From time immemorial, anthropocentrism has led us to think that human beings are the only species capable of recognizing themselves and having self-awareness. However, research has shown that this is not the case and that many other animals, such as dolphins, orangutans or elephants, could have this same capacity.

To study this phenomenon, the mirror test has been used, a test that, until now, has served to measure self-recognition or self-awareness in animals. And we say until now because in recent years, with the discovery that even ants or fish pass the test, part of the scientific community has questioned the validity of the test to measure this cognitive ability.

In this article we explain what the self-awareness mirror test is and what its limitations are. In addition, we review the latest research on this interesting phenomenon.

The self-awareness mirror test: what is it and what is it for?

The mirror test, developed in 1970 by Gordon G. Gallup Jr, is a test that measures the level of self-awareness and visual self-recognition. What the test determines is whether an animal can recognize its own reflection in a mirror as if it were an image of itself .

This test is quite simple: just put a mirror at the animal’s disposal and observe its behaviour. When the animal gets used to the mirror, the researchers mark with an odourless dye a part of its body that cannot be seen without the help of the mirror. In this way, if the animal reacts in a manner consistent with being aware that the dye is on its own body, positive evidence of self-awareness is obtained .

Behaviors that indicate that the animal is able to recognize itself in its mirror image include turning and adjusting the body to better see the mark in the mirror, or touching the mark with its own body or a finger while looking in the mirror. Animals that have until recently passed the mirror test have been: chimpanzees, bonobos, orangutans, dolphins, elephants, pigeons and, of course, humans.

However, recent research has detected that even some species of ants and fish have reacted positively to the self-awareness mirror test , which has generated great controversy in the scientific community, dividing opinion between those who believe that the test is not valid or conclusive and those who believe that it is necessary to rethink the implications it may have for the study of human self-awareness.

Research with labrid fish

One of the studies that has revolutionized the field of animal self-awareness research has been the research by Kohda et al. (2019) in which the behavior of a fish of the labrid family was observed under the conditions of the mirror test .

The results of the study concluded that the fish reacted to its reflection when observed in the mirror and met all the criteria of the mirror test. However, when the fish was provided with a colored tag in a modified tag test, the animal attempted to remove the tag by scraping its body in the presence of the mirror, but showed no response to the clear or colored tags in the absence of the mirror.

For the authors of the study, although the labrid fish shows behavioural responses that meet the test criteria established for other animals, the result does not imply that this species is self-conscious . However, the results of this research open up several questions that remain to be answered: is this test really valid for detecting self-awareness in animals? And if so, if this species of fish is self-aware, should we rethink the concept?

Does the mirror test really measure self-awareness?

The validity of a test such as the mirror test had not been seriously discussed until the publication of new research with animal species that, a priori, we would never have thought were capable of showing signs of self-awareness. The positive evidence in fish and ants has forced a large part of the scientific community to question whether the mirror test is a good measure of self-awareness.

Alex Jordan, an evolutionary biologist and one of the authors of the controversial study on labrid fish, is reluctant to point out that fish are as intelligent as chimpanzees or 20-month-old human babies, and questions the validity of the mirror test to measure the concept of self-awareness.

According to Jordan, one of the problems with the test is that vision is used to measure self-awareness. However, not all animals (or all humans) depend on sight as the predominant sense . For example, bats, which depend on their sonar to move around, may be self-conscious and we may simply not be able, as humans, to formulate a test that detects this because of our visual bias.

Similarly, although elephants can pass the mirror test, they are more dependent on smell than sight, and the sophistication of their consciousness may have led to misinterpretations. In this sense, this test may simply not be suitable for some animals, because we do not have the same sensory view of the world.

The “olfactory” mirror test

To overcome the visual bias of the self-awareness mirror test, Horowitz et al. (2017) designed a smell test for dogs that involved altering the smell of their urine . It should be noted that these animals have not passed the traditional test, as they are not able to recognize themselves in the mirror.

In the experiment, the researchers presented the dogs with several containers. Each of them with an olfactory stimulus: in one, the dog’s own urine; and in the other, a urine to which the smell had been altered. By observing the time each dog remained in the containers, it was found that they were able to distinguish between the olfactory “image” of themselves and the modified one , tracking their own smell more time when they had an additional smell accompanying them than when they did not.

The ecological validity of the olfactory test was examined by presenting the subjects with smells of other known or unknown dogs: the dogs spent more time investigating the smell of other canids than their own smell. Finally, in a second experiment, the dogs spent more time with the modified stimulus than with the modified odour alone, indicating that novelty alone did not explain their behaviour.

In short, the results of this research suggest that the behaviour of dogs implies some recognition of their own smell , which translated into the traditional self-awareness mirror test implies the existence of visual self-recognition or “self-awareness” in these animals. Something that should not surprise all those people who live with these domestic creatures.

Bibliographic references:

  • Bard, K. A., Todd, B. K., Bernier, C., Love, J., & Leavens, D. A. (2006). Self awareness in human and chimpanzee infants: ¿Qué se mide y qué significa la prueba de la marca y el espejo?. Infancy, 9(2), págs. 191 a 219.
  • Horowitz, A. (2017). Oliéndose a sí mismos: Los perros investigan más tiempo sus propios olores cuando se modifican en una prueba de “espejo olfativo”. Procesos de comportamiento, 143, pp. 17 – 24.
  • Kohda, M., Hotta, T., Takeyama, T., Awata, S., Tanaka, H., Asai, J. Y., & Jordan, A. L. (2019). Si un pez puede pasar la prueba de la marca, ¿cuáles son las implicaciones para la prueba de conciencia y autoconciencia en los animales?. PLoS biología, 17(2), e3000021.