How the Mirror Test Tries to Measure Animal Cognition

Bottlenose dolphin sees reflection in a mirror.
A bottlenose dolphin is reflected in a mirror May 4, 2001 at the Dolphins Plus marine mammal research and education center in Key Largo, Florida. Studies report that dolphins are able to recognize themselves in mirrors, which may be a sign of self-awareness. Joe Raedle/Getty Images

The “Mirror Test,” officially called the “Mirror Self-Recognition” test or MSR test, was invented by Dr. Gordon Gallup Jr. in 1970. Gallup, a biopsychologist, created the MSR test to assess the self-awareness of animals — more specifically, whether animals are visually able to recognize themselves when in front of a mirror. Gallup believed that self-recognition could be considered synonymous with self-awareness. If animals recognized themselves in the mirror, Gallup hypothesized, they could be considered capable of introspection.

How the Test Works

The test works as follows: first, the animal being tested is put under anesthesia so that its body can be marked in some way. The mark can be anything from a sticker on their body to a painted face. The idea is simply that the mark needs to be on an area that the animal can't normally see in its day-to-day life. For example, an orangutan’s arm wouldn’t be marked because the orangutan can see its arm without looking at a mirror. An area like the face would be marked, instead.

After the animal wakes up from the anesthesia, now marked, it is given a mirror. If the animal touches or otherwise examines the mark in any way on its own body, it “passes” the test. This means, according to Gallup, that the animal understands that the image reflected is its own image, and not another animal. More specifically, if the animal touches the mark more when it is looking in the mirror than when the mirror is not available, it means it recognizes itself. Gallup hypothesized that most animals would think the image was that of another animal and “fail” the self-recognition test.


The MSR test hasn’t been without its critics, however. An initial criticism of the test is that it may result in false negatives, because many species are not visually-oriented and many more have biological constraints around eyes, such as dogs, which are not only more likely to use their hearing and sense of smell to navigate the world, but who also view direct eye-contact as aggression.

Gorillas, for example, are also averse to eye contact and wouldn’t spend enough time looking in a mirror to recognize themselves, which has been posited as a reason why many of them (but not all of them) fail the mirror test. Additionally, gorillas are known to react somewhat sensitively when they feel they are being observed, which may be another reason for their MSR test failure.

Another criticism of the MSR test is that some animals respond very quickly, on instinct, to their reflection. In most cases, animals act aggressively toward the mirror, perceiving their reflection as another animal (and a potential threat.) These animals, such as some gorillas and monkeys, would fail the test, but this may also be a false negative, however, because if intelligent animals such as these primates took more time to consider (or were given more time to consider) the meaning of the reflection, they might pass.

Additionally, it has been noted that some animals (and perhaps even humans) may not find the mark unusual enough to investigate it or react to it, but this doesn’t mean they have no self-awareness. One example of this is a specific instance of the MSR test done on three elephants. One elephant passed but the other two failed. However, the two that failed still acted in a way that indicated they recognized themselves and researchers hypothesized that they just didn’t care enough about the mark or weren’t concerned enough about the mark to touch it.

One of the biggest criticisms of the test is that just because an animal can recognize itself in a mirror does not necessarily mean the animal is self-aware, on a more conscious, psychological basis.

Animals Who’ve Passed the MSR Test

As of 2017, only the following animals have been noted as passing the MSR test:

  • The following great apes: bonobos, chimpanzees, orangutans, and some gorillas.
  • Some Asian elephants, as discussed above, the hypothesis for why all elephants don’t pass is because they may just not be bothered enough to inspect any markings on themselves.
  • Bottlenose dolphins, who are very keen to inspect the marking and often make movements such as sticking out tongues or circling their heads.
  • Orca whales, who scientists believe anticipate the difference in their image after being marked, which indicates a high level of self-recognition).
  • Some bird species such as pigeons, keas, and magpies.
  • Myrmica genus ants, who seem to attempt to remove the marks when they can see themselves in a mirror and react differently when they are shown other ants through glass.

It should also be noted here that Rhesus monkeys, although not naturally inclined to pass the mirror test, were trained by humans to do so and then did “pass.” Finally, giant manta rays may also possess self-awareness and have been consistently studied to asses whether they do so. When shown a mirror, they react differently and seem very interested in their reflections, but they have not been given the classic MSR test yet.

The MSR may not be the most accurate test and may have faced a lot of criticism, but it was an important hypothesis at the time of its inception and it may be leading to even better tests for the self-awareness and the general cognition of different species of animals. As research continues to develop, we’ll have greater and deeper understandings into the self-awareness capacity of non-human animals.

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Nowakowski, Anjali. "How the Mirror Test Tries to Measure Animal Cognition." ThoughtCo, Aug. 27, 2020, Nowakowski, Anjali. (2020, August 27). How the Mirror Test Tries to Measure Animal Cognition. Retrieved from Nowakowski, Anjali. "How the Mirror Test Tries to Measure Animal Cognition." ThoughtCo. (accessed June 23, 2021).