi summer day, I stepped outside and spotted a gorgeous peacock pecking at the glass of the lecture hall next door. I found myself rooted to the spot, for the peacock, in all its majesty, was doing something completely daft – it kept pecking at its own reflection, perhaps believing it was challenging a rival. I chuckled to myself and walked away, realizing for the first time that this peacock couldn’t do what I effortlessly did every single day- it couldn’t recognize itself in the mirror!

I didn’t think much of it until years later, during a class discussion on consciousness and self-awareness. Our professor brought up the Mirror Test, a behavioural experiment designed by Gordon Gallup to assess an animal’s ability to recognize its own reflection. The animal’s body is marked in a spot it cannot see directly, such as the forehead. If it uses the mirror to investigate the mark, it is said to “pass” the test – an indication of visual self-recognition (Gallup 1970). He tested this theory on chimpanzees unfamiliar with mirrors. At first, these animals treated their reflections as other animals, displaying social behaviours such as vocalizing and threatening. Over time, however, these responses declined while self-directed behaviours increased – examining parts of their bodies they couldn’t normally see, picking their teeth and noses, and so on. Gallup also observed that this capacity for self-recognition was not displayed by stump-tailed macaques or rhesus monkeys. He described mirror self-recognition as “an advanced form of intellect”, that may not exist “below man and the great apes”.

That was the year 1970, though. Since then, a host of beings have been shown to pass this test, including Bottlenose dolphins (Reiss and Marino 2001) and Asian Elephants (Plotnik, De Waal, and Reiss 2006), Eurasian magpies (Prior, Schwarz, and Güntürkün 2008) and even fish (Kohda et al. 2023)!

But what does it mean to pass the Mirror Test?

Gallup believed that mirror self-recognition reflected an individual’s capacity for complex, abstract behaviours such as introspection and emotional regulation. Humans, too, don’t pass the mirror test until about 18-24 months of age. For a long while now, passing the Mirror Test has been a measure of “self-awareness” in an organism. Yet, as more research emerges, this capacity no longer appears confined to humans and great apes. Reiss and Marino’s work on bottlenose dolphins, for example, shows that these non-primates do very well on the Mirror Test, suggesting that perhaps self-recognition can be generalized to animals with larger brains relative to their body sizes, like dolphins.

However, is the mirror test a definitive measure of self-awareness? Recognizing one’s reflection offers no insights into the animal’s mental state – the animal may not be cognizant of its emotions and thoughts. Conversely, an animal may be self-aware yet fail the test. Take, for example, the octopus: a highly intelligent invertebrate that seemingly fails the Mirror Test. But octopi are known to be reliant on their chemical and tactile senses, rather than vision. Does their inability to pass this test reliably rule out their capacity for self-awareness? Similarly, dogs guided primarily by smell, perform well on an “Olfactory Self-Recognition” test – spending more time smelling unfamiliar scents than their own, likely because they can recognize the smell of their own selves (Horowitz 2017).

Another possibility is that self-recognition may not happen via a complex cognitive process at all. It may simply be a result of kinaesthetic visual matching, e.g., “when I move my fin, the reflection moves too.” The two possibilities have only been tested in cleaner wrasse fish so far. Cleaner fish, surprisingly, recognize themselves in the mirror. But do they do so because they have a mental image of what they look like, or because they see their mirror-selves moving the same way that they do? When presented with photographs of their own faces, cleaner fish recognize themselves, while they attack photographs of other fish, indicating that they do indeed have an idea “self-face”, much like us (Kohda et al. 2023)! All studies investigating “self-awareness” would benefit from rigorous investigation of this kind. 

To summarize, while the list of species that pass the Mirror Test grows tantalizingly, it is important to design experiments that probe the extent and mechanism of self-recognition. Nonetheless, contemplating these findings is humbling. It reminds us of the enormity of life, and how little we truly know. Like that peacock I saw attacking its reflection— what was it really thinking?

References:

Gallup, Gordon G. 1970. “Chimpanzees : Self-Recognition Lunar Surface Rocks and Fines :” Science 167(3914): 86–87.

Horowitz, Alexandra. 2017. “Smelling Themselves: Dogs Investigate Their Own Odours Longer When Modified in an ‘Olfactory Mirror’ Test.” Behavioural Processes 143(August): 17–24. http://dx.doi.org/10.1016/j.beproc.2017.08.001.

Kohda, Masanori et al. 2023. “Cleaner Fish Recognize Self in a Mirror via Self-Face Recognition like Humans.” Proceedings of the National Academy of Sciences of the United States of America 120.

Plotnik, Joshua M., Frans B.M. De Waal, and Diana Reiss. 2006. “Self-Recognition in an Asian Elephant.” Proceedings of the National Academy of Sciences of the United States of America 103(45): 17053–57.

Prior, Helmut, Ariane Schwarz, and Onur Güntürkün. 2008. “Mirror-Induced Behavior in the Magpie (Pica Pica): Evidence of Self-Recognition.” Animal Behavior: An Evolutionary Approach 6(8): 154–72.

Reiss, Diana, and Lori Marino. 2001. “Mirror Self-Recognition in the Bottlenose Dolphin: A Case of Cognitive Convergence.” Proceedings of the National Academy of Sciences of the United States of America 98(10): 5937–42.

Author and illustrator

Ayanthi Bhattacharya is currently a researcher hosted at the Tata Institute for Genetics and Society (TIGS), Bengaluru, India. She is working on Drosophila neurodevelopment. The broad question she is chasing is how a neural precursor cell knows which neurons to make. Each of these precursor cells receives a differential set of positional and temporal cues; Ayanthi’s work tries to understand how these precursors “read” these cues to produce the appropriate neurons.
Ayanthi’s research interests chiefly lie in developmental biology, behaviour, and Evo-Devo. In her spare time, she likes to sing, draw/design, and write a little. This is when she isn’t dancing to iconic Bollywood songs with her cats—Mitthu and Kiki!

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This article was written as part of Club SciWri’s first Science Writing Workshop, an initiative aimed at nurturing new voices in science communication and helping participants explore how to make complex ideas accessible to wider audiences.

Workshop conducted by Saurja Dasgupta, Sumbul Jawed Khan, Ananya Sen , Rohini Subrahmanyam, and Roopsha Sengupta

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